By R. Kalan. The College of Santa Fe. 2018.
Conse- heard in the normal ear 60 caps brahmi visa, while in conductive deafness brahmi 60 caps generic, the sound is best heard quently order brahmi 60caps mastercard, central lesions rarely result in a total unilateral hearing loss. In the Rinne test, a tuning fork (512 Hz) is placed The medial geniculate body is the thalamic station for the relay of au- against the mastoid process. When the sound is no longer perceived, the ditory information to the temporal cortex. In middle ear disease, the sound is not heard at the external meatus nuclei. Dynorphin-containing and histamine-containing ﬁbers are also after it has disappeared from touching the mastoid bone (abnormal or neg- present in the cochlear nuclei; the latter arises from the hypothalamus. Therefore, a negative Rinne test signiﬁes conductive noradrenergic projection to the cochlear nuclei and to the inferior col- hearing loss in the ear tested. In mild nerve deafness (cochlea or cochlear liculus originates from the nucleus locus ceruleus. Cells in the superior nerve lesions), the sound is heard by application of the tuning fork to the olive that contain cholecystokinin and cells in the nuclei of the lateral lem- mastoid and movement to the ear (the Rinne test is positive). In severe niscus that contain dynorphin project to the inferior colliculus. These include nausea, vomiting Clinical Correlations: There are three categories of deafness. Nerve deafness (sensorineural hearing loss) results from diseases There may also be general signs associated with increased intracranial involving the cochlea or the cochlear portion of the vestibulocochlear pressure (lethargy, headache, and vomiting). Central deafness results from damage to the cochlear nuclei or Central lesions (as in gliomas or vascular occlusions) rarely produce possibly their central connections. Injury to central auditory pathways and/or primary auditory mycin), or occlusion of the labyrinthine artery. Damage to the cochlear cortex may diminish auditory acuity, decrease the ability to hear cer- part of the VIIIth nerve (as in vestibular schwannoma) results in tinnitus tain tones, or make it difﬁcult to precisely localize sounds in space. High-frequency tients with damage to secondary auditory cortex in the temporal lobe hearing losses are most common. Abbreviations AbdNu Abducens nucleus MLF Medial longitudinal fasciculus ACNu Anterior (ventral) cochlear nucleus PCNu Posterior (dorsal) cochlear nucleus ALS Anterolateral system PulNu Pulvinar nuclear complex CC Crus cerebri RB Restiform body FacNu Facial nucleus RetF Reticular formation IC Inferior colliculus SC Superior colliculus IC,Br Inferior colliculus, brachium SCP,Dec Superior cerebellar peduncle, decussation IC,Com Inferior colliculus, commissure SO Superior olive IC,SL Internal capsule, sublenticular limb SpGang Spiral ganglion LGNu Lateral geniculate nucleus SpTTr Spinal trigeminal tract LL Lateral lemniscus TrapB Trapezoid body LL,Nu Lateral lemniscus, nucleus TrapNu Trapezoid nucleus MGNu Medial geniculate nucleus TTGy Transverse temporal gyrus ML Medial lemniscus Review of Blood Supply to Cochlear Nuclei, LL (and associated structures), Pontine Tegmentum, IC, and MGB STRUCTURES ARTERIES Cochlear Nuclei anterior inferior cerebellar (see Figure 5–14) LL, SO in Pons long circumferential branches of basilar (see Figure 5–21) IC long circumferential branches (quadrigeminal branches) of basilar, superior cerebellar (see Figure 5–27) MGB thalamogeniculate branches of posterior cerebral (see Figure 5–38) Optic, Auditory, and Vestibular Systems 227 Auditory Pathways PulNu LGNu MGNu TTGY Positions of LL and Related Structures IC,SL IC,Br IC,Com SC IC IC,Com LL IC ALS LL,Nu CC ML SCP,Dec FacNu LL LL SpTTr FacNu LL SO RetF ALS PCNu SO ML TrapNu TrapB RetF ACNu SpGang PCNu ACNu Hair cells in LL organ of corti RB LL SO ML TrapB 228 Synopsis of Functional Components, Tracts, Pathways, and Systems Vestibular Pathways 7–30 The origin, course, and distribution of the main afferent and Clinical Correlations: The vestibular part of the VIIIth nerve can efferent connections of the vestibular nuclei (see also Figures 7–13, be damaged by many of the same insults that affect the cochlear nerve 7–19, and 7–20). Damage to vestibular receptors of the vestibular nerve vestibular nuclei or pass to cerebellar structures via the juxtarestiform commonly results in vertigo. Secondary vestibulocerebellar axons originate from the vestibu- moving (subjective vertigo) or that objects in the environment are moving lar nuclei and follow a similar path to the cerebellum. They have equilibrium problems, an unsteady (ataxic) tions from the vestibular nuclei also course to the spinal cord through gait, and a tendency to fall to the lesioned side. Deﬁcits seen in nerve le- vestibulospinal tracts (see Figure 7–13), as well as to the motor nuclei sions—or in brainstem lesions involving the vestibular nuclei, include of the oculomotor, trochlear, and abducens nerves via the MLF.
Bile is composed of various salts discount 60 caps brahmi amex, pig- ments discount 60 caps brahmi fast delivery, and cholesterols that become concentrated as water is removed purchase 60caps brahmi visa. Cholesterols normally remain in solution, but under certain conditions they precipitate to form solid crystals. Large crystals may block the bile duct and have to be surgically removed. Pancreas The soft, lobulated pancreas is known as a mixed gland because it has both exocrine and endocrine functions. The endocrine func- tion is performed by clusters of cells called the pancreatic islets (islets of Langerhans). The islet cells secrete the hormones in- sulin and glucagon into the blood. As an exocrine gland, the pan- creas secretes pancreatic juice through the pancreatic duct (fig. The re- lease of bile and pancreatic juice into the duodenum is controlled by pancreas: Gk. Digestive System © The McGraw−Hill Anatomy, Sixth Edition Body Companies, 2001 664 Unit 6 Maintenance of the Body (a) (b) FIGURE 18. Pancreatic juice—the exocrine product—is secreted by acinar cells into the pancreatic duct. Scattered islands of cells, called pancreatic islets (islets of Langerhans), secrete the hormones insulin and glucagon into the blood. Structures in the mouth, there- The entire digestive system develops from modifications of an fore, are ectodermal in origin. The esophagus, pharynx, stomach, a elongated tubular structure called the primitive gut. These modi- fications are initiated during the fourth week of embryonic devel- opment. The primitive gut is composed solely of endoderm and for descriptive purposes can be divided into three regions: the foregut, midgut, and hindgut (exhibit I). Digestive System © The McGraw−Hill Anatomy, Sixth Edition Body Companies, 2001 EXHIBIT II Progressive stages of development of the foregut to form the stomach, duodenum, liver, gallbladder, and pancreas: (a) 4 weeks, (b) 5 weeks, (c) 6 weeks, and (d) 7 weeks. As the duodenum grows, it rotates smooth muscle layers are formed from mesoderm that develops clockwise, and the two pancreatic buds fuse (exhibit II). The dorsal border of the stomach undergoes more rapid Midgut growth than the ventral border, forming a distinct curvature. The During the fourth week of the embryonic stage (exhibit I), the caudal portion of the foregut and the cranial portion of the midgut is continuous with the yolk sac.
Those who spinal cord injury also have difﬁculty with experience spinal cord injury in adoles- temperature regulation buy brahmi 60caps amex, the work en- cence or preteen years may have added vironment should be climate controlled discount brahmi 60 caps with visa. Discussion and accom- and vocational interests and skills brahmi 60 caps on line, as well modation of sexual needs as well as reas- as his or her functional capacity after in- surance that sexual expression is still jury, are important considerations in voca- possible in their life are an important part tional placement. Consequently, periodic checkups should spinal cord injury, and information be instituted to identify those who are should be provided in the context of their experiencing difﬁculty or encountering personal values. Unless individuals with spinal cord in- Spina Biﬁda jury have an associated brain injury, they should experience no cognitive deﬁcits. Spina biﬁda is one of several different The level of injury determines, to a great congenital conditions known as neural tube 88 CHAPTER 3 CONDITIONS OF THE NERVOUS SYSTEM: PART II defects. These defects involve incomplete • Myelomeningocele, the most com- development of the brain, spinal cord, and/ mon and most severe form of spina or coverings of these structures. Other biﬁda, is a condition in which nerves neural tube defects besides spina biﬁda are of the spinal cord as well as the anencephaly, in which infants are born meninges protrude through the open- with underdeveloped brains and incom- ing of the vertebrae to the outer part plete skulls, and encephalocele, in which of the body. Because there is no pro- infants are born with a hole in the skull tective covering for the cord and through which brain tissue protrudes. In meninges, spinal ﬂuid may leak from most cases infants with either of these the protrusion, and the risk of infec- conditions do not survive, or if they do, tion is great. Al- and is a condition in which one or more though surgery is usually performed vertebrae are left open so that the spinal immediately to correct the defect, cord is exposed. Types of Spina Biﬁda Manifestations of Spina Biﬁda There are three types of spina biﬁda: Manifestations of spina biﬁda depend • Spina biﬁda occulta refers to an on the type, the part of the spinal cord opening in one or more vertebrae of affected, and the severity of the condi- the spinal column. They can range from mild, in which form of spina biﬁda, which does not there are few if any symptoms, to severe, involve any damage to the spinal in which there is muscle paralysis, loss of cord. Many individuals with this sensation, and loss of bowel and bladder form of spina biﬁda may be unaware control. In cases of hydro- form of the condition the meninges cephalus, surgical implantation of a shunt (protective coverings around the is necessary so that the ﬂuid can be spinal cord) protrude through the drained to prevent excessive pressure on opening in the spinal column. If hydrocephalus is not correct- protruding part is called a meningo- ed, mental retardation can result. In severe forms of the condition impinge on some cases surgery can correct this normal motor development. Depending problem so that there is little or no on the social, economic, and psychologi- damage to the nerves of the spinal cal circumstances of the individual and cord. In other instances, however, his or her available resources, cognitive individuals with a spinal meningo- development could also be affected. Al- cele may have residual effects result- though the condition itself is not progres- ing from spinal cord damage.
The mole- A cule cheap brahmi 60 caps mastercard, with its attached light chains buy brahmi 60 caps low price, exists as a functional dimer discount brahmi 60 caps otc, but the degree of functional independence of the two heads is not yet known with certainty. The assembly of individual myosin dimers into thick filaments involves close packing of the myosin molecules such that their tail regions form the “backbone” of the thick filament, with the head regions extending outward in a helical fashion. A myosin head projects every 60 de- I band Thick and thin filaments A band grees around the circumference of the filament, with each B one displaced 14. A, The arrangement of the elements the handles, with the heads projecting from the bundle. B, Cross sections through selected regions of the The myosin molecules are packed so that they are tail-to- sarcomere, showing the overlap of myofilaments at different parts tail in the center of the thick filament and extend outward of the sarcomere. Most of the length of the molecule consists of a long, straight portion, Other Muscle Proteins. In addition to the proteins di- often called the “tail” region, composed of light meromyosin rectly involved in the process of contraction, there are sev- (LMM). The remainder of the molecule, heavy meromyosin eral other important structural proteins. Titin, a large fila- (HMM), consists of a protein chain that terminates in a mentous protein, extends from the Z lines to the bare Tropomyosin Troponin Tn-T Tn-I Tn-C G-actin monomers Regulatory protein complex F-actin filament FIGURE 8. Nebulin, a filamentous protein Head portion that extends along the thin filaments, may play a role in sta- Tail portion S2 bilizing thin filament length during muscle development. The protein -actinin, associated with the Z lines, serves to S1 S1 Head Actin- anchor the thin filaments to the structure of the Z line. External to the cells, the protein laminin site forms a link between integrins and the extracellular matrix. S2 These proteins are disrupted in the group of genetic dis- eases collectively called muscular dystrophy, and their lack or malfunction leads to muscle degeneration and weakness and death (see Clinical Focus Box 8. Polymyositis is an inflammatory disorder that produces Myosin filament damage to several or many muscles (Clinical Focus Box 8. The progressive muscle weakness in polymyositis usu- ally develops more rapidly than in muscular dystrophy. New York: Springer-Verlag, tween the surface membrane and contractile filaments. In several forms of mus- these diseases is Duchenne’s muscular dystrophy cular dystrophy, both laminin and dystrophin are lacking (DMD) (also called pseudohypertrophic MD), which is an or defective. X-linked hereditary disease affecting mostly male children A disease as common and devastating as DMD has long (1 of 3,500 live male births). The recent identifica- gressive muscular weakness during the growing years, be- tion of three animals—dog, cat, and mouse—in which ge- coming apparent by age 4. A characteristic enlargement of netically similar conditions occur promises to offer signifi- the affected muscles, especially the calf muscles, is due to cant new opportunities for study.
Both of these responses the aortic arch and buy brahmi 60caps cheap, as its name suggests buy cheap brahmi 60 caps line, supplies blood to the raise the blood pressure and increase the strain on the heart discount 60 caps brahmi with mastercard. Circulatory System © The McGraw−Hill Anatomy, Sixth Edition Body Companies, 2001 560 Unit 6 Maintenance of the Body FIGURE 16. Circulatory System © The McGraw−Hill Anatomy, Sixth Edition Body Companies, 2001 Chapter 16 Circulatory System 561 FIGURE 16. It is a short vessel, rising superiorly through the Blood Supply to the Brain mediastinum to a point near the junction of the sternum and the The brain is supplied with arterial blood that arrives through four right clavicle. These vessels eventually unite on the inferior surface of artery, which extends to the right side of the neck and head, and the brain in the area surrounding the pituitary gland (fig. The value of four separate vessels coming The remaining two branches from the aortic arch are the together at one location is that if one becomes occluded, the left common carotid and the left subclavian arteries. The left three alternate routes may still provide an adequate blood supply common carotid artery transports blood to the left side of the to the brain. They pass superiorly through the transverse foramina of the cervical vertebrae and enter the skull through the foramen magnum. Within the cranium, the Arteries of the Neck and Head two vertebral arteries unite to form the basilar artery at the level The common carotid arteries course upward in the neck along of the pons. The basilar artery ascends along the inferior surface the lateral sides of the trachea (fig. Each common carotid of the brain stem and terminates by forming two posterior cere- artery branches into the internal and external carotid arteries bral arteries that supply the posterior portion of the cerebrum slightly below the angle of the mandible. The posterior communicating arteries this area, a pulse can be detected (see fig. At the base of are branches that arise from the posterior cerebral arteries and the internal carotid artery is a slight dilation called the carotid participate in forming the cerebral arterial circle (circle of Willis) sinus. The carotid sinus contains baroreceptors, which monitor surrounding the pituitary gland. Surrounding the carotid sinus are the carotid bodies, small neurovascular organs that contain chemoreceptors, which respond to chemical changes in the blood. Circulatory System © The McGraw−Hill Anatomy, Sixth Edition Body Companies, 2001 562 Unit 6 Maintenance of the Body Superficial temporal a. Circulatory System © The McGraw−Hill Anatomy, Sixth Edition Body Companies, 2001 Chapter 16 Circulatory System 563 FIGURE 16. The cerebral arterial circle (circle of Willis) consists of the arteries that ring the pituitary gland. Each internal carotid artery arises from the common areas or structures they serve. The principal vessels that arise carotid artery and ascends in the neck until it reaches the base of from the external carotid artery are the following: the skull, where it enters the carotid canal of the temporal bone.