Unit 2: Cardiac Physiology

Question 1

Definition of:

Isovolumic diastole or isovolumic relaxation

Answer 1

The period of time when both the aortic valve and mitral valve are closed

Aortic is closed; Mitral has yet to open

Question 2

Cardiac muscle contains FAST ________ channels and another set of SLOW _________ channels.

Answer 2

Cardiac muscle contains FAST sodium channels and another set of SLOW calcium-sodium channels.

Question 3

Definition of:

Isovolumic systole or isovolumic contraction

Answer 3

The period of time when both the mitral valve and the aortic valves are closed

Mitral valve closed; Aortic has yet to open

Question 3

How is End Diastolic Volume (EDV) effected in patients with A-fib?

Answer 3

Lack of stong atrial contraction → only recieve blood from passive filling (miss extra 30% from atrial contraction)

Question 4

Definition of:

End Diastolic Pressure (EDP) or LVEDP or RVEDP

Answer 4

The pressure in the ventricle at the end of diastole

Question 4

What creates the P wave?

Answer 4

Atrial Contraction or Depolarization

(SA node fired and caused atria to contract)

Question 5

In a cardiac action potential, what creates the plateau phase?

Answer 5

Calcium moving in

As calcium-sodium close slowly, the membrane potential remains positive for several milliseconds. Allows Ca⁺⁺ to to move in while K⁺ moves out = temporary net positive = plateau phase.

Question 6

Definition of:

Systole

Answer 6

Period of cardiac cycle when contraction is occuring

due to depolarization of the muscle

Question 7

What creates the QRS complex?

Answer 7

Ventricular Contraction or Depolarization

Question 8

In cardiac muscle, how does calcium enter the cell?

Answer 8

From the ECF

Question 9

Definition of:

End Systolic Volume (ESV)

Answer 9

Amount remaining in each ventricle after systole (50-60 ml)

Question 11

Definition of:

Diastole

Answer 11

When relaxation is occuring

represents repolarization

Question 12

What creates the T wave?

Answer 12

Ventricular Relaxation or Repolarization

Question 13

Definition of:

End Diastolic Volume (EDV) or LVEDV or RVEDV

Answer 13

Amount of blood that flows into ventricle during distole (120-130)

About 70% of that flows in passively; the rest is due to atrial contraction

Question 15

Why is the strength of contraction different in a cardiac cell compared to a muscle cell?

Answer 15

• Skeletal muscle: calcium released from SR to cause all cross bridges to fire
• Cardiac muscle: may not be the case - amout of cytosolic calcium determines number of cross bridges
• Amount is strongly influenced by ECF calcium levels

Question 16

Definition of:

Stroke Volume

Answer 16

Amount of blood ejected when ventricles contract (70 ml)

Question 17

In the cardiac cycle, what does blood flow in response to?

Answer 17

Pressure changes

Moves from area of high pressure to area of low pressure

Question 18

What is the exictation-contraction coupling process for cardiac muscle?

Answer 18

Same as skeletal muscle

(review from ex phys: action potential along sarcolemma → T tubles → release calcium from SR → calcium binds to troponin → troponin & tropomyosin repositioned exposing binding sites of actin → actin binds to myosin → “firing” or release of energy → actin slides over myosin → ADP and Pi released → freed myosin head binds to ATP → myosin returns to original position)