Master this deck with 16 terms through effective study methods.
Generated from uploaded pdf
Electrical potentials are crucial for various cellular functions, including communication between neurons, muscle contraction, and maintaining homeostasis. They arise from differences in ion concentrations across cell membranes.
No, action potentials can only be generated in excitable cells such as neurons and muscle cells. This is due to the presence of voltage-gated ion channels that allow for rapid changes in membrane potential.
The three main factors are the concentration gradients of ions (especially sodium and potassium), the permeability of the membrane to these ions, and the activity of ion pumps such as the sodium-potassium pump.
Local anesthetics block sodium channels in the neuronal membrane, preventing the influx of Na+ ions during depolarization, which inhibits the generation and propagation of action potentials, leading to a loss of sensation.
During depolarization, voltage-gated sodium channels open, allowing Na+ ions to rush into the cell, causing the membrane potential to become more positive and leading to the generation of an action potential.
During repolarization, sodium channels close and potassium channels open, allowing K+ ions to exit the cell. This movement of potassium ions restores the negative membrane potential, returning the cell to its resting state.
The 'all or nothing' principle states that once a threshold potential is reached, an action potential is generated and propagated along the axon without diminishing in strength. If the threshold is not reached, no action potential occurs.
The absolute refractory period is the time during which a second action potential cannot be initiated, regardless of the strength of the stimulus. This ensures unidirectional propagation of action potentials and prevents overlapping signals.
Hypercalcemia decreases neuronal and muscular excitability by stabilizing the membrane potential, making it less likely for action potentials to occur, which can lead to muscle weakness and reduced reflexes.
Hypocalcemia increases excitability in neurons and muscles, potentially leading to conditions such as tetany, where muscles contract uncontrollably due to heightened responsiveness to stimuli.
The opening of sodium channels during depolarization represents a positive feedback mechanism, as the influx of Na+ ions further depolarizes the membrane, leading to the rapid propagation of the action potential.
Examples include the cardiac rhythm of the heart, peristaltic movements in the intestines, and the rhythmic pattern of breathing, all of which are regulated by intrinsic pacemaker cells.
The plateau phase in cardiac action potentials prolongs the depolarization, preventing tetany in heart muscle and allowing for effective pumping of blood by ensuring that the heart has time to fill with blood before the next contraction.
During repolarization, voltage-gated potassium channels open, allowing K+ ions to flow out of the cell, which helps to restore the negative membrane potential and return the cell to its resting state.
Concentration gradients create differences in ion concentrations across the membrane, which drive the movement of ions through channels and pumps, ultimately establishing the resting membrane potential and influencing action potentials.
The sodium-potassium pump actively transports 3 Na+ ions out of the cell and 2 K+ ions into the cell, helping to maintain the concentration gradients necessary for the resting membrane potential and the generation of action potentials.