Heart II

Question 1

(Foetus) Function of Ductus Arteriosus?

Answer 1

Connects pulmonary artery with descending aorta
Protects the lungs against circulatory overload
Allows the right ventricle to strengthen

Question 2

(Foetus) Function of Ductus Venosus?

Answer 2

Foetal blood vessel connecting the umbilical vein to the IVC

Allows oxygenated blood to bypass the liver

Question 3

(Foetus) Function of Foramen ovale?

Answer 3

Hole in the interatrial septum

Shunts highly oxygenated blood from right atrium to left atrium

Question 4

Whats the first sound of the heart?

Answer 4

First sound occurs as AV valves close and signifies beginning of systole

Question 5

Whats the second sound of the heart?

Answer 5

Second sound occurs when SL valves close at the beginning of ventricular diastole

Question 6

Whats the electrical activation of the heart?

Answer 6

The inflow of Na ions across the cell membrane (depolarization)

Question 7

What are the events that lead up to a Cardiac Muscle Contraction?

Answer 7

Depolarization opens voltage-gated fast Na+ channels in the sarcolemma
Reversal of membrane potential from –90 mV to +30 mV
Depolarization wave in T tubules causes the SR to release Ca2+
Depolarization wave also opens slow Ca2+ channels in the sarcolemma
SR to release more Ca2+ (“calcium sparks”)
Ca2+ surge prolongs the depolarization phase (plateau - the cells continue to contract)

Question 8

Whats the anatomy of a Intrinsic cardiac conduction system?

Answer 8

Ability of cardiac muscle to depolarize and contract
A network of noncontractile (autorhythmic) cells
Initiate and distribute impulses to coordinate the depolarization and contraction of the heart
Even without nerve connections the heart continues to beat (i.e. transplantation)

Question 9

Whats the anatomy of Extrinsic regulation?

Answer 9

Autonomic nervous system regulation

Question 10

What is the first step of Depolarisation?

Answer 10

Pacemaker potential - 
This slow depolarization is 
due to both opening of Na+
channels and closing of K+
channels.

Question 11

What is the second step of Depolarisation?

Answer 11

Depolarization - The 
action potential begins when 
the pacemaker potential 
reaches threshold. 
Depolarization is due to Ca2+
influx through Ca2+ channels

Question 12

What is the third step of Depolarisation?

Answer 12

Repolarization - is due to 
Ca2+ channels inactivating and 
K+ channels opening. This 
allows K+ efflux, which brings 
the membrane potential back 
to its most negative voltage.

Question 13

Where is the Sinoatrial (SA) node?

Answer 13

Pacemaker- right atrial wall

Question 14

Where is the Atrioventricular (AV) node?

Answer 14

Inferior portion interA septum

Question 15

What is P Wave?

Answer 15

Atrial Depolarization

Question 16

What is QRS complex?

Answer 16

Ventricular Depolarization

Question 17

What is T wave?

Answer 17

Ventricular Repolarization

Question 18

What are the ECG caused conditions?

Answer 18

Tachycardia: abnormally fast heart rate (>100bpm)
(May lead to fibrillation)
Bradycardia: heart rate slower than 60bpm
(From Endurance training)