Autonomic nervous system

Question 1

Functions of ANS

Answer 1

Contracting/relaxing smooth muscle

Regulation of gland secretion

Conrtol of heart rate

Regulation of metabolism

Question 2

Organs that are controlled by sympathetic only

Answer 2

Sweat and blood vessels

Question 3

Organs controlled by parasympathetic only

Answer 3

Cilliary muscle of eye

Question 4

Pre ganglionic neuron (PrGN’s)

Answer 4

Cell body in CNS

Small and myelinated

Releases ACh which acts on nicotinic receptors on post synaptic neuron

Question 5

Post ganglionic neuron (PoGN’s)

Answer 5

Cell body in autonomic ganglion

Small diameter and NON myelinated

Synapse close to target organ

Releases noradrenaline

Question 6

The exception to the 2 neuron system

Answer 6

Adrenal medulla

Only one neuron straight from CNS to adrenal medulla

Considered a specialised ganglion

Question 7

Properties of nicotinic receptors

Answer 7

3 classes- muscle, autonomic neuronal, CNS neuronal

All are ligand gated ion channels, cation channel Na+ in, K+

Most ganglia innervated by several PrGN’s and require simultaneous signals to generate action potential

Generates fast excitatory ppost synaptic potential (fast epsp)

Question 8

Modulating autonomic ganglia transmission -Muscarinic receptors

Answer 8

M1- K+ channel closing
Slow excitatory PSP (slow epsp)

M2- increases K+ conductance
induces hyperpolarisation
Slow inhibitory PSP (ipsp)

Question 9

Cholinergic signalling in airways

Answer 9

ACh released from PoGN activates M3 on smooth muscle causing contraction

ACh that is floating about also attaches to M2 receptors on PoGN causing a reduce in the amount of ACh released

Question 10

Sympathetic vs parasympathetic influence on lung smooth muscle

Answer 10

Most innervation of lungs is parasympathetic however there is some sparse sympathetic innervation of lungs

There is also some sympathetic control via circulating adrenaline

Question 11

How do different receptor subtypes vary their response?

Answer 11

They mediate different responses by coupling to different secondary messenger systems

a2, b1, b2, b3 all use cAMP to activate kinase which phosporylates protein inducing cell response

a1 uses phospholipase and diacylglycerol to activate kinase and release Ca

Question 12

Adrenoceptor selectivity

Answer 12

Unselective for both Adrenaline (A)/Noradrenaline (NA)

A slightly more selective for beta2 and alpha2
NA slightly more selective for beta1 and alpha1

Question 13

Alpha1 (a1) adrenoceptor function

Answer 13

Constrict smooth muscle

-except in GI tract where it relaxes

Question 14

Alpha2 (a2) adrenoceptor function

Answer 14

presynaptic inhibition of neurotransmitter release

Question 15

Beta1 (b1) adrenoceptor function

Answer 15

increases heart rate and force of constriction

Question 16

Beta2 (b2) adrenoceptor function

Answer 16

Dilates/relaxes smooth muscle

Question 17

Beta3 (b3) adrenoceptor function

Answer 17

Thermogenesis in skeletal muscle

Question 18

2 types of presynaptic modulation

Answer 18

Homotropic- nerve inhibits itself

Heterotropic- other nerves inhibit them

Question 19

What are NANC transmitters?

Answer 19

Non adrenergic non cholinergic transmitters

These include ATP, neuropeptides, NO, prostaglandin, histamines, adenosine and bradykinin

They are used for the fine tuning of the autonomic system by changing onset/duration of action or by changing the ratio of transmitters released

Question 20

Co transmission

Answer 20

Sometime neurotransmitters released for desired effect

ATP has very fast onset but short
NA has slower onset but prolonged

So both released to achieve both a quick onset and prolonged action