Neuroscience Exam 1 Review: Action Potentials and Neuronal Biophysics

This set of vocabulary flashcards covers the primary concepts of neuronal signaling, including action potential phases, biophysical properties like resistance and capacitance, summation types, and the functional roles of various nervous system cells based on the exam assessment transcript.

Depolarization

The phase of the action potential where graded potentials reach a threshold, causing voltage-gated Na+ channels to open, increasing permeability, and allowing Na+ ions to rush into the cell.

Repolarization

The phase in which the cell returns toward equilibrium via the Na+/K+ pump (moving 3 Na+ out and 2 K+ in) and the closing of Na+ channels.

Hyperpolarization

The phase where the membrane potential becomes more negative than the resting potential due to slow-to-close K+ channels; it can also be caused by K+ ions leaving the cell during an IPSP.

Driving Force

A value representing the strength of ion flow rather than direction; it is high when the equilibrium potential ($E_{ion}$) is far away from the membrane potential ($V_m$).

Temporal Summation

A process where a single neuron fires signals repeatedly in quick succession to build upon previous potentials to reach the threshold for an action potential.

Spatial Summation

A process where multiple pre-synaptic partners (such as Neurons A, B, and C) fire at the same time to summate their graded potentials and reach threshold.

Interneuron

An engine of communication typically responsible for mediating signals between afferent sensory neurons and efferent motor neurons.

Afferents

Neurons in the Peripheral Nervous System (PNS) that project towards the Central Nervous System (CNS).

Glial Cells

Cells in the brain that serve as guideposts during development, recycle neuronal signaling materials, assist in cellular metabolism, and provide electrical insulation for neurons.

Voltage-gated Na+ current

A negative current that occurs when Na+ enters the neuron, resulting in the depolarization of the membrane.

Absolute Refractory Period

A period caused by the inactivation of voltage-gated Na+ channels, ensuring no inward Na+ current can be evoked to generate a second action potential.

Relative Refractory Period

A period during which a second action potential can be generated, but only if provided with enough current.

Myelin

A substance that increases membrane resistance ($R_m$), increases action potential conduction velocity, and decreases capacitance ($C$) while restricting voltage-gated Na+ channels to the Nodes of Ranvier.

Excitatory Post Synaptic Potential (EPSP)

A passive potential that slightly depolarizes a neuron without reaching the threshold for an action potential.

Stochastic Gating

The principle that ion channels open and close at random, though they are more likely to open as the membrane depolarizes ($V_m$ increases).

Resting Membrane Potential ($V_{rest}$)

The steady-state membrane potential, which is mostly dictated by K+ ions wanting to leave the cell following their chemical gradient.

$$R_m$$

The symbol for membrane resistance; higher $R_m$ (such as in neurons with fewer leak channels) allows graded potentials to travel farther.

$$R_i$$

The symbol for internal resistance of a neuron.

$$C$$

The symbol for capacitance.

$$g_{ion}$$

The symbol for conductance of a specific ion.

$$I_{ion}$$

The symbol for ionic current.

$\tau$ (Tau)

The symbol for the time constant.

$\lambda$ (Lambda)

The symbol for the length constant.