Lecture 15 study guide Flashcards
Define the resting membrane potential (RMP)
- The voltage difference across the
plasma membrane during rest - Inside of the cell is negative compared
to the outside (-70 mV)
Explain how ion concentration and membrane permeability contribute to the RMP
The resting membrane potential is determined by the uneven distribution of ions (charged particles) between the inside and the outside of the cell, and by the different permeability of the membrane to different types of ions.
Describe the role of the sodium-potassium (Na⁺/K⁺ ATPase) pump in stabilizing the RMP
Pumps 3 Na+ out and 2 K+
in using ATP
– Balances the differences
in plasma membrane
permeability
– Stabilizes resting
membrane potential
Which ion is most permeable at rest, and why?
Potassium ( K+ ) because many channels are open
Differentiate between leakage channels and gated channels.
A leakage channel always remains open for substances and ions, whereas the gated-ion channels open in response to the specific changes in the membrane potential of the channel
what are the different types of gated channels?
activation: closed at rest
inactivation: blocks the channel soon after opening
Describe the influence an electrochemical gradient has on ion movement
determines the direction that ions will flow through an open ion channel
Explain the relationship between current, voltage, and resistance as it applies to neurons (use the formula V = IR)
i = v/r, tells us that the current, i, flowing through a circuit is directly proportional to the voltage, v, and inversely proportional to the resistance, r.
How do graded potentials differ from action potentials in terms of strength and distance of signaling?
- action potential: all-or none:that occurs in the axon and is used for long-distance transmission of neural signals - graded potential is a variable-strength signal that depends on the strength of the stimulus and happens in the dendrites and cell body.
What determines whether a graded potential triggers an action potential?
When a graded potential causes hyperpolarization in a neuron, an action potential is not likely. If a graded potential causes depolarization, an action potential is more likely.
Describe the mechanism by which a graded potential spreads and dissipates. Be sure to include the role of ionic movement.
Graded potentials are produced by stimuli opening a gated channel and are local potentials. They cannot spread over long distances away from the stimulation. Sodium ions enter cells, attracted to negative charges on inner membrane surfaces.
Describe the phases of an action potential, including depolarization,
repolarization, and hyperpolarization.
1) Depolarization: activated sodium channels, deactivated potassium channels, 2) Repolarization: inactivated sodium channels, activated potassium channels, 3) Hyperpolarization: moving back to activation for the sodium channels, activated potassium channels, 4) Resting state: both sodium and potassium channels
Explain the “all-or-none principle” and how it relates to the threshold potential
An action potential occurs when the membrane depolarises to a certain threshold, if this threshold is not reached the action potential will not be triggered. This is referred to as the all-or-nothing principle in biology: it means that the power of a stimulus is not proportional to the power of the action potential.
What is the role of voltage-gated Na⁺ and K⁺ channels in the generation of an action potential?
those that allow sodium to cross the membrane (voltage-gated sodium channels) and those that allow potassium to cross the membrane (voltage-gated potassium channels).
Compare and contrast the absolute and relative refractory periods. When can another action potential be generated?
During absolute refractory, the neuron cannot fire another action potential. Relative refractory occurs after absolute refractory. During relative refractory, it is possible for the neuron to produce another action potential, but it requires a much greater stimulus to reach the threshold.
