Introduction to the Autonomic Nervous System

Question 1

Which limb of the autonomic nervous system has more of an effect on the Liver?

Answer 1

Sympathetic – causes hepatic gluconeogenesis and glycogenolysis

Question 2

Which limb of the autonomic nervous system dominates the lungs and the eyes at rest?

Answer 2

Parasympathetic

Lungs – causes partial bronchoconstriction

Eyes – allows near vision (constricts pupil)

Question 3

Describe the relationship between baroreceptor firing and parasympathetic discharge.

Answer 3

Baroreceptors are stimulatory to the parasympathetic nerves i.e. an increase in baroreceptor firing stimulates an increase in parasympathetic firing

Question 4

Describe the differences between sympathetic responses and parasympathetic responses.

Answer 4

Sympathetic: coordinated + divergent, 1:20

Parasympathetic: discrete + localised, 1:1

Question 5

Describe the difference in the transmission through nicotinic and muscarinic receptors.

Answer 5

Nicotinic is much faster

Question 6

What effect does parasympathetic dominance at rest have on the: lungs, gut, bladder and eyes?

Answer 6

Lungs – partial bronchoconstriction

Gut – increased gut motility

Bladder – increased urinary frequency

Eyes – short-sightedness

Question 7

Why would giving a ganglion blocker at rest cause constipation?

Answer 7

At rest the parasympathetic nervous system is dominant, which increases gastric motility. This means that a ganglion blocker will knock out this effect and cause constipation.

Question 8

Where are the 3 types of muscarinic cholinoceptor found?

Answer 8

M1 – neural tissue

M2 – cardiac

M3 – exocrine and smooth muscle

Question 9

Where are adrenoceptors found, what are they stimulated by and what type are they?

Answer 9

At (nearly) all effector organs innervated by post ganglionic sympathetic fibres

Stimulated by noradrenaline + adrenaline

Type 2 – G-protein coupled

Question 10

Describe the synthesis and breakdown of ACh

Answer 10

It is formed from acetyl CoA and choline by choline acetyltransferase

It is broken down by acetyl cholinesterase

Question 11

Describe the synthesis of Noradrenaline.

Answer 11

Tyrosine -> DOPA (enzyme: tyrosine hydroxylase)

DOPA -> dopamine (enzyme: DOPA decarboxylase)

Dopamine -> Noradrenaline (enzyme: dopamine beta-hydroxylase)

Last step takes place in a vesicle

Question 12

What are the 2 uptake mechanisms of noradrenaline?

Answer 12

Uptake 1: neuronal tissue – Monoamine Oxidase A (MAO-A)

Uptake 2: extraneuronal tissue – Catechol-O-Methyl Transferase (COMT)

Question 13

Main targets for autonomic nervous system

Answer 13

exocrine glands

smooth muscle

cardiac muscle

metabolism

host defence

Question 14

Main targets for Somatic nervous system

Answer 14

Skeletal muscle

inc. Diaphragm + respiratory muscle

Question 15

Main targets for neuroendocrine system

Answer 15

Growth, metabolism, reproduction, development,

Salt & water balance,

Host defence

Question 16

State the 2 divisions of the autonomic nervous system

Answer 16

Sympathetic

Parasympathetic

Question 17

Describe the autonomic response to drop in blood pressure

Answer 17

Arterial baroreceptor firing rate drops

Lose inhibition of the sympathetic system

Increases HR + BP

Question 18

Describe the effects of sympathetic innervation on: eyes, salivary glands, trachea and bronchioles

Answer 18

Eyes: Pupil dilation

Salivary glands: Thick viscous secretions

Trachea: Dilates

Question 19

Describe the effects of parasympathetic innervation on: eyes, salivary glands, trachea and bronchioles

Answer 19

Eyes: Pupillary constriction + ciliary muscle contraction

Salivary glands: Copious, watery secretion

Trachea: Constriction

Question 20

Describe the effects of sympathetic innervation on: skin, liver, kidney and adipose

Answer 20

Skin: Piloerection

Liver: Glycogenolysis + Gluconeogenesis

Kidney: Increased renin secretion

Adipose: Lipolysis

Question 21

Describe the effects of sympathetic innervation on: blood vessels to skeletal muscles and skin, mucous membranes and splanchnic area

Answer 21

Skeletal muscles: Dilation

Skin: Constriction

Question 22

Describe the effects of sympathetic innervation on: heart, GI system, ureters and bladder

Answer 22

Heart: Increase rate + contractility

GI: Decrease motility + tone, sphincter contraction

U+B: Relaxes detrusor, constriction of trigone + sphincter

Question 23

Describe the effects of parasympathetic innervation on: heart, GI system, ureters and bladder

Answer 23

Heart: Decrease rate and contractility

GI: Increase motility + tone, increase secretions

U+B: Contraction of detrusor, relaxation of trigone + sphincter

Question 24

Describe the cholinergic sympathetic response of skin

Answer 24

Increased sweating

Question 25

Which nervous system releases NA from post-ganglionic neurones?

Answer 25

Sympathetic

Question 26

Which neurotransmitter is used by the parasympathetic nervous system?

Answer 26

ACh

Question 27

What neurotransmitter is used by pre-ganglionic sympathetic neurones?

Answer 27

ACh

Question 28

Can ACh be released by sympathetic post-ganglionic neurones?

Answer 28

Yes E.g. On sweat glands

Question 29

Describe the journey of signalling in the enteric nervous system

Answer 29

Sensory neurone connected to mucosal chemoreceptors + stretch receptors Info relayed to submucosal + myenteric plexus via interneurones Motor neurones release ACh or substance P to contract smooth muscle Or Vasoactive intestinal peptide or NO to relax smooth muscle

Question 30

Which neurotransmitter is used by the somatic nervous system?

Answer 30

ACh

Question 31

Where are nicotinic receptors found, what are they stimulated by, what type are they and what is their speed?

Answer 31

At all autonomic ganglia Stimulated by nicotine + ACh Type 1 - Ionotropic Very fast

Question 32

Where are muscarinic receptors found, what are they stimulated by, what type are they and what is their speed?

Answer 32

At all effector organs innervated by post-ganglionic parasympathetic fibres Stimulated by muscarine + ACh Type 2 - G Protein coupled Slower

Question 33

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

Answer 33

Rest: Parasymp in control, keeps heart rate suppressed. If blocked, HR will increase Exercise: Symp. Becomes dominant, drives increased HR and BP. If blocked, there would be less of an increase

Question 34

List 4 adrenoceptors

Answer 34

Alpha 1 Alpha 2 Beta 1 Beta 2

Question 35

For ACh, when considering effects on the gut What and where is the drug target? What is the end result of the interaction?

Answer 35

1. Muscarinic receptor (M3) as parasympathetic 2. Gastric smooth muscle, acid producing cells of stomach, endocrine cells that produce gastrin in stomach 3. Contraction, increased acid production, increased gastrin secretion

Question 36

For Noradrenaline, when considering effects on heart rate What and where is the drug target? What is the end result of the interaction?

Answer 36

1. Adrenoceptors (B1) 2. Nodal tissue in heart that controls rate 3. Increase in HR

Question 37

Blockade of what target would cause the most significant rise in synaptic noradrenaline concentrations?

Answer 37

Uptake 1 transport protein as interferes with NA ability to leave synpase, so NA accumulates in synapse