Baroreceptor Reflex

Question 1

Define blood pressure

Answer 1

Outwards hydrostatic pressure exerted by the blood on blood vessel walls

Question 2

Define systemic systolic arterial blood pressure

Answer 2

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

Question 3

Define systemic diastolic blood pressure

Answer 3

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

Question 4

What is normal arterial BP?

Answer 4

Systolic = 90-120mmHg
Diastolic = 60-80mmHg

Question 5

Define hypertension

Answer 5

Clinic BP of 140/90mmHg or higher and daytime average of 135/85mmHg or higher

Question 6

Define pulse pressure

Answer 6

Difference between systolic and diastolic BP. Normally 30-50mmHg

Question 7

Define mean arterial BP (MAP)?

Answer 7

Average arterial BP during a single cardiac cycle which involves contraction and relaxation of the heart

Question 8

How is MAP estimated?

Answer 8

MAP = [(2x diastolic) + systolic] / 3
or MAP = DBP + 1/3 pulse pressure

Question 9

What MAP is needed to perfuse vital organs?

Answer 9

at least 60mmHg

Question 10

What happens when MAP deviates from set point?

Answer 10

Baroreceptors detect change and inform control centre in the medulla. This instructs the heart and blood vessels to bring about compensatory response (varying HR and stroke volume, and varying systemic vascular resistance respectively). This results in restoration of MAP to desired range

Question 11

Where are baroreceptors located and how do their signals reach medulla?

Answer 11

Carotid baroreceptors in carotid sinus - signal via CNIX
Aortic baroreceptors in aorta signal via CNX

Question 12

What happens in the medulla when MAP changes?

Answer 12

Receives CVS afferent information from baroreceptors. These synapse in nucleus tractus solitarius which integrates and relays information to other regions that control sympathetic and parasympathetic pathways

Question 13

What is MAP equal to?

Answer 13

MAP = cardiac output (CO) x systemic vascular resistance (SVR)
MAP = SV x HR x SVR

Question 14

What is cardiac output? What is it equal to?

Answer 14

Volume of blood pumped by each ventricle of the heart per minute. CO = Stroke volume (SV) x HR

Question 15

What is stroke volume?

Answer 15

Volume of blood pumped by each ventricle of the heart per heart beat

Question 16

What is systemic vascular resistance?

Answer 16

Sum of resistance of all vasculature in the systemic circulation

Question 17

How is stroke volume modified?

Answer 17

Regulated by ANS sympathetic nerves. If stimulated, increases force of contraction and stroke volume. SV increases if contractile strength of heart is increased.