Neuroscience: Resting Potential, Action & Graded Potentials

What is the typical resting membrane potential (RMP) of a neuron?

Approximately -70 mV

Which two factors primarily establish the resting membrane potential?

Leak channels (primarily K+ leaking out) and Na+/K+ pumps

What is the function of chemically gated channels and where are they located?

They respond to neurotransmitters and are located on dendrites and the soma

Where are voltage-gated channels primarily located?

Along the axon, particularly at the axon hillock

What is the difference between depolarization and hyperpolarization?

Depolarization moves the membrane potential toward 0 mV, while hyperpolarization makes it more negative than the RMP

What is the threshold potential required to trigger an action potential?

Approximately -55 to -60 mV

What characterizes a graded potential?

It is a local change in potential that decays over distance and is proportional to stimulus strength

What is the 'all-or-none' principle in action potentials?

Once the threshold is reached, a full action potential of fixed amplitude occurs regardless of stimulus strength

What ion movement causes the rapid depolarization phase of an action potential?

Na+ rushing into the cell

What ion movement causes the repolarization phase of an action potential?

K+ rushing out of the cell

What is the absolute refractory period?

A period during which no new action potential can be fired because Na+ channels are inactivated

How does the relative refractory period differ from the absolute refractory period?

A new action potential is possible during the relative refractory period, but only with a stronger-than-normal stimulus

What is saltatory conduction?

The process where action potentials 'jump' from node to node in myelinated axons

What are the Nodes of Ranvier?

Gaps in the myelin sheath with high densities of voltage-gated Na+ channels

How does axon diameter affect the speed of signal propagation?

Larger diameters increase speed by reducing internal resistance

Which type of nerve fiber is the fastest?

A fibers (large and myelinated)

How is stimulus intensity coded in the nervous system?

By the frequency of action potentials (number of APs per second)

What is the primary purpose of graded potentials?

To integrate signals at the dendrites/soma to reach the threshold at the axon hillock

What is the primary purpose of action potentials?

Long-distance signaling along the axon

What happens to the membrane potential during the brief hyperpolarization phase?

It becomes more negative than the RMP because K+ channels are slow to close