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1020 Human Physiology > Module 8 - Cardiac Cycle > Flashcards

Module 8 - Cardiac Cycle Flashcards

1
Q

Functions of Cardiac Cycle

A
  • Transport O2 & nutrients to all cells of body
  • Transport CO2 & waste from cells
  • Regulate body temperature & pH
  • Transport & distribute hormones & other substances
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2
Q

Right Atrium & Ventricle Function

A
  • Pumps blood to lungs
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3
Q

Left Atrium & Ventricle Function

A
  • Pumps blood to entire body
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4
Q

Left Ventricle

A
  • Contracts more forcefully to propel blood through entre circulatory system
  • Thicker wall
  • Requires more muscle
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5
Q

Right Ventricle

A
  • Thinner walls
  • Only pumps blood to lungs
  • Less forceful contraction
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6
Q

Heart Valves Purpose

A
  • Ensure 1 way flow of blood through heart (atrium to ventricle)
  • Prevent blood from backing up (returning to atrium during ventricle contraction)
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7
Q

Right Atrioventricular (AV) Valve

A
  • Tricuspid valve
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8
Q

Left Atrioventricular (AV) Valve

A
  • Bicuspid valve
  • Mitral valve
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9
Q

Aorta Function

A
  • Distributes blood from ventricle throughout body
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10
Q

Pulmonary Artery Function

A
  • Transports blood from right ventricle to lungs
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11
Q

Pulmonary Vein Function

A
  • Delivers blood back to heart after passing through lungs
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12
Q

Inferior Vena Cava Function

A
  • Delivers blood to heart from torso & lower limbs
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13
Q

Superior Vena Cava Function

A
  • Delivers blood from head & upper limbs to heart
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14
Q

Bundle of His Function

A
  • conduct action potentials from AV node to base(apex) of heart
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15
Q

Contractile Cells of Heart Components

A
  • Same proteins as actin/myosin
  • Arranged in bundles of myofibrils surrounded by SR
  • One nucleus
  • Many mitochondria
  • Short, branched cells
  • Joined by intercalated discs
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16
Q

Intercalated Disc Components

A
  • Tight junctions, bind cells
  • Gap junctions, movement of ions & current
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17
Q

Gap Junction Function

A
  • Allow myocardial cells to conduct action potentials from cell to cell
  • Without nerves
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18
Q

Nodal Cells

A
  • Contract weakly
  • Few contractile elements (myofibrils)
  • Spontaneously generate action potentials without nervous input
  • Self-excitable
  • Generate & transmit impulses through heart
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19
Q

Self-Excitability Pathway

A
  • Impulses originate in SA node (sinoatrial node)
  • Atria
  • AV node
  • Bundle of his
  • Purkinje fibers
  • Ventricular node
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20
Q

Sinoatrial Node (SA node) Permeability

A
  • Greater Na+ & Ca+ permeability
  • K+ permeability decreases overtime
  • Na+ permeability slightly higher than other cells
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21
Q

Sinoatrial Node (SA node) Characteristics

A
  • Fastest self-excitability
  • Slowest conduction speed
  • Located in upper posterior wall of right atrium
  • First to spontaneously depolarize
  • No stable resting potential
  • Create pacemaker potential
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22
Q

Threshold of SA Node

A
  • -40mV
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23
Q

Resting Potential of SA Node

A
  • -60mV
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24
Q

Steps of SA Node Action Potential

A
  • Membrane depolarizes to threshold
  • Special Ca++ channels open
  • Ca++ flows into cell
  • Ca++ channels close at same time K+ channels open
  • K+ flows out to repolarize cell
  • Cell returns to resting potential
  • Pacemaker potential begins depolarizing cell
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25
Q

Myocardial Steps of Action Potential

A
  • Action potential from SA node spreads through atrial muscle via gap junctions
  • Causing atrial contraction
  • Action potential travels to ventricles through AV node
  • Action potential travels through each branch of bundle of his to apex
  • Propagates through purkinje fibers
  • Rapidly distributes to ventricular muscle causing contraction
26
Q

Action Potential Conduction Throughout Heart

A
  • Speeds up through atrial muscle to ensure simultaneous contraction
  • AV node slows, holds up action potential (ensure atria finishes contraction)
  • Fast through bundle of his
27
Q

Electrocardiogram (ECG)

A
  • Represents electrical activity in areas of heart
28
Q

P Wave of ECG

A
  • Depolarization of atrial muscle
  • Leading to contraction
29
Q

QRS Complex of ECG

A
  • Depolarization of ventricular muscles
  • Leading to contraction
  • Longest waveform
30
Q

T Wave of ECG

A
  • Repolarization of ventricular muscles
31
Q

Systole Phase

A
  • Period of time heart muscle is contracting
32
Q

Diastole Phase

A
  • Period of time heart muscles relax
  • Chamber fills with blood
33
Q

Cardiac Cycle Characteristics

A
  • Combines heart events
  • Pressure & volume changes
  • ECG & valvular activity
  • Pressure changes for blood flow
  • Pressure gradient from high to low
34
Q

Atrial Systole Phase

A
  • Depolarization of atria (P wave)
  • Atrial pressure > ventricular pressure
  • AV valve already open
  • Blood flows into ventricles continuously
  • Ventricular volume increases
  • 20-30% of blood filling (end diastolic volume)
  • Atria contraction
35
Q

Isovolumetric Ventricular Contraction Phase

A
  • Depolarization of ventricles (QRS complex)
  • Ventricles contract
  • Increase in ventricular pressure
  • Ventricular pressure > atrial pressure
  • AV valve closes
  • No volume changes
  • Aortic pressure > ventricular pressure (aortic valve closes)
36
Q

Ventricular Systole Phase

A
  • Repolarization of ventricles (T wave)
  • Ventricular pressure > aortic pressure
  • Aortic valve opens
  • Blood leaves ventricles and flows into aorta
  • Ejection of blood from heart
  • Ventricular volume decreases
  • Some blood returns (end systolic volume)
37
Q

Isovolumetric Relaxation Phase

A
  • Ventricles relax causing pressure drop
  • Ventricular pressure < aortic pressure
  • Aortic valve closes
  • Ventricular pressure > atrial pressure
  • AV valve remains closed
  • No change in volume
38
Q

Late Ventricular Diastole Phase

A
  • Ventricles continue relaxing
  • Ventricular pressure < atrial pressure
  • AV valve opens
  • Blood flows into ventricles from atria
  • 80% of ventricular filling
  • Volume increases
  • P wave begins
39
Q

Order of ECG Events

A
  • atrial systole
  • iosvolumetric ventricular contraction
  • ventricular systole
  • isovolumetric relaxation
  • late ventricular diastole
40
Q

Ventricular Filling

A
  • 70-80% of blood enters relaxed ventricles during late ventricular diastole
  • 20-30% of blood enters during atria systole
41
Q

Ejection Period

A
  • Ventricular pressure > aortic pressure
  • Ventricles empty blood into aorta
42
Q

LUB 1st Sound

A
  • AV valve closes
  • During isovolumic ventricular contraction
43
Q

DUB 2nd Sound

A
  • Aortic & pulmonary semilunar valve close
  • During isovolumic relaxation
44
Q

Cardiac Output (CO)

A
  • Amount of blood in each ventricle pumps per minute
  • L/min
45
Q

Heart Rate (HR)

A
  • Number of heart beats per minute
46
Q

Stroke Volume (SV)

A
  • Amount of blood pumped by each ventricle during 1 contraction
  • Amount of blood ejected
  • mL/beat
47
Q

End Diastolic Volume (EDV)

A
  • Amount of blood in ventricle at end of diastole
  • mL
48
Q

End Systolic Volume (ESV)

A
  • Amount of blood in ventricles at end of systole
  • mL
49
Q

Cardiac Output Equation

A

CO = HR x SV

50
Q

Stroke Volume Equation

A

SV = EDV - ESV

51
Q

Resting Values

A
  • HR 70bpm
  • SV 70mL/beat
  • CO 5L/min
  • EDV 120mL
  • ESV 50 mL
52
Q

Increasing Cardiac Output

A
  • Increasing SV
  • Increasing HR
  • Increasing SV & HR
53
Q

Altering Stroke Volume (SV)

A
  • Input from ANS
  • ESV
  • EDV & preload
54
Q

EDV & Preload Alteration

A
  • Load on heart prior to contraction
  • Blood in ventricle stretches heart muscles
  • More blood in ventricles = higher EDV
  • More Ca++ into cell
  • More blood ejected & more forceful contraction
  • Lower ESV & higher SV
55
Q

ESV Alteration

A
  • Constriction on veins via ANS
  • Increases venous return
  • Repeated contraction & relaxation (exercise)
  • Pumps blood back to heart
  • Increases EDV, SV & CO
56
Q

ANS Controls

A
  • HR
  • Force of contraction
57
Q

PSNS Controls

A
  • Mostly SA & AV nodes
  • Atrial & ventricular muscles to lesser extent
  • Decreases HR through SA & AV Node
  • Decrease force of contraction to lesser extent
58
Q

SNS Controls

A
  • SA & AV nodes
  • Strongest on ventricular muscle
  • Increase HR & force of contraction
59
Q

PSNS Activation

A
  • Always activated at rest
  • Vagus nerve transmits signals to heart (vagal tone)
  • Shifts off if HR > 100bpm
60
Q

PSNS Ach Release

A
  • Nerves to heart activate release of Ach onto SA & AV nodes
  • Ach causes K+ channels to open
  • K+ leave cell creating hyperpolarization
  • Pacemaker potential decreases
  • Membrane takes longer to meet threshold & HR slows
61
Q

SNS Ne Release

A
  • Nerves to heart activate release of norepinephrine onto SA & AV Nodes
  • Causing Na+ & Ca++ channels to open
  • More positive ions enter SA nodal cell
  • Rapid depolarization & increase in pacemaker potential
  • Membrane reaches threshold faster & HR increases
62
Q

Frank Stirling Law

A
  • Increase of EDV causes increase in SV (vice versa)
  • Increase of blood volume causing increased stretch of muscles increasing force to pump blood out

1020 Human Physiology (16 decks)

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