Exitability Tissue

Question 1

Cardiac potential action (non-nodal cells) channels

Answer 1

Resting:

• ungated K
• IK1

Action potential:

0. Fast Na channels (QRS)
1. Na channels transitions to inactivated, transient K current
2. Ca channels L-type (depolarize), IKr (repolarize) (ST segment)
3. IKr + IK1 (T wave)
4. IK1

Question 2

Action potential (nodal cells)

Answer 2

4. T-type Ca inward, Ifunny Na (inward), K outward
5. L-type Ca
6. Voltage-gate K channels (repolarize)

There aren’t phase 1 and 2

Question 3

Height of waves in EKG

Answer 3

1. Mass of tissue
2. Change in potential
3. Orientation to the current flow

Question 4

Time of PR interval

Answer 4

120-200msec

Question 5

Time of QT interval

Answer 5

40-100 msec

Question 6

Reading EKG

Answer 6

1. Rhythm and rate
2. Waves
3. PR interval
4. Mean electrical axis

Question 7

Heart blocks

First degree characterizes

Answer 7

Slow conduction through AV
PR >200 msec
Rate and rhythm is normal

Question 8

Heart blocks

Second degree

Answer 8

Some impulses aren’t transmitted through AV
Every QRS is preceded by P, but not all P is followed by QRS

Mobitz 1: progressive prolongation of PR
Mobitz 2: PR is constant

Question 9

Heart block

Third degree

Answer 9

Complete dissociation of P waves and QRS complex
Impulses aren’t transmitted through AV node
Steady rhythm but very slow HR

Question 10

Atrial flutter characterized

Answer 10

Coordinated conduction
Saw-tooth
Rhythm steady

Question 11

Atrial fibrillation characteristics

Answer 11

Uncoordinated atrial conduction
No atrial contraction
Unsteady rhythm

Question 12

Hyperkalemia in ❤️

Answer 12

Sharp-spiked

Shorted QT

Question 13

Hypokalemia in ❤️

Answer 13

U waves

Prolonged QT

Question 14

Regulation of cytosolic calcium in muscle

Answer 14

1. Action potential
2. Dihydropyridine(DHP) removing block of Ryanodine receptor (RyR) in SR
3. Rise cytosolic Ca
4. Ca binds to troponin C, initiates cross-bridge cycle
5. Ca is pumped back into SR by SERCA
6. Resting