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Cardiovascular > Physiology > Flashcards

Physiology Flashcards

(100 cards)

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1
Q

what is automaticity

A

the ability of the heart to beat in the absence of external stimuli

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2
Q

what is normal sinus rhythm

A

automaticity originating from the sino atrial node

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3
Q

where is the SA node located

A

within the right atrium near the entrance of the SVC

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4
Q

what causes the wave of depolarisation within the SA node

A

K+ efflux

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5
Q

what causes the wave of repolarisation within the SA node

A

activation of L-type calcium channels and influx of calcium

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6
Q

describe calcium induced calcium release

A

increasing the concentration of intracellular calcium causes more to be released from the SR

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7
Q

what is the spread of the conduction of the heart after the SA node

A

atrio-ventricular node - bundles of His - perkinje fibres

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8
Q

the inner wall of the ventricles conduction is supplied by

A

perkinje fibres

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9
Q

where is the AV node located

A

base of the RA

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10
Q

the AV node slows/speeds up conduction between atria and ventricles

A

slows down

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11
Q

why is the speed of conduction slowed down at the AV node

A

to allow the atria to complete systole before the ventricles begin to contract

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12
Q

the AVN is the only point of conductivity between atria and ventricles true/false

A

true

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13
Q

in ventricular muscle action potential what is the change in voltage between phase 0 and phase 1

A

-90mV to +20mV

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14
Q

what does phase 0 of ventricular action potential represent

A

rapid Na influx

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15
Q

what does phase 1 of ventricular action potential represent

A

closure of Na channels

K efflux

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16
Q

what does phase 2 of ventricular action potential represent

A

Ca influx through L-type channels

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17
Q

what is phase 2 also known as and why

A

plateau phase because membrane potential is very close to its peak for some time

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18
Q

what does phase 3 represent

A

closure of Ca channels

K efflux

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19
Q

what does phase 4 of ventricular action potential represent

A

resting membrane potential at -90mV

closure of K channels

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20
Q

sympathetic nervous system __ heart rate and conductivity

A

increases

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21
Q

sympathetic nerves act act on __ mediated by __

A

B1 adrenoceptors mediated by adrenaline/noradrenaline

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22
Q

parasympathetic nerves ___ heart rate and conductivity

A

decrease conductivity but no effect on nodal cells

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23
Q

parasympathetic innervation through CN__

A

X

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24
Q

vagal tone increases/decreases the slope on pacemaker potential

A

decreases

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25
cardiac muscle is striated/non-striated
striated
26
what gives cardiac muscle its striated appearance
dark and light bands of myosin and actin
27
actin slides over myosin or myosin slides over actin?
actin slides over myosin
28
muscle fibres are arranged into what functional unit
sarcomeres
29
define stroke volume
volume of blood ejected by each ventricle per heartbeat | EDV - SSV
30
what does the frank-starling curve show
the more a ventricle is filled during diastole due to stretch of the myocytes, the greater the volume of ejected blood will be during followed contraction
31
heart failure has a negative inotropic effect - what does this mean
decreases contractility of the heart
32
define cardiac output
volume of blood ejected by each ventricle per minute | stroke volume x heart rate
33
what is the cardiac cycle describing
stages occurring from the beginning of one heart beat o the beginning of the next
34
what are the 5 events in the cardiac cycle
``` passive filling atrial contraction isovolumetric ventricular contraction ventricular ejection isovolumetric ventricular relaxation ```
35
what occurs during passive filling
pressure between atria and ventricles almost zero - AV valves open allowing passive venous return into ventricles
36
what % of blood moves from atria to ventricles by passive filling
80%
37
what occurs during atrial contraction
remaining volume moves between atria and ventricles | occurs between P and QRS complex
38
what happens during isovolumetric ventricular contraction
AV valves shut and pressure within the ventricles rises
39
what happens during ventricular ejection
ventricular pressure > aortic/pulmonary pressure so AV valves open
40
what happens during ventricular relaxation
blood moves through AV valves causing closure | ventricular pressure < atrial pressure so meaning AV valves open and new cycle starts
41
what is blood pressure
the outwards hydrostatic pressure exerted by the blood on vessel walls
42
systolic BP is during
contraction
43
diastolic BP is during
relaxation
44
the sounds heard when auscultating blood pressure are known as
Korotkoff sounds
45
1 korotkoff sound represents
systolic blood pressure
46
5/final sound represents
diastolic pressure - silence
47
what is the formula for calculating mean arterial blood pressure
(2xdiastolic + systolic)/3 1/3(systolic-diastolic + diastolic)
48
what is the normal range for mean arterial blood pressure
70-105mmHg
49
what are the main resistance vessels in the body
arterioles
50
what controls the short term regulation of blood pressure
baroreceptors
51
where are the baroreceptors located
aortic and carotid arteries
52
which cranial nerve supplies the carotid baroreceptor
glosspharyngeal nerve (CN IX)
53
which cranial nerve supplies the aortic baroreceptor
vagus nerve (CN X)
54
how do the baroreceptors change MAP
pressure sensors detect change in MAP - send signal to medulla - triggers effectors in heart to alter HR, SV, SVR
55
if blood pressure is high - baroreceptors causes HR, SV, SVR to increase/decrease
all decrease
56
what is postural hypotension
failure of the baroreceptors to respond immediately to a change in gravitational shift
57
postural hypotension is defined as
drop in systolic bp by 20mmHg or drop in systolic bp by 10mmHg plus dizziness, lightheadedness or blurred vision
58
what controls the long term regulation of blood pressure
regulation of extracellular fluid (composed of plasma volume and interstitial fluid) - through excess/deficit water and Na
59
what 3 hormonal systems regulate bp long term
RAAS natriuretic peptides ADH
60
what substance is released from the kidneys when bp is low
renin
61
renin goes on to activate __ regulated by which enzymes
angiotensin I - angiotensin II - aldosterone | angiotensin converting enzyme responsible for change
62
what effect does aldosterone have once released from adrenal cortex
causes sodium and water retention causing blood pressure to rise
63
natriuretic peptides provide the same/different response as RAAS
different - acts counter regulatory mechanism causing excretion of sodium and water
64
where is ANP released from
atria due to atrial distension
65
where is BNP released from
the brain in response to stretch in the ventricles
66
what is ADH
peptide hormone derived from pre-cursor in the hypothalamus | secretion stimulated by increase in extracellular fluid volume
67
what is the effect of ADH release
increases water reabsorption in kidney tubules and vasoconstriction of blood vessels
68
resistance to blood flow is directly proportional to
blood viscosity and length of vessel
69
resistance to blood flow is inversely proportional to
radius of the blood vessel to the power of 4
70
what is vasomotor tone
due to sympathetic stimulation blood vessels are partially constricted at rest
71
do parasympathetic nerves innervate arterial smooth muscle
no - except in the penis and clitoris
72
name some humoral agents that cause smooth muscle dilatation
histamine bradykinin nitric oxide
73
name some humoral agents that cause smooth muscle constriction
thromboxane | leukotrienes
74
define the term shock
abnormality of circulatory system resulting in decreased tissue perfusion
75
what is hypovolaemic shock
shock due to loss of blood volume - can be due to trauma, vomiting, diarrhoea
76
what causes cardiogenic shock
sustained hypotension due to reduced cardiac contractility. results in hypoperfusion of vessels
77
pneumothorax is an example of which type of shock
obstructive - SVC becomes obstructed and inter-thoracic pressure increases
78
what causes vasoactive shock
release of vasocative mediators such as NO causing excessive vasodilation
79
what causes neuorgenic shock
loss of sympathetic tone causing excessive vasodilation
80
compensatory mechanisms can maintain BP until how much blood is lost
30% of total volume
81
what is the bodys response to shock
increase sympathetic tone and vasoconstriction
82
what are some adaptations of coronary circulation to allow high oxygen demand
high number of capillaries high basal blood flow (at rest) high oxygen extraction rates
83
if the heart wants to increase oxygen to area what is done
must increase coronary blood flow because oxygen rate in blood is already so high
84
if coronary PO2 is low blood vessels vasodilate/vasoconstrict and why
vasodilate and oxygenation to that are needs to be improved
85
where specifically in the brain is very sensitive to hypoxia
grey matter
86
which arteries supply the brain
internal carotids | vertebral arteries
87
which arteries make up the circle of Willis
basilar and vertebral arteries
88
what range must cerebral blood pressure be within for correct perfusion and autoregulation
60-100mmHg
89
if MAP rises in cerebral circulation blood vessels dilate/constrict
dilate to decrease blood pressure
90
what blood pressure causes fainting and confusion in cerebral circulation
50mmHg or less
91
decrease in PCO2 causes vessels to
constrict
92
what causes a rise in intercranial pressure
trauma etc
93
what does an increase in intercranial pressure do to cerebral perfusion pressure and cerebral blood flow
reduces both
94
which substances can and cannot penetrate the blood brain barrier
O2 CO2 and glucose can all penetrate BBB | ions and proteins cannot
95
why can specific substances not pass the BBB
protects the neurones
96
what is the pressure within the pulmonary circulation
5-8mmHg
97
what mechanism prevents oedema in pulmonary circulation
absorptive forces are greater than filtration forces
98
hypoxia causes vaosdilatation/vasoconstriction in pulmonary arteries
vasoconstriction - diverts blood from poorly ventilated area of the lung
99
during exercise what happens to blood floow of skeletal muscle
increases
100
in skeletal muscle what overrides sympathetic vasoconstrictor activity
metabolic hyperaemia

Cardiovascular (8 decks)

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