By G. Orknarok. Saint Louis Christian College. 2018.
Epilepsy is neither a degenerating nor generally a worsening disorder but therapy needs to be maintained to avoid the possibility purchase levitra 20mg visa, however remote generic 20 mg levitra mastercard, of a seizure with all its potential personal and social problems cheap levitra 10mg online. That an episode arises and spreads from the synchronous as well as excessive discharge of a group of neurons (focus) means that not only must those neurons be in some way predisposed to so discharging but they can also recruit neurons that are otherwise normal discount levitra 10mg with mastercard. CLASSIFICATION Epileptic seizures are classified broadly as (a) partial or (b) general: (a) Partial seizures or epilepsy (PE). They may be simple or complex with the symptoms dependent on the cortical area affected. The former may just involve involuntary contractions of a group of muscles or a single limb (Jacksonian motor epilepsy) or abnormal but localised sensory disturbances (Jacksonian sensory epilepsy). They rarely last more than a couple of minutes and consciousness is not impaired. Complex partial seizures manifest themselves as bizarre behaviours which are also known as psychomotor or temporal lobe epilepsy, since a lesion (focus) is often found in that brain area. Repetitive and apparently purposeful movements vary from simple hand clenching or rubbing to more bizarre hand movements and walking. These can last a few minutes, often disrupt other ongoing activity or speech and the patient has no subsequent memory of them. Webster &2001 John Wiley & Sons Ltd 326 NEUROTRANSMITTERS, DRUGS AND BRAIN FUNCTION (b) Generalised seizures. These involve more, or even the whole, of the brain including the reticular system so that consciousness is lost, although in some instances (absence seizures) this is more a loss of awareness rather than any collapse. The two main forms are: (1) Grand mal (GM) or tonic±clonic seizures (TCS). It starts with a tonic spasm of all musculature and rigid extension of the body, a temporary cessation of respiration, generally salivation and often defecation and micturition. After about one minute this gives way to violent synchronous clonic jerking movements (convulsions) which may continue for a few minutes. The patient may remain unconscious for a longer period before recovering. In some cases the tonic and occasionally the clonic phrase can exist alone. They entail a brief and abrupt loss of awareness (consciousness) in which the patient suddenly ceases ongoing activity or speech and stares vacantly for a few seconds before recovering equally quickly. Motor disturbances are rare apart from blinking of the eyes and the patient has no recollection of the event. In addition to the above main categories seizures can be just myoclonic, isolated clonic jerks, or atonic, loss of postural control with just head drooping or the patient actually falling. Convulsions associated with metabolic disturbances are not considered to be epileptic. Perhaps the most striking is the 3 per second spike wave activity seen in most leads (cortical areas) in absence seizures, which can be invoked by hyperventilation. Otherwise distinctive EEG patterns are usually only found during an actual seizure, with burst spiking seen alongside clonus in TCS and abnormal discharges with the behavioural patterns of partial epilepsy and in particular that originating in the temporal lobe. ANIMAL MODELS OF EPILEPSY These are normally based on the use of either electrical stimulation or chemical convulsants. If they are applied locally to specific brain areas, the same approaches induce activity indicative of partial seizures. Also some animals can be bred in which seizures either occur spontaneously or can be induced easily by appropriate sensory stimulation. MODELS OF GENERALISED SEIZURES (1) Electric shock In the maximal electric shock (MES) test a supramaximal stimulus is applied bilaterally through corneal or auricular electrodes to induce tonic hind limb extension in rats or THE EPILEPSIES 327 (b) Generalised seizure (grand mal) (a) Normal Ð tonic±clonic type 1s (c) Generalised seizure (petit mal) (d) Partial seizure Ð absence seizure type Figure 16. Electroencephalograms are shown for, a normal subject (a), those suffering from general tonic±clonic seizures (grand mal, (b)), generalised absence seizures (petit mal, (c)), and partial seizures (d). Spikes are seen in both right- and left- sided leads from all three cortical areas, frontal (F), temporal (T) and occipital (C) in the generalised seizures (b, c) but only in the occipital leads in the example of partial seizures (d).
Pivot The articular cartilage that caps the articular surface of each bone and the synovial fluid that circulates through the joint The movement at a pivot joint is limited to rotation about a cen- during movement are protective features of synovial joints buy 10 mg levitra otc. In this type of articulation cheap 10 mg levitra fast delivery, the articular surface on one serve to minimize friction and cushion the articulating bones 10 mg levitra amex. Should trauma or disease render either of them nonfunctional buy discount levitra 10mg line, the two articu- bone is conical or rounded and fits into a depression on another lating bones will come in contact. Examples are the proximal articulation of the type of arthritis will develop within the joint. These closed sacs are com- monly located between muscles, or in areas where a tendon Condyloid passes over a bone. They function to cushion certain muscles and A condyloid articulation is structured so that an oval,convex ar- assist the movement of tendons or muscles over bony or ligamen- ticular surface of one bone fits into a concave depression on an- tous surfaces. This permits angular movement in two surrounds and lubricates the tendons of certain muscles, particu- directions,as in up-and-down and side-to-side motions. The radiocarpal joint of the wrist and the metacarpophalangeal joints are examples. Improperly fitted shoes or inappropriate shoes can cause joint related problems. People who perpetually wear high-heeled shoes often have backaches and leg aches because their posture Saddle has to counteract the forward tilt of their bodies when standing or walking. Their knees are excessively flexed, and their spine is thrust Each articular process of a saddle joint has a concave surface in forward at the lumbar curvature in order to maintain balance. This articulation fitted shoes, especially those with pointed toes, may result in the de- is a modified condyloid joint that allows a wide range of move- velopment of hallux valgus—a lateral deviation of the hallux (great toe) ment. One is at the articulation of the trapezium of the carpus with the first metacarpal bone (fig. Articulations © The McGraw−Hill Anatomy, Sixth Edition Companies, 2001 Chapter 8 Articulations 203 FIGURE 8. Bursae are commonly located between muscles or between tendons and joint capsules. The most frequent type of joint injury is a sprain, in which the supporting ligaments or the joint capsule are Ball-and-Socket damaged to varying degrees. Ball-and-socket joints are formed by the articulation of a rounded convex surface with a cuplike cavity (fig. This Knowledge Check multiaxial type of articulation provides the greatest range of movement of all the synovial joints. List the structures of a synovial joint and explain the func- humeral (shoulder) and coxal (hip) joints. Give an example of each type of synovial joint and de- Trauma to a synovial joint causes the excessive production of synovial fluid in an attempt to cushion and immobilize the joint. Articulations © The McGraw−Hill Anatomy, Sixth Edition Companies, 2001 204 Unit 4 Support and Movement FIGURE 8. Note the diagrammatic representa- tion showing the direction of possible movement. Note the diagrammatic repre- sentation showing the direction of possible movement. Note the diagrammatic representation showing the direc- bone articulates with the cavity of another. Articulations © The McGraw−Hill Anatomy, Sixth Edition Companies, 2001 Chapter 8 Articulations 205 FIGURE 8. Note the diagrammatic representation showing the direction of with the base of the first metacarpal bone. Suture Edges of articulating bones frequently jagged; None Sutures between bones of the skull separated by thin layer of fibrous tissue 2. Syndesmoses Articulating bones bound by interosseous ligament Slightly movable Joints between tibia-fibula and radius-ulna 3. Gomphoses Teeth bound into dental alveoli of bone by Slightly movable Dentoalveolar joints (teeth secured in periodontal ligament dental alveoli) Cartilaginous Joints Skeletal elements joined by fibrocartilage or hyaline cartilage 1. Symphyses Articulating bones separated by pad of fibrocartilage Slightly movable Intervertebral joints; symphysis pubis 2. Synchondroses Mitotically active hyaline cartilage located None Epiphyseal plates within long bones; between skeletal elements costal cartilages of rib cage Synovial Joints Joint capsule containing synovial membrane and synovial fluid 1.
The anterior funiculi thicken They are mostly noradrenergic and project below the pons to form the pyramids (A6) discount 20 mg levitra with visa. Here generic levitra 20mg mastercard, de- The anterior surface of the midbrain cheap 10 mg levitra otc, or scending pathways from the brain are re- mesencephalon quality 20 mg levitra, is formed by the cerebral layed to neurons extending to the cerebel- peduncles (A29) (descending cerebral path- lum. Between them lies the interpeduncu- The posterior surface of the brain stem is lar fossa (A30); its floor is perforated by covered by the cerebellum (C8). Upon its numerous vessels and is known as the pos- removal, the cerebellar peduncles are cut terior perforated substance. At the posterior through on both sides, namely, the inferior surface of the midbrain lies the tectal plate cerebellar peduncle (or restiform body) (or quadrigeminal plate) (BD31) with two (BD9), the middle cerebellar peduncle (or upper elevations, superior colliculi (D32), brachium pontis) (BD10), and the superior the relay station of the optic system, and cerebellar peduncle (or brachium conjunc- two lower elevations, the inferior colliculi tivum) (BD11). Removal of the cerebellum (D33), the relay station of the acoustic sys- opens the fourth ventricle (C12), the tent- tem. The floor of the fourth ventricle, the rhomboid fossa, thus becomes exposed (B). Medulla oblongata and pons together form the hindbrain, also known as rhombencephalon, named after this fossa. Anatomy of Brain Stem 101 III 29 31 30 IV 28 V VI 22 11 10 21 VII 23 9 VIII 27 IX 6 X 26 20 19 15 24 7 XII XI 25 16 5 17 4 C1 18 A Basal view of the brain stem B Dorsal view of the brain stem, rhomboid fossa 32 31 13 33 3 29 III IV 8 2 12 V 11 14 1 VII 10 VIII 9 VI IX C Subdivisions of the brain stem X XII 7 5 C1 D Lateral view of the brain stem Kahle, Color Atlas of Human Anatomy, Vol. The muscles supplied by these tube (A1) can still be recognized in the brain nerves are derived from the branchial arch stem. Hence, these nerves widening of thecentralcanal intothefourth haveoriginallybeenvisceromotornerves. Unlike viscerosensory (A6) regions, and sensory genuine striated muscles, they are not alarplate(A7)changestoamediolateralar- completely voluntary (e. The cranial nerve nu- clei in the medulla oblongata are arranged The trigeminal nerve (V) emerges from the according to this blueprint (A3) (p. The facial Cranial Nerves (B) nerve (VII) and the vestibulocochlear nerve According to classical anatomical nomen- (VIII) leave the medulla oblongata at the clature, there are 12 pairs of cranial nerves, cerebellopontine angle. The taste fibers of although the first two pairs are not really the facial nerve emerge as an independent peripheral nerves. The consists of the olfactory fibers, the bundled glossopharyngeal nerve (IX) and the vagus processes of sensory cells in the olfactory nerve (X) emerge dorsal to the olive. Supe- epithelium which enter the olfactory bulb rior ganglion of the vagus nerve (B15). The optical nerve (II) is a cervical roots of the accessory nerve (XI) cerebral pathway; the origin of the optical unite to form the spinal root (B16). The fibers, the retina, together with the pig- upper fibers originating from the medulla mented epithelium of the eyeball repre- oblongata form the cranial root; they run a sents an evagination of the diencephalon short course in the nerve and change over to (p. Optic chiasm (B9), optical tract the vagus nerve as internal branch (B17). The oculomotor nerve (III) it represents the remnants of several cervi- leaves the brain on the floor of the inter- cal nerves that have become included in the peduncular fossa (B11); the trochlear nerve brain region secondarily and now have only (IV) emerges at the dorsal surface of the rudimentary sensory roots. IV); the abducens nerve (VI) emerges from B20 Anterior perforated substance. Five nerves have developed from the B22 Choroid plexus (flower spray of Boch- branchial arch nerves of lower vertebrates: dalek) (p. Longitudinal Organization, Cranial Nerves 103 1 2 3 7 6 5 4 A Longitudinal organization of the medulla oblongata (according to Herrick) 8 I 18 9 19 20 II 21 10 III IV 13 V 11 12 VI VII VIII 14 17 X XII 15 IX XI 22 16 B Cranial nerves, base of the brain Kahle, Color Atlas of Human Anatomy, Vol. Three the wall of the cavernous sinus, the ophthal- bony depressions on each side correspond mic nerve (A14) extends with its branches to the basal aspects of the brain; the basal through the orbital fissure, the maxillary aspect of the frontal lobe lies in the anterior nerve (A15) through the round foramen, and cranialfossa(A1),thatofthetemporallobein the mandibular nerve (A16) through the oval the middle cranial fossa (A2), and the basal foramen. The brain stem rests on the clivus, its two layers form both a cover for the brain and the cerebellar hemispheres fit into the and the periosteum. From the confluence of these two layers are large venous sinuses sinuses (A19), the transverse sinus (A20) em- (p. Nerves and blood vessels pass braces the posterior cranial fossa and opens through numerous foramina in the base of intotheinternaljugularvein(A21).
The pia mater is specialized over the roofs of the ventricles quality 20 mg levitra, where it contributes to the for- Arachnoid mation of the choroid plexuses along with the arachnoid cheap levitra 10mg otc. This delicate discount levitra 20mg with visa, netlike membrane spreads over the mentum denticulatum purchase levitra 10 mg on line, which attaches the spinal cord to the CNS but generally does not extend into the sulci or fissures of dura mater (fig. Nervous Tissue and the © The McGraw−Hill Anatomy, Sixth Edition Coordination Central Nervous System Companies, 2001 380 Unit 5 Integration and Coordination TABLE 11. Nervous Tissue and the © The McGraw−Hill Anatomy, Sixth Edition Coordination Central Nervous System Companies, 2001 Chapter 11 Nervous Tissue and the Central Nervous System 381 Cerebrospinal fluid (CSF) is a clear, lymphlike fluid that forms a protective cushion around and within the CNS. CSF circulates through the various ventri- cles of the brain, the central canal of the spinal cord, and the sub- arachnoid space around the entire CNS. The cerebrospinal fluid returns to the circulatory system by draining through the walls of the arachnoid villi, which are venous capillaries. Ventricles of the Brain The ventricles of the brain are connected to one another and to the central canal of the spinal cord (figs. Each of the two lateral ventricles (first and second ventricles) is lo- cated in one of the hemispheres of the cerebrum, inferior to the corpus callosum. The third ventricle is located in the dien- cephalon, between the thalami. Each lateral ventricle is con- nected to the third ventricle by a narrow, oval opening called the interventricular foramen (foramen of Monro). The fourth ventricle is located in the brain stem between the pons and cere- bellum. The mesencephalic aqueduct (cerebral aqueduct) passes through the midbrain to link the third and fourth ventricles. The fourth ventricle also communicates posteriorly with the central canal of the spinal cord. Cerebrospinal fluid exits from the fourth ventricle into the subarachnoid space (fig. Internal hydrocephalus (hi'dro-sef'a˘-lus) is a condition in which cerebrospinal fluid builds up within the ventricles of the Meningitis, an inflammation of the meninges, is usually caused brain (fig. The arachnoid and the pia mater are tures have not yet strengthened or ossified, than in older individuals. Meningitis is accompa- If the pressure is excessive, the condition may have to be treated nied by high fever and severe headache. Untreated External hydrocephalus, an accumulation of fluid within the meningitis generally results in coma and death. The external pressure compresses neural tissue Knowledge Check and is likely to cause brain damage. Describe the location of the dural sinuses and the Cerebrospinal fluid buoys the CNS and protects it from me- epidural space. The brain weighs about 1,500 grams, but sus- pended in CSF its buoyed weight is about 50 grams. This means that the brain has a near neutral buoyancy; at a true neutral buoyancy, an object does not float or sink but is suspended in VENTRICLES its fluid environment. AND CEREBROSPINAL FLUID In addition to buoying the CNS, CSF reduces the damaging effect of an impact to the head by spreading the force over a larger The ventricles, central canal, and subarachnoid space contain area. Objective 23 Discuss the formation, function, and flow of cerebrospinal fluid. Nervous Tissue and the © The McGraw−Hill Anatomy, Sixth Edition Coordination Central Nervous System Companies, 2001 382 Unit 5 Integration and Coordination Interventricular aqueduct Lateral ventricle Interventricular foramen Third ventricle Mesencephalic Mesencephalic aqueduct aqueduct Fourth ventricle Central canal of spinal cord (a) (b) FIGURE 11. The clear, watery CSF is continuously produced by the fil- contains more sodium, chloride, magnesium and hydrogen, and tration of blood plasma through masses of specialized capillaries fewer calcium and potassium ions than does blood plasma. The ciliated ependymal cells cover the choroid although only 140–200 ml are bathing the CNS at any given plexuses, as well as line the central canal, and presumably aid the moment. A person lying in a horizontal position has a slow but movement of the CSF. The tight junctions between the ependy- continuous circulation of cerebrospinal fluid, with a fluid pres- mal cells also help to form a blood–cerebrospinal fluid barrier that sure of about 10 mmHg. An increase in amino acid glycine concentration, for which it is formed.
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 cheap levitra 10mg overnight delivery. 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 levitra 10 mg online. Fibers of both filled levitra 20mg with mastercard, ductule structure called the membranous labyrinth buy levitra 10 mg otc. 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. Trace the pathway of an olfactory stimulus from the olfac- and white matter called the olfactory bulbs. The olfactory bulbs tory hairs to the cerebral cortex,where interpretation occurs. Within the olfactory bulb, neurons of the olfactory nerves synapse with dendrites of neu- rons forming the olfactory tract. Sensory impulses are conveyed GUSTATORY SENSE along the olfactory tract and into the olfactory portion of the cerebral cortex,where they are interpreted as odor and cause the Taste receptors are specialized epithelial cells, clustered together perception of smell. Only about 2% of inhaled air comes in contact with the olfac- Objective 10 Identify the cranial nerves and the sensory tory receptors, which are positioned in the nasal mucosa pathways of gustation. Olfactory sensitivity can be increased by forceful sniffing, which draws the air into con- tact with the receptors. Taste Certain chemicals activate the trigeminal nerves (V) as well buds are specialized sensory organs that are most numerous on the as the olfactory nerves (I) and cause reactions. Pepper, for example, surface of the tongue,but they are also present on the soft palate may cause sneezing; onions cause the eyes to water; and smelling and on the walls of the oropharynx. The cylindrical taste bud is salts (ammonium salts) initiate respiratory reflexes and are used to revive unconscious persons. However, because of the caustic nature composed of numerous sensory gustatory cells that are encapsu- of smelling salts and the irreparable damage it may cause to the un- myelinated olfactory hairs, it is seldom used in first aid treatment of an unconscious person.