Epicardium: This serous membrane of smooth outer surface of heart
Myocardium: Middle layer composed of cardiac muscle cell and responsibility for heart contracting
Endocardium: Smooth inner surface of heart chambers
Regulation of the Heart
Intrinsic regulation: Results from normal functional characteristics, not on neural or hormonal regulation
Extrinsic regulation: Involves neural and hormonal control
Parasympathetic + sympathetic stimulation
Extrinsic Regulation
Parasympathetic stimulation
Supplied by vagus nerve, decreases heart rate, acetylcholine secreted
Sympathetic stimulation
Supplied by cardiac nerves, increases heart rate and force of contraction, epinephrine and norepinephrine released
Pacemaker Regulation
Once the pacemaker cells reach threshold, the magnitude and duration of the AP is always the same.
In order to change the frequency, the time between APs must vary.
The interval can only be changed in two ways.
The rate of depolarization can be changed
Heart Homeostasis
-Effect of BP
Baroreceptors monitor BP
=Effect of pH, co2,o2
Chemoreceptors monitor
-Effect of extracellular ion conc
Increase or decrease in extracellular K+ decreases heart rate
-Effect of body temp
HR increases when body temp inc
HR dec when..
Mean Arteriole Pressure
Average blood pressure in aorta
MAP=CO x PR
PR is total resistance against which blood must be pumped
CO is amount of blood pumped by heart per minute
CO=SV x HR
SV: Stroke volume of blood pumped during each heart beat
HR: Heart rate or number of times heart beats per minute
Cardiac reserve: Difference between CO at rest and maximum CO
Cardiac Arrhythmias
Tachycardia: HR in excess of 100bpm
Bradycardia: HR less than 60 bpm
Sinus arrhythmia: HR varies 5% during resp cycle + up to 30% during deep respiration
Premature atrial contractions: Occasional shortened intervals btwn 1 contraction
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