06-07 - Electrical Activity, Muscular Contraction & Cardiac Cycle Flashcards
The heart is auto…
Rhythmic
The nerve supply to the heart…
A) Regulates
B) Initiates
C) Regulates and initiates
…the heartbeat…
A) Regulates
There are two types of myocytes…
1) Work cells (that generate force)
2) Conducting cells
Initiation of the heartbeat occurs at the…
Sino-atrial Node (SAN)
Action potentials spread through the heart via (3)…
- Gap junctions
- Specialised conducting fibres
- Through functional syncytium of work cells
A syncytium is…
A multi-nucleic cell formed by fusion of cells
Current flows from the SA node to the AV node via the…
Internodal pathways
Current travels from the AV node to the apex of the heart via the…
Bundle of His
Current moves from the apex of the heart up and across the ventricles via the…
Purkinjie fibres
Heart rate is determined by the…
Sino-atrial node (SAN)
Heart rate can be altered by the…
Autonomic nervous system
In the event of SAN dysfunction…
Other cells can take over (but at a slower rate)
Contractors period occurs:
A) Before
B) After
C) During
…the refractory period…
C) During
Cardiac muscle has a long refractory period. This helps prevent…
Tetanus
An electrocardiogram (ECG) is…
A recording of heart activity made by placing electrodes on the skin
The 3 characteristic parts of an ECG are…
1) P Wave
2) QRS complex
3) T wave
The P wave of an ECG corresponds to…
Atrial polarisation
The QRS complex of an ECG corresponds to….
Ventricular depolarisation
The T wave of an ECG corresponds to…
Ventricular repolarisation
The QT interval is…
A) Constant
B) Dependent on stroke volume
C) Dependent on PQ interval
D) Dependent on heart rate
D) Dependent on heart rate
There are two types of arrhythmia (abnormal heart rhythm)…
1) Impulse propagation defects (heart block)
2) Impulse initiation defects (fibrillation)
An action potential from the adjacent heart cell causes voltage-gated channels to open, allowing Ca2+ to enter the cell.
This induces local release of more Ca2+ via…
Ryanodine receptor channels (RyR)
Local release of Ca2+ leads to Ca2+ spark. The summation of these sparks generates the…
Ca2+ signal
After the generation of the Ca2+ signal, Ca2+ binds to…
Troop in
