BIPN 100 Lecture Notes - Lecture 23: Afterload, Blood Pressure, Stroke Volume
13 Jun 2018
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BIPN 100 Lecture 23
5/30/2018
• Different afterloads
o At constant preload and different afterloads, there is less shortening of the
muscle until it reaches a maximum tension
o The heart cannot contract outside the total tension curve
• HTN increases afterload, meaning the heart has to pump with a larger force on
contraction to reach the pressure of the system
o B→C is isovolumic
o C→D is isometric
o Stroke volume=EDV-ESV
o B→D is systole
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o D→B is diastole
o Systolic pressure that’s generated is the peak between C and D
• Cardiac output
o Is the volume of blood pumped by one ventricle in a given period of time
o It indicates how efficiently the heart is working and total blood flow through the
system, but not how the blood is distributed in the body
o HR (bpm) x SV (ml/beat)
o Average stroke volume is 5L/min
• Regulation of heart function
o Intrinsic regulation
▪ Results from normal functional characteristics, not on neural or hormonal
regulation
▪ Starling’s law of the heart
o Extrinsic regulation
▪ Involves neural and hormonal control
▪ Parasympathetic stimulation
• Supplied by the vagus nerve
• Decreases HR
• Acetylcholine secreted
▪ Sympathetic stimulation
• Supplied by cardiac nerves
• Increases HR and force of contraction
• Epinephrine and norepinephrine released
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