Heart Physiology

Question 1

What is an equation to calculate blood pressure?

Answer 1

Cardiac output x total peripheral resistance

Question 2

What constitutes cardiac output?

Answer 2

Heart rate x stroke volume

Question 3

What is total peripheral resistance?

Answer 3

Resistance to forward flow of blood from the left ventricle

Question 4

What is systolic pressure?

Answer 4

Blood pressure during left ventricular contraction

Question 5

What is diastolic pressure?

Answer 5

Blood pressure during left ventricular relaxation/elastic recoil of large arteries

Question 6

Reason for regulating blood pressure

Answer 6

Maintain steady blood flow to tissues and organs

Avoid ischaemia, necrosis

Question 7

Hagen-Poiseuille equation

Answer 7

Change in pressure = (8 x viscosity x length x flow)/(Pi x radius^4)

Question 8

What is the main implication of Hagen-Poiseuille equation?

Answer 8

A small change in the radius of a blood vessel has a large effect on blood pressure (radius to the power of four)

Injections have a maximum output/unit time

Question 9

Pulse pressure

Answer 9

Systolic - diastolic

Question 10

Mean arterial pressure

Answer 10

Diastolic + 1/3 x pulse pressure

Question 11

Features of the fast control system of blood pressure

Answer 11

Sensors are mainly stretch receptors in the aorta, carotid arteries

Neural linking to brainstem

Effectors are cardiac output, vasomotor tone

Question 12

Features of the slow control system of blood pressure

Answer 12

Sensors in kidneys

Receptors detect stretch in blood vessels, diffusion of electrolytes

Respond with hormones that influence vasomotor tone, fluid/electrolyte balance

Question 13

Sensors of the fast control system

Answer 13

Stretch receptors in the carotid sinus, aortic arch

Question 14

Which nerves connect the carotid sinus, aortic arch stretch receptors to the brain stem?

Answer 14

Cranial nerves IX, X

Question 15

What do cranial nerves IX and X do (related to blood pressure)?

Answer 15

Connect the carotid sinus and aortic arch stretch receptors (baroreceptors) to the brainstem

Question 16

What occurs when the baroreceptors in the carotid sinus and aortic arch detect an increase in blood pressure?

Answer 16

Send more impulses to the inhibitory centres of the brainstem

Question 17

Where is the vasomotor area located?

Answer 17

In the brainstem

Question 18

Inputs to the vasomotor area
1)
2)
3)
4)

Answer 18

1) Baroreceptors
2) Chemoreceptors
3) Skeletal muscle proprioceptors
4) Hypothalamus (body temperature)

Question 19

Afferents from the vasomotor area

Answer 19

Vagus nerve

Sympathetic nervous system

Question 20

What does the vagus nerve afferent do?

Answer 20

Leads to the cardiac inhibitory function

Removed if higher heart rate is required

Question 21

What is the effect of sepsis on blood pressure?

Answer 21

Decreases blood pressure (systemic vasodilation)

Question 22

Effects of sympathetic activity on blood pressure
1)
2)
3)
4)

Answer 22

1) Increase heart rate, stroke volume
2) capacitance vessels - veins - change diameter
3) Resistance vessels - arterioles - change diameter
4) Adrenal gland secretes adrenaline

Question 23

Effectors of blood pressure
1)
2)
3)
4)

Answer 23

1) Heart
2) Veins (capacitance vessels)
3) Arterioles (resistance vessels)
4) Adrenal gland

Question 24

What does vasoconstriction of capacitance vessels do?

Answer 24

Emptying of blood in reservoirs into circulation

EG: Splanchnic bed

Question 25

Example of abnormal CNS control of blood pressure

Answer 25

Harlequin syndrome

Question 26

What is Harlequin syndrome?

Answer 26

Asymmetrical flushing and sweating of thorax, neck, face

Question 27

How does the kidney respond to a decrease in blood pressure?

Answer 27

Secretes renin

Question 28

What does the kidney detect, apropos of blood pressure?

Answer 28

Stretch receptors, electrolyte balance

Question 29

What does angiotensin do?

Answer 29

Vasoconstriction

Secretion of aldosterone

Question 30

What is renin converted to?

Answer 30

Vasopressin

Question 31

What does aldosterone do?

Answer 31

Retain sodium and water in kidney.

Increases blood pressure

Question 32

Potential dangers of faliure of fluid regulation: overload

Answer 32

Pulmonary oedema

Wound dehiscence

Question 33

Local effects of exercise
1)
2)
3)
4)
5)

Answer 33

1) Blood flow to skeletal muscle increases 30x
2) Potassium, CO2, temperature rise, O2 fall
3) Temperature rise leads to vasodilation
4) Number of open capillaries increases 10-100-fold
5) up to 100-fold increase in O2 consumption

Question 34

Systemic effets of exercise
1)
2)
3)

Answer 34

1) Arterial dilation
2) Vasodilation
3) Adrenaline secretion

Question 35

Change in percentage of blood flow received by muscles at rest and during exercise

Answer 35

13% to 88%

Question 36

Change in percentage of blood flow received by kidneys at rest and during exercise

Answer 36

19% to 1%

Question 37

Change in percentage of blood flow received by stomach at rest and during exercise

Answer 37

21% to 1%

Question 38

Change in percentage of blood flow received by brain at rest and during exercise

Answer 38

13% to 3%

Question 39

Orthostatic hypertension
1)
2)
3)
4)
5)
6)
7)

Answer 39

1) Move from a lying to a standing position
2) Decrease in arterial pressure
3) Detected by baroreceptors (carotid, aortic)
4) Decrease in firing from arterial baroreceptors
5) Reflex via the medullary cardiovascular centre
6) Increase sympathetic/decrease parasympathetic signals to the heart
7) Increase heart rate, stroke volume, arteries and veins contract

Question 40

When are chemoreceptors in the aorta stimulated?

Answer 40

Only when the heart is severely lacking in blood supply

Question 41

How is blood redirected to different organs?

Answer 41

Constriction and dilation of arterioles

Question 42

Response to significant blood loss

Answer 42

1) Reduced stretch in baroreceptors
2) Inhibition of vagal cardiac inhibition
3) Increase in heart rate, stroke volume
4) Sympathetic constriction of arterioles in skin, veins in splanchnic circulation
5) Juxtoglomerular apparatus in kidney stimulated by decrease in blood pressure, filtering in kidneys –> kidneys release renin
6) renin-angiotensin, aldosterone lead to increased fluid retention