Functioning of the Autonomic Nervous System

Question 1

What is innervated by the autonomic nervous system?

Answer 1

• Smooth and cardiac muscle
• Glands

Question 2

What is the arrangement autonomic fibres use to innervate targets?

Answer 2

Diffuse arrangement

Question 3

What structures make up the diffuse arrangement?

Answer 3

Varicosities (like “beads on a string”)

Question 4

Neurotransmitter(s) for sympathetic synapses

Answer 4

• Acetylcholine between pre- and post-ganglionic neurones
• Noradrenaline between post-ganglionic and effector

Question 5

Neurotransmitter(s) for parasympathetic synapses

Answer 5

Acetylcholine for all

Question 6

2 exceptions to neurotransmitter rule

Answer 6

• Sweat glands
• Adrenal medulla

Question 7

Why are sweat glands an exception?

Answer 7

They use ACh for both even though they are sympathetic

Question 8

Why is the adrenal medulla an exception?

Answer 8

• Is sympathetic
• ACh released between pre-ganglionic and AM cells
• Cells then release hormones to go to non-innervated receptors

Question 9

How does the autonomic function for most organs?

Answer 9

Dual innervation of sympathetic and parasympathetic working antagonistically

Question 10

How else can the autonomic function apart from antagonistic dual innervation?

Answer 10

• Dual innervation but not antagonistic
• Single innervation

Question 11

Examples of single innervation

Answer 11

• Sweat glands = sympathetic only
• Most blood vessels = sympathetic only (more = vasoconstriction, less = vasodilation)

Question 12

How are blood vessels of head and reproductive organs controlled?

Answer 12

• Sympathetic = vasoconstriction
• Parasympathetic = vasodilation

Question 13

How does dual, non-antagonistic control of salivary glands work?

Answer 13

• Sympathetic
  > Increased secretion
  > Vasoconstriction so less supply
  > Small amount of sticky saliva
• Parasympathetic
  > Increased secretion
  > Vasodilation so more supply
  > Lots of saliva

Question 14

How can sympathetic body-wide activation cause vasodilation in blood vessels?

Answer 14

• Most vessels have alpha receptors bound by noradrenaline causing vasoconstriction
• Special vessels in skeletal muscle and heart have beta receptors which binds adrenaline causing vasodilation
• Body-wide sympathetic = adrenal medulla activated to release adrenaline which binds beta receptors

Question 15

Where and how do the sympathetic and parasympathetic work together?

Answer 15

• Male sex organ
• Parasympathetic = erection
• Sympathetic = ejaculation