Autonomic Physiology

Question 1

Describe the anatomy of the sympathetic and parasympathetic branches if the ANS.

Answer 1

The ANS exists to control involuntary actions e.g. smooth muscle, focusing eyes, glandular secretions. The preganglionic fibres are small and myelinated white ramus, whereas the post-ganglionic are unmyelinated grey ramus. The sympathetic has a short preganglionic section so the ganglia lie close to the spinal cord. It branches from thoracic 1-12, lumbar 1-5.
The parasympathetic has long preganglic sections as the ganglia lie close to the target. It branches from cranial and sacral nerves.

Question 2

Describe the neurotransmitters, receptors and functional aspects of autonomoc innervation.

Answer 2

The parasympathetic uses the neurotransmitter acetylcholine, it acts on nicotinic followed by muscarinic receptors. It’s use is rest and digest.
The sympathetic uses the neurotransmitters acetylcholine followed by adrenaline/noradrenaline. It acts on nicotinic followed by alpha or beta receptors. It’s use is fight or flight.

Question 3

Airways

Answer 3

The sympathetic will dilate airways by acting on B2 receptors.
The parasympathetic will constrict airways by acting on muscarinic receptors.

Question 4

Heart

Answer 4

The sympathetic will increase heart rate via B2 receptors and strengthen beats via B1 receptors.
The parasympathetic will slower HR and has little effect on contraction via muscarinic receptors.

Question 5

Blood

Answer 5

The sympathetic diverts blood flow to muscles via alpha1/B2 receptors.
The parasympathetic diverts blood flow to the gut via muscarinic receptors

Question 6

Gut

Answer 6

Sympathetic; motility is decreased by alpha/beta receptors and enzymes are inhibited by alpha receptors.
Parasympathetic; motility increases and enzymes are stimulated by muscarinic receptors.

Question 7

Energy

Answer 7

Sympathetic; releases energy from stores by alpha/beta receptors.
The parasympathetic has no effect.

Question 8

Eyes

Answer 8

Sympathetic dilates pupils by alpha 1 receptors and focuses far away via B2 receptors.
Parasympathetic; pupils constrict and focus close up via muscarinic receptors.

Question 9

Hair

Answer 9

Sympathetic; stands on end

Parasympathetic; lies flat

Question 10

Salivary glands

Answer 10

Sympathetic; stimulates thick secretions via B receptors.

Parasympathetic; stimulates watery secretions via muscarinic receptors.

Question 11

Tone

Answer 11

Turning up/down. i.e. to increases the storage of energy you need to tone down the sympathetic system.

Question 12

B2 receptors

Answer 12

Relaxes smooth muscle

Question 13

Alpha receptors

Answer 13

Contracts smooth muscle

Question 14

Describe simple autonomic reflexes

Answer 14

BP, HR, peristalsis, sweating, urination.