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Cardiopulm > Cardiac Physiology - Heart > Flashcards

Cardiac Physiology - Heart Flashcards

1
Q

fibrous skeleton of the heart traits

A
  1. composed of dense connective tissue
  2. lies in the plane between atria and ventricles
  3. corresponds to atrioventricular groove/orifices of heart
  4. is present in the form of circular fibrous ring
  5. surrounds the 4 valves
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2
Q

myocardium

A

thickest region of heart, contains myocytes

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3
Q

endocardium

A
  • thin layer of connective tissue
  • covers valves
  • contiuous with endothelium layer of vessels
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4
Q

cardiac muscle cell traits

A
  • arranged in layers
  • all slow fiber types
  • innervated like smooth muscle
  • absolute refractory period
  • highly aerobic
  • require a continuous O2 supply
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5
Q

cardiac muscle cell traits pt2

A
  • calcium regulation: like smooth muscle
  • fibers contract simultaneously but in a graded fashion
  • gap junctions/intercalated disks
  • intrinsic HR
  • Purkinjee fibers: conduct current that initiates cardiate muscle contraction
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6
Q

cardiac cycle

A
  1. blood moves from high to low pressure
  2. pressure gradients lead to expulsion of blood from chamber
  3. volume changes in left chambers equal to right chambers
  4. cardiac valves control blood flow in context of pressure gradients
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7
Q

ventricular systole

A
  1. ejection continues until ventricular pressure < vessel pressure
  2. outflow doesn’t stop immediately after end of contraction
  3. ventricular pressure continues to fall after valve closes and myocardium relaxes
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8
Q

Ventricular diastole

A
  1. ventricles relax, pressure low
  2. ventricles fill with blood, increasing volume
  3. Atrial systole forces blood into ventricles (<30% of total ventricular filling)
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9
Q

Atrial diastole

A
  1. pressure < vena cava pressure

2. blood moving into atria, venous return

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10
Q

Atrial systole

A
  1. p wave initiates atrial contraction
  2. forces blood into ventricles
  3. “tops off the tank”
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11
Q

How do you track the electrical signal of the cardiac cycle?

A

EKG

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12
Q

What are the phases identified by heart sounds?

A

S1-4

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13
Q

T/F: pressure changes in R ventricle and pulm arteries are the same as those in the LV

A

False
the are very much smaller.

LV: 120/80
PA: 25/10

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14
Q

SA node

A
  1. responsible for initiating heart beat
  2. node cells slowly depolarize by themselves (pacemaker potential)
  3. vagus nerve stim decreases discharge rate of SA node
  4. autonomic nerve stim increases discharge rate of SA node
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15
Q

Positive chronotropic effect

A

increases HR (sympathetic)

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16
Q

Negative chronotropic effect

A

Decreases HR (parasympathetic)

17
Q

sympathetic innervation

A
  1. increases HR x3
  2. increases contraction strength x2
  3. net effect: increase in CO
  4. inhibition of sympathetic nerves = dec HR and contractility
18
Q

Parasympathetic innervations

A

“vagal stim”

  1. slows hr
  2. dec strength of contraction
  3. dec CO
  4. vagal fibers distributed mainly to SA and AV nodes

vagal stim regulates HR more than contractility

19
Q

SA node/Pacemaker potential

A
  1. pacemaker cells don’t need any outside innervation from ANS for AP
  2. Autonomic innervation can regulate depolarization w/pacemaker cells
20
Q

if CO is 5L and bpm is 72, then L/beat is

A

.07 L/beat

21
Q

what 3 variables influence SV

A

preload
afterload
contractility

22
Q

What happens with increased EDV?

A

stretches myocardium which increases the stretch of the heart muscle and increases the sensitivity of cardiac myocytes to Ca2

23
Q

Describe how frank starling mechanism allows for rapid adjustment to rise in peripheral resistance or afterload

A
  1. increased peripheral resistance temporarily decreases SV causing backup into ventricles
  2. more blood remains in ventricles, increasing EDV
  3. increased EDV causes ventricles to be stretched more, so they contract more strongly during next ventricular contraction
24
Q

increased afterload tends to _ SV

A

reduce

25
Q

increased afterload tends to _ SV

A

reduce

26
Q

contractility

A
  1. measure of cardiac pump function
  2. degree to which muscle fibers can shorten and generate force
  3. intrinsic ability of heart to contract
  4. reflects force or strength of cardiac contraction
27
Q

How do we assess contractility clinically?

A

ejection fraction

28
Q

ejection fraction

A
  1. under resting conditions: 50-75%
  2. Increased contractility increases EF
  3. decreased contractility decreases EF
  4. EF reflects basic muscle mechanics (rate and amount of cross bridge cycling)
29
Q

what increases and decreases contractility?

A

increase: sympathetic stim
decrease: parasympathetic stim

Cardiopulm (20 decks)

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