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DPT732: MAP II > MAPIISG1 - Heart > Flashcards

MAPIISG1 - Heart Flashcards

1
Q

What are the muscle types of Cardiac Muscle? (3)

A
  1. Atrial Muscle
  2. Ventricular Muscle
  3. Specialized excitatory and conductive muscle fibers
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2
Q

What is the purpose of Intercalated discs?

A

cell membranes that separate individual cardiac muscle cells

these, desmosomes, and adherns junctions help hold muscle cells together

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3
Q

What is the purpose of gap junctions?

A

communication pathway between cells

at intercalated discs where cell membranes fuse with each other in a way that they form permeable “communication”junctions - allow almost free diffusion of ions

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4
Q

What are the two similarities between skeletal and cardiac muscle?

A
  1. Striated (myosin/actin mechanism)

2. T-tubule mechanism (acting on sarcoplasmic reticulum)

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5
Q

What are the three differences between cardiac and skeletal muscle?

A
  1. T-tubule mechanism (direct diffusion of Ca2+, tubules store more)
  2. Action Potential (cardiac muscle plateau results in longer contraction)
  3. Strength of contraction (dependent on extracellular Ca2+)
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6
Q

What is the ventricular muscle fiber plateau due to?

A

presence of slow Na+ / Ca2+ channels

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7
Q

Is the ability of cardiac muscle to depolarize and contract extrinsic or intrinsic?

A

intrinsic

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8
Q

What are the 5 components of the intrinsic conduction system?

A
  1. Sinus Node = sinoatrial / S-A node
  2. Internodal pathway
  3. A-V Node
  4. A-V bundle of HIS
  5. Left and Right bundle branches of Purkinje fibers
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9
Q

Are the S-A node muscle fibers small or large in diameter?

A

small

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10
Q

Are the S-A node muscle fibers mostly contractile or non-contractile?

A

almost no contractile muscle fibers

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11
Q

How do the S-A node muscle fibers connect with the atrial muscle fibers?

A

directly

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12
Q

Does the S-A node have a less or more negative resting membrane potential than other cardiac muscle cells?

A

less negative resting membrane potential

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13
Q

Why does the S-A node have a less negative resting membrane potential?

A

cell membranes are naturally leaky to Na+ and Ca++ ions

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14
Q

What allows the sino-atrial node to self-excite?

A

Rate of discharge of SA is faster than AV or Purkinje fibers; it reaches threshold before others and can override self-excitation of others under normal circumstances

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15
Q

In the Cardiac Cycle, what is happening during diastole?

A

period of relaxation, heart filling with blood

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16
Q

What is End Diastolic Volume (EDV)?

A

amount of blood in ventricle at end of diastole or filling

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17
Q

In the Cardiac Cycle, what is happening during Systole?

A

period of ventricular contraction, ejects blood

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18
Q

What is End Systolic Volume (ESV)?

A

amount of blood left in ventricle after contraction

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19
Q

What is Ejection Fraction (EF)? (EDV - ESV) / EDV

A

fraction of EDV ejected

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20
Q

What is normal Ejection Fraction?

A

~60%

21
Q

What is happening during the P wave?

A

spread of depolarization through atrial tissue followed by contraction (increase in atrial pressure)

22
Q

What is happening during the QRS Complex?

A

spread of depolarization through ventricular tissue followed by contraction (increase in ventricular pressure)

23
Q

What is happening during the T wave?

A

repolarization of the ventricles which represents ventricular relaxation

24
Q

Majority of venous blood flows directly from the ___ to the ventricle.

A

atrium

25
Q

Explain how the atria acts as a “primer pump”

A

atrial contraction usually causes additional 20% of ventricle filling

26
Q

When is atrial function necessary?

A

“unnecessary” except during exercise

27
Q

Atrial Pressure Changes:
a wave -
c wave -
v wave -

A

Atrial Pressure Changes:
a wave - during atrial contraction
c wave - onset of ventricular contraction
v wave - end of ventricular contraction

28
Q

What is the status of the A-V valves during ventricular filling?

A

after systole, a-v vales open due to a build up of pressure in atria

29
Q

What is the status of the A-V valves and semilunar valves during Isovolumic Contraction?

A

early systole, AV and semilunar valves closed (no volume change in ventricle)

30
Q

What is the status of the A-V valves and semilunar valves during Isovolumic Relaxation?

A

early diastole, AV and semilunar valves closed (no volume change in ventricle)

31
Q

Define preload

A

end-diastolic pressure when the ventricle is filled; amount of tension on the muscle when it begins to contract

32
Q

Define afterload

A

pressure in the artery leading from the ventricle; load against which the muscle exerts its contractile force

33
Q

How do the chemical energy requirements differ between cardiac and skeletal muscle?

A

Cardiac has a greater dependency/almost exclusive relative on O2 for energy metabolize (oxidative) compared to skeletal muscle which can utilize anaerobic metabolic sources as well.

34
Q

How does cardiac muscle primarily derive its energy?

A

from oxidative metabolism of fatty acids (70-90% of energy sources)

35
Q

What are the other 10-30% energy sources cardiac muscle gets its energy?

A

some lactate and glucose

36
Q

What can cardiac muscle use from skeletal muscle?

A

lactic acid generated by skeletal muscle activity

37
Q

How many liters of blood does the heart beat per minute?

A

4-6?

38
Q

With heavy exercise, how many more times blood does the heart pump?

A

4-7x

39
Q

What 2 things are the blood volume pump regulated by?

A
  1. intrinsic cardiac regulation of pumping in response to changes in volume of blood flowing into the heart
  2. extrinsic control of heart rate and strength of heart pumping by the Autonomic Nervous System
40
Q

Describe the frank starling method

A

Heart automatically pumps incoming blood; amount of blood pumped determined primarily by rate of blood flow into heart

As cardiac muscle is stretched with returning blood volume, approach optimal length of actin and myosin fibers for contraction

41
Q

What effect does the SNS have on Cardiac Output and How?

A

(fright, exercise) via norepinephrine increases Cardaic Output

both via HR (pacemaker fires more rapidly) and contractility

42
Q

What effects does the PSNS have on Cardiac Output and How?

A

via vagus nerve decreased Cardiac Output

primarily via HR
acH hyperpolarizes membranes of cell - opens K+ channels

43
Q

During resting conditions, is the S-A node receiving impulses from the SNS or PNS?

A

both autonomic divisions continuously

44
Q

Is the dominant influence said the be inhibitory or excitatory during resting conditions?

A

inhibitory

45
Q

What is “vagal tone”?

A

if you disconnect the vagal nerves, HR increases ~25bmp almost immediately

46
Q

In what part of the cardiac cycle EKG would you expect to hear the first heart sound? Second?

A

First: QRS Complex Ventricular Contraction (depolarization)

Second: P Wave Ventricular Relaxation (repolarization)

47
Q

Define Isovolumic contraction

A

after AV valves close, before SL valves open; pressure rises and ~0.2 seconds requires for ventricle to build up sufficient pressure to push semilunar vales open - tension is building but little or no contraction is occurring

48
Q

Define Isovolumic relaxation

A

ventricles relax (blood remaining - ESV) and valves shut quickly by blood pushing back from from newely filled vessles ~.03 second ventricular muscles continue to relax even through no change in ventricular volume - interventricular pressure rapidly drop to their low diastolic levels

DPT732: MAP II (14 decks)

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