Cardiovascular homeostasis II

Question 1

What is the definition of Cardiac Output?

Answer 1

The amount of blood pumped by the ventricles in a minute

Question 2

What is the stroke volume?

Answer 2

Volume of blood ejected per minute

Question 3

What is afterload?

Answer 3

The force of contraction that the ventricles have to work against to push blood out of the ventricles into the aorta (related to aortic pressure)

Question 4

What is preload?

Answer 4

The load/tension exerted on the muscle walls just after diastole so prior to contraction

Question 5

What are the three major controls of cardiac output?

Answer 5

Nervous control, Intrinsic control and Atrial reflex

Question 6

What is EDV?

Answer 6

The volume of blood present at the very end of the diastolic phase just prior to contraction

Question 7

What is ESV?

Answer 7

The volume of blood present inside the ventricle immediately after contraction is completed

Question 8

What is the purpose of increasing the force of contraction

(under sympathetic control)

Answer 8

Increases stroke volume which Increases the venous return

contraction of vascular
smooth muscle cells in the
veins

Question 9

What does parasympathetic control do to the atria and ventricles?

Answer 9

Has no effect on ventricles but decreased atrial contractility

less blood pumped into ventricles - drop in stroke volume

Question 10

What is the Frank-Starling Mechanism?

Answer 10

Increase of blood filling up the ventricles causes the muscle fibres to stretch more, leading to a greater force of contraction and increased stroke volume

only occurs within normal physiological range

Question 11

How does the Frank-Starling mechanism work?

In terms of actin and myosin fibres

Answer 11

Increase stretching causes actin and myosin fibres to stretch to their optimal levels

Question 12

What kind of receptors do atria have in them?

Answer 12

Atria have low pressure receptors and they detect changes in blood volume

Question 13

What happens when a higher blood volume is detected?

Answer 13

The stretch receptors in the atria detect this and the cardiovascular inhibitory centre is activated

cardiovascular inhibitory centre is in the medulla

Question 14

What kind of receptors are found in the aortic arch?

Answer 14

Baroreceptors sense wall stretch/ increase in blood volume

these are also found in the carotid arch

Question 15

What are the two things that a reduction in sympathetic input to the kidney does?

Answer 15

Dilates the afferent arterioles
inhinits the renin-angiotensin aldosterone system

Question 16

What is the effect of dilating the afferent arterioles in the kidney?

Answer 16

It increases the flow of blood to the glomerulus which increases the GFR, more blood is filtered therefore the overal volume is decreased

Question 17

What is the effect of inhibiting the renin system when blood volume is too high?

Answer 17

Less Na+ is absorbed into the blood therefore less water is absorbed and blood pressure decreases

Question 18

What is the effect of inhibiting vasopressin release from the pituitary gland?

Answer 18

Vasopressin acts on the tubules in the nephron to increase H20 uptake via aquaporins

Vasopressin increases blood volume/ pressure

Question 19

What is the function of ANP?

Answer 19

ANP increases loss of Na+ and H20 therefore reducing blood volume

Question 20

What is the effect of CO and O2 demand on tissues whilst you are sleeping?

Answer 20

There is a decreased demand for O2 causing CO levels to drop and blood is only supplied to vital organs

Question 21

What is the O2 and CO2 concentrations during exercise/ work?

Answer 21

Increased O2 consumption so more blood is required by the muscles

Increased heart rate and vasodilation