1
Q
The pulmonary circuit is supplied by the _____ side of the heart.
A
right
2
Q
The systemic circuit is supplied by the ______ side of the heart.
A
left
3
Q
What are the 3 layers of the heart wall?
A
- Epicardium
- Myocardium
- Endocardium (endothelium)
4
Q
Pressure within chambers of the heart varies with …
A
heartbeat cycle
5
Q
How do pressure differences in the chambers of the heart drive blood flow?
A
- High pressure to low pressure
- Valves prevent backward flow of blood
- All valves open passively based on pressure gradient
6
Q
What is autorhythmicity?
A
the ability to generate own rhythm
7
Q
What do autorhythmic cells do?
A
- electrical signal passageway
- cells provide a pathway for spreading excitation through the heart
8
Q
What do pacemaker cells do?
A
- Spontaneously depolarizing membrane potentials generate action potentials
- Coordinate and provide rhythm to heartbeat
9
Q
What do conduction fibres do?
A
- Rapidly conduct action potentials
- Initiated by pacemaker cells
10
Q
Spread of excitation between cells make the _____ contract then _______.
A
- atria
- ventricles
11
Q
The coordination of the spread of excitation between cells is due to:
A
- gap junctions
- conduction pahtways
12
Q
What is concentrated at the intercalated discs?
A
- desmosomes
- gap junctions
13
Q
Intercalated discs are junctions between …
A
adjacent myocardial cells
14
Q
What do desmosomes do?
A
resist mechanical stress
15
Q
What do gap junctions do?
A
- link cardiac cells
- electrical coupling
16
Q
Why doesn’t contraction of the heart doesn’t occur the same way we think of blood flow?
A
Both atria contract and then both ventricles contract
17
Q
Describe the path of the initiation and conduction of an impulse.
A
- action potential initiated at SA node
- interatrial pathway
- AV node (some delay)
- to ventricals
18
Q
Impulse travels to ventricals via…
A
- bundle of His
- right and left bundle branches
- purkinje fibres
19
Q
Describe the intertribal pathway.
A
- SA node → right atrium → left atrium
- Rapid
- Simultaneous contraction of right and left atria
20
Q
Describe the internodal pathway.
A
SA node → AV node
21
Q
Describe AV node transmission.
A
- Only pathway from atria to ventricles
- Slow conduction: AV nodal delay = 0.1 sec
- Atria contract before ventricles
22
Q
How can heartbeat be controlled by pacemakers?
A
- Autorhythmic cells (“pacemaker potentials”)
- Spontaneous depolarizations (Caused by channels opening/closing)
23
Q
Describe electrical activity in pacemaker cells.
A
- no external stimulus required
- no steady resting membrane potential
- Changes in membrane permeability to: Na+, K+ and Ca++
24
Q
No steady resting membrane potential means…
A
- Immediate depolarization
- “ramping” = pacemaker potential
25
Name the 3 channels for changes in membrane permeability.
- K+ channels
- Funny channels
- T-type & L-type channels
26
What happens in the first part of pacemaker potential (slow depolarization)?
- K+ close
| - funny channels open
27
What happens in the last part of pacemaker potential (slow depolarization)?
T-type open
28
What happens during rapid depolarization?
L-type open
29
What happens during repolarization?
- L-type close
| - K+ open
30
What are the steps of cardiac action potential?
- depolarization
- brief repolarization
- plateau
- repolorization
- rest
31
What happens during depolarization?
Na+ in
32
What happens during brief repolarization?
Ca2+ in
33
What happens during depolarization?
K+ out
34
Cardiac contractile cells takes how long?
250-300 msec
35
Skeletal muscles take how long?
1-2 msec
36
How does excitation-contraction coupling in cardiac contractile cells have properties similar to skeletal muscles?
- t-tubules
- troponin-tropomyosin regulation
- SR and Ca2+
37
How does excitation-contraction coupling in cardiac contractile cells have properties similar to smooth muscles?
- Gap junctions
| - Extracellular Ca2+
38
What are the steps of excitation-contraction coupling in the heart?
1. Depolarization of cardiac contractile cell (Gap junction)
2. Calcium channels (Plasma membrane)
3. T tubules
4. Calcium release from the SR
5. Calcium binds to filaments
6. binding sites exposed
7. cross bridge cycle
39
AP travels down _______.
t tubules
40
Extracellular Calcium influx induces (“tells”) ____ to release ______ as well as signaled from ___ travelling down _____.
- SR
- calcium (CICR)
- AP
- t-tubules
41
Calcium binds to ______.
troponin
42
What is troponin?
- a protein on tropomyosin
| - causes tropomyosin to “move” out of the way and expose binding sites on actin for myosin filaments *stays bound*
43
What happens in the cross bridge cycle?
myosin binding to actin- slide-release
44
How does relaxation of cardiac muscle occur?
- calcium removed from cytosol
| - resting conditions reestablished
45
What are the 3 ways calcium is removed from cytosol in the heart?
- SR ATPase-pumped back into SR
- Plasma membrane atpase-pumped out into extracellular matrix
- Na+-Ca++ exchanger in plasma membrane
46
What happens during resting conditions?
Troponin and tropomyosin move back to their positions and cover binding sites
47
What does a electrocardiogram do?
- gives a look at the electrical activity of the heart on the surface of the skin
- Using electrical leads and electrodes – detects synchronicity of electrical signal provides a picture of what is happening
- Used clinically to detect abnormalities – collect HR data
48
How is your body a conductor?
Currents in body can spread to surface (ECG, EMG, EEG)
49
Distance and amplitude of spread depend on two factors:
- Size of potentials
- Synchronicity of potentials from other cells
(Heart electrical activity = synchronized)
50
What are the parts of the electrical activity of the heart?
- P wave
- QRS complex
- T wave
51
P wave signals:
atrial contraction
52
QRS complex signals:
ventricular contraction/systole
53
T wave signals:
ventricular relaxation/diastole
54
What is the P-Q interval?
time between conduction of signal through AV node
55
What is the Q-T interval?
time of ventricular systole (length of contraction phase)
56
What is the T-Q interval?
length of diastole or ventricular relaxation (when the heart is filling with blood
57
What is the R-R interval?
measure of HR, beginning of ventricular systole to the next contraction
58
What are the 2 main periods of the cardiac cycle?
- systole
| - diastole
59
What happens during systole?
contraction of ventricles
60
What happens during diastole?
relaxation of ventricles
61
Valve opening is dependent on...
pressure differences
62
What are the 4 phases of cardiac cycle?
1. ventricular filling
2. isovolumetric ventricular contraction
3. ventricular ejection
4. isovolumetric ventricular relaxation
63
Describe the ventricular filling phase.
- venous return
- AV valves open
- blood fills atria
- passive until atrial contraction
64
Describe the isovolumetric ventricular contraction phase.
- start of systole
- no change in volume
- all valves closed
- pressure in ventricles starts to increase
65
Describe the ventricular ejection phase.
- end of systole
- Ventricular pressure exceeds aortic- blood pumped out
- AV valves closed
- Semilunar open
- Valves close when pressure is greater outside chambers (aortic)
66
Describe the isovolumetric ventricular relaxation phase.
- beginning of diastole
- no change in volume
- relaxation: no blood in or out
- valves closed
PSIO 258: Elementary Physiology I
flashcards
Decks in class (14)
# Cards
-
Introduction to Physiology56
-
Cell Structure and Function90
-
Cellular Metabolism82
-
Cell Membrane Transport38
-
Cell Membrane Transport 219
-
Endocrine System 163
-
Endocrine System 267
-
Nerve Cells and Neuron Potentials 149
-
Nerve Cells and Neuron Potentials 242
-
Synaptic Transmission37
-
CNS 170
-
CNS 269
-
Muscle Physiology96
-
Cardiovascular System66
