5: Control of arterial blood pressure (1)

Question 1

What is blood pressure?

Answer 1

The outward pressure exerted on the walls of blood vessels by blood

Question 2

What is systemic systolic arterial blood pressure?

Answer 2

The pressure exerted on the walls of the aorta and systemic arteries when the heart contracts

Question 3

The systemic systolic arterial blood pressure should be no more than ___ mmHg under resting conditions.

Answer 3

140 mmHg

Question 4

What is systemic diastolic arterial blood pressure?

Answer 4

The pressure exerted on the walls of the aorta and systemic arteries when the heart relaxes

Question 5

The systemic diastolic arterial blood pressure should be no more than __ under resting conditions.

Answer 5

90 mmHg

Question 6

Blood flows in normal arteries in a ___ fashion.

Answer 6

laminar

Question 7

Is normal arterial blood flow audible when using a stethoscope?

Answer 7

No - it’s silent

Question 8

What would you hear if you auscultated a normal, patent artery?

Answer 8

Nothing

Question 9

If an external pressure (e.g a pressure cuff) exceeding the systolic blood pressure is applied to an artery, blood flow is ___. What sound would you hear on auscultation?

Answer 9

blocked

Nothing.

Question 10

If external pressure is between the systolic and diastolic blood pressure of an artery, blood flow becomes ___ whenever blood pressure exceeds cuff pressure.

Answer 10

turbulent

Question 11

Is turbulent blood flow audible through a stethoscope?

Answer 11

Yes!

Question 12

What is the name of the series of sounds you hear when recording a patient’s blood pressure?

Answer 12

Korotkoff sounds

Question 13

When is the first Korotkoff sound heard?

Answer 13

Peak systolic blood pressure

Question 14

What is the 5th, last Korotkoff sound and when is it heard (in terms of blood pressure)?

Answer 14

Total lack of sound after a muffled/muted sound

Heard at diastolic blood pressure

Question 15

What drives blood around the systemic circulation?

What is this more commonly known as?

Answer 15

Pressure gradient between the aorta and the right atrium

MEAN ARTERIAL BLOOD PRESSURE (MAP)

Question 16

What is mean arterial blood pressure?

Answer 16

The average blood pressure during a single cardiac cycle

Question 17

Keeping in mind that the diastolic phase of the cardiac cycle is around twice as long as the systolic phase, give an equation for mean arterial blood pressure.

Answer 17

MAP = [(2x diastolic pressure} + systolic pressure] / 3

Exam format: MAP = Diastolic pressure + 1/3 (Systolic pressure - diastolic pressure)

Question 18

If systolic blood pressure is 120mmHg and diastolic blood pressure is 75mmHg, calculate mean arterial blood pressure.

Answer 18

90 mmHg

Question 19

What are the normal values for systolic and diastolic blood pressure?

Answer 19

Systolic: <140 mmHg

Diastolic: <90 mmHg

Question 20

What is the normal range for mean arterial blood pressure?

Answer 20

70 - 105 mmHg

Question 21

A mean arterial blood pressure of at least __ mmHg is required to perfuse the coronary arteries, brain and kidneys.

Answer 21

60 mmHg

Question 22

Why must mean arterial blood pressure be regulated?

Answer 22

1. High enough to perfuse the vital organs (>60 mmHg for coronary arteries, brain and kidneys)
2. Low enough not to damage the blood vessels or put extra strain on the heart

Question 23

Give an equation for mean arterial blood pressure.

Answer 23

MAP = Cardiac Output (CO) x Total Peripheral Resistance (TPR)

Question 24

What is cardiac output?

Answer 24

The volume of blood pumped by each ventricle per minute

Question 25

Give an equation for mean arterial blood pressure, breaking it down into its constituent parts.

Answer 25

MAP = CO x TPR

so MAP = SV x HR x TPR

Question 26

What is total peripheral resistance?

Answer 26

The sum of resistance of all peripheral vasculature in the systemic circulation

Question 27

Which vessels are responsible for major resistance?

Answer 27

Arterioles

Question 28

Which receptors are responsible for short-term responses to MAP?

Answer 28

Baroreceptors

Question 29

What is the control centre which integrates information re: changes in MAP?

Answer 29

Medulla

Question 30

The short-term regulation of MAP is an example of…

Answer 30

negative feedback.

Question 31

Where are the baroreceptors found?

Answer 31

1) Aortic arch
2) Carotid sinus

Question 32

Which cranial nerves carry signals from the aortic and carotid baroreceptors respectively?

Answer 32

Aortic signals carried by CN X - vagus nerve

Carotid signals carried by CN IX - glossopharyngeal nerve

Question 33

A person’s ___ changes can influence the MAP.

Answer 33

postural

Question 34

When a person suddenly stands up, venous return to the heart decreases due to…

Answer 34

gravity.

Question 35

When MAP decreases, what happens to the firing rate of the baroreceptors?

Answer 35

Firing rate decreases

Question 36

How does the nervous system respond to a sudden MAP change (e.g when standing up suddenly) to restore MAP to normal?

Answer 36

Vagal tone to the heart decreases

Sympathetic tone increases

This increases the heart rate and stroke volume.

Sympathetic constrictor tone increase - vasoconstriction, TPR increases

Venous return and therefore stroke volume increases

The rapid increases in the constituent parts of MAP help return it to normal.

Question 37

Which disease results from the failure of baroreceptor responses to gravitational shifts in the blood, e.g when moving from horizontal to vertical positions?

Answer 37

Postural _hypo​_tension

Question 38

Baroreceptors only respond to (acute / chronic) changes in blood pressure.

Answer 38

acute

Question 39

Control of what helps to control MAP in the long term?

Answer 39

Blood volume