feedback control with cardiovascular system

Question 1

what is blood pressure?

Answer 1

outward pressure exerted by blood on blood vessel walls

Question 2

what is systolic blood pressure?

Answer 2

-pressure exerted by blood on the walls of the aorta and systemic arteries when the heart CONTRACTS
-normal 120 mmHg (resting)

Question 3

what is diastolic blood pressure?

Answer 3

pressure exerted by blood on the walls of the aorta and systemic arteries when the heart RELAXES
-normal 80 mmHg (resting)

Question 3

what is normal systolic range?

Answer 3

90-120 mmHg

Question 4

what is normal diastolic range

Answer 4

60-80 mmHg

Question 5

what is hypertension (what are the numerical values)?

Answer 5

-high blood pressure
-clinical bp 140/90 mmHg
-day time average 135/85 mmHg or higher

Question 6

what is pulse pressure?

Answer 6

different between systolic and diastolic blood pressures
-normal range 30-50 mmHg

Question 7

what is mean arterial blood pressure?

Answer 7

average arterial blood pressure during a single cardiac cycle (contraction/relaxation)

Question 8

what occurs during a normal cardiac cycle?

Answer 8

diastolic period is twice as long as the systolic period

Question 9

how is MAP calculated?

Answer 9

-MAP = [(2 x Diastolic) + Systolic] / 3 OR
MAP = Diastolic + (pulse pressure/3)

Question 10

what is the normal range of MAP?

Answer 10

70-105 mmHg

Question 11

what is the least amount of MAP needed and why?

Answer 11

-at least 60 mmHg
-needed to perfuse vital organs (brain/heart/kidney)

Question 12

why can the MAP not be too high?

Answer 12

-damages blood vessels (brain/kidney/eyes)
-extra strain on the heart

Question 13

what is hypotension?

Answer 13

-low blood pressure
-bp less than 90/60 mmHg

Question 14

what kind of mechanism does the CV system use?

Answer 14

negative feedback mechanism

Question 15

what are the sensors of the CV system

Answer 15

baroreceptors

Question 16

what are baroreceptors sensitive to?

Answer 16

pressure/stretch

Question 17

what do baroreceptors do?

Answer 17

when they detect stretch/pressure they send an impulse to the control centre (medulla)

Question 18

what happens when firing rate of baroreceptors increases?

Answer 18

-MAP increases

Question 19

what do baroreceptors regulate?

Answer 19

MAP

Question 20

what is the control centre of the CV system?

Answer 20

the medulla

Question 21

what does the medulla do?

Answer 21

receives afferent signals and sends instructions to the effectors (heart and blood vessels)

Question 22

what are the 2 types of baroreceptors?

Answer 22

-aortic baroreceptors
-carotid baroreceptors

Question 23

what is the nucleus tracts solitaries (NTS)?

Answer 23

1st synapse site for all CV system afferents in the medulla

Question 24

what are the effectors of the CV system?

Answer 24

-heart -blood vessels

Question 25

do baroreceptors respond to acute or chronic changes

Answer 25

-ONLY acute -firing rate will decrease if high blood pressure is sustained

Question 26

what varies in the heart as an effector?

Answer 26

-heart rate -stroke volume

Question 27

what varies in the blood vessels as an effector?

Answer 27

systemic vascular resistance

Question 28

how CAN MAP be calculated in relation to negative feedback?

Answer 28

MAP = Cardiac Output (CO) x Systemic Vascular Resistance (SVR)

Question 29

how is cardiac output (CO) calculated?

Answer 29

CO = Stroke Volume (SV) x Heart Rate (HR)

Question 30

what is cardiac output (CO)?

Answer 30

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

Question 31

what is stroke volume?

Answer 31

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

Question 32

what is systemic vascular resistance?

Answer 32

the sum of all resistance in the systemic circulation (everything BUT lungs)

Question 33

how ELSE CAN MAP be calculated in relation to negative feedback? (3 factors)

Answer 33

MAP = SV x HR x SVR

Question 34

how can MAP be regulated?

Answer 34

increasing/decreasing: -heart rate -stroke volume -systemic vascular resistance

Question 35

what is autorhythmicity?

Answer 35

hearts capability to beat rhythmically without external stimuli

Question 36

what is the heart modified by?

Answer 36

Autonomic (”involuntary”) Nervous system (ANS)

Question 37

what is the sympathetic division?

Answer 37

-simulation of the vagus nerve accelerates heart rate (tachycardia) -Noradrenaline acts on B1 receptors

Question 38

what is the parasympathetic division?

Answer 38

-simulation of the vagus nerve slows the heart rate (bradycardia) -Acetylcholine acts on muscarinic M2 receptors

Question 39

how is stroke volume regulated?

Answer 39

-sympathetic nerves -stimulation increases force of contraction

Question 40

how is heart rate increases

Answer 40

-sympathetic stimulation - noradrenaline acts on β1 receptors

Question 41

how is the systemic vascular resistance regulated?

Answer 41

vascular smooth muscles - sympathetic nerve fibres

Question 42

what are the main resistance vessels

Answer 42

arterioles

Question 43

what happens when there is a contraction of vascular smooth muscles?

Answer 43

-vasoconstriction -increases SVR and MAP

Question 44

what happens when there is a relaxation of vascular smooth muscles?

Answer 44

-vasodilation -decreases SVR and MAP

Question 45

what happens when there's an increase in BP

Answer 45

-barorecptors discharge increases -send impulse to medulla -decrease in sympathetic activity -increase in vagal (parasympathetic) activity →decreases HR →decreases SV (ventilation) (both cause decrease in CO) -decrease in sympathetic constrictor tone →vasodilation →decreases SVR This brings blood pressure back to normal (decreases BP)

Question 46

what happens when there's a decrease in BP

Answer 46

-barorecptors discharge is low -send impulse to medulla -increase in sympathetic activity -decrease in vagal (parasympathetic) activity →increase HR →increases SV (venoconstriction)(both cause increase in CO) -increase in sympathetic constrictor tone →vasoconstriction →increases SVR This brings blood pressure back to normal (increases BP)

Question 47

what is vasomotor tone?

Answer 47

tonic discharge of sympathetic nerves

Question 48

why are vascular smooth muscles partially constricted at rest?

Answer 48

continuous release of noradrenaline → because of tonic discharge

Question 49

what happens if there an increase in sympathetic discharge?

Answer 49

increase the vasomotor tone→ vasoconstriction

Question 50

what happens if there an decrease in sympathetic discharge?

Answer 50

decrease the vasomotor tone→ vasodilation

Question 51

is there any significant parasympathetic innervation of arterial smooth muscles?

Answer 51

no, except in penis and clitoris

Question 52

arterial and arteriolar smooth muscles are mainly supplied by....

Answer 52

sympathetic nerves