Exam 3: Autonomic Nervous System Flashcards Preview

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Flashcards in Exam 3: Autonomic Nervous System Deck (22):

Somatic Nervous System

-innervates skeletal muscle and receives sensory information from senses
-CNS and PNS components


Autonomic Nervous System

-innervates the viscera (organs)
-influences smooth muscle, cardiac muscle, and glands of skin and viscera
-CNS and PNS components
-controls the 4 F's ( Feeding, Fleeing, Fighting, Fornication)
-motor system


Hierarchy of ANS

-hypothalamus oversees ALL ANS activity, CEO/president
-middle management are the autonomic nervous centers in the brainstem (pons, mesencepalon, medulla)
-the ordinary workers are the preganglionic and postganglionic neurons


Somatic Motor

-uses a single neuron to go from spinal cord to skeletal muscle


Autonomic Motor

-uses two neurons to go from the spinal cord to the target tissue
-1st is preganglionic neuron
-2nd is postganglionic neuron


Preganglionic Neuron

-cell body located in CNS
-axon will synapse with the postganglionic neuron


Postganglionic Neuron

-cell body located in an autonomic ganglion
-this axon will connect to the target tissue (effector)


Why does ANS use 2 neurons in chain to an organ?

-ANS has a limited number of neurons
-allows for convergence and divergence of ANS info
-more efficient with 2 neurons


Sympathetic Division of ANS

-originates in lateral horns of T1-L2 region of spinal cord
-emergency situations
-fight or flight response
-mass activation effect-all parts of sympathetic divison may be turned on at once


Parasympathetic Division of ANS

-some cranial nerves and parts of the sacral region of the spinal cord
-maintains a homeostatic environment
-"rest and digest" response
-parasympathetic activity is usually discrete and localized



-most organs are innervated by both sympathetic and parasympathetic divisions
-most cranial and spinal nerves contain both somatic and autonomic axons


Parasympathetic Division (CN's and Sacral Components)

-cranial components are part of CN III (Oculomotor), VII (Facial), IX (Glossopharyngeal), and X (Vagus)
-sacral components from S2-S4 segments of the spinal cord
-pelvic splanchnic nerves are part of this division


Pelvic Splanchnic Nerves

-branches off spinal cord going directly to organs


Pathway for Axons

-Cell bodies of preganglionic motor neurons located in parts of certain cranial nerves, or in the sacral part of the spinal cord
-Preganglionic axons synapse in terminal ganglia which are located close to or on the organ being innervated
-Parasympathetic postganglionic axons travel from the terminal ganglia to the target organ


Sympathetic Division: Components

-cell bodies of preganglionic motor neurons in lateral horns of T1-L2 segments of spinal cord (preganglionic axons exit to spinal nerve then go into the
-white rami
-sympathetic trunks
-gray rami
-splanchnic nerve
-prevertebral (collateral) ganglia
-sympathetic postganglionic axons


White Rami

-runs from spinal nerve to sympathetic trunk
-entrance ramp
-axons are myelinated (white)


Sympathetic Trunks

-long chains of axons on either side of vertebral column
-sympathetic trunk (paravertebral) ganglia


Gray Rami

-runs form the sympathetic trunk to a spinal nerve
-sympathetic postganglionic axons
-exit ramp
-axons are unmyelinated (gray)


Splanchnic Nerves

-preganglionic axons that do not synapse in the sympathetic trunk ganglia


Prevertebral (Collateral) Ganglia

-splanchnic nerves synapse here
-located in front of vertebral column


Sympathetic Postganglionic Axons

-travel directly to target organ


Pathways for Preganglionic Sympathetic Axons

-all preganglionic axons enter the sympathetic trunk via the white ramus
-some synapse in the sympathetic trunk (and leave through the gray rami) to spinal nerves
-some preganglionic axons leave sympathetic trunk as splanchnic nerves, go to prevertebral ganglia to synapse