Physiology Flashcards
(162 cards)
1
Q
What is autorhymicity
A
electrical signals generated by the heart, capable of beating in the absence of external stimuli
2
Q
where does heart excitation occur
A
SAN
3
Q
if the heart is controlled by SAN it is said to be in ____
A
sinus rhythm
4
Q
what is pacemaker potential
A
slow depolarisation occurring due to decrease in potassium efflux and constant sodium influx and transient calcium influx from T type calcium channels
5
Q
what type of calcium channel causes rapid depolarisation of pacemaker cells?
A
L-type channels
6
Q
what causes repolarisation of pacemaker cells
A
inactivation of L-type calcium channels and activating potassium channels
7
Q
how do impulses from SAN reach AVN
A
gap junctions
8
Q
where do electrical impulses travel from AVN
A
bundle of his, dividing into purkinje fibres
9
Q
where is the AVN located
A
base of right atrium
10
Q
why are impulses delayed in AVN
A
to allow atrial systole to precede ventricular systole
11
Q
what is phase 0 of cardiac muscle
A
depolarisation by fast Na influx from -90 to +20mV
12
Q
What is phase 1 cardiac muscle
A
closure of Na channels and transient potassium efflux
13
Q
what is phase 2 cardiac muscle
A
calcium influx (L-type). plateau phase for few hundred milliseconds
14
Q
what is phase 3 cardiac muscle
A
repolarisation by calcium channel closure and potassium efflux
15
Q
what is phase 4 cardiac muscle
A
resting potential
16
Q
true/false - vagal done is dominant in resting conditions
A
true
17
Q
ACh acts on M_ receptors
A
2
18
Q
where may atropine be used and what does it do
A
extreme bradycardia
competitive antagonist of ACh
19
Q
ACh has a ____ chronotropic effect
A
negative
20
Q
sympathetic nerves supply
A
SAN, AVN, myocardium
21
Q
noradrenaline acts on
A
Beta 1 adrenoceptors
22
Q
noradrenaline causes a ____ chronotropic effect
A
positive
23
Q
Lead I ECG has electrodes on?
A
Left and right arm and earth on right leg
24
Q
Lead II ECG has electrodes on?
A
right arm and left leg with ground on right leg
25
Lead III ECG has electrodes on?
left arm and left leg with ground on right leg
26
true/false- cardiac muscle has nervous innervation
false - they are electrically coupled by gap junctions
27
cardiac muscle contains ____ which contains the contractile proteins ____ and ____
myofibril
| actin and myosin
28
how does calcium aid muscle contraction
causes a conformational change in troponin and tropomyosin to expose actin binding site to myosin binding site
29
What do T tubules of the sarcoplasmic reticulum carry?
action potentials
30
when calcium enters a cardiac myocyte it binds to channels on the SR. what does it cause
calcium induced calcium release
31
what si the refractory period
period following an action potential where it isn't possible to have another
32
why is the refractory period good for the heart
prevents generation of tetanic contraction
33
what is stroke volume
volume of blood ejected by the ventricle per minute
34
SV=?
EDV-ESV
35
what does starlings law state
the more the ventricle is filled with blood in diastole, the greater the volume ejected during systole
36
why does cardiac muscle stretch cause better contraction
calcium binds to troponin better so more myosin heads bind to actin for stronger contraction
37
does starlings law support ventricular matching of stroke volume
yes it does
38
what is afterload
resistance into where the heart is pumping
39
afterload prevents a full SV ejection. how else can the heart pump more blood out?
increases EDV so force of contraction is increased
40
noradrenaline causes a ____ inotropic effect
positive
41
noradrenaline causes increased cardiac contractility. what does this do to the frank starling curve?
left shift and slightly upwards
42
true/false - the parasympathetic system has innervatioon all over the heart
false - only over the atria
43
what is cardiac output
volume of blood pumped by each ventricle per minute
| CO=SV x HR
44
what is cardiac cycle
events occurring from one heartbeat to next
45
how long does diastole usually last
around 0.5s at 75 bpm
46
how long does systole usually last
around 0.3s at 75 bpm
47
during passive filling do the atria or ventricles have a higher pressure?
atria
48
what is the aortic pressure at passive filling roughly
80mmHg
49
atrial contraction is seen by what wave on ECG
P wave
50
what happens in isovolumetric ventricular contraction
ventricular pressure exceeds atrial pressure to close AV valve to produce S1
sharp pressure rise before opening of aortic valve
51
when does the aortic/pulmonary valve open
when ventricular pressure exceeds arterial pressure
52
what produces the dicrotic notch
vibration from closure of the aortic valve
53
isovolumetric ventricular relaxation is...
fall in ventricular pressure following systole
| when below atrial pressure AV valves open
54
S1 is caused by
closure of AV valves
55
S2 is caused by closure of?
Aortic and pulmonary valves
56
4 points of auscultaton
right of sternum 2nd intercostal
left of sternum 2nd intercosal
sternal edge 4th intercostal
5th intercostal mid clavicular line
57
why does aortic pressure not drop to zero during diastole
presence of elastic recoil
58
the pressure of JVP fluctuates with?
pressure change in the right atrium
59
what is blood pressure
hydrostatic pressure exerted by blood on blood vessel walls
60
how can hypertension be defined
clinical blood pressure of >140/90 mmHg or daytime average of >135/85
61
what is pulse pressure and what is the usual value
difference between systolic and diastolic BP, usually 30-50 mmHg
62
what is the equation for the driving pressure gradient of systemic circulation
Pressure gradient = MAP - CVP
63
What is MAP and how is it calculated?
Average arterial blood pressure in a single cardiac cycle
| ((2 x DBP) + SBP)/3
64
what is the normal range of MAP
70-105 mmHg
65
what MAP is required to perfuse brain, coronary arteries and kidneys
at least 60mmHg
66
what is SVR and what has the most resistance
systemic vascular resistance, sum of all resistance in vasculature. arterioles have the most resistance
67
BP postural changes are managed by what reflex
baroreceptor reflex
68
aortic baroreceptors signal via____
vagus nerve
69
carotid baroreceptors signal via _____
glossopharyngeal nerve
70
postural hypotension is caused by?
failure of baroreceptor responses to gravitational shifts
71
a positive result of postural hypotension is...
drop of systolic bp +/- symptoms by 20 mmHg in 3 mins OR
| drop of diastolic bp +symptoms by 10 mmHg
72
can baroreceptors lower chronically high BP
no, they reset to a higher BP
73
in the long term control of BP, what happens when plasma volume falls
fluid is shifted from interstitial fluid to plasma compartment
74
what two factors affect ECFV
water excess/deficit
| sodium excess or deficit
75
what does renin do
produced in kidneys and converts angiotensinogen to angiotensin I
76
what does angiotensin do?
ACE converts angiotensin I to angiotensin II
Systemic vasoconstriction
thirst and ADH release
Aldosterone release
77
what does aldosterone do?
increases sodium and water retention in kidneys
78
what stimulates renin production
renal artery hypotension
stimulation of renal sympathetic nerves
decreased sodium in renal tubular fluid
79
NPs are released in response to?
cardiac distention
80
what do NPs do?
cause kidney excretion of salt and water
decrease renin release
vasodilators to reduce SVR
81
two types of NP
ANP
| BNP
82
where is ANP stored/released
response to atrial distention
| atrial myocytes
83
what is the conversion for BNP
prepro-BNP to pro-BNP to BNP
84
where might serum BNP and pro-BNP be of use?
suspected heart failure
85
when is ADH released
reduced ECVF or increased ECF osmolality
86
what does ADH do
water reabsorption to concentrate urine
| small vasoconstriction- important in hypovolaemic shock
87
what vessels acciunt for the majority of SVR
arterioles
88
resistance to blood flow is directly proportional to _____ and ______ and inversely proportional to _____ by power 4
blood viscosity
blood vessel length
blood vessel radius
89
what is vasomotor tone?
tonic discharge of noradrenaline by sympathetic nerves on vascular smooth muscle
90
true/false - there is no parasympathetic innervation in vascular smooth muscle
false - there is in the penis and clitoris
91
adrenaline binding to alpha receptors causes...
vasoconstriction, in skin, gut and kidney
92
adrenaline binding to beta 2 receptors causes
vasodilation, in skeletal and cardiac muscles
93
angiotensin II acting on arterioles causes
vasoconstriction
94
ADH acting on arterioles causes
vasoconstriction
95
what local metabolites cause vasodilation and metabolic hyperaemia
```
increased local PCO2
increased H concentration (lower pH)
Increased extracellular potassium
increased osmolality of ECF
Adenosine release
```
96
what chemical agents cause vasodilation
histamine
nitric oxide
bradykinin
97
Nitric acid lasts how long and is secreted in response to?
a few seconds
| calcum release from endothelial stress
98
chemical agents causing vasoconstriction?
serotonin
thromboxane A2
leukotrienes
endothelin
99
endothelial produced vasodilators are pro/anti thrombotic, pro/anti inflammatory and pro/anti oxidant
anti thrombotic, anti inflammatory and antioxidant
100
endothelial produced vasoconstrictors are pro/anti thrombotic, pro/anti inflammatory and pro/anti oxidant
pro thrombotic, pro inflammatory and pro oxidant
101
cold causes vaso___
constriction
102
what is sheer stress on arterioles
arteriole dilation that causes further dilation to upstream arteries
103
what is the myogenic response
regulation of blood flow to brain to maintain blood pressure at constant levels
104
true/false- capillaries contain most of the bodys blood supply
false- veins do
105
venomotor tone increases
venous return, SV and MAP
106
skeletal muscle pump aids
venous return
107
how does the respiratory pump aid venous contraction
decrease in intrathoracic pressure and increase in intr-abdominal pressure on inspiration. causes increased pressure gradient for venous return
108
4 ways venous return is increased
blood volume
skeletal muscle contraction
respiratory pump
venomotor tone
109
metabolic hyperaemia can overcome vasomotor tone in exercise to cause ____
vasodilation
110
an increase in CO increases ____ BP and decreses _____ BP, causing an increase in _____
systolic
diastolic
pulse pressure
111
heart rate increase by sympathetic nerves does what to SAN and AVN
increases SAN firing rate
| decreases AVN delay
112
chronic cardiovascular responses to exercise
decreased levels noradrenaline and sympathetic tone
cardiac remodelling
Renin level decrease
less endothelial vasoconstrictors and more vasodilators
lowered arterial stiffening
113
what is shock
inadequate tissue perfusion and oxygenation resulting in anaerobic metabolism and accumulation
114
what is hypovolaemic shock
loss of blood volume decreasing venous return, EDV, SV, CO, BP and perfusion
115
what is cardiogenic shock
hypotension caused by decreased cardiac contractility
| decreased contractility lowers SV, CO, BP
116
what is obstructive shock and explain the mechanism within pneumothorax
shock due to obstruction
PTX increases intrathoracic pressure and decreases venous return
EDV decreases, SV, CO and BP
117
what is neurogenic shock
loss of sympathetic tone causing massive vaso/velodilation and decreased heart rate
Venous return, SVR and HR lost, CO decreased and BP
118
what is vasoactive shock
vasoactive mediator release causing massive veno/vasodilation
increased capillary permeability and loss of volume and vasodilation decrese venous return, EDV, SVR, SV, CO, BP
119
how do you treat shock
```
high flow O2
volume replacement (except cardiogenic, give inotropes)
chest drain tension PTX
adrenaline for anaphylaxis
vasopressors for septic shock
```
120
what is hypovolaemic shock caused by?
haemorrhage
| vomiting, diarrhoea, excess sweating
121
compensatory mechanisms maintain BP up to __% blood loss
30%
122
haemorrhagic shock presents as
small volume pulse and rapid
cool peripheries
decreased MAP
confusion, lethargy, coma if cerebral blood flow lost
123
what is TLOC
real or apparent loss of consciousness with loss of awareness and amnesia
loss of motor control, loss of responsiveness for short duration
124
causes of TLOC
TLOC mimic
head trauma
syncope
epileptic seizure
125
what is syncope
TLOC due to cerebral hypoperfusion with short duration and spontaneous complete recovery
126
what is reflex syncope
neural reflexes cause cardioinhibition and vasodepression to cause systemic hypotension
127
cardioinhibition is by ___ stimulation
vagal
128
vasodepression is caused by
depression of sympathetic activity to blood vessels
129
what is vasovagal syncope caused by and what is the commonality
very common
| caused by emotional distress or orthostatic distress
130
symptoms of vasovagal syncope, treatment and main main worry
nausea, dizziness, pallor, sweating
leg crossing or horizontal gravity to enhance venous return
injury when falling
131
what is situational syncope and how is it treated
syncope in response to a trigger
| treat cause if possible and consider cardiac pacing
132
what is carotid sinus syncope, who is it common in and treatment
syncope triggered by mechanical manipulation of neck, shaving or tight collar
elderly males
cardiac permanent pacing
133
what is orthostatic syncope and risk factors
failure of baroreceptor response to gravitational shifts in blood
age, prolonged bed rest, medicarions, disease, reduced intravascular volume
134
symptoms and diagnosis of orthostatic hypotension
lightheadedness, blurred vision, dizziness
in 3 mins:
drop in systolic of 20mmHg +/- symptoms
drop in diastolic of 10mmHg with symptoms
135
first steps for patient with TLOC
history
12 lead ECG
full physical exam
orthostatic BP measurement
136
what is cardiac syncope
cardiac event causing sudden CO drop, arrythmia, MI, structural disease, PE, aortic dissection
137
features that suggest cardiac syncope
```
structural abnormality of coronary heart disease
FHx sudden death young age
sudden palpitations before syncope
ECG arrythmia
syncope when supine or excretion
```
138
3 special features of coronary circulation
high basal blood flow
high capillary density
high oxygen extraction
139
3 ways to intrinsically cause vasodilation of coronary arteries?
decreased pCO2
metabolic hyperaemia
adenosine release
140
in which phase of pressure does coronary flow occur
diastole
141
when may coronary flow be reduced?
tachycardia, diastole would be shortened so blood flow limited
142
when adrenaline binds to B2 receptors does it cause vasodilation or vasoconstriction?
vasodilation
143
explain how sympathetic activity on the heart causes a vasodilator effect on coronary arteries
coronary arteries directly constricted but increased SV and HR causes metabolic hyperaemia, forcing them open
144
what supplies the brain with blood
internal carotids and vertebral arteries
145
what is the circle of willis and why is it good
basilar and carotids anastomose to form a circle of arterial blood supply
prevents total loss of cerebral perfusion if supply from one carotid artery is lost
146
the brain autoregulates blood pressure between ___-___ mmHg
60-160 mmHg
147
what pressure does blood have to fall under before confusion, brain damage and fainting usually occur
50 mmHg
148
hyperventilation causes fainting because....
lack of CO2 causes vasoconstriction
149
what is regional hyperaemia
blood flow adaptation to active parts of the brain
150
true/false - baroreceptors control blood pressure in the brain
false
151
normal ICP range is
8-13 mmHg
152
cerebral perfusion pressure =?`
CPP = MAP- ICP
153
what does an increase in ICP do to blood flow
it decreases it
154
what causes increased ICP
trauma, brain tumour
155
what is the blood brain barrier and what is it impermeable to
capillaries with tight intracellular junctions to prevent entry of hydrophilic ions to protect the brain from fluctuation of ion levels
156
what does the systemic bronchial circulation supply
bronchial tree
157
pulmonary resistance is high/low?
low
158
range of pulmonary blood pressure
systolic 20-25
| diastolic 6-12
159
true/false - hypoxia causes vasoconstriction in pulmonary arterioles
true - it is to divert blood from areas of poor ventilation
160
what is stronger in skeletal muscle? metabolic hyperaemia or sympathetic tone
metabolic hyperaemia
161
varicose veins causes?
pooling of blood in veins in leg due to incompetent valves
162
is there a decrease in blood volume due to varicose veins?
no, there is a chronic compensatory increase
