Org. Circuit Structure of the Autonomic Nervous System

Question 1

Somatic

Answer 1

Sensory (afferent) and motor (efferent) innervation of all body, except viscera in body cavities, smooth muscle and glands

Question 2

Autonomic

Answer 2

Visceral motor (efferent) system and associated sensory (afferent) fibers; subdivided

Question 3

Autonomic (ANS)

Answer 3

The ANS innervates involuntary muscle (smooth and modified cardiac) and glands.

Unlike the somatic motor system, whose neurons rapidly excite skeletal muscle, the actions of the ANS are multiple, widespread and relatively slow.

Question 4

Sympathetic (ANS)

Answer 4

produces the so-called “fight or flight” response
(catabolic effects: increasing heart rate and blood pressure, decreasing digestive functions, mobilizing glucose reserves)

Question 5

Parasympathetic (ANS)

Answer 5

produce responses associated with maintaining
homeostasis (anabolic effects [conservation of energy] decreasing heart rate and blood pressure, increasing digestive functions)

Question 6

Sympathetic division

Answer 6

The sympathetic chain (or paravertebral) ganglia runs the entire length of the vertebral column.

White rami communicans are found only at the levels at which presynaptic neurons leave the spinal cord (T1-L2,3).

Gray rami communicans are found at all levels of the chain of ganglia.

Other sympathetic ganglia are the prevertebral or paraaortic, found adjacent to the main branches of the abdominal aorta

Ganglia:
* celiac
* superior mesenteric * aorticorenal
* inferior mesenteric

Plexuses:
* cardiac
* pulmonary
* esophageal
* celiac
* superior mesenteric
* aorticorenal
* inferior mesenteric
* superior hypogastric
* inferior hypogastrics

T1-L2,L3

Question 7

Sympathetic division

Answer 7

Sympathetics to the head & neck: periarterial plexuses

Cardiopulmonary Splanchnics: formed by postsynaptic fibers

• Cardiac splanchnic nerves (cervical levels and T1-T2)

*Pulmonary splanchnic nerves (T3-T5)

Abdominopelvic Splanchnic: formed by presynaptic fibers

• Thoracic splanchnic nerves * Lumbar splanchnic nerves * Sacral splanchnic nerves

Question 8

Sympathetic division

Answer 8

Functions:
* Body wall
* Activation of sweat glands
* Activation of piloerector muscles
* Vasoconstriction (throughout the body, except in heart and skeletal muscle)

Question 9

Parasympathetic division

Answer 9

Presynaptic Neurons:

• Brainstem nuclei for cranial nerves III, VII, IX, X
• S2-S4 lateral horn
  Pelvic splanchnic nerves
  Postsynaptic Neurons:
• Parasympathetic ganglia in the head
• Neurons near or on the walls of the organs they innervate

Enteric Nervous System

Question 10

Parasympathetic division

Answer 10

Functions:
*Body wall

• THERE’S NO PARASYMPATHETIC INNERVATION TO THE BODY
  WALL OR EXTREMITIES
• THERE’RE NO PARASYMPATHETIC FIBERS IN THE VENTRAL OR DORSAL RAMI OF SPINAL NERVES

Question 11

Afferents

Answer 11

Although the ANS is considered a motor or efferent system, afferent fibers from the viscera travel along with these efferent fibers in the same nerve trunks or fibers.

The cell bodies of these afferents are also found in the dorsal root ganglion, as are the afferents associated with body wall and limb structures.

Question 12

Referred Pain

Answer 12

Both divisions of the ANS carry afferent fibers associated with a variety of sensory modalities.

However, pain fibers from the viscera are generally carried through nerve fibers of the sympathetic division (with some exceptions).

Question 13

Referred Pain

Answer 13

The pain usually radiates to the part of the body that is supplied by somatic sensory fibers associated with the same segment of the spinal cord that receives the visceral sensory fibers.

Heart: T1-T5
Stomach: T6-8
Liver & gallbladder: T7-T9, C3-5
Appendix: T10
Kidneys: T10-T11