PNB 2265 Lecture Notes - Lecture 10: Vagus Nerve, Stroke Volume, Cardiac Output

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The second heart sound (S2,
"dupp"), occurs:
During atrial systole
During early ventricular
systole
After late ventricular
systole
o Closing valves
After late ventricular diastole
Wigger’s Diagram
Cardiac Output
Cardiac output
o Stroke volume
(mL/beat)
MULTIPLIED BY:
Heart rate (beats/min)
o ~6L per min
Modulation of CO
Variations in heart rate and
stroke volume change cardiac
output
Heart Rate
Automatic
Doesn't need any myocytes
Pace maker are innervated autonomic and are adrenergic hormones
o Epi and norepi can change
o Innervated by sympathetic and parasympathetic
Autonomic Innervation (Both Innervate Pacemaker Cells)
Sympathetic
o Cardiac nerve
Adrenergic neurons
Release epi onto pace maker cells
o Cardioacceleratory center
o NE
o Can control both stroke volume and heart rate speed
Parasympathetic
o Vagus nerve
o Cardioinhibitory center
o ACh
Constantly released to slow down AP
o Decrease cAMP and decrease pace
o If you block parasympathetic: increase in basal heart rate in a person
o Not good at changing stroke volume, only heart rate
The vagus nerve decreases heart rate by decreasing the rate of SA node filling
Acceleration: GPCRs
Catecholamines: epinephrine, norepinephrine
In the heart, NE/E bind beta adrenergic receptors G-protein coupled receptors (Gs)
Beta Receptors on Heart to Respond to Epi and Norepi***
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