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Lecture

NROB60Lecture2.docx

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Department
Human Biology
Course
HMB320H1
Professor
L
Semester
Winter

Description
NROB60 Study Package Week 2 Homira OsmanWeek 2 Lecture May 13 2008Lecture TopicsLecture IIReadings 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 187Lecture Summaries L2The nervous system consists of two divisionsCNSPNSTwo parts of the CNS are the brain and the spinal columnThe brain consists of the cerebellum the cerebrum and the brain stemAll 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 CNS31 pairs of nerves leave the spinal cordEach nerve consists of incoming sensory fibers and outgoing motor fibersFibers divide into spinal roots where they attach to the cordThe PNS has two parts o Somatic PNSAll 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 nerveo Somatic includes all spinal nerves that innervateThe skinThe jointsThe muscles under voluntary control o Visceral PNS Also called involuntary vegetative or autonomic nervous system ANSNROB60 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 commandContraction and relaxation of muscles that forms the walls of intestines and the blood vessels called smooth muscles Rate of cardiac muscle contractionSecretory function of various glands Examples Blushing butterflies in stomach control of blood pressureo Visceral also referred to as the Autonomic or involuntary nervous system ANS o Innervate theInternal organsBlood vesselsGlandsVisceral sensory axons bring information about visceral function to the CNS Afferent and Efferent AxonsAfferento 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 Efferento Axons that emerge FROM the CNS to innervate the muscles and glands are efferentso 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 stemInnervate mostly the headEach 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 PNSMany carry a complex mixture of axons that perform different functions
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