Lecture 4 Cardiac Cycle and Circulation

Question 1

How long does the PQRST process take?

Answer 1

0.51 seconds

Question 2

What happens to the heart rate during strong sympathetic stimulation?

Answer 2

The T-P interval, which is where the EKG flatlines between peaks, shortens and can disappear (increasing HR).

Question 3

What happens during sinoatrial block?

Answer 3

Impulses from SA node are blocked, AV node is the new pacemaker, one PQRS-T wave skipped.

Question 4

What happens during ventricular fibrillation?

Answer 4

Some parts of ventricle contract while others relax, no coordinated contraction, fatal. Circus movements.

Question 5

How ventricular defibrillation is used to rectify fibrillation:

Answer 5

1000V DC applied for a few thousandths of a second, all heart becomes refractory, 3-5 seconds after a new pacemaker established.

Needs to be used fast, within 1 min of fibrillation.

Question 6

What is atrial flutter?

Answer 6

Single large impulse travels around atria in one direction, atria can beat 2-3 times faster than the ventricle.

Question 7

What is atrial fibrillation?

Answer 7

Often caused by atrial enlargement. Long conduction pathway, gives circus movements in atria - irregular and fast movements in atria.

Question 8

What is the result of atrial fibrillation?

Answer 8

No fatality, efficiency of pumping is however decreased by about 20-30%.

Question 9

What happens during cardiac arrest, and how can you fix it?

Answer 9

No electrical activity in the heart. Will need new pacemaker or prolonged CPR to reestablish rhythm.

Question 10

What are the four major functions of the circulatory system?

Answer 10

• Transport nutrients and hormones
• Transport waste away from tissues
• Maintain constant temperature
• Maintain homeostasis generally

Question 11

Blood flow is controlled in relation to…

Answer 11

Tissue requirements

eg how circulation can increase or decrease in digestion vs running

Question 12

Cardiac output is controlled by….

Answer 12

Local tissue flow - think Frank-Starling

Question 13

Arterial pressure is…

Answer 13

Independent of local blood flow control or cardiac output control. It’s all about regulating circulation of the organism as a whole.

Question 14

Qualities of aorta and large arteries

Answer 14

Blood is under high pressure, high flow volume and velocity, any severe constrictions or aneurisms are fatal.

Question 15

Qualities of arterioles

Answer 15

They exist within organs, have strong muscular walls, and can constrict to almost no flow - major site of resistance.

Question 16

Qualities of capillaries

Answer 16

They exist within organs, have very thin walls, low velocity but high volume.

Question 17

What are the three types of capillaries?

Answer 17

• Continuous (only gas and small molecules pass)
• Fenestrated (larger molecules can pass)
• Sinusoid (whole cells can scoot through)

Question 18

Qualities of venules

Answer 18

Collect blood from capillaries, thin wall and low pressure

Question 19

Qualities of larger veins

Answer 19

Reservoir of blood, thin and muscular wall, made of inferior and superior vena cava

Question 20

How much blood is in the systemic vs heart and pulmonary circulation?

Answer 20

80% in systemic, 20% in heart and pulmonary approximately.