Cardiovascular system and blood-Physiology (lectures 8 to 13)

Question 1

Mammalian cardiovascular system

Answer 1

Four chambered heart, Blood flows in one
direction, Arterial blood flows away from the heart, Venous blood flows towards the heart

Question 2

Heart pumps

Answer 2

Two: right and left pump
Equal flow through the toe circuits, contract simultaneously, Valves open and close to direct blood
Relaxation, atria contract first, ventricles contract second, relaxation

Question 3

Blood movement through the heart is gated by what?

Answer 3

Valves
-Atrioventricular (AV) valves control flow
between atria and ventricles
-Aortic and pulmonary valves control flow from ventricles out to circulatory vessels

Question 4

Cellular mechanism of cardiac contraction

Answer 4

-Actin(thin filament) and myosin(thick filament)
-Ca2+ levels go up, and more Ca2+ is released from sarcoplasmic reticulum
-Myosin binds to actin to form cross-bridges
-Myosin pulls on actin to shorten sarcomere and generate force
-Every myocyte activated during each heart beat

Question 5

How is the force of cardiac contraction increased?

Answer 5

Extent of cross-bridges formed not
maximized at rest…
-increase cytosolic Ca2+ level
-increase number of cross-bridges formed
-increase force of contraction.

Question 6

What happens during cardiac relaxation?

Answer 6

Decrease in cytosolic Ca2+ levels.
-Ca2+ pumped back into SR
-Cross-bridges release when ATP binds to myosin.
-Reduction in force means heart can relax.
-All cardiac myocytes relax each beat.

Question 7

Diastole and Systole

Answer 7

Diastole=Relaxation, Falling pressure
Systole=Contraction, Rising pressure

Question 8

Electrical and contractile cells of the heart

Answer 8

Electrical 1% - ‘pale’ striated appearance
Low actin and myosin
Contractile 99% - Striated appearance
High actin and myosin