Nervous System - Part 2

Vocabulary terms covering neuron structure, electrical signaling, action potential phases, and synaptic transmission based on the Chapter 48 lecture notes.

Neurons

Cells that transmit electrical signals throughout the body.

Glial cells

Cells that support neurons by nourishing them, regulating extracellular fluid, and insulating nerves.

Cell body (perikaryon)

The part of the neuron that contains organelles.

Dendrites

Neuron structures that carry signals TOWARD the cell body.

Axon

Neuron structure that carries signals AWAY FROM the cell body.

Sensory neurons

Neurons that transmit signals from the body's environment to the CNS.

Interneurons

Neurons located within the CNS that integrate sensory input.

Motor neurons

Neurons that transmit signals from the CNS to effectors or target organs.

Resting Potential

The membrane potential of a non-signaling neuron, typically between $-60$ to $-80\,mV$, where the inside is negative and outside is positive.

Sodium-potassium pump

An active transport mechanism that uses ATP to pump $3\,Na^+$ OUT and $2\,K^+$ IN to maintain resting potential.

Ungated channels

Ion channels that are always open and allow ions to flow in and out continuously.

Voltage-gated channels

Ion channels that open or close in response to a stimulus and can be inactivated by a ball blocking the pore.

Hyperpolarization

A change in membrane potential where the inside becomes MORE negative due to $K^+$ rushing out or negative ions rushing in.

Depolarization

A change in membrane potential where the inside becomes LESS negative due to $Na^+$ rushing in.

Threshold

The specific membrane potential ($\sim -50\,mV$) that, when reached, triggers an action potential via positive feedback.

Refractory period

A period during the undershoot phase when $Na^+$ channels are inactivated, preventing the generation of a new action potential and ensuring one-way signal travel.

Myelin sheath

Electrical insulation for axons formed by Schwann cells in the PNS or oligodendrocytes in the CNS.

Nodes of Ranvier

Gaps in the myelin sheath which are the only locations where voltage-gated $Na^+$ channels exist.

Saltatory conduction

The rapid transmission of a signal where the action potential "jumps" from one Node of Ranvier to the next.

Synaptic cleft

The gap between the presynaptic membrane and the postsynaptic membrane into which neurotransmitters are released.

EPSP (Excitatory Postsynaptic Potential)

A change in the postsynaptic membrane that occurs if the membrane depolarizes to the threshold, generating a new action potential.

IPSP (Inhibitory Postsynaptic Potential)

A change in the postsynaptic membrane where hyperpolarization occurs, inhibiting the generation of an action potential.