Neurons, Synapses, and Signaling

Comprehensive vocabulary list covering neuron structure, resting and action potentials, synaptic transmission, and major neurotransmitters based on lecture notes.

CNS (Central Nervous System)

The part of the nervous system where integration takes place, consisting of the brain and spinal cord.

PNS (Peripheral Nervous System)

The part of the nervous system that brings information into and out of the CNS, including cranial nerves, ganglia, and spinal nerves.

Dendrites

Highly branched extensions of a neuron that receive signals from other neurons and act as the input to the neuron.

Axon

A long extension of a neuron that transmits information as electrical signaling toward other cells.

Synapse

The junction where a neuron transmits information to another cell, such as another neuron or an effector cell.

Neurotransmitter

Chemical messengers that carry information across the synaptic cleft from a presynaptic cell to a postsynaptic cell.

Sensory neuron

A type of neuron that transmits information about external and internal stimuli.

Interneuron

Neurons that integrate information within the processing centers of the nervous system.

Motor neuron

A neuron that transmits signals to muscles or glands to trigger motor output.

Glia

Cells in the nervous system that support neurons and perform functions such as forming myelin sheaths.

Membrane potential

The difference in voltage across the plasma membrane of a cell.

Resting potential

The membrane potential of a neuron not sending signals, typically between $-60$ and $-80\,mV$.

Na+/K+ pump

A membrane protein that uses the energy of ATP to maintain $Na^+$ and $K^+$ concentration gradients across the plasma membrane.

Equlibrium Potential of Potassium ($E_K$)

The membrane potential at which the chemical and electrical forces on potassium are balanced, modeled as $-90\,mV$.

Equlibrium Potential of Sodium ($E_{Na}$)

The membrane potential at which the chemical and electrical forces on sodium are balanced, modeled as $+62\,mV$.

Gated ion channels

Ion channels that open or close in response to stimuli, forming the basis of electrical signaling in the nervous system.

Hyperpolarization

An increase in the magnitude of the membrane potential, making the inside of the cell more negative, often due to increased $K^+$ permeability.

Depolarization

A reduction in the magnitude of the membrane potential, making the inside of the cell less negative, often due to increased $Na^+$ permeability.

Graded potentials

Changes in polarization where the magnitude of the change varies directly with the strength of the stimulus.

Threshold

The specific membrane voltage value ($\sim -55\,mV$ for mammalian neurons) that must be crossed to trigger an action potential.

Action potential

A massive, all-or-none change in membrane voltage that carries information along axons.

Refractory period

A period after an action potential during which a second action potential cannot be initiated due to temporary inactivation of $Na^+$ channels.

Myelin sheath

An insulating layer produced by oligodendrocytes in the CNS and Schwann cells in the PNS that increases the speed of action potential conduction.

Nodes of Ranvier

Gaps in the myelin sheath where voltage-gated ion channels are at high density and where action potentials form.

Saltatory conduction

The process in myelinated axons where action potentials appear to jump from one node of Ranvier to the next.

Excitatory postsynaptic potential (EPSP)

A depolarization of the postsynaptic membrane that brings the membrane potential toward the threshold.

Inhibitory postsynaptic potential (IPSP)

A hyperpolarization of the postsynaptic membrane that moves the membrane potential further from the threshold.

Temporal summation

The effect produced when two or more EPSPs are generated at a single synapse in rapid succession, adding their effects together.

Spatial summation

The addition of EPSPs produced nearly simultaneously by different synapses on the same postsynaptic neuron.

Acetylcholinesterase (AChE)

The enzyme in the synaptic cleft that terminates the action of acetylcholine by breaking it down.

Glutamate

An amino acid that acts as a major neurotransmitter in the CNS and is involved in long-term memory.

Gamma-aminobutyric acid (GABA)

An amino acid neurotransmitter that acts by stimulating inhibitory postsynaptic potentials (IPSPs).

Biogenic amines

A group of neurotransmitters that includes epinephrine, norepinephrine, dopamine, and serotonin.

Substance P

A neuropeptide neurotransmitter that affects the perception of pain.

Endorphins

Neuropeptides that function as natural painkillers, acting on the same receptors as opiates like morphine.