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21 Cards in this Set
- Front
- Back
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Action Potential at SA Node
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Ca ion influx brings it up to -40mV (threshhold)
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Autonomic Tone Affecting heart Rate
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Dual innervation - sympathetic and parasympathetic
In healthy, resting individuals, parasympathetic effects dominate - Acetylcholine is released If parasympathetic activity increases, the heart rate declines If sympathetic activity increases, the heart rate increases |
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Autonomic Tone Affecting heart Rate - Effects on SA Node
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The sympathetic and parasympathetic divisions alter heart rate by changing the ionic permeabilities of cells in the conducting system
Acetylcholine (released by parasympathetic) opens chemically gated K+ channels (positive ions leak out)- this slows the rate of spontaneous depolarization and extends the duration of repolarization so the heart rate slows Norepinephrine (sympathetic) opens sodium-calcium channels; this influx of positively charged ions increases the rate of depolarization and shortens the period of repolarization so the SA node reaches threshold faster and you get a quicker heartbeat |
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Action Potential in Cardiac Muscle
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See pg. 701
Rapid depolarization - from sodium influx Plateau - from Ca ion entry Repolarization - from K ion loss |
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Skeletal vs. Cardiac Muscle Action Potentials
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Skeletal muscle - Action potential and contractiojn are much shorter duration than cardiac muscle
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Action Potential
Inhibition |
? Postsynaptic potential
Inhibition makes it harder to contract |
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Arrhythmias
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Problems with electrical conduction
Flutter Fibrillation Tachycardia Bradycardia |
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Arrhythmias
Flutter |
200-300 beats/min
Beats are coordinated Can turn into fibrillation |
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Arrhythmias
Fibrillation |
200-300 beats/min
Beats are uncoordinated Carn arise from flutter |
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Arrhythmias
Tachycardia |
Greater than 100 beats/min
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Arrhythmias
Bradycardia |
Less than 60 beats/min
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Heart Murmurs
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Abnormal heart sounds due to abnormal valve closure
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Pressure and Volume changes
Step 1 |
Atria and Ventricles in diastole - quiescent period; AV valves are open
Semilunar valves are closed Ventricles have passive filling - over 70% get filled |
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Pressure and Volume changes
Step 2 |
Atrial systole
Atria contract and deliver remaining 20-30% of blood to ventricles End diastolic volume - volume of blood in ventricles at the end of ventricular diastole ( which is when atrial systole ends) EDV is greatest amount of blood in ventricles |
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Pressure and Volume changes
Step 3 |
Ventricles contract (systole)
Increase in ventricular pressure AV valves close First heart sound is lub - when AV valves close Isovolumetric contraction - all valves are closed; pressure increases, but volume doesn't change |
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Pressure and Volume changes
Step 4 |
Ventricles still contracting
Semilunar vlaves open Blood is ejected from ventricles |
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Pressure and Volume changes
Step 5 |
Pressure in aorta and pulmonary trunk increase
Semilunar valves close - second sound (dub) Isovolumetric relaxation - all valves closed; volume stays the same, but pressure in ventricles is decreasing |
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Pressure and Volume changes
Step 6 |
Atria are filling and as pressure increase in the atria, the AV vavles open again
Ventricular filling begins again |
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Blood Pressure
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If blood vessels are constricted, total peripheral resistance is increases and blood pressure is increased
If vessels are dilated, total peripheral resistance is decreased and pressure is decreased |
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Stroke Volume
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Amount of blood ejected from ventricles per beat
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Heart
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see pg 705, 707, 708
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