Lecture 8 - Autonomic Nervous System

Question 1

What type of neurons are present in the peripheral nervous system?

Answer 1

Unipolar neurons i.e. only has one extension from the cell body

Question 2

What 2 types of glial cell are present in the PNS?

Answer 2

Schwaan cells - wrap around axon to form myeline sheath, increases signal speed
Satellite cells - surround cell bodies in ganglia, regulates gas, neurotransmitter and nutrient levels

Question 3

Where are ganglia and what is within them?

Answer 3

Always outside the CNS
Collections of the cell bodies of the peripheral neurons
Also where the autonomic neurons synapse with eachother

Question 4

What 3 things does the autonomic nervous system act on?

Answer 4

Smooth muscle (including vasculature and GI tract) 
Endocrine and exocrine glands
Cardiac muscle

Question 5

Pathway of a SNS response, including where it originates from

Answer 5

Originates craniosacral
Short preganglionic fibre exits through dorsal horn, release Ach to synapses with nAchR on postganglionic fibre in ganglion, long postganglionic fibre releases NA
OR
Short preganglionic that synapses directly onto the target organ (if endocrine gland)

Question 6

Pathway of a PSNS response

Answer 6

Originates throracolumbar
Long preganglionic fibre exits through dorsal horn, release Ach to synapses with nAchR on postganglionic fibre in ganglion, short postganglionic fibre releases Ach

Question 7

Which organs are only innervated by the SNS and not the PSNS?

Answer 7

Adrenal gland
Sweat glands
Some blood vessels

Question 8

Examples of two organs that have dual innervation

Answer 8

Heart

Liver

Question 9

2 advantages of dual innervation

Answer 9

Faster control

More fine-tuned control

Question 10

Describe the process of Ach synthesis and breakdown

Answer 10

In nerve terminals, acetyl coeznyme A from mitochondria, and choline uptaken from interstitial fluid that comes from the diet, form Ach.
Ach broken down by acetylcholine esterase

Question 11

Describe the process of adrenaline synthesis

Answer 11

Tyrosine consumed in diet or protein breakdown
Tyrosine hydroxylase converts it into L-Dopa
Dopa decarboxylase converts it into dopamine
Dopamine hydroxylase converts it into norepinephrine
PNMT converts it into epinephrine

Question 12

How is noradrenaline signalling stopped?

Answer 12

Inactivated by monoamine oxidase
The NET (norepinephrine transporter) re uptakes it back into cells

Question 13

What receptors can Ach bind to?

Answer 13

nAchR - on muscle, in ganglia or in the CNS

mAchR - M1-5

Question 14

What receptors can adrenaline bind to?

Answer 14

alpha 1,2

beta 1-3

Question 15

Are preganglionic neurons and postganglionic neurons excitatory or inhibitory?

Answer 15

Preganglionic always excitatory as release Ach

Postganglionic can be either - M2 and M4 coupled to Gai subunit, which is inhibitory

Question 16

Which g protein subunit is each receptor linked to?

Answer 16

Gs - b1, b2, b3
Gi - a2, M2, M4
Gq - a1, m1, m3, m5

Question 17

Describe how preganglionic firing can result in a more delayed/prolonged EPSP?

Answer 17

Low frequency firing = Ach release = activates nAchR = fast EPSP
High frequency firing = Ach release and LHRH peptide release = LHRH binds postsynaptic peptidergic receptor = activation of GIRK channels = delayed EPSP

Question 18

What is the name for drugs that enhance and oppose the action of the parasympathetic and sympathetic nervous systems?

Answer 18

Parasympathomimetic
Parasympatholytic
Sympathomimetic
Sympatholytic

Question 19

Name two parasympathomimetic drugs and explain how they work

Answer 19

1. Carbachol - Stimulation of cholinergic receptors

2. Neostigmine - Reversible inhibition of AchE, acts on motor end plate, treats myasthenia gravis

Question 20

Name two parasympatholytic drugs and and explain how they work

Answer 20

1. Atropine - Competitive antagonism of muscarinic Ach receptors
2. Nicotine - Persistent depolarisation of Ach receptors, preventing repeated excitation

Question 21

Name 2 examples of sympathomimetic drugs and explain how they work

Answer 21

1. Salbutamol - b2 agonist used to treat asthma

2. Amphetamine - antagonist of NET

Question 22

Name 2 examples of sympatholytic drugs and explain how they work

Answer 22

1. Reserpine - antihypertensive, blocks VMAT to prevent NA packaging into vesicles
2. Methyldopa - inhibitor of DOPA decarboxylase

Question 23

How does parasympathetic innervation exert control over heart rate?

Answer 23

1. PSNS releases Ach
2. Ach binds M2 receptors on heart
3. Gby subunit activates GIRK channels in pacemaker cardiomyocytes, potassium efflux, less frequent depolarisation
4. Gi subunit inhibits adenylate cyclase, reducing cAMP and PKA, less phosphorylation of L-type calcium channels, reduced contractility

Question 24

How does sympathetic innervation exert control over heart rate?

Answer 24

1. SNS releases NA
2. NA binds B1 and B2 receptors on the heart
3. Gs subunit activates adenylate cyclase, increasing cAMP and PKA, phosphorylation of L-type calcium channels

Question 25

Which part of the brain is in charge of autonomic nervous system control?

Answer 25

Hypothalamic paraventricular nucleus

Question 26

What is the mechanism of action of alcohol and the short term effects?

Answer 26

Positive allosteric modulator of the GABAa receptor

Anxiety relief, sedation, hypnosis, anaesthesia, death

Question 27

What are the effects of chronic alcohol intake?

Answer 27

Chronic intake can lead to demyelination, causing

1. Conduction block
2. Slowed conduction
3. Impaired ability to conduct high frequency impulses

Question 28

Name 3 symptoms of acute alcohol withdrawal

Answer 28

Tachycardia
Diaphoresis (Increased sweating)
Hypertension