Feedback control in the Cardiovascular system

Question 1

what is blood pressure?

Answer 1

the outwards “hydrostatic” pressure entered by blood on the blood vessels walls

Question 2

what is systolic blood pressure? + normal values

Answer 2

• the pressure entered by the blood on the walls of the aorta and systemic arteries when the heart contracts
• normally >140 mmHg (resting rate)

Question 3

what is diastolic blood pressure? + normal value

Answer 3

• the pressure exerted by the blood on the walls of the aorta and systemic arteries when the heart relaxes
• normally >90 mmHg (resting value)

Question 4

what is pulse pressure? + normal values

Answer 4

• the difference between systolic and diastolic blood pressure
• normally 30 -50 mmHg

Question 5

what is mean arterial blood pressure (MAP)? + normal values

Answer 5

• the average blood pressure during a single cardiac cycle
• must be regulated in a narrow range
• normally 70-105 mmHg
• MAP of at least 60mmHg is needed tp perfuse vital organs
• if MAP is too high, it puts strain on the heart/blood vessels

Question 6

how to calculate MAP (mean arterial blood pressure)

Answer 6

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

Question 7

what values are associated with hypertension?

Answer 7

• clinic blood pressure of 140/90 mmHg or higher
• daytime average of 135/85 mmHg or higher

Question 9

describe the control of blood pressure using baroreceptors?

Answer 9

• baroreceptors sense the change in blood pressure (sensitive to stretch)
• firing rate increases when MAP increase and decreases when MAP decreases
• Medulla receives afferent signals (via CN IX and X) and sends instructions to the effectors- heart and blood vessels
• Only respond to acute changes - firing decreases if high blood pressure is sustained

Question 10

what is cardiac output?

Answer 10

• volume of blood pumped by each ventricle of the heart per minute

Question 11

what is SVR?

Answer 11

• the sum of all resistance in the systematic circulation

Question 12

what is stroke volume?

Answer 12

• volume of blood pumped by each ventricle of the heart per heartbeat

Question 13

how to calculate cardiac output (CO)

Answer 13

CO = stroke volume (SV) x heart rate (HR)

Question 14

How to calculate MAP using SVR

Answer 14

MAP = SV x HR x SVR

Question 16

how is MAP regulated?

Answer 16

• MAP can be regulated by regulating HR, SV & SVR
• SV regulated by sympathetic nerves (Autonomic nervous system) - stimulation increase force of contraction
• HR is increased by sympathetic stimulation (Autonomic nervous system) - NORADRENALINE acts on beta1 receptors
• SVR regulated by vascular smooth muscles - sympathetic nerve fibres (autonomic nervous system)
• arterioles are the main resistance vessels

Question 16

describe vasomotor tone?

Answer 16

• vascular smooth muscles partially constricted at rest - caused by tonic discharge of sympathetic nerves

increased sympathetic discharge
- vasoconstriction