Lecture 7: ANS Flashcards Preview

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Flashcards in Lecture 7: ANS Deck (22):

Is the ANS an effector or motor system independent of sensory input?

NO! The ANS receives substantial sensory information at the spinal cord, brainstem, and cerebral hemisphere levels.


How many efferent neurons comprise the autonomic efferent system?

2; one preganglionic and its fiber and a postganglionic and its fiber that innervates smooth muscle, cardiac muscle, and glands.


What are the three divisions of the ANS?

1. Sympathetic (Thoracolumbar) System
2. Parasympathetic (Craniosacral) System
3. Enteric Nervous System


What are the neurotransmitters for the preganglionic sympathetic neurons?

Acetylcholine (adrenal glands)


What are the neurotransmitters for the postganglionic sympathic neurons?


**The exception to this is Acetylcholine being used for sweat glands and the erector pili muscle.


What are the neurotransmitters for both the pre and post ganglionic parasympathetic nervous system?



What are the neurotransmitters for the enteric nervous system?

A variety plus neuropeptides.


Where are the primary ANS neurons of origin located?



Where are the secondary neurons of the sympathetic system located?

in the interomediolateral gray matter of the T1-L3 spinal cord


Where are the secondary neurons of the parasympathetic system located?

in the cranial nerve nuclei and the sacral neurons


Describe the path for preganglionic spinal outflow for the sympathetic nervous system.

1. The secondary neuron originates in the intermedioateral zone (LATERAL HORN) of the spinal cord gray matter.
2. It exits the spinal cord via the LATERAL ROOT and then travels through short segment of the peripheral nerve before entering the WHITE COMMUNICATING RAMI to gain access to the PARAVERTEBRAL SYMPATHETIC CHAIN GANGLIA.
3. Here it may take 1 of 3 courses (a. Synapse b. Travel rostral or caudal before exiting or c. exit and synapse in a more peripherally located prevertebral ganglion)


Describe the organization for he preganglionic outflow of the parasympathetic nervous system.

5 parasympathetic cranial nerve nuclei
4 cranial ganglia
sacral outflow


Edinger-Westphal Nucleus

Located in the midbrain.
Exits via CNIII to control pupillary constriction.


Superior and Inferior Salivatory Nuclei

Located at the upper medulla level.
Exits via CNVII (to lacrimal and salivary glands) and CNIX (to parotid gland), respectively.


Dorsal motor nucleus of the vagus and the nucleus ambiguous.

Located at the middle medulla level.
Exits via CNX to decrease heart rate, constrict the bronchial tree, dilate intestinal blood vessels, and increases peristalsis.


Sacral Parasympathetic Outflow

From S2-S4 with innovation of the descending and sigmoid colon , rectal and bladder sphincter muscles, prostate and other genital organs.


Myenteric (Aurbachs) Plexus

Primarily responsible for regulating gut smooth muscle and therefore gut motility.
Located between the longitudinal and circular muscle layers.


Submucosal (Meissners) Plexus

Regulates glandular secretions .
Located beneath the circular muscle layer.


What is the final common pathway of gut motility?

Thought the enteric nervous system with Ach as the effector neurotransmitter.


What is the cause of Horner's Syndrome?

A lesion of the sympathetic fibers at any point along the line from the hypothalamus to the ciliary nerve will cause Horner's Syndrome on the side of the lesion.


What other symptom would be expected in a Horner's Syndrome patient with a lesion that is centrally placed, i.e. within the brainstem or the spinal cord?

Loss of sweating over the entire side of the body with the lesion since all sympathetic function below the lesion would be lost


What other symptom would be present in a Horner's Syndrome patient if the lesion were peripheral, i.e. at the T1-2 nerve root or more distally placed?

Loss of sweating only on the face, head and neck on the same side as the lesion.