Anatomy and Cell Biology 3319 Chapter 15: reading 15 autonomic nervous system (463-474)

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OVERVIEW OF THE AUTONOMIC NERVOUS SYSTEM
ANS is system of motor neurons that innervate the smooth muscle, cardiac
muscle, and glands of the body
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regulates visceral functions like HR, BP, digestion, urination
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ANS is the general visceral motor division of the peripheral nervous system
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general visceral sensory system monitors the activities of the visceral organs so
that the autonomic motor neurons can make adjustments as needed to ensure
optimal performance of visceral functions
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Comparison of the Autonomic and Somatic Motor Systems
somatic motor system innervates skeletal muscles
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each somatic motor neuron runs from the CNS all the way to the muscle being
innervated
each motor unit consists of a single neuron plus the skeletal muscle cells
that it innervates
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typical somatic motor axons are thick, heavily myelinated fibers that conduct
nerve impulses rapidly
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motor unit in the ANS includes a chain of 2 motor neurons
preganglionic neuron: cell body lies iwthin the CNS
preganglionic axon/fiber: synapses with postganglionic neuron in a
peripheral autonomic ganglion
postganglionic axon/fiber: extends to the visceral organs
preganglionic neuron signals the postganglionic neuron which stimulates
muscle contraction or gland secretion in the effector organ
preganglionic axons are thin, lightly myelinated fibers
postganglionic axons are even thinner and unmyelinated
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impulses are conducted through the ANS more slowly than the somatic motor
system
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autonomic ganglia are motor ganglia containing the cell bodies of motor neurons
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Divisions of the ANS
2 divisions: sympathetic and parasympathetic
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both divisions have chains of 2 motor neurons that mostly innervate the same
visceral organs
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sympathetic division mobilizes the body during extreme situations such as fear,
exercise, or rage
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parasympathetic division enables body to unwind and relax and works to
conserve body energy
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sympathetic division: responsible for fight or flight
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reading 15: autonomic nervous system (463-474)
Monday, November 5, 2018
11:17 AM
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sympathetic division: responsible for fight or flight
high HR, dilated pupils, cold/sweaty skin
bronchioles dilate, increasing uptake of O2
liver releases more sugar
nonessential functions (digestion/motility of uniary tract) are inhibited
input to blood vessels servicing skeletal muscles rises, causing smooth
muscle of the vessels to relax so the vessels dilate, bringing more blood to
the active muscles
input to the smooth muscle in other blood vessels stimulates contracting,
producing vasoconstriction, forcing the heart to work harder to pump blood
causes BP to rise
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parasympathetic division: more active when the body is at rest
HR and respiratory levels are low and GI tract is digesting food
pupils are constricted
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autonomic neuropathy: damage to eh autonomic nerves, which may occur as a
complication of diabetes
inability to control HR, BP, and blood sugar levels
digestion and respiratory functions, urination, sexual response and vision
are affected
may go untreated because its symptoms are widespread and commonly
associated with other conditions
detected via non-invasive heart rate variability test
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sympathetic division
thoracolumbar division because fibers
emerge from thoracic and superior lumbar
parts of spinal cord
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long postganglionic fibers
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ganglia lie near the spinal cord and vertebral
column and postganglionic fibers extend from
these ganglia and travel to their target organs
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fibers branch profusely allowing each
sympathetic neuron to influence a number of
different visceral organs, enabling many
organs to mobilize simultaneously during
fight or flight response
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most postganglionic axons release
norepinephrine (adrenergic fibers)
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craniosacral division
because fibers emerge from
the brain (cranial part) and
the sacral spinal cord (sacral
part)
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short postganglionic fibers
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ganglie lie far from the CNS,
in or near the organs
innervated (quite short)
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fibers dont branch
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effects are localized and
discrete
-
postganglionic
neurotransmitter is
acetylcholine (cholinergic
fibers)
-
-
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Document Summary

Ans is system of motor neurons that innervate the smooth muscle, cardiac muscle, and glands of the body regulates visceral functions like hr, bp, digestion, urination. Cranial outflow preganglionic fibers run in oculomotor (iii), facial (vii), glossopharyngeal (ix), and vagus (x) nerves cell bodies are located in the motor cranial nerve nuclei in the gray matter of the brain stem. Oculomotor nerve (iii) parasympathetic fibers of the oculomotor nerve innervate smooth muscles in the eye to bulge, allowing focusing on close objects in the field of vision. 2 neuron pathway preganglionic axons in the oculomotor nucleus in the midbrain postganglionic cell bodies lie in cillary ganglion, in the posterior part of the orbit lateral to the optic nerve. Gray rami contain only the postganglionic fibers headed for peripheral structures these fibers are unmyelinated occur on all the sympathetic trunk ganglia because sweat glands, arrector pili, and blood vessels must be innervated in all body segments.

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