Cardiovascular system

Question 1

What is cardiac output (CO)?

Answer 1

The volume of blood ejected per minute from the left ventricle into the aorta

Question 2

What is cardiac output determined by?

Answer 2

1. the stroke volume- the amount of blood ejected by the left ventricle during each beat
2. heart rate- the number of heartbeats per minute

Question 3

What is the first factor which regulates stroke volume?

Answer 3

-the degree of stretch in the heart before it contracts
-the greater the force of contraction during systole, the more forcefully it contracts

Question 4

What is the second factor which regulates stroke volume?

Answer 4

-The forcefulness of contraction of individual ventricular muscle fibres
-the heart can contract more or less forcefully when certain substances are present:
-stimulation of the sympathetic nervous system increases the force of contraction of cardiac muscle
-inhibition of the sympathetic nervous system decreases the force of contraction

Question 5

What is the third factor which regulates stroke volume?

Answer 5

-the pressure required to eject blood from the ventricles

Question 6

What other factors affect resting heart rate regulation?

Answer 6

age, gender, physical fitness, body temperature

Question 7

What effect does an increase and decrease in body temperature have on heart rate?

Answer 7

-increased temperature= increases heart rate by causing SA node to discharge more rapidly
-decreased temperature= decreases heart rate and force of contraction

Question 8

What do the interconnected negative feedback systems control and how?

Answer 8

blood pressure and blood flow by adjusting heart rate, stroke volume, vascular resistance and blood volume

Question 9

What 3 thing does the cardiovascular centre in the medulla oblongata control?

Answer 9

1. helps regulate heart rate and stroke volume
2. neural and hormonal negative feedback systems that regulate blood pressure and blood flow to specific tissues
3. receives input from 3 types of sensory receptors (proprioceptors, baroreceptors, chemoreceptors)

Question 10

What do proprioceptors control?

Answer 10

monitor movements of joints and muscles, provide input to the CV centre during physical activity to cause a rapid increase in heart rate

Question 11

What do baroreceptors control?

Answer 11

-located in the aorta, internal carotid arteries and other large arteries in the neck and chest
-send impulses to cardiovascular centre to regulate blood pressure

Question 12

What do chemoreceptors control?

Answer 12

-monitor blood levels of o2, co2 and H+ located in the two carotid bodies in the common carotid arteries and in the aortic body in the arch of the aorta
-the CV centre responds by increasing sympathetic stimulation of arterioles and veins, producing vasoconstriction and increasing blood pressure