DSA 1

Question 1

Division of the peripheral NS.

Answer 1

Peripheral nervous system (PNS) is divided into a sensory (afferent) division and a motor (efferent) division.

• Sensory (afferent) division
  
  • 1. Somatic sensory subdivision: general sensory information we are consciously aware of.
  • 2. Visceral sensory subdivision: sensory information from organs that monitor organ status
• Motor (efferent) division
  
  • 1. Somatic nervous system: controls skeletal muscle contraction
  • 2. Autonomic nervous system: Involuntary body functions and maintain internal homeostasis. It innervates smooth muscle of organs, the heart, and glandular secretion
       * A. Sympathetic
       * B. Parasympathetic

Question 2

What is the neuron pathway in the ANS?

Answer 2

ANS has a 2-neuron system that goes from the CNS–> organs.

Presynaptic neurons- located in CNS

Postsynaptic neurons- located in periphery

Question 3

Features of the sympathetic NS

• Catabolic/Anabolic
• Distrubution?

Functions?

Answer 3

• Catabolic- uses energy to prepare for fight or flight.
• It is distributed to all vascularized portions of the body
  
  • Ex. Responsible for vasoconstriction of vessels (except coronary arteries). Dilates the coronary arteries.
• Bronchodilation
• Ejaculation

Question 4

Features of the parasympathetic NS

• Catabolic/Anabolic
• Distrubution?
• Functions?

Answer 4

• Anabolic- promotes normal function by conserving NRG to help rest and digest
• Restricted to the head, neck, and body cavity viscera but it is not found within the body walls or limbs.
• Responsible for glandular secretion except sweat glands
• Produces erection

Question 5

Describe the presynaptic and postsynaptic fibers of the sympathetic NS and parasympathetic NS

Answer 5

Question 6

Path of sympathetic NS neurons

Answer 6

1. [CB of the presynpatic sympathetic neurons] are located in the lateral gray horn of the SC between T1 and L2/3.
2. Exit via the ventral root–> spinal nerves
3. Spinal nerves–> white rami communicans
4. White rami communicans–> short pre-synaptic nerves will synapse with long postsynaptic neurons in the sympathetic chain/paravertebral ganglia.

*Some neurons can also synapse with ganglia outside of the chain, called prevertebral (collateral) ganglia.

5. Post-synaptic neurons then re-enter the spinal nerves via gray rami communicans
6. Distributed throughout the entire body via ventral and dorsal rami

Question 7

What do white rami communicans do?

Answer 7

carry the pre-synaptic sympathetic axons from the spinal nerve –> sympathetic trunk ganglia.

Question 8

What do gray rami communicans do?

Answer 8

They carry postsynaptic sympathetic fibers back to the spinal nerve to travel to effectors.

Question 9

Where are white rami communicans found?

Answer 9

T1-L2/3

Question 10

Where are gray rami communicans found? Why?

Answer 10

C1- coccyx

because postsynaptic sympathetic innervation is distributed to body walls and extremeties.

Question 11

Do pre-synaptic sympathetic neurons always synapse with sympathetic chain at the same level?

Answer 11

No.

Sometimes, especially in the cervical and sacral levels, the axons carried by the white rami communicans enter the sympathetic chain, but instead of synapsing at the same vertebral level, they travel up or down the chain before synapsing with postsynaptic neurons at another level.

Question 12

Do presynaptic sympathetic chain neurons always synapse with sympathetic chain ganglia?

Answer 12

No.

Neurons in the abdomen and the pelvis do not have to synapse with ganglia in the sympathetic chain. I

nstead, presynaptic sympathetic neurons go through the sympathetic trunk and exit via thoracic splanchnic nerves to synapse on collateral ganglia on the abdominal aorta, celiac and superior and inferior mesenteric ganglia. -

Once the axons synapse in collateral ganglia, they then follow the blood vessels and go to organs supplied by these vessels.

Question 13

Presynaptic sympathetic neurons that do not synapse in the sympathetic chain do what?

Answer 13

They inhibit the activity of muscles and glands in the visceral organs.

*The collateral ganglia are located near branches of the abdominal aorta and are referred to by their location*

Question 14

What is the adrenal medulla?

Answer 14

Important organ of the sympathetic NS.

Presynaptic sympathetic neurons that exit from T8- L1 will pass through sympathetic trunk without synapsing–>

enter the abdomen as splachnic nerves–>

chromaffin cells in the adrenal medulla: release NE and Epi.

Question 15

The parasympathetic Ns has neuronal outflow from where?

Answer 15

Brain and sacral area

Question 16

Parasympathetic NS cranial outflow

Answer 16

1. [Presynaptic neurons in brainstem]–>
2. exit via CN 3, 7, 9, 10–>
3. synapse with post-synaptic neurons in the head, neck, thorax and abdomen that they innervate.

Question 17

Where are the postsynaptic neurons assx with CN 3, 7 and 9 located?

Answer 17

four ganglia—ciliary, pterygopalatine, submandibular and otic ganglia, lying near the target organs.

Question 18

What is the sacral outflow of the ParasympatheticNS?

Answer 18

• [Presynaptic parasympathetic neurons] in the sacrum are located in the visceral motor region of the spinal gray matter of the intermediolateral column of S2-S4.
• Exit via pelvic splanchnic nerves.
• Hypogastric plexus carries the neurons and allows them to synapse with postsynaptic neurons in the organs in the pelvis and lower abdomen.

Question 19

Parasympathetic/symapthetic innervation is not distributed to the body wall or extremities.

Answer 19

PARASYMPATHETIC

Question 20

Enteric NS

Made up of neurons from where?

Fx?

Answer 20

Enteric NS is made up of neurons in the wall of the GI tract from the esophagus to the anus

Functions: autonomous functions such as the coordination of GI reflexes (both sensory and motor and hence is sometimes referred to as the ”gut brain”).

The enteric neurons also includes postsynaptic neurons for cranial nerve X and the pelvic splanchnic nerves.