Meloxicam

Kristin E. McKinney, MD

• Assistant Professor of Radiology
• Division of Ultrasound
• University of Colorado Hospital
• Aurora, Colorado

Astrocytes (astr-stz; aster arthritis in end of fingers order online meloxicam, star) are glial cells that are starshaped because cytoplasmic processes extend from the cell body arthritis diet chart in hindi order meloxicam 15 mg with visa. These extensions widen and spread out to form foot processes arthritis and arthroplasty the knee free download generic meloxicam 15 mg with mastercard, which cover the surfaces of blood vessels (table 11 arthritis knee grade 4 generic 7.5 mg meloxicam with mastercard. They do this by releasing chemicals that promote the formation of tight junctions (see chapter 4) between the endothelial cells of capillaries atrophic arthritis definition buy genuine meloxicam online. The endothelial cells with their tight junctions form the blood-brain barrier, which determines what substances can pass from the blood into the nervous tissue of the brain and spinal cord. The blood-brain barrier protects neurons from toxic substances in the blood, allows the exchange of nutrients and waste products between neurons and the blood, and prevents fluctuations in blood composition from affecting brain functions. Reactive scar-forming astrocytes also limit the regeneration of the axons of injured neurons. Cell body Cell body Axon Axon Axon (a) A multipolar neuron has many dendrites and an axon. Dendrites and sensory receptors are specialized to receive stimuli, and axons are specialized to conduct action potentials. Astrocytes also release chemicals that promote the development of synapses and help regulate synaptic activity by synthesizing, absorbing, and recycling neurotransmitters. One oligodendrocyte can form myelin sheaths around axons of multiple neurons (table 11. Ependymal Cells Ependymal (ep-endi-ml) cells line the ventricles (cavities) of the brain and the central canal of the spinal cord (table 11. Specialized ependymal cells and blood vessels form structures called choroid plexuses (koroyd plekss-ez; table 11. The choroid plexuses secrete the cerebrospinal fluid that flows through the ventricles of the brain (see chapter 13). The ependymal cells frequently have patches of cilia that help circulate cerebrospinal fluid through the brain cavities. Ependymal cells also have long processes at their basal surfaces that extend deep into the brain and the spinal cord and seem, in some cases, to have astrocyte-like functions. However, unlike oligodendrocytes, each Schwann cell forms a portion of the myelin sheath around only one axon (table 11. Satellite cells surround neuron cell bodies in sensory and autonomic ganglia (table 11. Besides providing support and nutrition to the neuron cell bodies, satellite cells protect neurons from heavy-metal poisons, such as lead and mercury, by absorbing them and reducing their access to the neuron cell bodies. Areas of the brain or spinal cord that have been damaged by infection, trauma, or stroke have more microglia than healthy areas. In addition, action potentials travel along myelinated axons more rapidly than along unmyelinated axons (see "Propagation of Action Potentials" in section 11. In myelinated axons, Schwann cells or oligodendrocyte extensions repeatedly wrap around a segment of an axon to form a series of tightly wrapped membranes rich in phospholipids, with little cytoplasm sandwiched between the membrane layers (figure 11. One way to picture the overlapping wrappings, especially for Schwann cells, is to imagine rolling up a hot dog (axon) inside a tortilla (Schwann cell). The tightly wrapped Oligodendrocytes Oligodendrocytes (oli-g-dendr-stz) have cytoplasmic extensions that can surround axons. Within about 3­5 days, the axons in the part of the nerve distal to the cut break into irregular segments and degenerate. This occurs because the neuron cell body produces the substances essential to maintain the axon, and these substances have no way of reaching parts of the axon distal to the point of damage. As the axons degenerate, the myelin part of the Schwann cells around them also degenerates, and macrophages invade the area to phagocytize the myelin. The Schwann cells then enlarge, undergo mitosis, and finally form a column of cells along the regions once occupied by the axons. If the ends of the regenerating axons encounter a Schwann cell column, they grow more rapidly, and reinnervation of their target is likely. If the ends of the axons do not encounter the columns, they fail to reinnervate their target. It normally takes about 2 weeks for the axonal sprouts to enter the Schwann cell columns. After the axons grow through the Schwann cell columns, new myelin sheaths form and the neurons reinnervate the structures they previously supplied. Treatment strategies that increase the probability of reinnervation involve bringing the ends of the severed nerve close together surgically. When a section of nerve is destroyed as a result of trauma, a surgeon can perform a nerve transplant to replace the damaged segment. The transplanted nerve eventually degenerates, but it does provide Schwann cell columns through which axons can grow. An oligodendrocyte has several processes, each of which forms part of a myelin sheath. The cell bodies of the oligodendrocytes are a short distance from the axons they ensheathe, and fewer oligodendrocytes than Schwann cells are present. Neuron cell body Axon Site of injury Schwann cell Muscle fiber (a) Muscle atrophies. After reinnervation, the muscle can become functional and hypertrophy (increase in size). Without innervation from the nerve, muscle function is completely lost, and the muscle remains atrophied. The astrocytes provide structural support and play a role in regulating what substances from the blood reach the neurons. Neuron Microglial cell Foot processes Astrocyte Capillary Oligodendrocytes Oligodendrocyte Ependymal cells Cilia (a) Ciliated ependymal cells lining the ventricles of the brain and the central canal of the spinal cord help move cerebrospinal fluid. Neuron cell body Schwann cells Node of Ranvier Axon Myelin sheath Ependymal cells (b) Satellite cells membranes constitute the myelin sheath and give myelinated axons a white appearance because of the high lipid concentration. At these locations are slight constrictions where the myelin sheaths of adjacent cells dip toward the axon but do not cover it, leaving an area where the myelin sheath is much thinner and about 2­3 m in length. Although the axon at a node of Ranvier is not wrapped in myelin, Schwann cells or oligodendrocytes extend across the node and connect to each other. Instead, the axons rest in invaginations of the Schwann cells or oligodendrocytes (figure 11. Thus, each axon is surrounded by a series of Schwann cells, and each Schwann cell can simultaneously surround more than one unmyelinated axon. The process continues rapidly until the end of the first year after birth and continues more slowly thereafter. The importance of myelinated axons is dramatically illustrated in diseases that gradually destroy the myelin sheath, such as multiple sclerosis and some cases of diabetes mellitus. Action potential transmission is slowed, resulting in impaired control of skeletal and smooth muscles. Explain the three types of neurons based on structure, and give an example of where each type is found. Which type of glial cell supports neurons and blood vessels and promotes formation of the blood-brain barrier These groupings give nervous tissue distinctive areas, called gray matter and white matter. Because gray matter consists of groups of neuron cell bodies and their dendrites, where there is very little myelin, these areas are darker in appearance. Conversely, because white matter consists of bundles of parallel myelinated axons, they are whitish in color. Predict 3 A 75-year-old man was found unconscious in his bathroom after falling and hitting his head. Evidence indicated that the man had suffered two strokes, both due to blocked blood vessels. One had occurred a few weeks earlier; the other had occurred very recently and may have led to the fall. Autopsy findings also indicated that, when the man hit his head, some damage to his brain occurred as well. Based on what you know about inflammation and the cellular structure of the brain, describe what the pathologist found in each of the damaged areas of the brain. Describe and state the location of the following: nerve tracts, nerves, the brain cortex, nuclei, ganglia. Describe a resting membrane potential and explain how it is created and maintained. Explain the factors that determine action potential frequency and the five levels of stimulation. Describe the effect of myelination on the speed of action potential propagation, as well as other factors that affect the speed of action potential conduction. Like computers, humans depend on electrical signals to communicate and integrate information. Action potentials are an important means by which cells communicate with other cells in the many areas of the body. For example, stimuli-such as light, sound, and pressure-act on specialized sensory cells in the eye, ear, and skin to produce action potentials, which are conducted from these cells to the spinal cord and brain. Action potentials originating within the brain and spinal cord travel to muscles and certain glands to regulate their activities. Our ability to perceive our environment, perform complex mental activities, and respond to stimuli depends on action potentials. For example, the brain interprets action potentials received from sensory cells as vision, hearing, or touch. Complex mental activities, such as conscious thought, memory, and emotions, result from action potentials. The contraction of muscles and the secretion of certain glands occur in response to action potentials generated within them. A basic knowledge of the electrical properties of cells is necessary for understanding many of the normal functions and pathologies of the body. Permeability characteristics of the plasma membrane cells use to carry out their functions. There is a higher concentration of Na+ and Cl- outside the cell than inside the cell, while there is a higher concentration of K+ on the inside of the cell. We describe this distribution of ions as a concentration gradient (see chapter 3). For Na+, there is a steep concentration gradient from the outside of the cell to the inside of the cell. For K+, the concentration gradient is the opposite of the concentration gradient for Na+. For K+, there is a steep concentration gradient from the inside of the cell to the outside of the cell. In addition to a high concentration of K+ in the cell cytoplasm, there is also a high concentration of negatively charged molecules, such as proteins, and other molecules that contain phosphate. Permeability Characteristics of the Plasma Membrane Differences in intracellular and extracellular concentrations of ions result primarily from the sodium-potassium pump and the permeability characteristics of the plasma membrane. Neurons expend energy to maintain an uneven distribution of ions across the plasma membrane. By transporting K+ into the cytoplasm, the sodium-potassium pump maintains the high concentration of K+ in the cytoplasm. Simultaneously, the sodium-potassium pump maintains the higher concentration of extracellular Na+ (see figure 3. As noted in chapter 3, the plasma membrane is selectively permeable, thus allowing some, but not all, substances to pass through it. Negatively charged proteins are regularly synthesized Ionic Concentration Differences Across the Plasma Membrane As you learned in chapter 9, electrically excitable cells, such as muscle cells and neurons, operate through ion movements across the plasma membrane. As you will see, many of the principles you studied for skeletal muscle fibers also apply to neurons. Cells have different concentrations of ions in the cytoplasm when compared with the extracellular fluid around the cell. Because proteins are large and relatively insoluble, they cannot easily diffuse across the plasma membrane and stay inside the cell (figure 11. Because negatively charged Cl- is repelled by the negatively charged proteins and other negatively charged ions inside the cell, Cl- exits the cell, which results in a higher concentration of Cl- outside the cell than inside. Leak Ion Channels Leak ion channels, or nongated ion channels, are always open and are responsible for the permeability of the plasma membrane to ions when the plasma membrane is unstimulated, or at rest (figure 11. Each ion channel is specific for one type of ion, although the specificity is not absolute. The number of each type of leak ion channel in the plasma membrane determines the permeability characteristics of the resting plasma membrane to different types of ions. The plasma membrane is more permeable to K+ and Cl- and much less permeable to Na+ because the membrane has many more K+ and Cl- leak ion channels than Na+ leak ion channels. Gated Ion Channels Gated ion channels are closed until opened by specific signals. By opening and closing, these channels can change the permeability of the plasma membrane. Ligand-gated ion channels are stimulated to open by the binding of a specific molecule to the receptor site of the ion channel. The receptor site of the ion channel is located on its extracellular side, which allows it to receive signals from the environment. The specific molecule that binds to the receptor site can be referred to as a ligand. Ligands could be neurotransmitters or hormones, but there is one particular ligand for each ligand-gated ion channel. For example, the neurotransmitter acetylcholine released from the presynaptic terminal of a neuron is the ligand that binds to a ligand-gated Na+ channel in the membrane of a muscle fiber. As a result, the Na+ channel opens, allowing Na+ to enter the fiber (see figure 9. Ligand-gated ion channels + exist for Na+, K+, Ca2, and Cl-, and these channels are common in nervous and muscle tissues, as well as in glands.

As the basilar membrane vibrates arthritis pain relief daily express order meloxicam mastercard, hair cells along a large part of the basilar membrane are stimulated relief arthritis jaw purchase meloxicam 7.5 mg with mastercard. In other areas rheumatoid arthritis disease buy meloxicam visa, a low frequency of afferent action potentials may be transmitted rheumatoid arthritis hypersensitivity meloxicam 7.5 mg purchase fast delivery, whereas in the optimally vibrating regions of the basilar membrane a high frequency of action potentials is initiated arthritis diet dogs 7.5 mg meloxicam order with amex. There are approximately twice as many nerve cells in the cochlear ganglion as there are hair cells. Over 90% of the afferent axons synapse with inner hair cells-about 10­30 axons per hair cell. Only a few, small-diameter afferent axons synapse with the three rows of outer hair cells. Action potentials from those efferent axons stimulate the contraction of actin filaments within the hair cells, causing them to shorten. This adjustment in the height of the outer hair cells, attached to both the basilar membrane and the tectorial membrane, fine-tunes the tension of the basilar membrane and the distance between the basilar membrane and the tectorial membrane. For example, loud music (amplified to 120 db) can impair hearing, although the actual amount of damage can vary from person to person. The defects may not be detectable on routine diagnosis, but they include decreased sensitivity to sound in specific narrow frequency ranges and decreased ability to discriminate between two pitches. Researchers have also investigated the effects of prolonged use of earbuds or earphones on hearing. Many feel that this type of exposure to sound, particularly loud music, could result in hearing loss. Loud music, however, is not as harmful as the sudden sound of a nearby gunshot at 140 db. This sound is too sudden for the attenuation reflex to protect the inner ear structures, and the intensity is great enough to cause auditory damage. In fact, gunshot noise is the most common recreational cause of serious hearing loss. These action potentials are compared with one another, and the strongest action potential, corresponding to the area of maximum basilar membrane vibration, is taken as standard. Efferent action potentials then are sent from the superior olivary nucleus back to the spiral organ to all regions where the maximum vibration did not occur. These action potentials inhibit the hair cells from initiating additional action potentials in the sensory neurons. Thus, only action potentials from regions of maximum vibration are sent to the cortex, where they become consciously perceived. As a result of this localization, neurons along a given portion of the cochlea send action potentials to the cerebral cortex only in response to specific pitches, allowing for the recognition of a wide variety of sounds. Like the keys of a piano, the hair cells of the spiral organ are "tuned" to specific pitches. Action potentials near the base of the basilar membrane stimulate neurons in a certain part of the auditory cortex, which interpret the stimulus as a highpitched sound, whereas action potentials from the apex stimulate a different part of the cortex, which interprets the stimulus as a low-pitched sound. As high-amplitude sound waves reach the ear, the perilymph, endolymph, and basilar membrane vibrate more intensely, and the hair cells are stimulated more intensely. As a result of the increased stimulation, more hair cells send action potentials at a higher frequency to the cerebral cortex, where this information is perceived as a greater sound volume. Explain why it is much easier to perceive subtle musical tones when music is played somewhat softly, as opposed to very loudly. Those filaments can move the K+ channels along the plasma membrane, tightening or loosening the tip links. Likewise, the response of an inner hair cell to stimulation is graded and can increase up to a point of saturation (when all the K+ channels are open maximally). A 100 nm (1-degree) deflection of the stereocilia results in a response that is 90% of maximum. The vestibulocochlear nerve functions as two separate nerves carrying information from two separate but closely related structures. These neurons in turn either synapse in or pass through the superior olivary nucleus. Neurons terminating in this nucleus may synapse with efferent neurons returning to the cochlea to modulate pitch perception. This reflex pathway dampens loud sounds by initiating contractions of these muscles (the sound attenuation reflex). Neurons synapsing in the superior olivary nucleus may also join other ascending neurons to the cerebral cortex. Ascending neurons from the superior olivary nucleus travel in the lateral lemniscus. All ascending fibers synapse in the inferior colliculi, and neurons from there project to the medial geniculate nucleus of the thalamus, where they synapse with neurons that project to the cortex. These neurons terminate in the auditory cortex in the dorsal portion of the temporal lobe within the lateral fissure and, to a lesser extent, on the superolateral surface of the temporal lobe (see chapter 13). Neurons from the inferior colliculus also project to the superior colliculus, where reflexes that turn the head and eyes in response to loud sounds are initiated. Starting with the auricle, trace a sound wave into the inner ear to the point at which action potentials are generated in the cochlear nerve. Describe the neuronal pathways for hearing, from the cochlear nerve to the cerebral cortex. Balance the organs of balance are divided structurally and functionally into two parts. The second part, the dynamic labyrinth, is associated with the semicircular canals and is involved in evaluating movements of the head. However, the utricle and saccule each contain a specialized patch of epithelium about 2­3 mm in diameter called the utricular macula and the saccular macula (mak-l; figure 15. The utricular macula is oriented parallel to the base of the skull, and the saccular macula is perpendicular to the base of the skull. The utricular and saccular maculae resemble the spiral organ and consist of columnar supporting cells and hair cells. The "hairs" of these cells consist of numerous microvilli, called stereocilia, and one cilium, called a kinocilium (k-n-sil-m). The hairs are embedded in the otolithic membrane, a gelatinous mass weighted by the presence of otoliths (t-liths), tiny, crystallike structures composed of protein and calcium carbonate (figure 15. The gelatinous mass moves in response to gravity, bending the hair cells and initiating action potentials in the associated neurons. The stereocilia function much as the stereocilia of cochlear hair cells do, with tip links connected to gated K+ channels. Deflection of the hairs toward the kinocilium results in depolarization of the hair cell, whereas deflection of the hairs away from the kinocilium results in hyperpolarization of the hair cell. If the head is tipped, otoliths move in response to gravity and stimulate certain hair cells (figure 15. The hair cells are constantly being stimulated at a low level by the otolith-weighted covering of the maculae; however, as this covering moves in response to gravity, the intensity of hair cell stimulation changes. This pattern of stimulation-and the subsequent pattern of action potentials from the numerous hair cells of the maculae- can be translated by the brain into specific information about head position or acceleration. Much of this information is not perceived consciously but is dealt with subconsciously. The body responds by making subtle tone adjustments in the muscles of the back and neck, which are intended to restore the head to its proper neutral, balanced position. The dynamic labyrinth consists of three semicircular canals at nearly right angles to one another, one lying nearly in the transverse plane, one in the coronal plane, and one in the sagittal plane (figure 15. This arrangement of the semicircular canals in these three body planes, much like the x, y, and z axes of a three-dimensional structure, enables a person to detect movement in all directions. Within each ampulla, the epithelium is specialized to form a crista ampullaris (krist am-p-lars), which is structurally and functionally very similar to the sensory epithelium of the maculae. Each crista consists of a ridge or crest of epithelium with a curved, gelatinous mass, the cupula (koopoo-l), suspended over the crest. The cupula contains no otoliths and therefore does not respond to gravitational pull. Instead, the cupula is a float that is displaced by fluid movements within the semicircular canals. Endolymph movement within each semicircular canal moves the cupula, bends the hairs, and initiates action potentials (figure 15. As the head begins to move, the endolymph does not move at the same rate as the semicircular canals. This difference displaces the cupula in a direction opposite the direction the head is moving, resulting in relative movement between the cupula and the endolymph (figure 15. As movement continues, the fluid of the semicircular canals begins to move and catches up with the cupula, and stimulation stops. As the head stops moving, the endolymph continues to move because of its momentum, displacing the cupula in the same direction as the head was moving. Because displacement of the cupula is most intense when the rate of head movement changes, this system detects changes in the rate of movement rather than movement alone. As with the static labyrinth, the information the brain obtains from the dynamic labyrinth is largely subconscious. Neuronal Pathways for Balance Neurons synapsing on the hair cells of the maculae and cristae ampullares converge into the vestibular ganglion, where their cell bodies are located (figure 15. In addition to vestibular sensory input, the vestibular nucleus receives input from proprioceptive neurons throughout the body, as well as from the visual system. In sobriety tests, people are asked to close their eyes while their balance is evaluated, because alcohol affects the proprioceptive and vestibular components of balance (cerebellar function) to a greater extent than it does the visual portion. A reflex pathway allows a person to maintain visual fixation on an object while the head is in motion. To demonstrate this function, try spinning a person around about 10 times in 20 seconds, then stopping him or her and observing eye movements. The eyes track in the direction of motion and return with a rapid recovery movement before repeating the tracking motion. If then asked to walk in a straight line, the person deviates in the direction of rotation; if asked to point to an object, his or her finger deviates in the direction of rotation. Describe how the utricular macula and saccular macula function in static equilibrium. However, their ability to identify specific odors correctly decreases, especially in men over age 70. Crossing the bar was invigorating, and Earl was surprised that all those warnings about seasickness did not seem to apply to him. At last, the boat arrived at the fishing site, the engine was cut, and the sea anchor was set. For the first time, Earl noticed the unpleasant mixture of smelly bait and diesel fumes. Earl felt a little light-headed and a bit drowsy; then he began to feel nauseated, and his face became pale. Eventually, his nausea intensified and he leaned over the boat rail and vomited into the ocean. Seasickness is a form of motion sickness, which consists of nausea, weakness, and other dysfunctions resulting from stimulation of the semicircular canals during motion, as may occur while riding in a boat, an automobile, an airplane, a swing, or an amusement park ride. It occurs because the brain simultaneously perceives differing sensory input from the semicircular canals, eyes, and proprioceptors in the lower limbs. Motion sickness can be decreased by closing the eyes or looking at a distant object, such as the horizon. Antiemetics, such as anticholinergic or antihistamine medications, can counter the nausea and vomiting. Scopolamine is an anticholinergic drug that blocks acetylcholine-mediated transmission in the parasympathetic nervous system. Scopolamine can be administered transdermally in the form of a patch placed on the skin behind the ear (Transdermal-Scop). Cyclizine (Marezine), dimenhydrinate (Dramamine), and diphenhydramine (Benadryl) are antihistamines that affect the neural pathways from the vestibule. The lenses of the eyes lose flexibility as a person ages, because the connective tissue of the lenses becomes more rigid. Recall that this condition, called presbyopia, is the most common age-related change in the eyes. The most common visual problem in older people requiring medical treatment, such as surgery, is the development of cataracts. Macular degeneration, which affects visual acuity in the center of the visual field, is the leading cause of vision loss in people over the age of 60. Other age-related defects affecting vision include glaucoma and diabetic retinopathy. As people age, the number of hair cells in the cochlea decreases, leading to age-related hearing loss, called presbyacusis (prezb-koosis). Two types of hearing impairment have been identified: conductive and sensorineural. In conductive hearing loss, the spiral organ and neuronal pathways for hearing function normally, but there is a mechanical deficiency in the transmission of sound waves from the external ear to the spiral organ. Conductive hearing loss often can be treated-for example, by removing earwax blocking the external auditory canal or by replacing or repairing the auditory ossicles. If the degree of conductive hearing loss does not justify surgical treatment, or if treatment does not resolve the hearing loss, a hearing aid may be worn to help transmit the amplified (louder) sound waves through the conductive blockage and provide normal stimulation to the spiral organ. People with sensorineural hearing loss commonly use hearing aids, which produce amplified sound waves that stimulate the spiral organ more than normal, helping overcome the perception of reduced sound volume.

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The hard palate arthritis psoriasis medication meloxicam 15 mg purchase otc, or bony palate arthritis diet for humans meloxicam 15 mg buy with visa, forms the majority of the floor of the nasal cavity (and the roof of the mouth) rheumatoid arthritis x ray images generic 15 mg meloxicam fast delivery. Sutures join four bones to form the hard palate: the palatine processes of the two maxillary bones form the anterior two-thirds of the hard palate rheumatoid arthritis ribbon 7.5 mg meloxicam order with visa, and the horizontal plates of the two palatine bones form the posterior one-third of the hard palate arthritis pain dogs symptoms meloxicam 15 mg purchase otc. The hard and soft palates separate the nasal cavity from the mouth, enabling humans to chew and breathe at the same time. Individual Bones of the Skull the skull, or cranium, is composed of 22 separate bones (table 7. A cleft lip results if the maxillae do not form normally, and a cleft palate occurs when the palatine processes of the maxillae do not fuse with one another. A cleft palate produces an opening between the nasal and oral cavities, making it difficult to eat or drink or to speak distinctly. A cleft lip alone, or both cleft lip and palate, occurs approximately once in every 1000 births and is more common in males. A cleft palate alone occurs approximately once in every 2000 births and is more common in females. Each temporal bone holds one set of auditory ossicles, which consists of the malleus, incus, and stapes. The 22 bones of the skull are divided into two portions: the braincase and the facial bones. The braincase, or neurocranium, consists of 8 bones that immediately surround and protect the brain. They include the paired parietal and temporal bones and the unpaired frontal, occipital, sphenoid, and ethmoid bones. The 14 facial bones, or viscerocranium, form the structure of the face in the anterior skull. They are the maxilla (2), zygomatic (2), palatine (2), lacrimal (2), nasal (2), inferior nasal concha (2), mandible (1), and vomer (1) bones. The frontal and ethmoid bones, which are part of the braincase, also contribute to the face. The mandible is often listed as a facial bone, even though it is not part of the intact skull. The facial bones protect the major sensory organs located in the face: the eyes, nose, and tongue. The bones of the face also provide attachment points for the muscles involved in mastication (mas-ti-kshn; chewing), facial expression, and eye movement. The jaws (mandible and maxillae) possess alveolar (al-v-lr) processes with sockets for the attachment of the teeth. The bones of the face and their associated soft tissues determine the unique facial features of each individual. Name the foramina that allow the passage of the following nerves and blood vessels: optic nerve, olfactory nerve, vestibulocochlear nerve, incisive nerve, facial nerve, carotid artery, and internal jugular vein. State the bone features where the following muscles attach to the skull: neck muscles, throat muscles, muscles of masti cation, muscles of facial expression, and muscles that move the eyeballs. The hyoid bone is the only bone in the body not directly attached to another bone. Instead, muscles and ligaments attach it to the skull, so the hyoid "floats" in the superior aspect of the neck just below the mandible. Attachment point for temporalis muscle Superior and inferior temporal lines Special Feature Forms lateral wall of skull Parietal eminence Superior temporal line Inferior temporal line (b) Temporal Bone (Right)-Lateral and Medial Views Landmark Carotid canal (shown in figures 7. Vertebral Column the vertebral column performs five major functions: (1) It supports the weight of the head and trunk, (2) it protects the spinal cord, (3) it allows spinal nerves to exit the spinal cord, (4) it provides a site for muscle attachment, and (5) it permits movement of the head and trunk. The vertebral column usually consists of 26 bones, called vertebrae, which can be divided into five regions: 7 cervical vertebrae (vert-br), 12 thoracic vertebrae, 5 lumbar vertebrae, 1 sacral bone, and 1 coccygeal (kok-sij-l) bone (figure 7. To remember how many vertebrae are in each region, think of mealtimes: 7, 12, and 5. The developing embryo has about 33 or 34 vertebrae, but by adulthood the 5 sacral vertebrae have fused to form 1 bone, and the 4 or 5 coccygeal bones usually have fused to form 1 bone. Two of the curves appear during embryonic development and reflect the C-shaped curve of the embryo and fetus within the uterus. When the infant raises its head in the first few months after birth, a secondary curve, which is convex anteriorly, develops in the neck. Later, when the infant learns to sit and then walk, the lumbar portion of the column also becomes convex anteriorly. Thus, in the adult vertebral column, the cervical region is convex anteriorly, the thoracic region is concave anteriorly, the lumbar region is convex anteriorly, and the sacral and coccygeal regions together are concave anteriorly. These spinal curvatures help accommodate our upright posture by aligning our body weight with our pelvis and lower limbs. General Features of the Vertebrae the general structure of an individual vertebra is outlined in table 7. The protection of the spinal cord is achieved by the body and the vertebral arch, which projects posteriorly from the body. The vertebral arch is divided into left and right halves, and each half has two parts: the pedicle (pedi-kl; foot), which is attached to the body, and the lamina (lami-na; thin plate), which joins with the lamina from the opposite half of the arch. The vertebral foramina of adjacent vertebrae combine to form the vertebral canal, which contains the spinal cord and cauda equina (see figure 12. A transverse process extends laterally from each side of the arch between the lamina and the pedicle, and a single spinous process lies at the junction between the two laminae. Lordosis (lr-dsis; hollow back) is an exaggeration of the convex curve of the lumbar region. Kyphosis (k-fsis; hump back) is an exaggeration of the concave curve of the thoracic region. It is most common in postmenopausal women but can also occur in men and becomes more prevalent as people age. Scoliosis (skl-sis) is an abnormal lateral and rotational curvature of the vertebral column, which is often accompanied by secondary abnormal curvatures, such as kyphosis (figure 7B). Contrary to popular belief, scoliosis in school-age children is not associated with carrying overly heavy backpacks. Studies have shown that, although back pain is common in backpack-bearing school kids, structural changes in the vertebral column are not. Treatments for abnormal spinal curvature depend on the age and overall medical condition of the person. However, most treatments include repeated examinations to monitor the status of the curvature, a back brace, and surgery when the curving is not slowed by bracing. Much vertebral movement is accomplished by the contraction of the skeletal muscles attached to the transverse and spinous processes (see chapter 10). Each intervertebral foramen is formed by intervertebral notches in the pedicles of adjacent vertebrae. Movement and additional support of the vertebral column are made possible by the vertebral processes. Each vertebra has two superior and two inferior articular processes, with the superior processes of one vertebra articulating with the inferior processes of the next superior vertebra (table 7. The region of overlap and articulation between the superior and inferior articular processes creates a smooth articular facet (faset; little face) on each articular process. Because the cervical vertebrae are rather delicate and have small bodies, dislocations and fractures are more common in this area than in other regions of the column. The atlas has no body and no spinous process, but it has large superior facets, where it articulates with the occipital condyles on the base of the skull. The joint between the occipital condyles and the atlas allows the head to move in a "yes" motion and to tilt from side to side. The axis has a highly modified process on the superior side of its small body called the dens, or odontoid (-dontoyd; tooth-shaped) process. The dens fits into the enlarged vertebral foramen of the atlas, and the atlas rotates around this process. The spinous process of the seventh cervical vertebra, which is not bifid, is quite pronounced and Intervertebral Disks During life, intervertebral disks of fibrocartilage, which are located between the bodies of adjacent vertebrae (figure 7. The intervertebral disks consist of an external annulus fibrosus (an-ls f-brss; fibrous ring) and an internal, gelatinous nucleus pulposus (pl-pss; pulp). The disk becomes more compressed with increasing age, so the distance between vertebrae-and therefore the overall height of the individual-decreases. The annulus fibrosus also becomes weaker with age and more susceptible to herniation. Regional Differences in Vertebrae the vertebrae in each region of the vertebral column have specific characteristics that tend to blend at the boundaries between regions (table 7. The most prominent spinous process in this area is called the vertebral prominens. This is usually the spinous process of the seventh cervical vertebra, but it may be that of the sixth cervical vertebra or even the first thoracic. The superior articular facets face superiorly, and the inferior articular facets face inferiorly. Previously, a piece of hipbone from either the patient or a donor was inserted into the space vacated by the damaged disk. The vertebrae adjacent to the removed disk are usually further anchored together with a titanium plate held in place with titanium screws inserted into the vertebral bodies. Eventually, the adjacent vertebrae become fused by new bone growth across the gap. The bright white structures are the screws and the plate that were added for stability. A laminectomy is the removal herniated part of the disk may push against of a vertebral lamina, or vertebral arch. A and compress the spinal cord, cauda equina, or hemilaminectomy is the removal of a portion spinal nerves. These procedures reduce the normal function of this nervous tissue the compression of the spinal nerve or spinal and produces pain and numbness in the limb cord. The inferior lumbar and inferior nucleus pulposus, leaving the annulus fibrosus cervical intervertebral disks are the most com- intact. This commonly occurs in "rear-end" automobile accidents and athletic injuries, in which the body is quickly forced forward while the head remains stationary. A common injury resulting from whiplash is fracture of the spinous processes of the cervical vertebrae or a herniated disk due to an anterior tear of the annulus fibrosus. These injuries can cause posterior pressure on the spinal cord or spinal nerves and strained or torn muscles, tendons, and ligaments. The first 10 thoracic vertebrae have articular facets on their transverse processes, where they articulate with the tubercles of the ribs. Additional articular facets are on the superior and inferior margins of the body where the heads of the ribs articulate. The head of most ribs articulates with the inferior articular facet of one vertebra and with the superior articular facet for the rib head on the next vertebra down. The fifth lumbar vertebra or first coccygeal vertebra may become fused into the sacrum. Conversely, the first sacral vertebra may fail to fuse with the rest of the sacrum, resulting in six lumbar vertebrae. The superior articular facets face medially, and the inferior articular facets face laterally. When the superior articular surface of one lumbar vertebra joins the inferior articulating surface of another lumbar vertebra, the resulting arrangement adds strength to the inferior portion of the vertebral column and limits rotation of the lumbar vertebrae. Because the lumbar vertebrae have massive bodies and carry a large amount of weight, fractures are less common, but ruptured intervertebral disks are more common in this area than in other regions of the column. Describe some expected differences between the vertebrae of a person who engages in regular vigorous physical exercise and those of a person who never exercises. The transverse processes of the sacral vertebrae fuse to form the lateral parts of the sacrum. The superior surfaces of the lateral parts are wing-shaped areas called the alae (l; wings). The anterior edge of the body of the first sacral vertebra bulges to form the sacral promontory (see figure 7. The sacral promontory can be felt during a vaginal examination, and it is used as a reference point when measuring the pelvic inlet. The coccygeal vertebrae are much smaller than the other vertebrae and have neither vertebral foramina nor well-developed processes. The coccyx is easily broken when a person falls by sitting down hard on a solid surface. Coccyx Rib Cage the rib cage, or thoracic cage, protects the heart and lungs within the thorax and forms a semirigid chamber, which can increase and decrease in volume during respiration. It consists of the thoracic vertebrae, the ribs with their associated costal (rib) cartilages, and the sternum (figure 7. The superior 7 pairs are called true ribs, or vertebrosternal (vertbr-sternl) ribs; they articulate with the thoracic vertebrae and attach directly through their costal cartilages to the sternum. The inferior 5 pairs, or false ribs, articulate with the thoracic vertebrae but do not attach directly to the sternum. The eighth, ninth, and tenth ribs, the vertebrochondral (vert-br-kondrl) ribs, are joined by a common cartilage to the costal cartilage of the seventh rib, which in turn is attached to the sternum. Two of the false ribs, the eleventh and twelfth ribs, are also called floating ribs, or vertebral ribs, because they do not attach to the sternum. The costal cartilages are flexible and permit the rib cage to expand during respiration. A separated rib is a dislocation between a rib and its costal cartilage that allows the rib to move, override adjacent ribs, and cause pain. First, the head articulates with the bodies of two adjacent vertebrae and the intervertebral disk between them. The head of each rib articulates with the inferior articular facet of the superior vertebra and the superior articular facet of the inferior vertebra.

The term molecular mass is used for convenience for ionic compounds arthritis for dogs medicine generic meloxicam 7.5 mg online, even though they are not molecules arthritis questions and answers purchase meloxicam toronto. Intermolecular forces include hydrogen bonds and the properties of solubility and dissociation tylenol arthritis pain gel caps meloxicam 15 mg purchase online. Hydrogen Bonds Molecules with polar covalent bonds have positive and negative "ends arthritis in spine quality meloxicam 15 mg. When hydrogen forms a covalent bond with oxygen arthritis pain upon waking 15 mg meloxicam purchase visa, nitrogen, or fluorine, the resulting molecule becomes very polarized. If the positively charged hydrogen of one molecule is attracted to the negatively charged oxygen, nitrogen, or fluorine of another molecule, a hydrogen bond forms. For example, the positively charged hydrogen atoms of a water molecule form hydrogen bonds with the negatively charged oxygen atoms of other water molecules (figure 2. These hydrogen bonds are essential for the unique properties of water (see section 2. An important role of hydrogen bonds is to help build the shape of complex molecules. Solubility and Dissociation Solubility is the ability of one substance to dissolve in another- for example, sugar dissolving in water. Charged substances, such as sodium chloride, and polar substances, such as glucose, readily dissolve in water, whereas nonpolar substances, such as oils, do not. Substances dissolve Intermolecular Forces Intermolecular forces are the weak electrostatic attractions that exist between oppositely charged parts of molecules, or between ions and molecules. Electron-Dot Formula the bonding electrons are shown as dots between the symbols of the atoms. Hydrogen atom Oxygen atom Carbon atom in water when they become surrounded by water molecules. If the positive and negative ends of the water molecules are more attracted to the charged ends of other molecules than to each other, the hydrogen bonds between the ends of the water molecules break, and water molecules surround the other molecules, which become dissolved in water. When ionic compounds dissolve in water, their ions dissociate, or separate, from one another because cations are attracted to the negative ends of water molecules and anions are attracted to the positive ends of water molecules. When NaCl dissociates in water, sodium and chloride ions separate, and water molecules surround and isolate the ions, thereby keeping them in solution (figure 2. When molecules (covalent compounds) dissolve in water, they usually remain intact, even though they are surrounded by water molecules. Cations and anions that dissociate in water are sometimes called electrolytes (e-lektro-ltz) because they have the capac l ity to conduct an electric current, which is the flow of charged particles. These currents can be detected by electrodes on the surface of the body because the ions in the body fluids conduct electric currents. Molecules that do not dissociate form solutions that do not conduct electricity and are called nonelectrolytes. Maintaining the proper balance of electrolytes is important for keeping the body hydrated, controlling blood pH, and ensuring the proper function of muscles and nerves. Polar Covalent Bond An unequal sharing of electrons between two atoms results in a slightly positive charge (+) on one side of the molecule and a slightly negative charge (-) on the other side of the molecule. Intermolecular Bonds Hydrogen Bond the attraction of oppositely charged ends of one polar molecule to another polar molecule holds molecules or parts of molecules together. In an emergency, administering intravenous solutions can restore electrolyte and fluid balance. The positively charged Na+ are attracted to the negatively charged (-) oxygen (red) end of the water molecule, and the negatively charged Cl- are attracted to the positively charged (+) hydrogen (blue) end of the water molecule. Summarize the characteristics of synthesis, decomposition, reversible reactions, and oxidationreduction reactions. Distinguish between chemical reactions that release energy and those that take in energy. An example is the synthesis of the complex proteins of the human body from amino acid "building blocks" obtained from food (figure 2. Second, in other reactions, a reactant can be broken down, or decomposed, into simpler, less complex products. An example is the breakdown of carbohydrate molecules into glucose molecules (figure 2. Third, atoms are generally associated with other atoms through chemical bonding or intermolecular forces; therefore, to synthesize new products or break down reactants, it is necessary to change the relationship between atoms. Synthesis Reactions A synthesis reaction is when two or more reactants chemically combine to form a new and larger product. The synthesis reactions occurring in the body are collectively referred to as anabolism (a-nab o-lizm). The growth, maintenance, and repair of the body could not take place without anabolic reactions. An example of a synthesis reaction is the combination of two amino acids to form a dipeptide (figure 2. Synthesis reactions in which water is a product are called dehydration (water out) reactions. As the atoms rearrange as a result of a synthesis reaction, old chemical bonds are broken and new chemical bonds are formed. A chemical reaction occurs when atoms, ions, molecules, or compounds interact either to form or to break chemical bonds. The substances that enter into a chemical reaction are called reactants, and the substances that result from the chemical reaction are called products. This reaction is also a dehydration reaction because it results in the removal of a water molecule from the amino acids. This reaction is also a hydrolysis reaction because it involves the splitting of a water molecule. The decomposition reactions occurring in the body are collectively called catabolism (ka-tab-o-lizm). They include the digestion of food molecules in the intestine and within cells, the breakdown of fat stores, and the breakdown of foreign matter and microorganisms in certain blood cells that protect the body. All of the anabolic and catabolic reactions in the body are collectively defined as metabolism. An example of a decomposition reaction is the breakdown of a disaccharide (a type of carbohydrate) into glucose molecules (figure 2. Note that this reaction requires that water be split into two parts and that each part be contributed to one of the new glucose molecules. Reactions that use water in this manner are called hydrolysis (h-droli-sis; water dissolution) reactions. Oxidation-Reduction Reactions Chemical reactions that result from the exchange of electrons between the reactants are called oxidation-reduction reactions. When sodium and chlorine react to form sodium chloride, the sodium atom loses an electron and the chlorine atom gains an electron. The loss of an electron by an atom is called oxidation, and the gain of an electron is called reduction. The transfer of the electron can be complete, resulting in an ionic bond, or it can be partial, resulting in a covalent bond. Because one atom partially or completely loses an electron and another atom gains that electron, these reactions are called oxidation-reduction reactions. In a reversible reaction, the reaction can run in the opposite direction, so that the products are converted back to the original reactants. When the rate of product formation is equal to the rate of the reverse reaction, the reaction system is said to be at equilibrium. At equilibrium, the amount of reactants relative to the amount of products remains constant. The following analogy may help clarify the concept of reversible reactions and equilibrium. Because the players can move in either direction (on or off the field), this is like a reversible reaction. Imagine that the players on the bench are the reactant and the players on the field (lined up in formation) are the product. At equilibrium, the amount of reactant relative to the amount of product is always the same. When some players on the bench run onto the field an equal number of players run off the field, so equilibrium is maintained. An important reversible reaction in the human body involves carbon dioxide and hydrogen ions. Carbonic Predict 5 When hydrogen gas combines with oxygen gas to form water, is the hydrogen reduced or oxidized Using the terms reactant and product, describe what occurs in a chemical reaction. Contrast synthesis and decomposition reactions, and explain how catabolism and anabolism relate to these two types of reactions. Kinetic (ki-netik) energy is the form of energy that is actually doing work and moving matter. However, if the ball is released and falls toward the floor, it has kinetic energy. According to the conservation of energy principle, the total energy of the universe is constant. Therefore, energy is neither created nor destroyed, but it can take on different forms. For example, the potential energy in the ball is converted into kinetic energy as the ball falls toward the floor. Conversely, the kinetic energy required to raise the ball from the floor is converted back into potential energy. Many of the activities of the human body, such as moving a limb, breathing, and circulating blood, involve mechanical energy. In any chemical reaction, the potential energy in the chemical bonds of the reactants can be compared with the potential energy in the chemical bonds of the products. If the potential energy in the reactants is less than that in the products, energy must be supplied for the reaction to occur. As a result of the breaking of existing bonds, the formation of new bonds, and the input of energy, these products have more potential energy than the reactants (figure 2. If the potential energy in the chemical bonds of the reactants is greater than that of the products, the reaction releases energy. For example, the chemical bonds of food molecules contain more potential energy than the waste products that are produced when food molecules are decomposed. Heat Energy Heat energy is a form of energy that flows from a hotter object to a cooler object. Temperature is a measure of how hot or cold a substance is relative to another substance. For example, when a moving object comes to rest, its kinetic energy is converted into heat energy by friction. Some of the potential energy of chemical bonds is released as heat energy during chemical reactions. Human body temperature is maintained by heat produced as a by-product of chemical reactions. As a result of breaking the existing bonds and forming new bonds, these products have less potential energy than the reactants, and energy is released (figure 2. The second is energy released from those chemical bonds, Speed of Chemical Reactions Molecules are constantly in motion and therefore have kinetic energy. A chemical reaction occurs only when molecules with sufficient kinetic energy collide with each other. As two molecules move closer together, the negatively charged electron cloud of one molecule repels the negatively charged electron cloud of the other molecule. The nuclei in some atoms attract the electrons of other atoms, resulting in the breaking and formation of new chemical bonds. Activation energy is the minimum amount of energy that the reactants must have to start a chemical reaction (figure 2. Even reactions that release energy must overcome the activation energy barrier for the reaction to proceed. For example, heat in the form of a spark is required to start the reaction between oxygen and gasoline vapor. Once some oxygen molecules react with gasoline, the energy released can start additional reactions. Given any population of molecules, some of them have more kinetic energy and move about faster than others. Even so, at normal body temperatures, most of the chemical reactions necessary for life proceed too slowly to support life because few molecules have enough energy to start a chemical reaction. Catalysts (kata listz) are substances that increase the rate of chemical reactions without being permanently changed or depleted themselves. Enzymes (enzmz), which are discussed in greater detail later in l the chapter, are proteins that act as catalysts. Enzymes increase the rate of chemical reactions by lowering the activation energy necessary for the reaction to begin (figure 2. An enzyme allows the rate of a chemical reaction to take place more than a million times faster than it would without the enzyme. As temperature increases, reactants have more kinetic energy, move at faster speeds, and collide with one another more frequently and with greater force, thereby increasing the likelihood of a chemical reaction. For example, when a person has a fever of only a few degrees, reactions occur throughout the body at an accelerated rate, increasing activity in the organ systems, such as the heart and respiratory rates. For example, in cold weather, the fingers are less agile, largely because of the reduced rate of chemical reactions in cold muscle tissue.

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