Revision

Question 1

What is the normal range of plasma K+?

Answer 1

3.5- 5.5 mmol/L

Question 2

What is the RMP of a cardiac myocyte?

Answer 2

-80 mV

Question 3

Why are cardiac myocytes so sensitive to changes in plasma potassium?

Answer 3

K+ permeability dominates the rmp

Question 4

What effect does hyperkalaemia have on the cardiomyocye action potential?

Answer 4

SLOW UPSTROKE

Ek becomes less negative, so the membrane depolarises.This inactivates some voltage gated Na+ channels .

Question 5

What can you do to treat hyperkalaemia?

Answer 5

Calcium gluconate - decrease excitability

Insulin - facilitates glucose uptake into cells, K+ follows

Question 6

What effect does hypokalaemia have on the cardiomyocyte AP?

Answer 6

Lengthens AP, delaying repolarisation

Question 7

What is a danger associated with a lengthened AP?

Answer 7

Lead to arrhythmia - early after depolarisations and ventricular fibrillation.

Question 8

How does a ventricular septal defect affect pulmonary circulation?

Answer 8

Damage to pulmonary vasculacuture leading to vascular re-modelling and increased pulmonary resistance.
May lead to Eisenmenger syndrome where shunt is reversed.

Question 9

What proportion of a thoracic cage should be occupied by the heart shadow?

Answer 9

50%

Question 10

What 3 congenital defects lead to acyanotic L to R shunts?

Answer 10

1. Patent ductus arteriosus
2. Atrial septal defect
3. Ventricular septal defect

Question 11

What action must be taken immediately in infants born with transposition of the great arteries

Answer 11

Drugs given to maintain ductus arterioles and foramen ovale until surgical correction.

Question 12

What are the segments of the primitive heart tube?

Answer 12

Aortic roots
Truncus arteriosus 
Bulbus cordis
Ventricle
Atrium
Sinus Venosus

Question 13

What does the RA develop from?

Answer 13

Most of primitive atrium

Part of sinus venosus

Question 14

What does the LA develop from?

Answer 14

Small part of primitive atrium

Absorbs proximal parts of pulmonary veins

Question 15

What is the sequence of atrial pressure changes?

Answer 15

A wave
C wave
X descent 
V wave
Y descent

Question 16

What catecholamine receptor is present in the eye to cause pupil dilation?

Answer 16

Alpa 1

Question 17

What cholindergi receptor is present in the eye to cause pupil constriction?

Answer 17

M3

Question 18

Which cranial nerve is the vagus nerve?

Answer 18

10th

Question 19

Where does the vagal nerve synapse with post-ganglionic fibres?

Answer 19

Epicardial surface or SA and AV node.

NOT myocardium

Question 20

Where do post-ganglionic fibres from the sympathetic trunk innervate the heart?

Answer 20

SA node, AV node and myocardium

Question 21

How does the parasympathetic input to the heart result in negative chronotropy?

Answer 21

M2 receptors are alpha i coupled. Decrease cAMP and beta,gamma subunit increases K+ conductance, cell moves further away from threshold.

Question 22

Which vasculature have B2 receptors as well as a1?

Answer 22

Coronary, skeletal muscle and liver

Question 23

At physiological concentration, which vascular receptors will adrenaline bind to?

Answer 23

B2, but at higher levels will activate alpa 1.

Question 24

How does activation of B2 receptors cause vasodilation?

Answer 24

Gs coupled, cAMP and PKA. PKA opens K+ channels and inhibits MLCK causing relaxation.

Question 25

What local metabolites have a strong vasodilator effect?

Answer 25

Adenosine, H+, K+, increase pCO2

Question 26

What is most important for ensuring skeletal and coronary muscle is perfused?

Answer 26

Release of active metabolites! More important then B2 activation.

Question 27

Where are baroreceptors?

Answer 27

Carotid sinus

Aortic arch

Question 28

What is dobutamine and when might it be given?

Answer 28

B1 agonist

Cardiogenic shock

Question 29

Give an example of a muscarinic agonist and what it might be used to treat.

Answer 29

Pilocarpine - glaucoma