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NROB60 Study Package: Week 2 Homira Osman Week 2: Lecture May 13, 2008 Lecture Topics Lecture II Readings: The Peripheral Nervous System (Pages 172, 173); The Cranial Nerves (Pages 173, 232, 233); The Meninges (Pages 173, 174); The Ventricular System (Pages 174, 213); Development of the Nervous System (Pages 180 to 187) Lecture Summaries [L2] - The nervous system consists of two divisions: CNS & PNS - Two parts of the CNS are the brain and the spinal column - The brain consists of the cerebellum, the cerebrum, and the brain stem - All parts of the nervous system other than the brain and spinal cord comprise the peripheral nervous system (PNS) - The PNS consists of the nerves and nerve cells that lie outside the CNS - 31 pairs of nerves leave the spinal cord - Each nerve consists of incoming sensory fibers and outgoing motor fibers - Fibers divide into spinal roots where they attach to the cord - The PNS has two parts: o Somatic PNS All spinal nerves that innervate the skin, the joints, and the muscles that are under voluntary control are part of the somatic PNS The somatic motor axons, which command muscle contraction, derive from motor neurons in the ventral spinal cord The cell bodies of the motor neurons lie within the CNS Their axons are mostly in the PNS The somatic sensory axons, which innervate and collect information from the skin, muscles, and joints, enter the spinal cord via the dorsal roots The cell bodies of these neurons lie outside the spinal cord in clusters called the dorsal root ganglia There is a dorsal root ganglion for each spinal nerve o Somatic includes all spinal nerves that innervate: The skin The joints The muscles under voluntary control o Visceral PNS Also called involuntary, vegetative, or autonomic nervous system (ANS) NROB60 Study Package: Week 2 Homira Osman Consists of the neurons that innervate the internal organs, blood vessels, and glands Visceral sensory axons bring information about visceral function to the CNS Pressure and oxygen content of blood in the arteries Visceral motor fibers command: Contraction and relaxation of muscles that forms the walls of intestines and the blood vessels (called smooth muscles) Rate of cardiac muscle contraction Secretory function of various glands Examples: Blushing, butterflies in stomach, control of blood pressure o Visceral also referred to as the Autonomic or involuntary nervous system (ANS) o Innervate the: Internal organs Blood vessels Glands - Visceral sensory axons bring information about visceral function to the CNS - Afferent and Efferent Axons - Afferent o Axons of the PNS bringing information INTO the CNS are afferents o Somatic sensory axons enter through the dorsal roots (Afferent) o Cell bodies lie outside the CNS in clusters called dorsal root ganglia o One dorsal root ganglion for each spinal nerve - Efferent o Axons that emerge FROM the CNS to innervate the muscles and glands are efferents o Somatic motor axons (control of muscle contraction) derive from motor neurons in the ventral spinal cord (Efferent) o Cell bodies lie within the CNS o Axons are in the PNS - The Cranial Nerves - 12 pairs - Arise from the brain stem - Innervate (mostly) the head - Each nerve has a name and a number - Some are part of the CNS (contained solely within the central nervous system) o Others are part of the visceral PNS - Many carry a complex mixture of axons that perform different functions NROB60 Study Package: Week 2 Homira Osman NROB60 Study Package: Week 2 Homira Osman Number & Name Axon Type Functions ___________________ I Olfactory Sensory - smell II Optic Sensory - sight III Oculomotor Motor - movement of eye and eyelid - control of pupil size IV Trochlear Motor - movements of the eye V Trigeminal Both - sensation of touch to the face - chewing VI Abducens Motor - movements of the eye VII Facial Both - facial expression muscles - taste VIII Auditory-Vestibular Sensory - hearing and balance IX Glossopharyngeal Both - muscles of throat - salivary glands - taste - detection of blood pressure X Vagus Both - control of heart, lungs, & abdominal organs XI Spinal Accessory Motor - muscles of throat and neck XII Hypoglossal Motor - movement of tongue
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