Neuroscience: Resting Membrane Potential and Nervous System Organization

Vocabulary flashcards covering resting membrane potential, ion driving forces, hyper/hypokalemia, nervous system divisions, and neuronal cell types.

Equilibrium Potential

The membrane potential that exactly opposes the movement of an ion down its concentration gradient.

Potassium Equilibrium Potential ($E_K$)

The membrane potential at which the electrical force inward exactly balances the chemical concentration force outward for potassium ions, calculated as $-94\,mV$ (or $-90\,mV$ in combined ion models).

Sodium Equilibrium Potential ($E_{Na}$)

The membrane potential at which the inward chemical force of sodium is exactly opposed by an outward electrical force, equal to $+60\,mV$.

Resting Membrane Potential ($V_m$)

The membrane potential of an inactive cell, which ranges from $-40\,mV$ to $-90\,mV$ in excitable cells (and is typically $-70\,mV$ in resting neurons).

Relative Charge Scale

A measurement convention where the extracellular fluid (ECF) is set to $0\,mV$ (ground), giving the intracellular fluid (ICF) a relative charge such as $-70\,mV$ or $-2$ relative units.

Influx

The net movement of ions or molecules into the cell.

Efflux

The net movement of ions or molecules out of the cell.

$\text{Na}^+/\text{K}^+$ ATPase

An electrogenic primary active transporter that pumps $3\,\text{Na}^+$ out of the cell for every $2\,\text{K}^+$ pumped into the cell, maintaining ionic concentration gradients and a negative intracellular charge.

Depolarization

A shift in the cell's membrane potential that makes it less negative than the resting potential.

Hyperpolarization

A shift in the cell's membrane potential that makes it more negative than the resting potential.

Repolarization

The return of the membrane potential toward the resting potential following a depolarization.

Normokalemia

The physiological state in which blood plasma $\text{K}^+$ concentration is within the normal range of $3.5\text{--}5\,mM$.

Hyperkalemia

An increased blood $\text{K}^+$ concentration (greater than $6\,mM$) that depolarizes cells and brings the resting membrane potential closer to threshold.

Hypokalemia

A decreased blood $\text{K}^+$ concentration (less than $3.5\,mM$) that hyperpolarizes the cell membrane, moving it farther from threshold.

Central Nervous System (CNS)

The division of the nervous system consisting of the brain (containing $80\text{--}100\text{ billion}$ neurons) and spinal cord (containing $100\text{ million}$ neurons) that acts as the integrating center.

Peripheral Nervous System (PNS)

All nervous tissue outside the brain and spinal cord, including cranial and spinal nerves, ganglia, plexuses, and sensory receptors.

Afferent Neurons

Sensory neurons that transmit information about stimuli (such as temperature, pressure, and light) toward the Central Nervous System (CNS).

Efferent Neurons

Neurons (motor and autonomic) that carry signals away from the Central Nervous System (CNS) to target cells.

Interneurons

Complex branching neurons located entirely within the Central Nervous System (CNS) that facilitate communication between neurons.

Somatic Motor Neurons

Efferent neurons that control voluntary skeletal muscles.

Autonomic Neurons

Efferent neurons divided into sympathetic and parasympathetic branches that control involuntary targets like cardiac muscle, smooth muscle, glands, and adipose tissue.

Enteric Nervous System

A network of neurons in the digestive tract that can operate autonomously or be controlled by the CNS via the autonomic division of the PNS.

Neurons

The basic signaling units of the nervous system, typically consisting of a cell body (soma), dendrites, and an axon.

Glia

Support cells in the nervous system, such as astrocytes and oligodendrocytes, that intertwine with neurons to provide maintenance and functional support.

Dendrites

Neuronal processes that receive incoming electrical and chemical signals from neighboring cells and convey them toward the cell body.

Axons

Long extensions of neurons that carry outgoing signals away from the integrating center to target cells.

Pseudounipolar Neurons

Sensory neurons that feature a single process acting as an axon, formed during development by the fusion of the dendrite with the axon.

Bipolar Neurons

Neurons with two relatively equal processes extending from opposite sides of the central cell body, specialized for senses like smell and vision.

Anaxonic Neurons

Interneurons in the Central Nervous System that lack an apparent long axon.

Multipolar Neurons

Neurons characterized by multiple branching dendrites and a single long axon, typical of efferent neurons and many CNS interneurons.

Nerve

A bundle of peripheral neuronal processes bound together by connective tissue sheaths (epineurium, perineurium, endoneurium) that can carry sensory, motor, or mixed signals.