Autonomic Nervous System

Question 1

Where is sympathetic outflow from

Answer 1

Thoracic (T1-12) and lumbar (L1-2) regions

Question 2

Where is parasympathetic outflow from

Answer 2

Cranial nerves (III, VII, IX, X) and sacral (S2-4) regions

Question 3

What do adrenaline and noradrenaline act on

Answer 3

Adrenergic receptors
a-receptors
B-receptors

Question 4

What does activation of the sympathetic system cause in the iris (2) (what is the outcome)

Answer 4

Activates alpha1-receptors on the radial muscle of the iris causing it to contract
Relaxation of the ciliary muscles surrounding the lens

Outcome = pupil becomes larger

(Therefore eye drops which dilate the pupil are either alpha1 agonist or muscarinic antagonists)

Question 5

What does activation of the parasympathetic system cause in the iris (what is the outcome)

Answer 5

Activates muscarinic receptors on the sphincter muscle of the iris causing it to contract

Outcome = pupil becomes smaller

Question 6

What does activation of the sympathetic system cause in the ciliary muscle (what is the outcome)

Answer 6

Activates beta2-receptors on ciliary muscle around lens - this relaxes (B2relaxed) the ciliary muscle and eye focuses far away

Question 7

What does activation of the parasympathetic system cause in the ciliary muscle (what is the outcome)

Answer 7

Activates muscarinic receptors on ciliary muscle around the lens causing ciliary muscle to contract and eye focuses close up

Question 8

What does activation of the parasympathetic system do to the heart

Answer 8

Release of acetylcholine —> decreased heart rate

Question 9

What is the effect of the sympathetic system in the lung

Answer 9

Relaxation of smooth muscle