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Cardiovascular system > Regulation of stroke volume & heart rate > Flashcards

Regulation of stroke volume & heart rate Flashcards

1
Q

what are the effects of the sympathetic system on heart rate

A

the sympathetic nervous system releases the hormones to accelerate the heart rate

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2
Q

what are the effects of the parasympathetic system on heart rate

A

stimulating the parasympathetic nervous system increases the resting potential and decreases the rate of diastolic depolarisation; under these circumstances the heart rate slows

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3
Q

what is the effect of the sympathetic system on stroke volume

A

stroke volume increases,

heart rate and contractility also increases

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4
Q

what activates the sympathetic nervous system

A

exercise

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5
Q

what are the effects of preload on stroke volume

A

increase in stroke volume

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6
Q

what are the effects of after load on stroke volume

A

increasing after-load reduces stroke volume

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7
Q

what is after-load

A

it is the stress in the wall of the left ventricle during ejection, i.e. it is the end load against which the heart contracts to eject blood

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8
Q

what are the components after-load is broken into

A

one factor is the aortic pressure the left ventricular muscle must overcome to eject blood

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9
Q

what are factors that affect after-load

A

age
increased blood pressure
hypertension
constriction of the arteries

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10
Q

what else does increasing after-load effect, apart from reducing stroke volume

A

increasing after-load also increases left ventricular end-diastolic pressure

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11
Q

what does preload refer to

A

the end diastolic volume that stretches the right or left ventricle of the heart to its greatest dimensions under variable physiologic demand

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12
Q

what does after load to

A

it is the end load against which the heart contracts to eject blood

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13
Q

after load is readily broken into components, describe one factor

A

it is the aortic pressure the left ventricular muscle must overcome to eject blood

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14
Q

what forms the atrioventricular node

A

pacemaker cells

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15
Q

where is the atrioventricular node

A

the area between the ventricles

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16
Q

describe how sympathetic nerves control heart rate

A

sympathetic nerves release noradrenaline, which acts on beta receptors on the sinoatrial node, which increases pacemaker potential - leading to tachycardia - an increased heart rate

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17
Q

how do sympathetic nerves control heart rate

A

sympathetic nerves increase heart rate

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18
Q

describe parasympathetic and sympathetic activity whilst you are doing exercise

A

parasympathetic activity decreases

sympathetic activity increases

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19
Q

describe parasympathetic and sympathetic activity at rest

A

parasympathetic and sympathetic nerves always have ongoing activity at rest

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20
Q

where are beta 1 receptors present

A

on the sinoatrial node

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21
Q

describe how parasympathetic nerves control heart rate

A

parasympathetic nerves hyperpolarise the cells in the sinoatrial node

  • resulting in it taking longer for the pacemaker potential to reach threshold
  • making the interval between each heart beat longer
  • resulting in bradycardia
  • the heart rate is slowing down
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22
Q

how does the parasympathetic nerves control heart rate

A

parasympathetic nerves act to decrease heart rate

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23
Q

what does acetylcholine bind to

A

muscarinic receptors

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24
Q

what is the vagus

A

each of the 10 pairs of cranial nerves

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25
what does the vagus supply
the heart, lungs, upper digestive tract, and other organs of the chest and abdomen
26
what do the 10 pairs of cranial nerves release
acetylcholine
27
describe how the vagus controls heart rate
- the vagus releases acetylcholine - acetylcholine acts on muscarinic receptors on the sinoatrial node - the pacemaker cells in the sinoatrial node hyper-polarise - the slope of the pacemaker potential decreases - resulting in the heart rate decreases = bradycardia
28
how does the vagus control heart rate
the vagus decreases the heart rate activity of the 10 pairs of cranial nerves = bradycardia
29
describe starling's law
the energy of contraction is proportional to the initial length of the cardiac muscle fibre
30
how is tension formed
by the myosin cross bridges
31
what is the result of more cross bridges
the stronger contraction you can produce
32
what is the result of a shorter acting muscle length
the actin filaments start interfering with one another, therefore there is not as good cross bridge formation, therefore there is a weaker strength of contraction
33
in cardiac muscle what does stretching of a muscle fibre depend on
the end diastolic volume - how much blood is in the ventricle at the end of the filling phase
34
describe the ventricle filling phase and contraction relationship
the more blood you have squeezed into the ventricle during the filling phase will stretch that muscle more, therefore the more contraction you are going to get
35
describe preload
the amount of stretch put on a muscle before it starts to contract
36
in life what is preload affected by
the end diastolic volume
37
because preload is affected by the end diastolic volume, what can end diastolic volume plotted against
stroke volume
38
what is stroke volume
the amount of blood pumped by the left ventricle of the heart in one contraction
39
what is the volume of stroke volume normally
NOT all the blood contained in the left ventricle it is normally 2/3s of the blood in the ventricle 2/3s of the blood in the ventricle is expelled with each beat
40
what is end diastolic volume
it is the volume of blood in the right and/or left ventricle at end load i.e. the end of the filling phase
41
what is the end diastolic volume essentially
the amount of blood in the ventricles just before systole
42
what is systole
the phase of the heartbeat when the heart muscle contracts and pumps blood from the chambers into the arteries
43
what is the result if stronger tension is induced
the heart will eject more blood
44
what is the result if you squeeze more blood into the heart
you get more stretch on the muscle, therefore the strength of contraction is stronger
45
what is the consequence of preload being affected by the end diastolic volume
stroke volume is resultantly affected
46
what does stroke volume increase in response to
an increase in the end diastolic volume when all other factors remain constant
47
what does the starling curve describe
that the amount of blood pumped by the left ventricle of the heart on one contraction increases as the volume of blood filing the heart increases, this is when all other factors remain constant
48
how does cardiac muscle respond to more/excess blood coming back to the heart resulting in a bigger end diastolic volume
the cardiac muscle is just going to contract harder and you will get a bigger stroke volume
49
what is the result if less blood comes back to the heart?
decreased end diastolic volume decreased preload decreased stroke volume
50
what is the result of an increased end diastolic volume
an increased stroke volume
51
what is the result of a decreased end diastolic volume
aa decreased stroke volume
52
describe the blood pumped on both sides of the heart
the left and right sides of the heart always pump the same amount of blood
53
why is the heart rate on both sides of the heart the same?
because they share the same pacemaker, so stroke volume has to be the same as well
54
what is venous return
it is the rate of blood flow back to the heart
55
what does venous return limit
cardiac output
56
what is after load in relation to the heart
it is the force that the muscle is trying to work against
57
describe afterload
it is the pressure against which the heart must work to eject blood during systole
58
what is stopping the pushing of the opening of the aortic valve
the mean arterial pressure
59
what does total peripheral resistance affect
the aortic pressure
60
what is aortic pressure
the blood pressure at the root of the aorta
61
what does an increase in total peripheral resistance result in
increase in aortic pressure decrease in stroke volume as the ventricle will have to work harder to push open the aortic valve therefore there is less energy to eject blood
62
what is afterload set by
the arterial pressure
63
what does arterial pressure depend on
the total peripheral resistance
64
what types of vessels are venules/veins
capacitance vessels - hold blood
65
what do venules/veins affect
preload
66
what types of vessels are arterioles
resistance vessels they stop the blood getting out, they redirect blood to different regions of the body when you want to
67
what do arterioles affect
afterload
68
what do you affect each time you are contracting the capacitance vessels
you are affecting the preload
69
what is the affect on stroke volume when arterioles are constricted
stroke volume decreases
70
in relation to the sympathetic system describe how sympathetic nerves regulate stroke volume
- sympathetic nerves release noradrenaline and adrenaline from the adrenal medulla - both then act on beta 1 receptors on the myocytes - this increases contractility - this gives a stronger but shorter contraction - therefore increases stroke volume
71
describe how sympathetic nerves affect stroke volume
stroke volume increases by increasing contractility
72
describe how parasympathetic nerves affect stroke volume
can be increased or decreased | these nerves really have very little effect on stroke volume as they have very little to do with contractility
73
where do parasympathetic nerves innervate
parasympathetic nerves innervate at the top of the heart and nodes quite a lot but don't quite get down to the ventricles therefore stimulating these nerves does next to nothin to the strength of contraction
74
state four ways of pathological regulation of stroke volume
hypercalcemia hypocalcemia ischaemia barbiturates
75
describe how hypercalcemia can regulate stroke volume
as there is more calcium coming in during the cardiac action potential more cross bridges are being formed
76
what is hypercalcemia
high calcium concentration in plasma
77
describe how hypocalcemia can regulate stroke volume
less calcium coming in curing the cardiac action potential results in weaker cardiac contraction starling curve shifts down and to the right
78
describe how ischaemia can regulate stroke volume
due to poor bloody supply, the effected side of the heart is going to contract less strongly starling curve shifts down and to the right
79
how do barbiturates regulate stroke volume
they depress the action of the heart and shift the starling curve down and to the right
80
what is cardiac output equal to
it is heart rate multiplied by stroke volume
81
what is the average cardiac output equal to
5 lites a minute
82
what is the result of an electronic pacemaker
increase heart rate decrease cardiac output decrease stroke volume because decrease end diastolic volume decrease preload decrease stroke volume
83
what is the result of a physiological pacemaker e.g. exercise natural reaction
``` increase heart rate decrease vagal tone increase sympathetic tone increase venous return increase contractility decrease systole decrease total peripheral resistance decrease afterload increase cardiac output ```
84
how do sympathetic nerves regulate heart rate
increases heart rate
85
how do parasympathetic nerves regulate heart rate
decreases heart rate
86
in terms of stroke volume regulation, what is the result when preload is equal to end diastolic volume
increase in stroke volume
87
in terms of stroke volume regulation, what is the result when after load is equal to end diastolic volume
decrease stroke volume
88
describe neural regulation of stroke volume
sympathetic nerves increase stroke volume

Cardiovascular system (34 decks)

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