Conductile Cell
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Terms in this set (50)
Conductile Cell
pacemaker cells of the heart that initiate depolarization and contraction
Contractile Cells
generate the pressures within the atrium and ventricle that propels the blood out of the chambers
Autorhythmicity
ability to beat spontaneously and repetitively in the absence of input from the nervous system due to pacemaker cells
Functional Syncytium
Cells in the heart are electrically coupled together via gap junctions (nexuses) causing a wave of depolarization
Resting Membrane Potential of the SA node Pacemaker Cells
-50 to -60 mV
Why do SA node pacemaker cells have a higher resting membrane potential than skeletal muscle cells? (2)
1. I(f) channel causes a steady influx of Na+
2. NO K1 channel that would hyperpolarize and inhibit the cell
Steps of the action potential in SA node pacemaker cells
I(f) channel is always open and permeable to Na+ and Ca2+ creating the resting membrane potential
1. When the K+ channel closes, the I(f) channel is uninhibited and depolarizes the cell to threshold
2. At threshold membrane potential the voltage-gated Ca2+ channel opens, causing an influx of Ca2+ and rapid depolarization
3. Voltage-gated K+ (TEA-type/rectifier type) channels open slowly and then repolarize the cell
Image: Steps of the action potential in SA node pacemaker cells
Rate of action potentials in the SA node pacemaker cells
exceeds 100 per minute
Differences between ventricular cells and SA nodal cells (2)
1. Fast voltage-dependent Na+ channel
2. Potassium channel (K1)
Steps of the action potential in ventricular cells
Phase 0: Fast voltage-dependent Na+ channel opens w/ causing rapid depolarization
Phase 1: Voltage-dependent Na+ channels close, while voltage-gated Ca2+ channels open & stay open for a long time causing plateau
Phase 2: K1 channels close (no effect)
Phase 3: . Voltage-gated K+ (TEA-type/rectifier type) channels open and then repolarize the cell
Phase 4: K1 channels open at voltages between -90 and -50 mV, this channel is responsible for maintaining resting membrane potential (-80 to -90 mV)
Image: Steps of the action potential in ventricular cells