7. Electrical & Molecular Mechanisms Of The Heart And Vassculature

Question 1

What is the cardiac output of average 70kg man?

Answer 1

5L/min

Question 2

What happens to the concentration gradient & electrical gradient at the equilibrium potential for an ion?

Answer 2

They become equal

Question 3

What is the resting membrane potential for cardio myocytes ?

Answer 3

-85 to -95 mV

Question 4

How does action potential in axon and skeletal muscle last?

Answer 4

0.5-1ms

Question 5

How long does it take for depol to occur in SA node and cardiac ventricle ?

Answer 5

100ms

Question 6

What causes a pacemaker potential ?

Which channels are used?

How are these channels activated?

Answer 6

Funny currents

HCN channels

By hyperpolarisation/negative membrane potential (

Question 7

What causes the upstroke in an AP of a pace maker cell?

Answer 7

L type ca2+ channels opening = ca+2 influx

Question 8

Where in the heart is depolarisation the fastest ?

Answer 8

SA node

Question 9

Where in the heart is there automaticity?

Answer 9

SA node and AV node

Question 10

What do pacemakers cells do?

Answer 10

Sets the rhythm

Question 11

What is asystole ?

Answer 11

No beating of the heart

No APs fired

Question 12

If action potentials fire to slowly this’s it’s called..

Answer 12

Bradycardia

Question 13

If action potentials fire too quickly this is called…

Answer 13

Tachycardia

Question 14

If action potential firing/electrical activity in heart becomes random this is called…

Answer 14

Fibrillation

Question 15

What is the normal range of k+ concentration ?

Answer 15

3.5-5.5 mmol.L^-1

Question 16

In hyperkalaemia what happens to the resting membrane potential of cells?

Answer 16

It becomes more +ve - closer to threshold.

Question 17

What does hyperkalaemia do to the action potential ?

Answer 17

• slower upstroke
• depolarise the membrane
• more inactivated na+ channels
• narrowing of AP

Question 18

What can hyperkalaemia lead to ?

Answer 18

Asystole

Question 19

What is mild hyperkalaemia?

Answer 19

5.5-5.9mmol/L

Question 20

What is moderate hyperkalaemia?

Answer 20

6.0-6.4 mmol/L

Question 21

What is severe hyperkalaemia?

Answer 21

> 6.5mmol/L

Question 22

What is the treatment for hyperkalaemia?

Answer 22

• calcium gluconate
• Calcium chloride
• insulin + glucose

Question 23

What does hypokalaemia do to the action potential of cardio myocytes ?

Answer 23

Increases the duration

Delays repolarisation

Question 24

What are early after depolarisations ?

When do they occur?

Answer 24

Oscillations in membrane potential

Occur when there is a delayed repolarisation

Question 25

If the action potential is prolonged what 3 things is the patient more prone to getting?

Answer 25

Arrhythmias Early after depolarisations VF