Physiology- Feedback Control from the CVS

Question 1

Blood pressure

Answer 1

the outward hydrostatic pressure exerted by the blood on the vessel walls

Question 2

How is systemic arterial blood pressure expressed in clinical practice?

Answer 2

As systolic and diastolic blood pressure

Question 3

Systemic systolic arterial blood pressure

Answer 3

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

<140mmHg

Question 4

Systemic diastolic arterial blood pressure

Answer 4

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

<90mmHg

Question 5

Hypertension

Answer 5

Clinical BP >140/90mmHg

Day time average BP of >135/85mmHg

Question 6

Pulse pressure

Answer 6

Difference between systolic and diastolic blood pressure

30-50mmHg

Question 7

Mean Arterial Blood Pressure

Answer 7

The average arterial blood pressure during a single cardiac cycle

Question 8

Why is MAP not obtained by averaging the systolic and diastolic pressures?

Answer 8

diastole lasts approx 2x as long as systole

Question 9

How do you calculate MAP?

Answer 9

[(2xdia)+sys]/3

dia+(PP/3)

Question 10

Normal range of MAP and minimum value needed to perfuse brain, heart and kidneys

Answer 10

normal range: 70-105mmHg

min: 60mmHg

Question 11

Name the controlled variable, sensor, control centre and compensatory response in the context of negative feedback response for blood pressure

Answer 11

CV: MAP
S: baroreceptors
CC: medulla
E: heart and blood vessels
CR: HR, SV, SVR

Question 12

Where are the carotid baroreceptors found and how do their signals reach the medulla?

Answer 12

Carotid sinus

via the IXth CN

Question 13

Where are the aortic baroreceptors found and how do their signals reach the medulla?

Answer 13

Aorta

via the Xth CN

Question 14

What kind of receptors are baroreceptors?

Answer 14

Mechanoreceptors which are sensitive to stretch

Question 15

if MAP increases, what happens to the firing rate in baroreceptor afferent neurones?

Answer 15

Increases

Question 16

Where is the site of the first synapse for all CVS afferents in the medulla and what does it do?

Answer 16

Nucleus Tractus Solitarius

relays info to other regions of the brain

Question 17

What happens when the NTS relays info to other regions of the brain?

Answer 17

it generates vagal outflow to the heart, relays to the nucleus ambiguous and regulates spinal sympathetic neurones

Question 18

Relationship between MAP, CO and SVR

Answer 18

MAP= CO x SVR

Question 19

Cardiac output

Answer 19

the volume of the blood pumped by each ventricle per minute

CO=SVxHR

Question 20

Stroke volume

Answer 20

Vol of blood pumped by each ventricle per heart beat

Question 21

Systemic Vascular Resistance

Answer 21

Sum of resistance of all vasculature in the systemic circulation

Question 22

Autorhythmicity

Answer 22

the heart is capable of beating rhythmically in the absence of external stimuli

Question 23

How does sympathetic division cause tachycardia?

Answer 23

noradrenaline acts on B1 receptors

Question 24

How does parasympathetic division cause bradycardia?

Answer 24

Acetylcholine acts on muscarinic receptors, stimulating CNX/vagus nerve

Question 25

What regulates SVR?

Answer 25

Vascular smooth muscle Arterioles are the main site SVR

Question 26

How does contraction of vascular smooth muscle effect MAP?

Answer 26

Causes vasoconstriction, increasing SVR and MAP

Question 27

Which type of nerve fibres supply vascular smooth muscle and what is the nt involved?

Answer 27

Sympathetic noradrenaline acting on alpha receptors

Question 28

Vasomotor tone

Answer 28

Vascular smooth muscle is partially constricted at rest

Question 29

What causes vasomotor tone?

Answer 29

tonic discharge of sympathetic nerves, resulting in continuous release of noradrenaline

Question 30

In what circumstances do baroreceptors respond?

Answer 30

acute changes