Physiology Flashcards
1
Q
Pacemaker potential in SAN/AVN(slow depolarisation to threshold) is from ___ to ___ mV
It is due to ___ + ___
A
-60 to -40mV
slow Na+ influx - If and Ib - funny current and background Na current
ICaT - transient Ca2+ influx
decreased Ik - less K+ efflux
2
Q
The action potential in SAN/AVN(rapid depolarisation) is from ___ to ___ mV
It is due to ___
A
-40 to +10mV
Voltage-gated Ca2+ channels open for rapid influx of Ca2+ - ICaL
3
Q
Repolarisation in SAN/AVN is from ___ to ___mV
It is due to ____ + ____
A
+10mV to -60mV
K+ channels open (efflux - increase Ik) and Ca2+ channels close
4
Q
Electrical impulse travels between myocytes through ____
A
gap junctions
5
Q
3 stages of SAN/AVN electrical activity
A
pacemaker potential - spontaneous slow depolarisation
action potential - rapid depolarisation
Repolarisation
6
Q
____ and ____ allow rapid conduction of AP to ventricles
A
Bundle of His, its branches and the Purkinje fibres
7
Q
Resting potential in cardiac myocytes is
A
-90mV
8
Q
Phase 0 of cardiac myocyte AP is from __ to __mV
Due to ___
A
-90 to +30mV - depolarisation
Fast Na+ influx
9
Q
Phase 1 of cardiac myocyte AP is due to ___
A
transient K+ efflux (Ito)
closure of Na+ channels
10
Q
Phase 2 of cardiac myocyte AP =___
Due to ___
A
Plateau phase
Opening of voltage-gated Ca2+ (influx - ICaL)
INaL (late Na influx) w. NCX1 (1Ca in:3Na out)
11
Q
Phase 3 of cardiac myocyte AP = ___
Due to ___
A
Repolarisation
K+ channels open (efflux) Ik
closure of Ca2+ channels
12
Q
Phase 4 of cardiac myocyte AP =
A
maintained at -90mV
13
Q
______ is the dominating ennervation of the SAN at rest
A
Vagal tone (parasympathetic)
14
Q
Normal HR at rest =
A
60-100bpm
15
Q
Vagal nerve causes release of __ to ___ receptor in the _____
A
ACh to M2 receptor
SAN and AVN
16
Q
Parasympathetic effect on pacemaker potential in SAN
A
hyperpolarisation, threshold increases = -ve chronotropic
Increases perm. to K+ and decreases perm. to Na+ & Ca2+
17
Q
Parasympathetic NS has a chronotropic+/ionotropic effect on the heart
A
-ve chronotropic
NO IONOTROPIC
18
Q
Sympathetic nerves supply _____ in the heart
A
SAN, AVN and myocardium
19
Q
Parasympathetic effect on the AVN
A
increases delay
20
Q
Sympathetic nerves causes release of __ to __ receptors in the heart
A
noradrenaline beta1 adrenoceptor
21
Q
Effect of sympathetic NS on SAN
A
threshold decreases, decreased perm to K+ increased perm to Na+ and Ca2+ - increases slope of pacemaker potential
=> +ve chronotropic effect
22
Q
Sympathetic NS has a chronotropic+/ionotropic effect on the heart
A
+ve chronotropic and ionotropic effect
23
Q
QRS complex =
A
ventricular depol.
masked atrial repol.
24
Q
T wave =
A
ventricular repol.
25
PR interval =
mainly AVN delay
26
ST interval =
ventricular systole
27
TP interval =
diastole
28
P wave =
atrial depolarisation
29
Desmosomes are located in ___ and provide ___ allowing ___
the intercalated discs
mechanical adhesion
tension development between myocytes
30
In the heart: Myosin + ___ -> + ___ = ____ formation allowing for binding to _____
ATP ; Ca2+ ; cross-bridge ; actin
31
In the heart: actin + myosin -> ___ + _______ -> ____
ADP, Pi + energy released ; powerstroke as myosin bends ; A + M detach
32
Excitation-contraction coupling in cardiac myocytes
systolic Ca2+ influx at Phase 2 stimulates CICR from SR so binding site on actin available for myosin
33
location of SR
covers myofibrils in muscle cells
34
effect of increased intracellular Ca2+ in actin myosin binding
Ca2+ binds to troponin on tropomyosin and pulls it away from the binding site on actin
35
Long refractory period in cardiac myocytes is from ___ to ___
depolarisation to repolarisation
36
Stroke volume definition =
blood vol ejected from each ventricle per heart beat
| EDV-ESV
37
Intrinsic control of stroke volume =
change in diastolic length of myofibrils (EDV/preload determined by venous return)
38
Staling's law of the heart
increased EDV/venous return => increased stroke volume
39
stretch in cardiac myocytes ____ troponin affinity for Ca2+
Stretch increases troponin affinity for Ca2+
40
Optimal fibre length in cardiac myocytes =
stretched
41
Starling's law partially compensates for a decreased SV as ____
heart doesn't eject full volume so EDV increases => SV increases by Starling's law
42
Extrinsic control of stroke volume =
sympathetic NS to ventricular myocytes
| Hormones - adrenaline and noradrenaline
43
How does the symp. NS cause +ve ionotropic effect on ventricular myocytes?
cAMP mediated Ca2+ channels activated = increase force
| Shifts Starling curve to the left (contractility at a given EDV is greater)
44
Aortic area on the chest =
2nd intercostal space
| R of sternum
45
Pulmonary area on the chest =
2nd intercostal space
| L of sternum
46
Tricuspid area on the chest
4th intercostal space
| L of sternum
47
Mitral area on chest
5th intercostal space
| Mid-clavicular line
48
a wave in JVP =
atrial contraction
49
c wave in JVP =
tricuspid valve bulges into R atrium as ventricles contract
50
v wave in JVP =
atrial filling
51
The dicrotic notch in aortic pressure occurs at ____ due to ____
the end of ventricular systole
| closure of the aortic valve
52
isovolumetric ventricular contraction and relaxation occur when
the AV valves and the aortic/pulmonary valves are shut
53
Ib background Na current in the pacemaker potential is due to ___
"leaky cells" = influx of Na
54
If (funny current) is mediated by _____
HCN channels
| hyperpolarisation-activated cyclic nucleotide gated channels (influx Na and efflux K)
55
beta 1 stimulation in AVN causes _____ by increasing ____
increased conduction velocity
| If and ICa
56
beta 1 stimulation in SAN causes ____ by ____
increased HR
steeper pacemaker potential slope by If+ ICa increase
lowers threshold by increasing ICa
57
beta 1 stimulation causes +ve ionotropic effect by ____
increase Ca2+ influx and sensitise tropomyosin to Ca2+
58
beta 1 stimulation causes an increase in _____ activity which speeds up ___
NaKATPase
| repolarisation
59
Sympathetic enervation of the heart causes the length of systole + diastole to _____
Both shorten
60
ACh to M2 receptors in SAN+AVN cause ____ subunits to open ____ causing ______
βγ ; GIRK (K+ channels) hyperpolarisation
61
Parasympathetic NS increases SAN threshold by ____
decreasing ICa
62
Parasympathetic NS does not supply the _____ in the heart
ventricular myocytes
63
AVN delay is increased by the parasympathetic NS by ___
decreased Ca2+ channel activity and GIRK hyperpolarisation
64
Parasympathetic NS ____ atrial refractory period and may => ____
shortens
| atrial arrhythmias
65
HCN channels are activated by
hyperpolarisation
| cAMP
66
SERCA =
| Its role is to ____
SR Ca2+ATPase
| sequestration of Ca2+ into the SR so cardiac myocytes relax
67
CICR is caused by Ca2+ activating ____ receptors
ryanodine type 2 (RyR2 receptors)
68
greatest p.d. detected when lead is _____ to dipole
parallel
69
Limb lead I goes from ___ to ___
R arm (-ve) to L arm (+ve)
70
Limb lead II goes from ___ to ___
R arm (-ve) to L leg (+ve)
71
Limb lead III goes from ___ to ___
L arm (-ve) to L leg (+ve)
72
Depolarisation towards a +ve electrode causes
upwards deflection in ECG
73
P wave's normal duration=
0.08 - 0.1s
74
normal duration of QRS =
less than or equal to 0.12s
75
Q wave = ____ depol of ___
L->R depol of intraventricular septum
76
R wave = depol of ____
main ventricular mass down towards the apex
77
S wave = depol of ___
ventricle from apex upwards
78
T wave = repol of ventricles from ___ to ___
epicardium to endocardium towards the apex
79
normal PR interval =
0.12 - 0.2s
80
aVR lead electrodes =
```
L arm and L leg (-ve) to
R arm (+ve)
```
81
aVL lead electrodes
```
R arm and L leg (-ve) to
L arm (+ve)
```
82
aVF lead electrodes
```
R and L arm (-ve) to
L leg (+ve)
```
83
V1 is placed ____
4th intercostal space R of sternum
84
V2 is placed ___
4th intercostal space L of sternum
85
V4 is placed ____
5th intercostal space L midclavicular line
86
V5 is placed ____
5th intercostal space L anterior axillary line
87
V6 is placed ___
5th intercostal space L mid axillary line
88
V1 and V2 look at the ____
septum
89
V2-4 look at the ____
anterior of the heart
90
V5-6 look at the ____
lateral border of the heart
91
1st Korotkoff sound =
peak systolic pressure
92
5th Korotkoff sound =
no sound! diastolic pressure
93
MAP equations
2dbp+sbp/3
dbp + 1/3(sbp-dbp)
COxTPR
94
normal MAP =
70-105mmHg
95
___ MAP = can't perfuse heart brain and kidneys
less than 60mmHg
96
Short term control of bp is by ___
baroreceptor reflex
97
baroreceptor firing increases if ___
bp increases
98
baroreceptors are found in ___
| and enervated by ___
```
carotid sinus (CN IX)
aortic arch (CN X)
```
99
Reflex that prevents postural hyypotension
baroreceptor reflex
100
Parasympathetics decrease MAP by
decreasing HR => decreased CO
101
Sympathetics increase MAP by
increase HR and SV => increase CO
| increase TPR and venous return
102
Long term regulation of MAP is by ____ adjusting ___
hormones
| blood volume
103
Hormones involved in MAP regulation =
RAAS - Angiotensin II and aldosterone
ANP
ADH/vasopressin
104
Renin is released from ____
juxtaglomerular apparatus (macula densa (monitor tubular Na) extraglomerular mesangial cells and granular cells (release renin))
105
Renin is released in response to ___ (3)`
renal artery lbp
stim of renal sympathetic nerves
decreased Na concn in renal tubular fluid
106
___ is made up of ___ +___ and controls MAP by __
| ___ makes up 1/3 of total body fluid
```
extracellular fluid (ECF) = plasma (PV) + interstitial volume
PV controls MAP
ECF =1/3TBF
```
107
Angiontensinogen is produced in the ___ in response to ___
liver
| renin
108
ACE is produced by ____
the lungs - pulmonary vascular endothelium
109
Angiotensin II stimulates ___
aldosterone release
systemic vasoconstriction
ADH release and thirst
110
Aldosterone is released from ___
| acts on the ___ causing ___
```
adrenal cortex (a steroid hormone)
kidneys - Na and H20 retention
```
111
RAAS increases MAP by increasing __ + ___
plasma volume and TPR
112
ANP is synthesised in ___
atrial myocytes
113
ANP is released when ___ and causes ___ and___
atrial distension occurs (hypervolaemia)
kidneys excrete more Na and H20
vasodilation
114
ADH is synthesised in ___ and stored in ___
hypothalamus
| posterior pituitary
115
ADH is released when ___ receptors located ___ sense ___
osmoreceptors ; in brain close to hypothalamus ; ^ plasma osmolarity
116
ADH effects:
reabsorption of H2O from kidney tubules
| vasoconstriction
117
vasodilating substances eg. __
| activate ___ on endothelial membrane ->^_->___ activates __ to turn ___ into ___+___
bradykinin, ADP, 5-HT
| GPCR > ^Ca2+ > eNOS = l-arginine + O2 -> citrulline + NO
118
NO activates ___ and ___
| End result = vasodilation
Ca2+ dependant K+ channel (K+ efflux)> hyperpolarisation
| guanylate cyclase catalyses gTP>cGMP activates protein kinase G
119
Endothelin causes ___ by acting on ___ causing ___
vasoconstriction (most potent vasoconstrictor)
| ETa receptors on SM => ^Ca2+
120
Increase synth of endothelin
adrenaline, angiotensin II, ADH
121
decrease synth of endothelin
NO, A/B/CNP, sheer stress
122
pulse pressure =
sbp-dbp
123
TPR =
| Mainly controlled by
blood viscosity x length of vessel/radius^4
| arteriolar radius
124
Intrinsic control of vascular SM=
metabolic changes (chemical and humoural), temperature, myogenic stretch response
125
main control of brain bp by effect on vascular SM
myogenic response to stretch
126
Factors that increase venous return:
sympathetic nerves, contraction of skeletal muscle
| increased respiratory pump, increased blood volume
127
Exercise causes a ___ pulse pressure by ____
wider - increasing sbp and decreasing dbp
128
local metabolic changes that cause vasodilation
increased CO2, H+, extracellular K+, osmolarity of ECF, adenosine (from ATP)
decreased O2
129
local vasodilators =
histamine, bradykinin, NO (serotonin)
130
local vasoconstrictors =
endothelin, leukotrienes, thromboxane A2 (serotonin)
131
hydrophobic core of lipoproteins =
cholesteryl ester and triglycerides
132
hydrophilic coat of lipoproteins=
monolayer of amphipathic cholesterol
phospholipids
more/=1 apoprotein
133
HDL has apo
A1 and A2
134
LDL has apo
apoB100
135
VLDL has apo
apoB100
136
chylomicrons have apo
ApoB48
137
Function of apoB containing lipoproteins
deliver tri.s to muscle/adipose tissue
138
ApoB lipoprotein involved in exogenous pathway=
formed in ____
transports ____
chylomicrons
intestinal cells
dietary tri.s
139
ApoB lipoprotein involved in endogenous pathway=
formed in ___
transports ___
VLDL
liver
tri.s synthed in liver
140
lipidation of ApoB lipoproteins is performed by ___
MTP - adds ApoB to lipoprotein
141
Most of the cholesterol in chylomicrons is from __
75% bile salts
| 25% dietary
142
ApoB lipoproteins are activated by
apoCII on HDL
| allows delivery of tri.s
143
___ allows ApoB lipoproteins to bind to ___ which ___ tri.s allowing them to ___
ApoCII ; LPL ; hydrolyses ; enter the tissues
144
LPL is released from ___
capillary endothelium in adipose and muscle cells
145
Once LPL dissociates from chylomicrons+VLDL ___ is transferred to HDL in exchange for ___ and they =
ApoCII for ApoE
| =remnant (cholesteryl ester rich)
146
after chlomicrons+VLDL become remnants they go to the ___ where they are metabolised by ___
liver
| hepatic lipase
147
Receptor mediated endocytosis in hepatocytes clear __
all apoB48 and 50% of apoB100 remnants
148
hepatic lipase remove tri.s from ____ to form ____which then becomes ___ as ___ is lost and only ___ remains
50% of apoB100 remnants
| IDL>LDL - apoE is lost, apoB100 remains
149
LDL receptors (esp. in hepatocytes) bind to LDL > _____ > ____ where cholesterol is released by ____ >LDL receptor is
endocytosed>lysosome>hydrolysis>recycled to the membrane
150
LDL uptake by LDL receptors => (3)
inhibits HMG CoA reductase (de novo chol synth)
storage of cholesterol
less LDL receptor expression
151
___ is released when vessel endothelium is damaged. It is oxidised to form ___
LDL>atherogenic oxidised LDL (OXLDL)
152
OXLDL is taken up by ___ and converted to ___
macrophages> cholesterol laden foam cells
153
inflammatory substances released in vessel damage =>
division and proliferation of SM cells into intima and collagen laid down
ie. plaque and fibrous cap form
154
Function of HDL
reverse transport of cholesterol
| blood->liver
155
HDL is formed in the ___
liver
156
cholesterol and cholesteryl ester are taken into hepatocytes when HDL interacts with
SRB1 (scavenger receptor)
157
In plasma - ___ mediates the transfer of cholestryl ester from HDL to VLDL+LDL
This =
CETP - chol. ester transfer protein
| indirect chol. return to liver
158
High tri.s damage the ____
pancreas
159
Extra O2 to cardiac tissue is only achieved by ____ as o2 extraction is already at 75% (compared to 25% normal tissues)
increasing blood flow
160
Intrinsic control of coronary artery blood flow __
| Extrinsic control of coronary artery blood flow ___
intrinsic: metabolic hyperaemia causes decreased PO2 -> vasodilation
extrinsic: sympathetics = constriction (overridden by intrinsic) and adrenaline vasodilation
161
Pulmonary bp normally =
20-25/6-12mmHg
162
pulmonary capillary pressure =
| systemic =
8-11mmHg
| 17-25mmHg
163
hypoxia causes pulmonary vessels to
vasoconstrict - to divert blood away from poorly ventilated areas of lung
164
Blood volume _____ in varicose veins to compensate therefore CO ___
blood volume increases
| CO remains the same
165
Exchangeable proteins pass though capillary endothelial cells by ___
vesicular transport
166
forces favouring filtration in capillaries
Pc (capillary hydrostatic P)
+
πi (interstitial fluid osmotic P)
167
forces opposing filtration in capillaries
πc (capillary osmotic P)
+
Pi (interstitial hydrostatic P)
168
arteriolar end net filtration pressure =
| favours ___
+10mmHg
| filtration
169
venular end net filtration pressure =
| favours ___
-8mmHg
| reabsorption
170
which is greater in a day filtration or reabsorption in capillaries?
Filtration by 2-4litres
| Excess is returned as lymph
171
Filtration/reabsorption is favoured in pulmonary capillaries as ___ is low and __ is normal
reabsorption ( still is a nett filtration movement though)
Pc is low
πc is normal
172
Oedema causes
1) increase capillary P =
2) increase venous P =
3) decreased plasma osmotic P =
4) lymphatic insufficiency =
5) changes in cap. permeability =
1) arteriolar dilatation
2) LV failure (pulmonary)
RV failure (peripheral)
prolonged standing (ankles)
3) plasma protein
173
Isoelectric complex =
| The axis lies ____ to the isoelectric complex
positive and negative deflections are equal in size
| at 90degrees
