1 - Electrical Ppts of the ❤️

Question 1

1. Fibrous covering of the heart?
2. Portions of #1?
3. Attachment?
4. Function?
5. What can you find in between #2? Function of #5?

Answer 1

1. Pericardium
2. Parietal and Visceral Pericardium
3. Attachment: Sternum, Vertebrae, Diaphragm (S.V.D.)
4. Function: To make the heart stay in its normal position even if there’s activity
5. In between the parietal & visceral PC, there’s the pericardium fluid (~50-150 mL spnt fluid filled with PPLs); Function: (1) to diminish friction while heart is in activity and (2) to protect from infection

Question 2

What is the thickest chamber of the heart? Why?

Answer 2

L ventricle because it has to produce a lot of pressure to push the blood into the peripheral circulation.

R ventricle is thinner because it has to bring the blood to the lungs (a low pressure type of circulation) for reoxygenation

Question 3

Valves of the heart?

Answer 3

Left: Aortic and Mitral

Right: Pulmonic and Tricuspid

Question 4

T or F. If auscultating for valves, use the anatomical position.

Answer 4

No! Anatomical position is not the same as the clinical position.

Question 5

When you stimulate your excitable cell, you have 2 responses to stimulation?

Answer 5

1. Electrical response/event
   - Shown by ECG
2. Mechanical event
   - Shown in Wiggler’s diagram

Question 6

2 types of cells in the heart?

Answer 6

1. Conducting cells
   - SA node, Purkinje fibers (responsible for initiation of the electrical event of your AP)
2. Contractile cells
   - for pumping action of heart
   - Cardiac muscle and cardiac myocyte (different histologically; coming from conducting cells)

Question 7

What is automaticity in the context of your heart?

Answer 7

Automaticity
-is the spontaneous generation of the action potential of your electrical event
(The potential are expressed by your conducting cells)
-Spontaneous depolarization (You don’t need outside stimuli to initiate AP)

Question 8

Characteristics of ion channels responsible for the different phases of the slow response action potential

Answer 8

Selective, voltage-sensitive, time-dependent

VoTS

Question 9

3 Phases of the Slow Response Action Potential

Answer 9

Phase 4: RMP

Phase 0: Depolarization Phase

Phase 3: Repolarization Phase

Question 10

Explain the Slow Response AP

Answer 10

Phase 4: Resting MP
Occurs right after phase 3 of the previous AP
However, in contrast to nerve, you do not have a straight line for resting MP primarily due to opening of special channel which allows Na+ to enter cell (called funny current of Na+)
This is your peak potential. Then, it will be joined by Ca2+ ions (before reaching threshold potential) due to opening of transient Ca2+ channel
Then, when you reach your threshold potential, these channels will be closed and only the long lasting Ca2+ channels will remain open to cause the depolarization or phase 0 of slow response AP
Note: Ca2+ channels are slow to open and slow to close
*Again, depolarization phase is due to the opening of L type Ca2+ channels so you allow Ca2+ to get inside cell causing depolarization
After depolarization phase, Ca2+ channels will start to close and K+ channels open
Allowing efflux of K+ from the cell causing downslope of AP or the repolarization phase
K+ channels do not close easily so some are still open and remain open until equilibrium potential is reached

Question 11

Effect of sympathetic and parasympathetic stimulation to the slow response action potential?

Answer 11

Sympathetic = shorter and steeper sloper of the RMP = Faster HR

Parasympathetic = longer or more slanted slope before having the DEPOLARIZATION AND REPOLARIZATION PHASE = Slower HR

Question 12

What can you do to increase the firing of your SA node/HR?

Answer 12

> Give Beta 1 adrenergic receptors like Epinephrine and Norepinephrine
Give Muscarinic Antagonists = reduces parasympathetic activity
Have Hypokalemia (Low blood K+ levels)

Question 13

What can you do to increase activity of your vagus nerve -> Parasympathetic activity?

Answer 13

> Decrease firing of your SA node
Use beta blockers
Hyperkalemia

Question 14

What is the primary pacemaker? Can other cells be the primary pacemaker in a normal human being?

Answer 14

Primary pacemaker: SA node ONLY

If other cells in the conducting system fires beyond their innate/natural firing rate —> increase Na/K ATPase activity —> hyperpolarization of these cells —> SA node will be left

Question 15

3 tracts between SA and AV node?

Answer 15

1. Bachmann-James (ant internodal tract)
2. Wenckebach (Middle IT)
3. Thorel (Post IT)

Question 16

Only portion separating the atrium from the ventricle? Function?

Answer 16

AV node
-Fxn: For the AV/physiologic delay
(Importance: To assure that the ventricles are already filled before it contracts; sufficient time for ventricular volume to have sufficient cardiac output)
-Limits number of impulses being conducted from atrium to ventricles

Question 17

T or F. Once the baseline is reached again in a slow response AP, you can restimulate them again.

Answer 17

False! The refractory period is time dependent.

Question 18

Fast Response AP

Answer 18

In fast response AP, go back to K+ (RMP)
K+ channels are open; sodium and ca channels are close
So RMP is due to K+
What happens?
Opening of fast sodium channels
Overshoot
Depolarization phase bc of the sudden influx of Na+ into your cell
And the max rise of upstroke reflects magnitude of Na conductance into the cell = so mas madaming Na+ pumasok sa cell = mas mabilis at mas mataas upshoot ng depolarization phase
By the time it reaches the peak, some K channels will open so there’ll be an efflux of some K+ ions causing this downstroke or slight repolarization phase
However, it will be met by the opening of calcium channels resulting in the influx of Ca2+ = in effect, you also have an increase in Ca2+
Although some of the K+ channels will remain open with the K+ exiting the cell, you have initially for the plateau, you have more Ca2+ entering the cell than K+ exiting the cell
However, after plateau phase, and Ca2+ channels will start to close, there’ll be more K+ exiting the cell then Ca2+ getting inside of cell = this will cause repolarization phase or phase 3 of fast response AP

Question 19

Location of Fast and Slow Response?

Answer 19

Fast response: in ventricular muscles

Slow response: Conducting cells, SA node

Question 20

Refractory period of skeletal ms. Vs cardiac myocyte?

Answer 20

The Electrical Response/Fast Response AP contraction is overlapping the absolute refractory period = can’t tetanize

Question 21

Why is there a period of refractoriness?

Answer 21

Because the ion channels have not recovered from the previous activity/AP

Question 22

What is the effective refractory period?

Answer 22

Abs RP + Time when you can’t restimulate it because you need some more time to have another AP in the conducting cell

Question 23

Electrophysiologic Properties of Cardiac Tissues

Answer 23

CARER

1. Conduction
2. Automaticity
3. Refractoriness
4. Excitability
5. Rhythmicity

Question 24

What is arrhythmia?

Answer 24

Irregular heartbeat/HR
Bradycardia = below 60 bpm
Tachycardia = above 100 bpm