ESA 4 revision

Question 1

How long is diastole?

Answer 1

0.55s

Question 2

How long is systole?

Answer 2

0.35s

Question 3

What happens to cardiac cycle when heart rate increases?

Answer 3

Diastole shortens, systole remains the same

Question 4

How does hyperkalaemia affect the cardiac action potential?

Answer 4

Ek decreases. Depolarisation of myocytes causes deactivation of Na+ channels. Slowed upstroke.

Initial increase in excitation as depolarising…then decrease as inactivation.

Question 5

What are the risks of hypokalaemia?

Answer 5

Repolarisation delayed.

EAD risk ventricular fibrillation.

Question 6

How does depolarisation lead to myocyte contraction?

Answer 6

Depolarisation -> L-type Ca channels in T tubule system open.
RyR -> calcium release from SR
= calcium induced calcium release

Question 7

How does the parasympathetic nervous system decrease chronotropy?

Answer 7

M2 receptor is Gi coupled.
Decreased cAMP - decreased HCN activity.
Increase K+ conductance - further from threshold.

Question 8

How does parasympathetic innervation of the heart differ from sympathetic innervation?

Answer 8

PS - vagus nerve synapses with SA and AV node

Sympathetics synapse at SA and AV node but also myocardium itself to alter inotropy.

Question 9

Where do blood vessels have both alpha 1 and beta 2 receptors?

Answer 9

Liver
Myocardium
Skeletal muscle

Question 10

What is the most important factor in maintaining perfusion in skeletal and coronary muscle?

Answer 10

Local metabolites - adenosine, K+, H+ have a stronger vasodilator effect than B2-receptor activity.

Question 11

What is pilocarpine?

Answer 11

Muscarinic agonist

Used to treat glaucoma - M3 activates constrictor papillae.

Question 12

Give an example of a muscarinic antagonist and its use.

Answer 12

Atropine

Increase HR - vagal bradycardia

Question 13

How can you calculate mAP?

Answer 13

(SVxHR) x TPR

diastolic + 1/3 systolic

Question 14

What mechanism is responsible for short term blood pressure regulation?

Answer 14

Baroreceptor reflex - re-sets normal after 15 minutes

Question 15

What are the actions of ANP?

Answer 15

Vasodilation of afferent arteriole - increase GFR

Inhibit Na+ reabsorption to cause natriuresis

Question 16

What effect does dopamine have on blood pressure?

Answer 16

Decreases BP - vasodilation and decrease NaCl reabsorption.

Question 17

What are the boundaries for stages of hypertension?

Answer 17

Stage 1 - > 140/90
Stage 2 - > 160/100
Severe - 180 systolic or 110 diastolic

Question 18

What blood changes are characteristic of Conns syndrome?

Answer 18

Hypokalaemia

Hypernatraemia + hypertension

Question 19

How does Cushings syndrome cause hypertension

Answer 19

Acts on mineralocorticoid receptor at high conc - aldosterone effect.