intro to autonomic nervous system

Question 1

3 parts of the CNS

Answer 1

autonomic NS (exocrine glands, smooth muscle, cardiac muscle, metabolism, host defence)

somatic NS (skeletal muscle, including the diaphragm and respiratory muscle)

neuroendocrine system (growth, metabolism, reproduction, development, 
salt & water  balance, host defence)

Question 2

define sympathetic and parasympathetic

Answer 2

sympathetic= fight and flight 
parasympathetic= rest and digest

Question 3

balance of ANS in particular tissues:

• lungs
• eyes
• liver

Answer 3

• lungs = dominated by the parasympathetic (there is a p[atrial level of constriction so that it can be constricted further and dilate)
• eyes = dominated by the parasympathetic at rest as you need your smooth muscle to be partially constricted so it can change in both directions
• liver = largely sympathetic

Question 4

Pupil in darkness- determine which ANS

branch is dominant

Answer 4

sympathetic

leads to pupil dilation- fight or flight response

Question 5

stomach when there is food around- determine which ANS

branch is dominant

Answer 5

parasympathetic (via vagus nerve)
acid production stimulated
-rest and digest

Question 6

basal control of the heart- how does it work?

Answer 6

influenced by arterial baroreceptors

• high BP
• high baroreceptor firing
• parasympathetic stimulated
• sympathetic inhibited
• heart rate decreases

parasympathetic dominated heart at rest
sympathetic is totally in control of the arterioles

Question 7

principal targets and function of the ANS

Answer 7

see slide

Question 8

differences between parasympathetic and sympathetic responses

Answer 8

parasympathetic = discrete and localised (1:1, preganglionic: post ganglionic)

sympathetic= coordinated and divergent

Question 9

Identify the transmitters released from pre- and postganglionic fibres in the parasympathetic nervous systems.

Answer 9

(cranial/ sacral) 
long preganglionic neurone 
ACh
short post ganglionic neurone 
ACh 
effector organ

Question 10

Identify the transmitters released from pre- and postganglionic fibres in the sympathetic nervous systems.

Answer 10

(thoracic/ lumbar) 
short preganglionic neurone 
ACh
long post ganglionic neurone 
NA 
effector organ 

EXCEPTIONS: 
short preganglionic neurone 
ACh
adrenal medulla 
A/NA 
effector organ 

AND 
short preganglionic neurone 
ACh
long post ganglionic neurone 
ACh
effector organ such as sweat glands

Question 11

what is the enteric nervous system

Answer 11

In action:
-responds to various stimuli within the GI tract
Sensory neurone connected to mucosal chemoreceptors and stretch receptors detect chemical substances in the gut lumen or tension in the gut wall caused by food.
Information relayed to submucosal and myenteric plexus via interneurons.
Motor neurones release acetylcholine or substance P to contract smooth muscle or vasoactive intestinal peptide or nitric oxide to relax smooth muscle

Question 12

Identify the transmitters released from the somatic nervous system

Answer 12

ACh

Question 13

Classify the receptors found in the parasympathetic NS

Answer 13

(cranial/ sacral) 
long preganglionic neurone 
ACh 
-nicotinic 
short post ganglionic neurone 
ACh 
-muscarinic 
effector organ

Question 14

nicotinic receptors

• where each type is found
• the signalling systems they each employ
• what type

Answer 14

At all autonomic ganglia (usually at the start of postganglionic neurone)
Stimulated by nicotine/acetylcholine
Type 1 - Ionotropic

Question 15

muscarinic receptor

• where each type is found
• the signalling systems they each employ
• what type

Answer 15

At all effector organs innervated by
post ganglionic parasympathetic fibres
Stimulated by muscarine/acetylcholine
Type 2 – G-protein coupled

Question 16

Sub-types of muscarinic cholinoreceptors

Answer 16

M1 – Neural (Forebrain – learning & memory)

M2 – Cardiac (Brain – inhibitory autoreceptors)

M3 – Exocrine & smooth muscle (Hypothalamus – food intake)

Question 17

adrenoreceptors

• where each type is found
• the signalling systems they each employ
• what type

Answer 17

At all effector organs** innervated by
post ganglionic sympathetic fibres
Stimulated by noradrenaline/adrenaline
Type 2 – G-protein coupled

Question 18

Where are the a1,a2,b1,b2 receptors found

Answer 18

see slide

Question 19

Summarise the processes involved in the biosynthesis, release and metabolism of acetylcholine,

Answer 19

• acety Co A + choline
• forms Ach + CoA
• ACh is packed into a vesicle
• Calcium influx in triggered by an action potential, causes the release f ACh
• ACh diffuses across synapse and binds to receptor
• ACh is then broken down by acetylcholinesterase
• this forms choline and acetate

Question 20

Summarise the processes involved in the biosynthesis, release and metabolism of noradrenaline

Answer 20

-Tyrosine converted into DOPA via tyrosine hydroxylase
-DOPA is converted into Dopamine via DOPA decarboxylase
-Dopamine is packaged into vesicles and then converted to NA by Dopamine
Beta Hydroxylase
-NA is then released when the action potential comes along and triggers calcium
influx
-NA binds to the adrenoceptor
-NA is NOT broken down in the synapse. It is either removed by:
oUptake 1 -back into the neuronal tissue
oUptake 2-into extra neuronal tissue
-Once it has been taken up it
is broken down by:
oMonoamine Oxidase (MAO)
-mainly in neuronal tissue, into metabolites
oCatechol
Or Methyl Transferase (COMT)- degredation, mainly in extraneuronal tissue

Question 21

Blockade of which of the following targets would cause the most significant rise in synaptic noradrenaline concentrations?
Tyrosine hydroxylase
DOPA decarboxylase
Uptake 1 transport protein
Monoamine oxidase
Cathecol-O-methyl transferase

Answer 21

Uptake 1 transport protein