By O. Thorek. Seton Hill College.

Also compare these im- the pupillary light reflex discount 30 mg paxil mastercard, all in the ipsilateral eye. In D (T2-weighted), the unique in that it is the only cranial nerve to exit the posterior (dorsal) trochlear nerve is seen passing through the ambient cistern around the aspect of the brainstem and is the only cranial nerve motor nucleus to lateral aspect of the midbrain (compare with Fig. The Cranial Nerves 41 A Basilar pons Trigeminal nerve Facial nerve Abducens nerve Flocculus Vestibulocochlear Pyramid nerve B Internal carotid artery Temporal lobe Trigeminal nerve Basilar artery Middle cerebellar Trigeminal nerve peduncle Basilar pons Fourth ventricle Pontine tegmentum Cerebellum C Temporal lobe Trigeminal Trigeminal ganglion ganglion Basilar artery Trigeminal nerve Superior cerebellar artery Tegmentum of pons Basilar pons Fourth ventricle Anterior lobe of cerebellum D E Third ventricle Midbrain Crus cerebri tegmentum Interpeduncular Root of trigeminal fossa nerve Sensory root of the trigeminal nerve Basilar pons Basilar pons Pyramid 2-42 The trigeminal nerve (V) is the largest of the cranial nerve in the coronal plane (D, E). In addition, the MRI in C clearly illustrates roots exiting the brainstem (A). It exits at an intermediate position on the position of the trigeminal ganglion in the middle cranial fossa. The fifth nerve, and these latter three, are mixed nerves in that pain within the V2–V3 territories frequently triggered by stimuli they have motor and sensory components. The causes are probably multiple and shown in axial MRI (B, T1-weighted; C, T2-weighted) and in coronal may include neurovascular compression by the superior cerebellar planes (D, E, both T1-weighted images). Note the characteristic ap- artery (see the apposition of this vessel to the nerve root in C), multi- pearance of the root of the trigeminal nerve as it traverses the sub- ple sclerosis, tumors, and ephaptic transmission within the nerve or arachnoid space (B and C), the origin of the trigeminal nerve, and the ganglion. MRI in the axial plane, B, C, D, (all T2-weighted im- mor have hearing loss, tinnitus and equilibrium problems, or vertigo. Also notice the character- weakness (seventh root), numbness (fifth root), or abnormal corneal istic appearance of the cochlea (B, C) and the semicircular canals (C). Treatment is usually by surgery, radiation In addition to these two cranial nerves, the labyrinthine branch of the therapy, or a combination thereof. The Cranial Nerves 43 A Facial nerve Abducens nerve Vestibulocochlear nerve Glossopharyngeal Olivary eminence nerve Vagus nerve Postolivary sulcus Preolivary sulcus Hypoglossal nerve B Preolivary sulcus Pyramid Retroolivary sulcus (postolivary sulcus) Olive (inferior) Glossopharyngeal Glossopharyngeal nerve nerve Flocculus Restiform body Fourth ventricle Tonsil of cerebellum Cerebellum C Pyramid Olive (inferior) Retroolivary sulcus Vagus nerve Fourth ventricle Tonsil of cerebellum Cerebellum D Pyramid Olivary eminence Vagus nerve Postolivary sulcus Restiform body Vagus nerve Fourth ventricle Tonsil of cerebellum 2-44 The glossopharyngeal (IX) and vagus (X) nerves (A) exit the cle is smaller. The ninth and tenth cranial nerves and the spinal portion lateral aspect of the medulla via the postolivary sulcus; the ninth nerve of the accessory nerve (XI) exit the skull via the jugular foramen. Glossopharyngeal neuralgia is a lancinating pain originating from These nerves are generally in line with the exits of the facial and the territories served by the ninth and tenth nerves at the base of the trigeminal nerves; all of these are mixed nerves.

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They produce ATP paxil 10 mg cheap, which is re- ganelles and vesicles is mediated by dynein, another MAP. In In the axon, anterograde transport occurs at both slow the axon terminal, mitochondria provide both a source of and fast rates. The rate of slow axoplasmic transport is 1 to energy for processes associated with synaptic transmission 2 mm/day. Structural proteins, such as actin, neurofilaments, CHAPTER 3 The Action Potential, Synaptic Transmission, and Maintenance of Nerve Function 59 and microtubules, are transported at this speed. They are transported to transport is rate limiting for the regeneration of axons fol- the growth cone by slow axoplasmic transport. The rate of fast axoplasmic trans- The direction of axonal growth is dictated, in part, by port is about 400 mm/day. Fast transport mechanisms are cell adhesion molecules (CAMs), plasma membrane glyco- used for organelles, vesicles, and membrane glycoproteins proteins that promote cell adhesion. In dendrites, anterograde trans- (N-CAM) is expressed in postmitotic neurons and is partic- port occurs at a rate of approximately 0. Dendritic ularly prominent in growing axons and dendrites, which transport also moves ribosomes and RNA, suggesting that migrate along certain types of glial cells that provide a protein synthesis occurs within dendrites. The secretion of tropic factors In retrograde axoplasmic transport, material is moved from by target cells also influences the direction of axon growth. This provides a mechanism When the proper target site is reached and synaptic con- for the cell body to sample the environment around its synap- nections are formed, the processes of growth cone elonga- tic terminals. In some neurons, maintenance of synaptic con- tion and migration are terminated.

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A seizure occurs when abnormal electrical nose may be detected from a spinal tap legs over the course of several days discount 30 mg paxil otc, which activity overwhelms the brain’s normal performed in the lumbar region. A focal seizure originates from a also loses urinary bladder control and Visit our Online Learning Center at http://www. Peripheral Nervous © The McGraw−Hill Anatomy, Sixth Edition Coordination System Companies, 2001 Peripheral Nervous System 12 Introduction to the Peripheral Nervous System 401 Cranial Nerves 403 Spinal Nerves 413 Nerve Plexuses 415 Developmental Exposition: The Peripheral Nervous System 426 Reflex Arc and Reflexes 427 Clinical Case Study Answer 430 Chapter Summary 432 Review Activities 433 Clinical Case Study Following an auto accident, a 23-year-old male was brought to the emergency room for treat- ment of a fractured right humerus. Although the skin was not broken, there was an obvious de- formity caused by an angulated fracture at the midshaft. While conducting an examination on the patient’s injured arm, the attending orthopedist noticed that the patient was unable to ex- tend the joints of his wrist and hand. What structure could be injured in the brachial region of this patient that would ac- count for his inability to extend his hand? List the muscles that would be affected and describe the movements that would be diminished. Hints: Because the nervous system functions to coordinate body movement, nerve trauma may be expressed in structures far removed from the site of injury. FIGURE: Trauma to a particular body region may cause profound effects elsewhere. This underscores the importance of visualizing regional anatomy (see chapter 10) and knowing vascular routes and innervation pathways. Peripheral Nervous © The McGraw−Hill Anatomy, Sixth Edition Coordination System Companies, 2001 Chapter 12 Peripheral Nervous System 401 The peripheral nervous system (PNS) is that portion of the ner- INTRODUCTION TO THE vous system outside the central nervous system. The PNS conveys PERIPHERAL NERVOUS SYSTEM impulses to and from the brain and spinal cord. Sensory receptors within the sensory organs, nerves, ganglia, and plexuses are The peripheral nervous system consists of all of the nervous tis- all part of the PNS, which serves virtually every part of the body sue outside the central nervous system, including sensory recep- (fig. It The nerves of the PNS are classified as cranial nerves or provides a communication pathway for impulses traveling be- spinal nerves depending on whether they arise from the brain or tween the CNS and the rest of the body.