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What happens in the heart when an action potential is generated in the SA node?
Myocardial contraction
What happens in a heart when an action potential is generated in the SA node?
It simulates the node, which then sends impulses to the AV node, which disperses these impulses through the cardiac muscle to cause a cardiac cycle (rhythmic beating and relaxing of atria and ventricles)
Why is the cardiac action potential longer?
The reason why cardiac muscle has a longer action potential is to extend the absolute refractory period to prevent another action potential. If too many action potentials stimulate the cardiac muscle it can get into tetanus which keeps the heart continuously contracted without relaxation.
Why do you keep the heart from entering tetanus?
The action potential of cardiac muscle is prolonged consisting of the depolarization spike and plateau and a repolarization period. The action potential causes a long refractory period of about 250-400 milliseconds in the heart.
Does atrial systole occur before or after the firing of the sinoatrial node?
The SA node makes the action potential for the heart. Atrial systole must occur after the action potential.
How do the waves of depolarization generated by the autorhythmic cells spread to the muscle cells?
Autorhythmic cells in the heart generate electrical impulses that spread through the atria and ventricles via specialized conduction pathways, such as the atrioventricular node, bundle of His, and Purkinje fibers. These pathways allow for coordinated depolarization of the muscle cells, ultimately leading to contraction of the heart chambers.
What are autorhythmic fibers?
They are fibres which generate AP(action potential) which trigger heart contractions.
How can electrolyte imbalance control your heart function?
Electrolytes such as Sodium and potassium help the heart contract through a process called action potential. When the heart is at -60 MV the cell will open up allowing sodium into the cardiac cells causing a contraction. Look up action potential.
What are pacemaker potentials and the action potential they trigger?
Pacemaker potentials are automatic potentials generated and are exclusively seen in the heart. They arise from the natural "leakiness" of the membrane that pacemaker cells have, resulting in passive movement of both Na+ and Ca2+ across the membrane, rising the membrane potential to about -40mV. This results in a spontaneous depolarization of the muscle that has a rise in the curve that is nowhere near as steep as the action potential of other cells. Upon depolarization, the cell will return back to its resting membrane voltage, and continue the potential again.
What is blood flow generated by?
The flow of blood times the resistance of the blood vessels.
Which cells cause resting membrane potentials to continually depolarize?
Cells with unstable resting membrane potentials, such as pacemaker cells in the heart or neurons in the brain, can continually depolarize due to the presence of a "funny" current (If) that slowly depolarizes the cell until it reaches the threshold for an action potential to be generated.
What is the cause of compensatory pause after an extrasystole?
Extrasystole is due to the irregular contraction of the ventricle before the atria. When this happens, an action potential is elicited and the ventricle contracts. The action potential had a refractory period, during which the intrinsic heart rate attempts to fire but cannot elicit a contraction. This is why extrasystole is often referred to as skipping a beat. The compensatory pause is the time it takes for the beat to resume normal contraction.
