Introduction to the ANS

Question 1

What are the autonomic target organs?

Answer 1

AUTONOMIC NS:

• Exocrine glands
• Smooth/muscle
• Cardiac muscle
• Metabolism
• Host defence

Question 2

What are the two branches of the autonomic nervous system?

Answer 2

• Sympathetic (fight or flight)
• Parasympathetic (rest and digest)

Question 3

Pupil when you enter a dark room

Answer 3

Sym Oculomotor nerve Q

Question 4

Stomahc when youy smell food

Answer 4

Para Vagus

Question 5

Heart when losing excessive fluid through sweating

Answer 5

Sym Lower HR = vagal (para)

High HR = Sym - Lose fluid = low blood presssure = low baroreceptor firing rate

Question 6

What are the principal targets and functions of the autonomic NS?

Answer 6

Question 7

Where on the diagram would noradrenaline be released from?

Answer 7

D and F

PARASYMPATHETIC:

• Cranial or sacral
• Long preganglionic fibre (usually projects down into the tissue itself)
• Short postganglionic fibre
• Both ACh

SYMPATHETIC:

• Thoracic or lumbar
• Short preganglionic fibre
• Long postganglionic
• Mostly pre=ACh, post=NA
• Exception 1: pre = ACh innervate adrenal medulla, post = A (80%) + NA(20%)
• Exception 2: pre and post = ACh (ACh drives secretion even though it is controlled by sympmathetic response)

Question 8

TRUE OR FALSE:

PNS = coordinated response (very divergent)

Answer 8

FALSE

PNS = discrete/localised (little divergence 1:1 pre vs post)

SNS = coordinated response (very divergent, up to 1:20 pre vs post)

Question 9

Enteric nervous system

Answer 9

Under PNS and SNS control but also local

Enteric = response without the brain Slide 22 [pic]

Question 10

Somatic nervous system

Answer 10

ACh used to control skeletal muscle Slide 23 [pic]

Question 11

Acetylcholine receptors

Answer 11

Muscarinic or nicotinic Slide 25 [pic]

Question 12

Nicotinic receptors

Answer 12

Ion channel linked receptor Important for speed of affect At all autonomic ganglia Stimulated by nicotine/acetylocholine Slide 26 [pic]

Question 13

Muscarinic

Answer 13

At all effector organs innervated by post ganglionic parasypathetic fibres Stimuated by muscarine/acetylocholine Type 2 - G-protein coupled Slide 27 [pic]

Question 14

True or false: Nicotinic at effector organs

Answer 14

FALSE Nicotinic present throughout ANS at the postganglionic fibre NOTE: if a drug targets nicotinic receptors, the whole ANS will be affected

Question 15

Which of the following effects would be observed after blockade of nicotinic acetylcholine receptors in an individual at rest? 1. Bronchoconstriction 2. Increased sweat production 3. Constipation 4. Increased urinary frequency 5. Short-sightedness

Answer 15

3 - constipation EXPLANATIONS: 1 - bronchodilation 2 - decreased sweat production (block = lose effect) 3 - para = stimulates muscle contraction. Therefore, blocking parasympathetic NS = constipation 4 - para = stimulates urine production. Therefore blocking para = decreased urinary freq 5 - para = allow near vision. Therefore block para = vision projects outwards

Question 16

What effect would blockade of nicotinic acetylcholine receptors have on heart rate at rest and during exercise?

Answer 16

At rest = increase HR (suppress PNS) Exercise = less increase HR (less SNS innervation)

Question 17

Sub-types of muscarinic cholinoceptors

Answer 17

M1 - neural (forebrain = learning and memory) M2 - cardiac (brain = inhibitory autoreceptors) M3 - exocrine and smooth muscle (hypothalamus = food intake) M4 - periphery = prejunctional nerve endings (inhibitory) M5 - striatal dopamine release NOTE: Year 2 , only need to know M123

Question 18

Adrenoceptors

Answer 18

At all effector organs innervated by post ganglionic sympathetic fibres Stimulated by NA/A Type 2 - G-protein coupled Slide 34/35 [pic]

Question 19

Important to consider for all drugs

Answer 19

1. What is the drug target? (E.g. adrenoreceptors/muscarinic/nicotinic receptors) 2. Where is the drug target? 3. What is the end result of interaction? NOTE: with pharmacology, we usually think of ‘exogenous’ drugs, but can apply to ‘endogenous’ agents as well

Question 20

Biosynthesis and metabolism of acetylcholine, noradrenaline and adrenaline

Answer 20

1. Precursor enzymatically converted to neutrotransmitter 2. Packaged into vesicle 3. Ca2+ influx 4. Exocytosis 5. Neurotransmitter released into synapse 6. Receptor on postsynaptic membrane 7. Activated 8. Degraded

Question 21

Biosynthesis and release and metabolism of ACh

Answer 21

Slide 42 [pic] If ACh happens to bounce and come into contadct with acetylocholine-esterase, it will degrade If ACh binds to receptor = response Eventually all ACh will be degraded

Question 22

Biosynthesis, release and metabolism of noradrenaline

Answer 22

Slide 43 [pic] Need 3 different enzymes to liberate NA NA not metabolised in synapse - removed by transport proteins in both presynapse and postsynapse NA responses are quick

Question 23

Blockade of which of the following targets would cause the most significant rise in synaptic noradrenaline concentrations? 1. Tyrosine hydroxylase 2. DOPA decarboxylase 3. Uptake 1 tranpsort protein 4. Noamine oxidase 5. Cathecol-O-methyl transferase

Answer 23

3 - uptake 1 transport protein Slide 43 [pic]