Quiz 3 - Autonomic Nervous System Flashcards Preview

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Flashcards in Quiz 3 - Autonomic Nervous System Deck (31):

the ANS is the ____ portion of the nervous system

visceral motor (efferent)


what do visceral motor neurons innervate?

smooth muscle, cardiac muscle, blood vessels, glands. also associated with hair follicles (arrector pilli muscles) and the eye

DO NOT innervate skeletal muscle!!!


2 classifications of visceral efferent neurons

parasympathetic and sympathetic



contains many neurons bundled together in a common epineurium


all spinal nerves contain all four types of neurons, but branches of spinal nerves may contain ______ than four components



visceral efferent component

-unique b/c it consists of a two-neuron chain of multipolar neurons
-synapse between the two occurs in PNS within the ganglion
-first neuron of chain: cell body in nucleus in CNS; its axon is called the preganglionic fiber
-second neuron of chain: cell body in ganglion in PNS; its axon is called the postganglionic fiber


are there synapses in dorsal root ganglia?

no! they contain the cell bodies of afferent neurons


cell bodies of the first neuron in the sympathetic system

-T1-L2/L3 regions of spinal cord
-axons of these neurons leave the spinal cord thru the ventral root, travel in the spinal nerve, then enter a chain of sympathetic ganglia called the sympathetic trunk/chain.
-some of the neurons synapse in the ganglia of the chain, while others travel further to synapse in ganglia in the abdomen or pelvis
-axons of second neuron go to target organ


cell bodies of the first neuron in the parasympathetic system

-brainstem and S2-S4 region of spinal cord
-these neurons travel to their target and synapse in the parasympathetic ganglia that are located near or within the organ wall
-thus the second neuron of the 2-neuron chain is very short for parasympathetic neurons


sympathetic stimulation causes:

-increased HR
-dilated pupils
-increased sweating
-dilated bronchial tree
-diverted blood to skeletal muscles


cell bodies of preganglionic sympathetic neurons

lateral horn of T1-L2/L3; thus, sympathetic division is often called the thoracolumbar division


cell bodies of postganglionic sympathetic neurons

ganglia in the PNS, which can either be in the sympathetic chain/trunk (paravertebral) or prevertebral (associated with the abdominal/pelvic plexuses in the abdominopelvic cavity)


ganglia of the sympathetic chains

-located along the lateral aspects of the vertebral column, extending from the base of the skull to the coccyx


what connects the sympathetic chain to the spinal nerves?

the rami communicantes


white rami communicans

the branch that sympathetic neurons use to enter the sympathetic chain


gray rami communicans

the branch that sympathetic neurons use to exit the sympathetic chain


the ganglia in the sympathetic chains are typically spaced so there is ____ associated with each vertebral level


*the exception to this is the cervical region!


sympathetic chain ganglia in the cervical region

-merge to form the superior, middle, and inferior cervical (stellate) ganglia


axons of preganglionic sympathetic neurons

-exit spinal cord thru the ventral root, pass thru the spinal nerve, and enter the sympathetic chain thru the WRC


sympathetic destinations can be grouped into 4 categories

1. limbs/body wall
2. head
3. thoracic cavity
4. abdominopelvic cavity


route 1: limbs/body wall

-target: T10 spinal segment
-since there are sympathetics that arise from the T10 region of the spinal cord, the neurons do not need to travel up or down the sympathetic chain


route 2: head

-preganglionic sympathetic neurons must travel up the chain from T1-L2 to reach the superior cervical ganglion
-postganglionic neurons travel on 2 nerves, called the internal and external carotid nerves, which extend from the sympathetic chain into the head by traveling with major blood vessels


route 3: thoracic cavity

-some of the preganglionic neurons travel up the chain before synapsing, due to the location of the heart during development
-sympathetic chain to thoracic cavity via cardiac nerves


route 4: abdominopelvic cavity

-preganglionic neurons do not synapse in the sympathetic chain, but instead in the prevertebral ganglia in the abdomen or pelvis
-nerves that connect sympathetic chain to the abdominopelvic cavity are called splanchnic nerves.
-some of the splanchnic nerves arise from the thoracic levels of the sympathetic chain, whereas others arise from lumbar and sacral levels (thus some preganglionic neurons travel down the chain)


functions of parasympathetic division

-digestion, excretion, and conservation of body energy
-decreases HR, constricts pupils, constricts bronchial tree, increases peristalsis, increases secretion of digestive enzymes


cell bodies of parasympathetic preganglionic neurons

found in the brainstem associated w/ certain cranial nerves (CN III, VII, IX, X) as well as in the lateral horns of the S2-S4 regions of the spinal cord

**thus parasympathetic division is sometimes called the craniosacral division


parasympathetic preganglionic axons

-travel in cranial nerves and sacral splanchnic nerves
-travel out to target organ


pelvic splanchnic nerves

preganglionic parasympathetic neurons that arise in the lateral horn of the S2-4 levels of spinal cord


CN X and pelvic splanchnic nerves innervate ______

-structures in the thorax, abdomen, and pelvis
-ganglia associated with these nerves are typically located in the wall of the organ, or in a plexus that is near the target organ


postganglionic neurons of parasympathetic system are

very short


referred pain

visceral AFFERENT