PST2106 DIAGNOSTIC TECHNIQUE 2026
ACTUAL EXAM TEST WITH COMPLETE
ACTUAL QUESTIONS AND CORRECT
ANSWERS GRADED A+
Where is propagation of action potential occur and how does it
continue? Correct Answer • Action potential at any point on cell
membrane acts as stimulus to adjacent regions of cell membrane
- Excitation process, once started, is spread along length of cell
and onto next cell, then next... (mexican wave). Important in
myocardial tissue for the contractile cells work together to form a
nice coordinated contraction.
- Stimulus that is strong enough to cause cell to reach threshold
and depolarise spreads quickly across cell membrane from one
cell to another
- Cardiac action potential can be divided into five phases (phases
0 to 4)
How does the electrolyte ______ cause contraction of the heart?
Correct Answer when calcium enters the cell it binds to the
receptors on the cytoplasma reticulum, releasing more calcium
and crosslinks in the sliding filaments in the cardiac muscle and
causes contraction
,Contractile cell (Cardiac) action potential Phases Correct Answer
Phases:
0. Rapid depolarization pwave (-85mV -90mV. Threshold 40mV.
End 20mV)
- P wave: atrial deporlarisation.
- Fast Voltage gated Na+ channels open, ^ positive ions in cell to
20mV (open only for fraction of milliseconds)
- Action potential when reaches threshold potential
- Inside cell becomes positively charged
1. initial repolarization
- Fast Voltage gated sodium Na+ channels closed
- Voltage gated potassium K+ channels begin to open and lost
from cell (0mV)
- Decrease of positive ions in cell and drop in membrane potential
• trying to Return cell membrane to its resting permeability state
(but held up)
2. plateau
- balance of potassium leaving and calcium entering
- Slow Voltage gated Ca2+ Channels open
- Triggers large secondary release of calcium from intracellular
storage sites (cytoplasmic reticulum) and initiates myocardial
contraction
,- K+ efflux continues to leave cell
?- Inward calcium current maintains cell in prolonged
depolarisation state allowing muscle contraction before another
depolarisation
- Allows contraction (QRS ventricals) and relaxation. To allow
emptying of the atrium and ventricles.
- Phase only present in myocardial cell's action potentials
- without calcium there's only electricity, no mechanical pumping
3. rapid repolarization (more) 40mV
- Slow Voltage gated: Ca2+ channels close; K+ open outflow
- In cell more negative
- initiated by calcium and outflow of potassium
- repolarisation complete by end of this phase
- T wave - repolarisation ventricles (atrial behind)
4. resting potential (more) - 90mV
- T-P segment rest and refill
High K+ permeability
- Return to resting membrane potential
- In cell negative
, - pump, active Trasport ATP- ADP. 3 Na2+ out, 2 K+ in. against
concentration gradient. Relative refractory period, unable to
generate impulse till complete
Second to last phase in cardiac action potential phases Correct
Answer 3. rapid repolarization
- Slow Voltage gated Ca2+ channels close
- Slow voltage gated K+ channels open outflow
- In cell more negative
- Membrane potential also returns to its resting state
- Phase initiated by calcium and outflow of potassium
Repolarisation is completed by end of this phase
last phase of action potential cardiac Correct Answer 4. resting
potential (-85mV) (brief Moment in between
impulses/contractions)
- High K+ permeability
- Returned to its resting membrane potential
- In cell more negative to outside
- To restore sodium (3 out) and potassium (2 in) pump through
active transport (ATP-ADP - drop phosphate molecule) against
concentration gradient
- relative refratory period where another impulse can't be
generated until finished
ACTUAL EXAM TEST WITH COMPLETE
ACTUAL QUESTIONS AND CORRECT
ANSWERS GRADED A+
Where is propagation of action potential occur and how does it
continue? Correct Answer • Action potential at any point on cell
membrane acts as stimulus to adjacent regions of cell membrane
- Excitation process, once started, is spread along length of cell
and onto next cell, then next... (mexican wave). Important in
myocardial tissue for the contractile cells work together to form a
nice coordinated contraction.
- Stimulus that is strong enough to cause cell to reach threshold
and depolarise spreads quickly across cell membrane from one
cell to another
- Cardiac action potential can be divided into five phases (phases
0 to 4)
How does the electrolyte ______ cause contraction of the heart?
Correct Answer when calcium enters the cell it binds to the
receptors on the cytoplasma reticulum, releasing more calcium
and crosslinks in the sliding filaments in the cardiac muscle and
causes contraction
,Contractile cell (Cardiac) action potential Phases Correct Answer
Phases:
0. Rapid depolarization pwave (-85mV -90mV. Threshold 40mV.
End 20mV)
- P wave: atrial deporlarisation.
- Fast Voltage gated Na+ channels open, ^ positive ions in cell to
20mV (open only for fraction of milliseconds)
- Action potential when reaches threshold potential
- Inside cell becomes positively charged
1. initial repolarization
- Fast Voltage gated sodium Na+ channels closed
- Voltage gated potassium K+ channels begin to open and lost
from cell (0mV)
- Decrease of positive ions in cell and drop in membrane potential
• trying to Return cell membrane to its resting permeability state
(but held up)
2. plateau
- balance of potassium leaving and calcium entering
- Slow Voltage gated Ca2+ Channels open
- Triggers large secondary release of calcium from intracellular
storage sites (cytoplasmic reticulum) and initiates myocardial
contraction
,- K+ efflux continues to leave cell
?- Inward calcium current maintains cell in prolonged
depolarisation state allowing muscle contraction before another
depolarisation
- Allows contraction (QRS ventricals) and relaxation. To allow
emptying of the atrium and ventricles.
- Phase only present in myocardial cell's action potentials
- without calcium there's only electricity, no mechanical pumping
3. rapid repolarization (more) 40mV
- Slow Voltage gated: Ca2+ channels close; K+ open outflow
- In cell more negative
- initiated by calcium and outflow of potassium
- repolarisation complete by end of this phase
- T wave - repolarisation ventricles (atrial behind)
4. resting potential (more) - 90mV
- T-P segment rest and refill
High K+ permeability
- Return to resting membrane potential
- In cell negative
, - pump, active Trasport ATP- ADP. 3 Na2+ out, 2 K+ in. against
concentration gradient. Relative refractory period, unable to
generate impulse till complete
Second to last phase in cardiac action potential phases Correct
Answer 3. rapid repolarization
- Slow Voltage gated Ca2+ channels close
- Slow voltage gated K+ channels open outflow
- In cell more negative
- Membrane potential also returns to its resting state
- Phase initiated by calcium and outflow of potassium
Repolarisation is completed by end of this phase
last phase of action potential cardiac Correct Answer 4. resting
potential (-85mV) (brief Moment in between
impulses/contractions)
- High K+ permeability
- Returned to its resting membrane potential
- In cell more negative to outside
- To restore sodium (3 out) and potassium (2 in) pump through
active transport (ATP-ADP - drop phosphate molecule) against
concentration gradient
- relative refratory period where another impulse can't be
generated until finished
