Physiology Exam 2 2
Terms
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- How does the heart provide for circulatory blood flow and maintain bp?
- By delivering the necessary CO
- How is CO regulated?
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Heart rate - pacemaker cells
Strok Vol - Starlings
contractility - adrenal medulla
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secretes epinephrine from vagus
acts as NE does - Autonomic Regulation of the Heart
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Area symp para
SA inc HR dec HR
AV inc cond dec cond
atrialm inc cont dec contr
ventm inc cont dec cont
little
effect on
contracti
pacemakers - intrinsic rate of SA node
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remove symp and para input
~100 - Atropine
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Muscarinic blocker
Blocks Parasympathetics
Inhibits AcH
Increases HR - Propranolol
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Beta adrenergic blocker
Blocks sympathetic
decreases HR - Slope and Effect of autonomic system
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1. Sympathetics increase slope and HR
2. Parasympathetics decrease slope and HR
To decrease slope:
1. hyperpolarize w/ paraympethetics via K channel
2. Decrease sympathetic input
To increase slope:
1. Open depolarizing channels w/ sympathetic input leads to faster AP - How do you increase HR?
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1. Increase plasma epinenphrine
2. Increase activity of sympathetic nerves B1 receptors (NE)
3. Decrease Para activity (muscarinic) - Regulation of Stroke Volume
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1. Increase end diastolic volume which lengthens the cardiac muscle and allows for maximal contraction due to length/tension relationship (Starling's Law)
VERY important b/c if you give heart more blood it WILL pump it; prevents pooling
Allows matching cardiac output b/w left and right - Sympathetic input and contractility
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1. Sympathetic stimualtion creates a new upward shifted Starling curve of increased contractility
2. This increases ejection fraction
3. This increases stroke volume -
Positive Inotropic Effect
Negative Inotropic Effect -
Increased contractility
decreased Contractility - Physiology of Sympathetic Input on Contraction
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1. increases Ca influx
2. increases strength of contraction
3. increases rate of Ca remova from cytoplasm
4. strengthens and shortens the contractile twitch - How do you increase SV?
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1. Increase EDV
2. Activate Sympathetic
3. Increase plasma epinephrine - Regulation Of CO
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cardiac muscle HR
inc epi inc epi
sympa sympa
inc EDV Dec para