regulation of mean arteriole blood pressure

Question 1

what is blood pressure

Answer 1

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

Question 2

what is systemic systolic arterial blood pressure

Answer 2

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

Question 3

what is systemic diastolic arterial blood pressure

Answer 3

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

Question 4

what is the ideal normal systolic arterial blood pressure range for an adult under 80

Answer 4

90-120mmHg

Question 5

what is the ideal normal diastolic arterial blood pressure range for an adult under 80

Answer 5

60-80mmHg

Question 6

what is hypertension defined as in a clinic and a daytime average

Answer 6

• clinic blood pressure of 140/90mmHg
• day time average of 135/85mmHg
  (hyper means high)

Question 7

why are the values for clinic blood pressure and daytime average different when talking about hypertension

Answer 7

because in a clinic peoples blood pressures may be altered by the environment e.g. feeling stressed whereas a day time average gives a more accurate result

Question 8

what does the ‘/’ mean in blood pressure

Answer 8

systolic/diastolic

Question 9

what is pulse pressure and what is a normal value for pulse pressure

Answer 9

the difference between systolic and diastolic blood pressure e.g. 120/80 mmHg, pule pressure = 40mmHg
- pulse pressure is normally between 30 and 50mmHg

Question 10

what is the mean arteriole blood pressure (MAP)

Answer 10

the average arterial blood pressure during a single cardiac cycle, which involves contraction and relaxation of the heart

Question 11

what is a cardiac cycle

Answer 11

all of the events that occur from the beginning of one heart beat to the beginning of the next

Question 12

why is the MAP not obtained by taking an average off the systolic and diastolic pressures

Answer 12

because the diastolic portion of the cardiac cycle is about twice as long as the systolic part
- therefor you can’t compare/average them as they weren’t over the same time frame

Question 13

what is the simplest way to measure the mean arterial blood pressure

Answer 13

MAP= [(2 X diastolic) + systolic] / 3
- in mmHg

Question 14

what is a less common way to measure the mean arterial blood pressure

Answer 14

MAP = diastolic + (1/3 of pulse pressure)
- pulse pressure = difference between systolic and diastolic blood pressure

Question 15

what is a normal range for mean arteriole blood pressure

Answer 15

70 - 105mmHg

Question 16

what is the minimum mean arteriole blood pressure required to survive and why

Answer 16

60mmHg
- this is the minimum needed to perfuse (provide blood to) vital organs like the brain, heart and kidneys
(fighting against gravity to get blood up to the brain)

Question 17

why must the MAP not be too high

Answer 17

because it could damage blood vessels or place an extra strain on organs like the brain, kidneys or eyes

Question 18

where are baroreceptors

Answer 18

found in the wall of blood vessels and the heart
- the main ones are the carotid baroreceptor (in the carotid artery in the neck) and the aortic baroreceptors (in the aorta)

Question 19

what will happen if there is a change in the mean arteriole blood pressure

Answer 19

• the change will be detected by baroreceptors and a message will be sent to the cardiovascular control centre in the medulla
• the control centre then sends a signal out to the effectors to bring about a change which counteracts the initial change
  e.g. heart; varying heart rate or stroke volume
  blood vessels; varying systemic vascular resistance

Question 20

what kind of receptors are baroreceptors

Answer 20

mechanoreceptors that are sensitive to stretch
(when the arterial blood pressure is adequate the walls of the artery stretch, too low and it won’t, to high and it’ll stretch too much)

Question 21

describe in detail what will happen when there is a change to the MAP

Answer 21

• baroreceptors will send afferent impulses to the cardiovascular control centre in the medulla of the brain stem
• the cardiovascular control centre receives CVS afferent information
• nucleus tractus solitarius (NTS) is site of the 1st synapse for all CVS afferents in the medulla
• NTS integrates and relays information to other regions that controls the pathways of the two divisions (parasympathetic and sympathetic) of the autonomic (“involuntary”) nervous system to heart and blood vessels

Question 22

what is the cardiac output (CO)

Answer 22

the total volume of blood pumped by each ventricle of the heart per minute
CO = stroke volume (SV) x heart rate (HR)

Question 23

what is stroke volume

Answer 23

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

Question 24

how can the MAP be calculated without the systolic or diastolic pressures

Answer 24

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

Question 25

what is systemic vascular resistance (SVR)

Answer 25

a sum of the resistance (used to create blood pressure) of all vasculature (blood vessels) in the systemic circulation

Question 26

how can the MAP be calculated using three different things

Answer 26

MAP = stroke volume x heart rate x systemic vascular resistance

Question 27

what 3 things could the mean arteriole blood pressure be regulated by

Answer 27

by regulating the - heart rate - stroke volume - systemic vascular resistance (like the equation)

Question 28

where are the electrical signals which control the heart generated and what does this mean

Answer 28

generated within the heart meaning the heart is capable of beating rhythmically in the absence of external stimuli - this is called autorhythmicity

Question 29

what is the heart modified by

Answer 29

the autonomic nervous system (ANS)

Question 30

what is tachycardia

Answer 30

acceleration of heart rate

Question 31

what is bradychardia

Answer 31

slowing down of heart rate

Question 32

how does the sympathetic division of the autonomic nervous system affect the heart

Answer 32

when stimulated, it accelerates the heart rate (tachycardia) - the neurotransmitter noradrenaline (norepinephrine in America ) acts on Beta1 receptors

Question 33

how does the parasympathetic division of the autonomic nervous system affect the heart

Answer 33

when stimulated it stimulates the vagus nerve (10th cranial nerve) and slows down the heart rate (bradycardia) - the neurotransmitter acetylcholine acts on muscarinic (M2) receptors

Question 34

what is stroke volume modified by and how is it controlled by this

Answer 34

the autonomic nervous system - sympathetic nerves innervate (supply an organ with nerves) the ventricular myocardium - stimulation increases the force of contraction and increases stroke volume (the vagus/parasympathetic nerve has little direct effect on ventricular contraction)

Question 35

when does stroke volume increase

Answer 35

when the contractile strength of the heart is increased

Question 36

what is intrinsic (within the heart itself) control of stroke volume controlled through

Answer 36

the Frank Starling mechanism

Question 37

what vessel has the most systemic vascular resistance

Answer 37

arterioles

Question 38

what is systemic vascular resistance regulated by and how

Answer 38

smooth muscle - contraction of vascular smooth muscle causes vasoconstriction and increases SVR and MAP (pressure upstream) - relaxation of vascular smooth muscle causes vasodilation and decreases SVR and MAP

Question 39

what type of nerve fibres are vascular smooth muscles supplied by

Answer 39

sympathetic nerve fibres - the neurotransmitter noradrenaline acts on alpha receptors

Question 40

what does vasomotor tone mean and what is this caused by

Answer 40

it means that vascular smooth muscles are partially constricted at rest (tense = tone) - caused by tonic discharge of sympathetic nerves resulting in continuous release of noradrenaline

Question 41

what is the only reason that the baroreceptor reflex will work

Answer 41

when there is an acute change to arterial blood pressure - their activity decrease if high arterial blood pressure is sustained

Question 42

what is control of MAP in the longer term controlled by

Answer 42

controlled by control of blood volume mainly via hormones

Question 43

describe the different routes that could be taken when MAP is acutely increased

Answer 43

diagram in ppt

Question 44

describe the different routs that could be taken when the MAP is actutely decreased

Answer 44

diagram in ppt

Question 45

what will an increase in sympathetic discharge cause

Answer 45

an increase in the vasomotor tone causing vasoconstriction (increase SVR and MAP - more pressure upstream)

Question 46

what will a decrease in sympathetic discharge cause

Answer 46

a decrease in vasomotor tone causing vasodilation (decreased SVR and MAP)

Question 47

is there much parasympathetic innervation of arterial smooth muscle

Answer 47

not significantly - the exceptions are the penis and the clitoris