HS2-13 Autonomics of the Thorax

Question 1

What are the targets of sympathetic fibers in the thoracic wall?

Answer 1

smooth muscle (vasomotor/pilomotor)

sweat glands (sudomotor)

Question 2

How do postganglionic fibers with thoracic targets actually reach their thoracic targets?

Answer 2

fibers travel in gray rami, followed by the spinal nerves and their branches

Question 3

What are the two primary smooth muscle targets of sympathetic fibers in the thoracic wall?

Answer 3

walls of blood vessels (vasomotor)

hair follicles (pilomotor)

Question 4

(T/F) There is parasympathetic innervation to smooth muscle/sweat gland structures in the thoracic wall.

Answer 4

False. There is only sympathetic innervation to these structures.

Question 5

Describe the pathway of the vagus nerve in the thorax. (3)

Answer 5

descending from neck, vagus nerves run in mediastinum posterior to main bronchi

formation of anterior (from left vagus) vagal trunk and posterior (from right) vagal trnk

vagal cardiac branches

Question 6

What is the function of the vagal cardiac branches?

Answer 6

parasympathetic, presynaptic fibers for cardiac plexus

Question 7

What is an autonomic plexus?

Answer 7

combination of sympathetic and parasympathetic fibers that provides autonomic innervation to an organ/group of organs

Question 8

Describe the organization of the sympathetic and parasympathetic fibers found in an autonomic plexus.

Answer 8

sympathetic fibers are postganglionic

parasympathetic fibers are preganglionic

Question 9

(T/F) Parasympathetic fibers of all plexuses in the thorax originate from the vagus nerve.

Answer 9

True.

Question 10

Give two examples of autonomic plexuses found in the thorax.

Answer 10

cardiac plexus

esophageal plexus

Question 11

Describe the sympathetic contribution to the cardiac plexus. (2)

Answer 11

cardiac nerves (from cervical sympathetic ganglia)

cardiac branches from thoracic paravertebral ganglia

Question 12

What is the function of the sympathetic contributors to the cardiac plexus? (2)

Answer 12

increases heart rate

increases contractility (which increases speed and force)

Question 14

Describe the parasympathetic contributions to the cardiac plexus.

Answer 14

right and left vagus nerves, via their cardiac branches

Question 15

What is the function of the parasympathetic contributors to the cardiac plexus? (4)

Answer 15

slow heart rate

reduce contractility

increase muscle tone in smooth muscles of airways

increase secretion of airway glands

Question 16

Explain the phenomenon of referred pain the context of the cardiac plexus.

Answer 16

afferent pain fibers from heart run with sympathetic fibers of cardiac plexus and share pathway with somatic sensory fibers of upper body structures, which is why you feel pain in your back or arm if you have cardiac ischemia

Question 17

How do the abdominal viscera receive their sympathetic innervation?

Answer 17

thoracic splanchic nerves

Question 18

Where are the neurons/cell bodies for the thoracic splanchic nerves located?

Answer 18

lateral horn at lower thoracic (T5-T12) levels

Question 19

Describe the pathway of sympathetic innervation to the abdominal viscera. (6)

Answer 19

lateral horn of lower thoracic levels

ventral horn + spinal nerve → sympathetic trunk

run through paravertebral ganglia to form 3 splanchic nerves

splanchic nerves pierce diaphragm

synapse at prevertebral ganglia (anterior to aorta)

then run in organ plexuses to target organ

Question 20

What are the three major thoracic splanchic nerves? Identify their origin.

Answer 20

greater splanchic nerve = from T5-T9

lesser splanchic nerve = from T10-T11

least splanchic nerve = from T12