ANS Physiology (complete)

Question 1

What are the general characteristics of the ANS?

Answer 1

• Involuntary
• Diffuse projections (not specific)
• Slow action
• Innervates SM, cardiac muscle, and gland cells
• Disynaptic (always 2 synapses)

Question 2

What are the 3 subdivisions of the ANS?

Answer 2

1) Sympathetic (fight/flight)
2) Parasympathetic (rest/digest)
3) Enteric – semi-autonomous control of digestion

Question 3

Describe the general anatomy of the sympathetic ANS

Answer 3

• Preganglionic neurons originate in thoracic and lumbar spinal cord
• Ganglia located near spinal cord
• 1:10 ratio of pre- to post-ganglionic neurons

Question 4

Describe the general anatomy of the parasympathetic ANS

Answer 4

• Preganglionic neurons originate in brainstem and sacral spinal cord
• Ganglia located near target organs
• 1:3 ratio of pre- to post-ganglionic neurons

Question 5

What is the neurotransmitter used in preganglionic neurons in the ANS?

Answer 5

Acetylcholine (ACh)

Question 6

What are the neurotransmitters used in post-ganglionic neurons of the sympathetic ANS?

Answer 6

• Norepinephrine (NE)

- Epinephrine

Question 7

What is the neurotransmitter used in post-ganglionic neurons of the parasympathetic ANS?

Answer 7

ACh

Question 8

What are the receptors of ACh?

Answer 8

• Nicotinic (depolarizes cell, symp)

OR

• Muscarinic (relaxes cell, parasymp)

Question 9

What are the receptors of NE?

Answer 9

• Alpha-adrenergic

- Beta-adrenergic

Question 10

Describe the adrenal medulla as a sympathetic ganglion

Answer 10

• innervated by pregang symp neurons

- releases NE and epinephrine to bloodstream => sympathomimetic effects

Question 11

Describe the ways ANS regulates HR and force of contraction

Answer 11

Sympathetic stimulation:

• ^ NE => ^ BP
• ^ HR and contractile force
• Vasoconstriction

Parasymp stimulation:

• ^ ACh => Decreased BP
• Decreased HR and contractile force

Question 12

Describe how the baroreceptor reflex affects ANS output

Answer 12

• Low BP => ^ in sympathetic output

- High BP => ^ in parasympathetic output

Question 13

Describe the humoral response to low BP that’s controlled by the hypothalamus

Answer 13

• Can stimulate release of hormones that affect BP
• Vasopression (ADH) is a good example
• Low BP detected by subfornical organ => release of vasopression
• Causes vasocontriction => acts on kidneys to ^ H2O retention