3.3.3. Visceral Innervation

Question 1

Two divisions of autonomic nervous system

Answer 1

1. Sympathetic 2. Parasympathetic

Question 2

Tor F, the autonomic system, like the somatic system, contains one neuron cell body that resides in the CNS with an axon that extends into the PNS which activates it’s effector organ?

Answer 2

F, both the parasympathetic and sympathetic portions within the efferent limb of the autonomic system contain two neurons in series. The cell body of the preganglionic neuron resides in CNS. The cell body of the postganglionic neuron resides in ganglion within the PNS.

Question 3

Name some features generally associated with the sympathetic nervous system

Answer 3

This is known as “fight or flight” responses which include but are not limited to: increasing heart rate, heart contractility, pupil dilation (mydriasis), closure of sphincters (bladder and anus)

Question 4

Where do postganglionic sympathetic cell bodies reside

Answer 4

Reside in the intermediolateral cell columns of the spinal cord between T1 and L2/3 levels. Recall, the autonomic sympathetic ganglia was an anatomy lab hit list item.

Question 5

Name the primary neurotransmitters for sympathetic and parasympathetic postganglionic nerve cells

Answer 5

1. sympathetic = norepinephrine

2. parasympathetic = acetylcholine

Question 6

Name the two varieties of sympathetic spinal nerve connections.

Answer 6

1. White rami communicantes: this is the preganglionic sympathetic nerve outflow tract from the spinal cord. It is white since it contains mostly myelinated axons.
2. Gray rami communicantes: This contains postganglionic nerve cell fibers of the sympathetic system.
   * Every spinal nerves receives a gray ramus from the sympathetic chain, but only those next to T1-L2/3 send a white ramus to the chain because some fibers do not synapse in the closest ganglia but travel up or down within the chain prior to synapse. Also, some sympathetic nerves travel straight through the ganglia chain and travel to synapse in ganglia located along the aorta and its’ main branches that supply thoraco/abdomino/pelvic organs

Question 7

Where do visceral sympathetic (splanchnics) synapse?

Answer 7

In prevertebral ganglia near the aorta

Question 8

Where are parasympathetic neuron cell bodies located?

Answer 8

near the brainstem or spinal cord (S2-S4)

Question 9

Describe pelvic splanchnics

Answer 9

They are a relatively small but important group of parasympathetic nerves that arise in the intermediolateral cell column of the sacral spinal cord, S2-S4. These fibers exit the spinal cord in ventral roots and leave as pelvic splanchnics which innervate pelvic viscera and the distal part of the transverse colon along with the entire descending and sigmoid colon. The greater (T5-T9), lesser (T10-T11), and least (T12) splanchnic nerves arise in the thorax, travel through the diaphragm, and synapse in the prevertebral ganglia from which they distribute to the abdominal viscera.

Question 10

What comprises the inferior hypogastric plexuses

Answer 10

The hypogastric nerves (sympathetic) and the pelvic splanchnics (parasympathetic) form the inferior hypogastric plexuses that embrace the lateral aspects of the pelvic viscera (eg. prostate, bladder, rectum, and uterus) which are vulnerable to damage during surgery on the pelvic viscera.

Question 11

Name the two divisions of the PNS

Answer 11

1. Autonomic: described as unconscious/ involuntary NS to the viscera. It is an adjunct or adjustment to organ activity.
2. Somatic: described as voluntary

Question 12

Targets of sympathetic nerves

Answer 12

1. smooth muscle
2. cardiac muscle
3. glands
4. fat