Autonomic NS and CVS

Question 1

What transmitters and post-synaptic receptors are used in parasympathetic neurotransmission?

Answer 1

Pre-ganglionic releases Ach -> nicotinic Ach receptors ->

Postganglionic Ach -> muscarinic (cholinergic) receptors to target tissue

Question 2

What transmitters and post-synaptic receptors are used in sympathetic neurotransmission?What are the 2 exceptions to this?

Answer 2

Preganglionic releases Ach -> nicotinic Ach receptors

Postganglionic releases NA

Exception:
1. Cholingergic innervation to sweat glands (Ach released to target tissue)

2. Chromaffin cells recieve Ach from pre-ganglionic and release adrenaline into bloodstream

Question 3

What are the largest ganglia in the ANS and where do they synapse and innervate?

Answer 3

2 coeliac ganglia: synapse with post-ganglionic neurones in upper abdomen and innervate most of GIT

Question 4

What defines an adrenoceptor?

Answer 4

A G protein-coupled receptor that responds to NA and adrenaline: alpha 1+2 and beta 1+2

Question 5

Why are muscarinic receptors not adrenoceptors even though they’re G protein-coupled receptors?

Answer 5

They are cholinergic (respond to Ach), not NA and adrenaline.

Question 6

Briefly describe the action of baroreceptors, where are they located?

Answer 6

Carotid sinus and aortic arch:

Hypotension -> less pressure/stretch -> less baroreceptor firing -> increased sympathietic/decreased PS = vasoconstriction, increased HR/contractility/BP

Carotid massage/increased pressure -> (+) baroreceptors -> increased AV node refractory period/decreased HR and vasodilation

Question 7

Where are the atrial receptors? What do they do?

Answer 7

R atria, sense low venous pressure

Question 8

Where do receptors of the aortic arch and carotid sinus transmit PS innervation to?

Answer 8

Aortic arch -> VAGUS
Carotid sinus -> CN IX

-> solitary nucleus (in medulla oblongata)

Question 9

Explain how sympathetic nerves influence the heart

Answer 9

Postganglionic fibres from T1-4 -> release NA on B1 adrenoceptors -> increase HR and FOC

Question 10

What are the 2 types of Ca2+ channels in a pacemaker cell?

Answer 10

T Type: initiate depolarisation

L Type: open for the main upstroke

Question 11

What type of adrenoceptor do most arteries and veins have vs skeletal and coronary muscle? Which is more common

Answer 11

Vessels/veins: a1
Skeletal/coronary muscle: b2

b2>a1

Question 12

What happens to pacemaker cells once NA has been released onto B1 adrenoceptors in the heart? (2 things)

Answer 12

Activates adenylyl cyclase (ATP - cAMP)

cAMP is ligand to HCN channels -> more funny current -> faster AP -> (+) HR

cAMP -> PKA -> phosphorylation of calcium channels increase calcium entry during AP -> CICR -> (+) FOC

Question 13

How are pacemaker cells influenced parasympathetically? (2)

Answer 13

M2 receptors inhibitory:
1. decrease cAMP -> less HCN channel action -> lower HR

2. Increased K+ conductance: MP stays (-) despite HCN channels allowing small Na+ influxes

Question 14

Which adrenoceptor does adrenaline have a higher affinity for between B2 and A1? What is the overall effect?

Answer 14

B2: vasodilation easier than vasoconstriction

Question 15

What happens when a1 adrenoceptors in vessels are activated?

Answer 15

GQ pathway:

Phospholipase C -> PIP2 dissociates into IP3 and DAG

• IP3 increases Ca2+ influx from SER
• DAG -> PKA

=increased intracellular Ca2+ -> sm muscle contraction

Question 16

What happens when B2 adrenoceptors in vessels are activated?

Answer 16

GS pathway:

Increased cAMP -> (+) PKA

1. Opens K+ channels -> cell stays hyperpolarisation
2. Phosphorylates and inactivates myosin light chain kinase necessary for smooth muscle contraction

=vasodilation

Question 17

What is Dobutamine used for?

Answer 17

B1 agonist: increases HR

Question 18

Name a B2 agonist drug and its action on the body

Answer 18

Salbutamol

Heart: vasodilator
Lungs (asthma): bronchodilator

Question 19

What does chronotropic and inotropic mean? Which input and receptor do both of these things?

Answer 19

Chronotropic: Increase HR
Inotropic: increase FOC

NA on B1 receptors in heart pacemaker cells

Question 20

Which ion are HCN channels sensitive to? (other than Na+)

Answer 20

K+: Repolarisation (less k+) -> (+) HCN

*less intracellular K+ means MP becomes more (-), so HCN channels allow more Na+ influx to bring MP back up

Question 21

Which vessels have B2 and A1 adrenoceptors?

Answer 21

Liver, skeletal muscle, myocardium

Question 22

Name one muscarinic agonist and one antagonist

Answer 22

Agonist: pilocarpine
Antagonist: Atropine

Question 23

When should and shouldn’t you give propanolol?

Answer 23

Propanolol is a non-specific B1 AND B2 antagonist:

• decreases HR and FOC (antagonizing B1)
• bronchoconstriction (antagonizing B2) = don’t give in asthma

Question 24

When could you give adrenaline?

Answer 24

Anaphylactic shock

Question 25

How is glaucoma treated and why?

Answer 25

Muscarinic receptor agonist has a PS effect -> pupil constricts -> more fluid can drain