Autonomic nervous system

Question 1

Features of the ANS

Answer 1

• part of the PNS
  Involuntary control -
• Regulates operation of the internal organs
• Maintains internal environment
• Innervates smooth muscle, cardiac muscle, glands

Question 2

3 divisions of the ANS

Answer 2

• SYMPATHETIC
• PARASYMPATHETIC
• ENTERIC (The “Little Brain”)

Question 3

Origins of sympathetic and parasymp innervation

Answer 3

Parasymp - brainstem

sym - T1-L2 region of spinal cord

parasymp - s2-s4 region of spinal cord

Question 4

Path of axons in ANS

Answer 4

• Axons do not pass directly to the effector organs
• They form disynaptic pathways
• Except symp supply to adrenal medulla

Question 5

What is the main type of neurotransmitter within the autonomic ganglia

Answer 5

• Acetylcholine is the main neurotransmitter
• Binds to nicotinic receptors on postganglionic neurons
• Ionotropic ligand-gated(fast)
• Acetylcholine opens pore and depolarises neuron

Question 6

What is the main neurotransmitter in postganglionic sympathetic neurons

Answer 6

• Noradrenaline is the main neurotransmitter
• Except sweat glands use acetylcholine
• binds to adrenergic receptors on the effector organ

Question 7

What are the type of adrenergic receptors on the effector organ

Answer 7

• Metabotropic g-protein coupled(slow)

- Multiple subtypes alpha1, alpha2, beta1, beta2 and beta3

Question 8

Location of alpha1 adrenergic receptors

Answer 8

• On blood vessel smooth muscle

Question 9

Use of prazosin

Answer 9

• alpha1 antagonists are used to treat hypertension

Question 10

Location of beta1 adrenergic receptors

Answer 10

• On heart

Question 11

Effect of atenolol on beta1 adrenergic receptors

Answer 11

• Atenolol - beta1 antagonists are used to treat hypertension

Question 12

Location of beta2 adrenergic receptors

Answer 12

• On bronchial smooth muscle

Question 13

Effect of salbutamol on beta2 adrenergic receptors

Answer 13

• Beta2 agonists are used to treat asthma

Question 14

What is the main neurotransmitter within adrenal medulla

Answer 14

• Acetylcholine is the main neurotransmitter

Question 15

What does acetylcholine bind to within adrenal medulla

Answer 15

• Binds to nicotinic receptors on chromaffin cells

Question 16

Effect of acetylcholine on nicotinic receptors within adrenal medulla

Answer 16

• Causes release of adrenalin/noradrenalin into circulation

- Direct activation of sympathetic effector organs

Question 17

Main neurotransmitter in postganglionic parasymp neurons

Answer 17

• Acetylcholine is the main neurotransmitter

Question 18

What type of receptors does acetylcholine bind to in postganglionic parasympathetic neurons

Answer 18

• Binds to muscarinic receptors on the effector organ

- Metabotropic G-protein coupled(slow)

Question 19

Effect of atropine on cholinergic-muscarinic receptors

Answer 19

• Cholinergic-muscarinic antagonist(lowers parasymp activity)
• Used to treat bradycardia, dilate pupils, reduce glandular secretions

Question 20

Effect of sympathetic activity on the cardiac muscle

Answer 20

• increases pacemaker activity + contractile force

Question 21

Effect of sympathetic activity on the bronchi of lungs

Answer 21

• Causes bronchodilation

Question 22

Effect of sympathetic activity on the sweat glands

Answer 22

• Causes sweat secretion

Question 23

Effect of sympathetic activity on hair follicles

Answer 23

• causes piloerection

Question 24

Effect of sympathetic activity on blood vessels

Answer 24

• Vasoconstriction in skin and vasodilation in skeletal muscles

Question 25

Effect of sympathetic activity on abdomino-pelvic viscera

Answer 25

- Inhibits peristalsis + gastric secretion - Stimulates glucagon secretion - Stimulates secretion of adrenaline from adrenal medulla

Question 26

Location of paravertebral ganglia

Answer 26

- Interconnected paravertebral ganglia extends from cervical to sacral levels

Question 27

How do preganglionic fibres enter sympathetic trunk

Answer 27

- Through white rami communications | - From T1-L2 spinal nerves only

Question 28

What does the lateral horn contain

Answer 28

- Cell bodies of preganglionic neurons

Question 29

What do white ramus communicans contain

Answer 29

- myelinated preganglionic neurons

Question 30

What do grey ramus communicans contain

Answer 30

- Unmyelinated postganglionic neurons

Question 31

Pathway of preganglionic fibres upon entering the trunk

Answer 31

- Synapse in ganglion(same level or travel to another level) - Pass through ganglion into splanchnic nerves to synapse in prevertebral ganglia

Question 32

What are mass responses

Answer 32

- Sympathetic responses are mass responses | - Allows coordinated activity at multiple levels

Question 33

Path of postganglionic fibres in the symp system from the sympathetic trunk

Answer 33

- From sympathetic trunk, postganglionic fibres follow of two routes: 1) To the periphery(sweat glands, hair follicles, blood vessels) - via grey rami communications back into spinal nerves 2) To the viscera(heart, lungs, head) - via medial branches/plexus

Question 34

Path from prevertebral ganglia in symp system

Answer 34

- From prevertebral ganglia, postganglionic fibres form plexus around viscera

Question 35

What are the 3 cervical ganglia in cervical symp trunk

Answer 35

- Superior - Middle - Inferior