By H. Ayitos. Monterey Institute of International Studies.
In these patients buy lopid 300mg on line, relief of pain is of paramount con- dressing or walking in the dark buy lopid 300 mg. Treatment of chronic pain often requires the use of moderate pain-reducing drugs (analgesics) or intense narcotic drugs order 300mg lopid free shipping. Sensory Organs © The McGraw−Hill Anatomy, Sixth Edition Coordination Companies, 2001 Chapter 15 Sensory Organs 493 FIGURE 15. Pain originating from the myocardium of the heart may be perceived as coming from the skin of the left arm because sensory impulses from these two organs are conducted through common nerve pathways to the brain. Proprioceptors are located in and around synovial joints, in Neural Pathways for Somatic Sensation skeletal muscle, between tendons and muscles, and in the inner ear. They are of four types: joint kinesthetic receptors, neuromus- The conduction pathways for the somatic senses are shown in cular spindles, neurotendinous receptors, and sensory hair cells. Sensations of proprioception and of touch and pres- sure are carried by large, myelinated nerve fibers that ascend in • Joint kinesthetic receptors are located in synovial joint the posterior columns of the spinal cord on the ipsilateral (same) capsules, where they are stimulated by changes in body po- side. These fibers do not synapse until they reach the medulla sition as the joints are moved. They consist of the medulla oblongata with second-order sensory neurons, informa- endings of sensory neurons that are spiraled around special- tion in the latter neurons crosses over to the contralateral (oppo- ized individual muscle fibers (fig. Third-order sensory caused by the lengthening or stretching of the individual neurons in the thalamus that receive this input in turn project to fibers, and thus provide information about the length of the postcentral gyrus in the cerebral cortex. Sensations of heat, cold, and pain are carried by thin, un- • Neurotendinous receptors (Golgi tendon organs) are lo- myelinated sensory neurons into the spinal cord. They within the spinal cord with second-order association neurons that are stimulated by the tension produced in a tendon when cross over to the contralateral side and ascend to the brain in the the attached muscle is either stretched or contracted. Fibers that mediate touch and pres- • Sensory hair cells of the inner ear are located in a fluid- sure ascend in the ventral spinothalamic tract. Fibers of both filled, ductule structure called the membranous labyrinth. Sensory Organs © The McGraw−Hill Anatomy, Sixth Edition Coordination Companies, 2001 494 Unit 5 Integration and Coordination Extrafusal fibers Intrafusal fibers: Nuclear chain fibers Skeletal muscle Nuclear bag fiber Peripheral nerve (Motor and sensory neurons) Connective tissue sheath Muscle Sensory neurons spindle Sensory neuron Neurotendinous receptors Motor neurons Tendon Bone Motor end plates (a) (b) FIGURE 15. Also, because of decussation (crossing- over), somatic information from each side of the body is projected Knowledge Check to the postcentral gyrus of the contralateral cerebral hemisphere. List the different types of cutaneous receptors and state All somatic information from the same area of the where they are located. What portion of the brain inter- body projects to the same area of the postcentral gyrus. List the receptors that that receive sensory information from different parts of the body respond to pain and the structures of the brain that (see fig. Such a map is greatly distorted, however, be- are particularly important in the perception of pain cause it shows larger areas of cerebral cortex devoted to sensation sensation. The dis- proportionately large areas of the caricature-like sensory ho- 8. Discuss why it is important for a physician that there is a higher density of sensory receptors in the face and to know the referred pain sites. Using a flow chart, describe the neural pathways leading from cutaneous pain and pressure receptors to the postcen- tral gyrus. Sensory Organs © The McGraw−Hill Anatomy, Sixth Edition Coordination Companies, 2001 Chapter 15 Sensory Organs 495 FIGURE 15. Olfac- tion functions closely with gustation (taste) in that the receptors Olfactory receptors are the dendritic endings of the olfactory nerve for both are chemoreceptors, which require dissolved substances (I) that respond to chemical stimuli and transmit the sensation of for stimuli. Olfactory receptor cells are located in the nasal mucosa within the roof of the nasal cavity on both sides of the nasal sep- Objective 8 Describe the sensory pathway for olfaction. Olfactory cells are moistened by the surrounding glandular goblet cells. The cell bodies of the bipolar olfactory Olfactory reception in humans is not highly developed compared cells lie between the supporting columnar cells. Because we do not rely on each olfactory cell contains several dendritic endings, called smell for communicating or for finding food, the olfactory sense olfactory hairs that constitute the sensitive portion of the recep- is probably the least important of our senses. These unmyelinated dendritic endings respond to air- in detecting the presence of an odor rather than its intensity. Sensory Organs © The McGraw−Hill Anatomy, Sixth Edition Coordination Companies, 2001 496 Unit 5 Integration and Coordination Olfactory Olfactory bulb nerve fibers Cribriform plate of ethmoid bone Olfactory receptor cells Supporting columnar epithelial cells (b) Nasal cavity Olfactory (a) hairs FIGURE 15. The unmyelinated axons of the olfactory cells Knowledge Check unite to form the olfactory nerves, which traverse the foramina 10.
When it contracts 300mg lopid visa, the mastoid process cheap 300 mg lopid with visa, strengthens bones and muscles purchase 300mg lopid free shipping, but it also contributes to a which is located posteriorly at the base of the skull, is pulled forward, healthy circulatory system and thus ensures an adequate blood causing the chin to rotate away from the contracting muscle. This ex- plains why the patient who had his left sternocleidomastoid muscle re- supply to all body tissues. If an older person does not maintain moved would have difficulty turning his head to the right. Muscular System © The McGraw−Hill Anatomy, Sixth Edition Companies, 2001 290 Unit 4 Support and Movement (a) (b) (c) (d) FIGURE 9. Muscular System © The McGraw−Hill Anatomy, Sixth Edition Companies, 2001 Chapter 9 Muscular System 291 FIGURE 9. Muscular System © The McGraw−Hill Anatomy, Sixth Edition Companies, 2001 292 Unit 4 Support and Movement FIGURE 9. Source: From Hollingsworth JW, Hashizuma A, Jabbn S: Correlations Between Tests of Aging in Hiroshima Subjects: An Attempt to Define Physiologic Age. She also notes pain in the area order a CT scan (L = lumbar vertebrae; P = of her left hip and left lower quadrant of her psoas major muscle). On physical exam, she has a QUESTIONS PP L mild fever and slight tenderness on the left 1. What is the fluid collection indicated side of her abdomen, and you note that by the arrow on the CT scan? Muscular System © The McGraw−Hill Anatomy, Sixth Edition Companies, 2001 Chapter 9 Muscular System 293 CLINICAL PRACTICUM 9. Why is the knee held in a slightly superiorly displaced, and the knee is ex- flexed position? Most hernias occur in the normally injection into a heavily muscled area to muscle. The most common shinsplints Tenderness and pain on the four common hernia types: site is the buttock. Motor neurons conduct nerve impulses to and the maintenance of posture and body the more movable attachment. Muscle bundles, called impulses away from the muscle fiber to all muscle tissue are irritability, fasciculi, are covered by perimysium. Muscles muscles include those that act on the that oppose or reverse the actions of other girdles and those that move the segments muscles are antagonists. Muscular System © The McGraw−Hill Anatomy, Sixth Edition Companies, 2001 294 Unit 4 Support and Movement Skeletal Muscle Fibers and Types of (d) The A bands stay the same length Naming of Muscles (pp. Each skeletal muscle fiber is a and thin) do not shorten during of shape, location, attachment, multinucleated, striated cell. Most muscles are paired; that is, the right membrane called a sarcolemma. The neuromuscular junction is the area a Z line, and the subunit between two consisting of the motor end plate and the Muscles of the Axial Skeleton Z lines is called the sarcomere. They are summarized in the thin (actin) myofilaments over and and the muscle fibers it innervates. An eyebrow is drawn toward the midline the quadriceps femoris muscle may act on (a) one motor unit per muscle fiber. Which of the following is not used as a (c) the nasalis (d) the vastus lateralis means of naming muscles? A flexor of the shoulder joint is flexes the ankle joint and inverts the foot (b) action (a) the pectoralis major. Muscular System © The McGraw−Hill Anatomy, Sixth Edition Companies, 2001 Chapter 9 Muscular System 295 Essay Questions 10. Give three examples of synergistic muscle 17–year-old male lost function of his right multinucleated. Describe the special characteristics of identify the antagonistic muscle group happen to the function of the affected muscle tissue that are essential for muscle for each. Define fascia, aponeurosis, and compartments of the muscles of the muscles relative to the shoulder, elbow, retinaculum. Based on function, describe exercises that the muscle fibers and fasciculi within fossa.
Different conditions produce different relation- to pump 1% more blood than the left heart each minute ships between stroke volume (or work) to end-diastolic fiber without a compensatory mechanism 300 mg lopid mastercard, the entire blood vol- length buy lopid 300 mg line. For example purchase lopid 300mg without prescription, increased sympathetic nerve activity ume of the body would be displaced into the pulmonary causes release of norepinephrine (see Chapter 3). A similar error in the oppo- nephrine increases the force of contraction for a given end- site direction would likewise displace all the blood volume diastolic fiber length (Fig. Fortunately, Starling’s law pre- contraction causes more blood to be ejected against a given vents such an occurrence. If the right ventricle pumps aortic pressure and, thus, raises stroke volume. A change in slightly more blood than the left ventricle, left atrial filling (and pressure) will increase. As left atrial pressure increases, Norepinephrine Normal Digitalis Failure End-diastolic fiber length End-diastolic volume End-diastolic pressure Atrial pressure End-diastolic fiber length End-diastolic ventricular pressure FIGURE 14. Several other combinations of variables can be used to plot a on the ventricular function curve. In constant, and stroke volume can be substituted for stroke work if ar- heart failure, contractility is decreased, so that stroke volume terial pressure is constant. End-diastolic fiber length and volume are and/or stroke work are decreased at a given end-diastolic fiber related by laws of geometry, and end-diastolic volume is related to length. Digitalis raises the intracellular calcium ion concentration end-diastolic pressure by ventricular compliance. CHAPTER 14 The Cardiac Pump 241 the force of contraction at a constant end-diastolic fiber length reflects a change in the contractility of the heart. B (The cellular mechanisms governing contractility are dis- cussed in Chapter 10. When an increase in contractility is accompanied by an increase in arterial pressure, the stroke volume may remain constant, and the increased contractility will not be evident by plotting the stroke volume against the end-diastolic fiber length. However, if stroke work is plotted, a leftward shift of the ventricular function curve is observed (see Fig. A ventricular function curve with stroke volume on the ordi- Time nate can be used to indicate changes in contractility only when arterial pressure does not change. During heart failure, the ventricular function curve is shifted to the right, causing a particular end-diastolic fiber length to be associated with less force of contraction and/or shortening and a smaller stroke volume. As described in Chapter 10, cardiac glycosides, such as digitalis, tend to B normalize contractility; that is, they shift the ventricular curve of the failing heart back to the left (see Fig. A Time The collection of ventricular function curves reflecting changes in contractility in a particular heart is known as a family of ventricular function curves. In the normal heart, the force of contraction is also increased by myocardial hypertrophy. A Regular, intense exercise results in increased synthesis of contractile proteins and enlargement of cardiac myocytes. B The latter is the result of increased numbers of parallel my- ofilaments, increasing the number of actomyosin cross- bridges that can be formed. As each cell enlarges, the ven- Force (load) tricular wall thickens and is capable of greater force development. The ventricular lumen may also increase in size, and this is accompanied by an increase in stroke vol- FIGURE 14. The hearts of appropriately trained athletes are capa- volume, and the force-velocity relationship are shown for (A) ble of producing much greater stroke volumes and cardiac normal and (B) elevated aortic pressure. These changes slows the velocity of shortening, decreasing ventricular empty- are reversed if the athlete stops training. In heart disease, al- though myocardial hypertrophy initially has positive ef- fects, it ultimately has negative effects on myocardial force development. A thorough discussion of pathological hy- Fortunately, the heart can compensate for the de- pertrophy is beyond the scope of this book. The second determinant of stroke terial pressure causes the left ventricle to eject less blood volume is afterload (see Table 14.
Since the molecular cut-off of the dialysis membrane is in the region of 6±20 kDa (depending on the type of membrane used) generic 300 mg lopid amex, this technique can also be used to measure release of some small neuropeptides (e cheap 300 mg lopid amex. One advantage of microdialysis is that it enables the study of transmitter release in specific brain areas or nuclei lopid 300mg fast delivery. To ensure its correct placement, the probe is implanted, under anaesthesia, by sterotaxic surgery. Another advantage is that the probe can be anchored in place with dental cement and experiments carried out later, in conscious freely moving animals once they have recovered from the anaesthetic. Indeed, comparison of results from studies carried out on both anaesthetised and freely moving subjects has revealed drug interactions with anaesthetics that can affect transmitter release: anaesthetic-induced changes in the regulation of noradrenaline release by a2-adrenoceptors is a case in point. It is also possible to carry out long-term 88 NEUROTRANSMITTERS, DRUGS AND BRAIN FUNCTION Figure 4. The length of membrane below the probe support can be altered (1±10 mm)to suit the size of the animal and the brain area being studied. Flow rates are normally below 2 ml/min or repeated studies on the same animals but this requires a slight modification of the technique. Unfortunately, for a variety of reasons, each microdialysis probe can be used for only a few hours and so it has to be replaced each day. However, the presence of the guide cannula makes this a relatively straightforward process that requires only light sedation of the animal. A further advantage of microdialysis is that, unlike the push±pull cannula or the cortical cup, the perfusion medium does not come into direct contact with the tissue being studied. This reduces damage caused by turbulence as well as enzymic degradation of the transmitter. For instance, acetylcholine, but not cholinesterase, will penetrate the probe membrane. Finally, because solutes will pass out of the probe, as well as into it, the probe can also be used for infusing ions (Fig. This avoids many of the problems that arise when trying to determine the synaptic actions of drugs when these are administered systemically. The rate at which the probes are perfused with aCSF is a compromise between the time required for the solutes in the CSF to reach equilibrium with those in the probe (the slower, the better)versus the ideal time-frame for studying changes in transmitter release (the shorter, the better). In general, flow rates of around 1±2 ml/min are used and the time which elapses between taking samples is determined by how much transmitter NEUROTRANSMITTER RELEASE 89 Figure 4. The graph shows efflux of noradrenaline in the frontal cortex of anaesthetised rats. Increasing the concentration of K in the medium infused via the probe increases noradrenaline efflux whereas removing Ca2 reduces it is needed for analysis: i. It is acknowledged that the solutes are not in equilibrium with the CSF outside the probe. In any case, the efficiency of the probe membrane limits the net influx (or efflux)of solutes to about 10± 20% of the theoretical maximum. It should also be borne in mind that the microdialysis probe is not sampling the transmitter in the synapse: only that transmitter which escapes metabolism in, or reuptake from, synapses will migrate towards the probe. In the drug-free state, any change in the transmitter concentration in the dialysis samples is usually assumed to indicate a change in its rate of release from nerve terminals; this is supported by the spontaneous efflux of transmitters being Ca2-dependent and K- sensitive (Fig. However, efflux does not always reflect release rate, especially if experimental interventions (e. Voltammetry This can be carried out in vitro (in brain slices, cultured cell preparations)or in vivo and involves penetrating the experimental tissue with a carbon-fibre electrode of 5±30 mmin diameter (Fig. This serves as an oxidising electrode and the Faradaic current generated by the oxidation of solutes on the surface of the electrode is proportional to their concentration. Obviously, only neurotransmitters which can be oxidised can be measured in this way so the technique is mainly limited to the study of monoamines and their metabolites. The amplitude of each peak on the ensuing voltammogram is a measure of solute concentration and individual peaks can be identified because different 90 NEUROTRANSMITTERS, DRUGS AND BRAIN FUNCTION Figure 4. Changes in the concentration of transmitters are monitored by rapid cycles of voltage scans (e. Since a complete scan takes only about 20 ms, the time resolution with voltammetry is much better than with microdialysis and is suitable for studying rapid, transient changes in transmitter release. One difficulty with this method is that all oxidisable solutes in the external medium will be incorporated into the voltammogram and interfering peaks can be a problem.
8 of 10 - Review by H. Ayitos
Votes: 295 votes
Total customer reviews: 295