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Phcol 402 > 01/20/16 > Flashcards

01/20/16 Flashcards

1
Q

Background of Cardiac Output

A
  • Heart pumps blood around the body
  • Left heart pumps oxygenated blood
  • Right heart pumps deoxygenated blood
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2
Q

Anatomy of the heart

A
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3
Q

Anatomy of the heart; cartoon illustration

A
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4
Q

The Cardiac Cycle

A
  • Molecular/electrical/physiologicaleventsthat occur from the start of one heartbeat to the start of the next heartbeat
  • Consists of 2 periods:
  • Diastole:
    • relaxation,heart fills with blood
    • BP~80mmHg
  • Systole:
    • contraction, heart ejects blood
    • BP~120mmHg
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5
Q

Diastole

A
  • Venous return fills atria
  • AV valve opens
  • ~75% blood flows directly into ventricles
  • Atrial priming
    • pumps remaining 25% blood into ventricles
  • AV valve closes
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6
Q

Systole

A
  • Ventricles fill with blood
  • Increase in pressure
    • Isometric contraction
    • Aortic/pulmonary valves open
  • Blood ejected
    • 70% fast, 30% slow
  • Ventricles relax
  • Aortic/pulmonary valves close
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7
Q

What is cardiac output?

A
  • Cardiac output=Stroke volume * Heart Rate
    • CO=SV*HR
  • Stroke Volume
    • Blood volume ejected by ventricles/beat
  • Heart Rate
    • # heart beats/min
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8
Q

Calculating Cardiac Output

A
  • Cardiac output (mL/min)=Stroke volume (mL/beat)*Heart rate (beats/min)
  • Average resting heart rate:
    • ~70 beats/min
  • Average resting stroke volume:
    • ~70 mL/beat
  • Cardiact output=70*70=4900 mL/min
    • or ~5 L/min
  • During exercise, CO increases 7 fold
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9
Q

Preload and Afterload

A
  • Determinants of stroke volume
  • Preload
    • Tension of ventricular muscle before contraction
    • Determined by left ventricular end diastolic volume/pressure (LVED/LVEP)
  • Afterload
    • Pressure against which ventricles pump blood
    • Determined by total peripheral resistance
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10
Q

Excitiation-Contraction Coupling

A
  • Generation of electrical impulses:
    • Sinus node
    • AV node
  • Propogation of impulses:
    • Internodal pathways
    • Bachmann’s bundle
    • AV node, Bundle of His
    • Purkinje fibers
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11
Q

Cardiac Electrophysiology

A
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12
Q

Ion Channels Confirmational States

A
  • Resting
    • Closed, can be opened
  • Activated
    • Open, ions flowing
  • Inactivated
    • Closed, can’t be opened
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13
Q

Generation of Cardiac Rhythmicity

A
  • Sinus (sinoatrial) node
    • “Pacemaker region”
    • Small specialized muscle
    • Located in right atrium
    • Controls heart rate
    • Origin of spontaneous action potential
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14
Q

Spontaneous Action Potentials

A
  • HCN channels
    • hyperpolarization cyclic nucleotide gated
  • Phase 0:
    • Ca2+ enters: ICa-L
  • Phase 3:
    • K+ exits: IKS/IKR
  • Phase 4:
    • Na+ enters: If
    • Ca2+ enters: ICa-T/ICa-L
  • Key:
    • L: long
    • S: short
    • T: transient
    • F: funny
    • KS: slow delayed rectifier
    • KR: rapid delayed rectifier
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15
Q

Transmission of Cardiac Current

A
  • Internodal pathways/Bachmann’s bundle
    • Spread current through atria
  • AV node/Bundle of His
    • Electrically separate atria and ventricles
    • Delays current transmission to ventricles
    • Has spontaneous activity
      • Ectopic pacemaker
  • Purkinje Fibers
    • Spreads currents through ventricles
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16
Q

Transmission of Cardiac Impulses

A
17
Q

Non-spontaneous action potential

“cardiac action potential”

A
  • Phase 0
    • Na+ enters: INa
  • Phase 1
    • K+/Cl- exits: Ito1/Ito2
  • Phase 2
    • K+ exits: IKs
    • Ca2+ enters: ICa-L
  • Phase 3
    • K+ exits: IKs/IKR/IK1
  • Phase 4
    • Resting membrane potential
18
Q

Cardiomyocyte Contraction

A
  • Increase [Ca2+]i through L-type Ca2+ channels
  • Ca2+ spread through transverse T-tubules
  • Ca2+ opens rynodine receptors on sarcoplasmic reticulum
    • Calcium induced calcium release
  • Ca2+ binds troponin-C
  • Releases tropomyosin from actin
  • Increases actin-myosin cross-bridging
19
Q

Channels and Proteins in Cardiomyocyte Contraction: Illustration

A
20
Q

Troponin and Myosin Chains in Cardiomyocyte Contraction: Illustration

A
21
Q

Thick/Thin Filament in Cardiomyocyte Contraction: Illustration

A
22
Q

Factors affecting Cardiac Output

A
  • Frank-Starling Mechanism
  • Autonomics
    • Sympathetic nervous system
    • Parasympathetic nervous system
  • Renin-Angiotensin-Aldosterone System
23
Q

Frank-Starling Mechanism

A
  • “Within physiological limits, the heart pumps all the blood that it receives without allowing excessing damming of blood in the veins”
  • Increase in venous return
    • Cardiomyocyte contractility
  • Increase stroke volume
24
Q

Autonomic Regulation of Cardiac Output

A
  • Parasympathetic Nervous System
    • Decrease HR and SV
    • Dominant at rest
  • Sympathetic Nervous System
    • Increase HR and SV
    • Dominant during exercise/stress
25
Q

Autonomic Nervous System: Innervation Illustration

A
26
Q

Parasympathetic Effects

A
  • Vagal nerves release acetylcholine
    • SA and AV nodes
  • Acetylcholine stimulates M2-muscarinic receptors
  • Increase K+ channel opening
  • Decrease sinoatrial node rhythm
  • Decrease AV node transmission
27
Q

Sympathetic Effects

A
  • Sympathetic nerves release norepinephrine throughout heart
  • Stimulates Beta-1-adrenergic receptors
  • Increase Ca/Na channel opening
  • Increase SA node rhythm
  • Increase AV node transmission
  • Increase force of atrial/ventricular contraction
28
Q

Autonomic nervous system regulation of spontaneous action potential

A
  • PSNS→rest
    • Decrease AP frequency
    • Increase phase 4 duration
    • Decrease HR→Decrease CO
  • SNS→excercise, stress
    • Increase AP frequency
    • Decrease phase 4 duration
    • Increase HR→Increase CO
29
Q

Baroreceptor Reflex

A
  • Rapid, fine control of CVS
  • Sensory baroreceptors
    • Carotid sinus/aortic arch
    • Detect BP changes
  • Increase BP
    • Increase PSNS activity
    • Decrease CO
  • Decrease BP
    • Increase NS activity
    • Increase CO
30
Q

Renin-Angiotensin-Aldosterone System

A
  • Decrease BP in kidney nephron macula densa
    • Renin secreted into circulation
  • Renin→angiotensin to angiotensin I
  • Angiotensin converting enzyme (ACE)
    • angiotensin-I to angiotensin-II
  • Increase aldosterone
  • Increase plasma volume
  • Increase BP
  • Increase CO

Phcol 402 (11 decks)

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