Ch 37

Neuron

A nerve cell that transfers information within the body.

Electrical signals

Long-distance signals used by neurons to communicate.

Chemical signals

Short-distance signals used by neurons to communicate.

Ganglia

Simple clusters of neurons where processing of information takes place.

Cell body

The part of a neuron that contains most of its organelles.

Dendrites

Highly branched extensions of a neuron that receive signals from other neurons.

Axon

A much longer extension of a neuron that transmits signals to other cells.

Axon hillock

The cone-shaped base of an axon where signals are generated.

Synapse

The junction where branched ends of axons transmit signals to other cells.

Neurotransmitters

Chemical messengers that pass information from transmitting neurons to receiving cells.

Glial cells

Supporting cells required by neurons in vertebrates and most invertebrates.

Sensory input

The stage of information processing where sensory neurons transmit information about external stimuli or internal conditions.

Integration

The stage of information processing where interneurons analyze and interpret the sensory input.

Motor output

The stage of information processing where motor neurons transmit signals to glands or muscle cells, causing a response.

Central nervous system (CNS)

The organization of neurons that carry out integration.

Peripheral nervous system (PNS)

The organization of neurons that carry information into and out of the CNS.

Resting potential

The membrane potential of a neuron not sending signals.

Ion pumps

Proteins that use ATP to maintain ion gradients across the plasma membrane.

Ion channels

Selectively permeable channels in the plasma membrane that allow ions to pass through.

Equilibrium potential

The membrane voltage for a particular ion at equilibrium.

Graded potentials

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

Threshold

The level of depolarization required to initiate an action potential.

Refractory period

The period after an action potential where a second action potential cannot be initiated.

Action potential

An electrical signal that travels along the axon of a neuron, allowing for communication between neurons.

Depolarization

The process of the membrane potential becoming less negative, leading to the generation of an action potential.

Na+ channels

Sodium channels that allow the flow of sodium ions into the neuron during depolarization.

Synaptic terminals

The ends of the axon where neurotransmitters are released to communicate with other neurons.

Inactivated Na+ channels

Sodium channels that are closed and unable to allow the flow of sodium ions, preventing the action potential from traveling backward.

Nodes of Ranvier

Gaps in the myelin sheath where voltage-gated Na+ channels are found, allowing for the formation of action potentials in myelinated axons.

Myelin sheath

Insulation around axons, produced by glia (oligodendrocytes in the CNS and Schwann cells in the PNS), which enables fast conduction of action potentials.

Saltatory conduction

The process by which action potentials in myelinated axons jump between the nodes of Ranvier, increasing the speed of conduction.

Synapses

The junctions between neurons where communication occurs through the release and reception of neurotransmitters.

Chemical synapses

Synapses where communication occurs through the release of chemical neurotransmitters.

Neurotransmitter

A chemical messenger that carries information from the presynaptic neuron to the postsynaptic cell.

Synaptic vesicles

Small sacs in the synaptic terminal that store neurotransmitters.

Ligand-gated ion channels

Ion channels in the postsynaptic cell that open upon binding of a neurotransmitter, generating a postsynaptic potential.

Excitatory postsynaptic potentials (EPSPs)

Depolarizations that bring the membrane potential of the postsynaptic cell closer to the threshold for generating an action potential.

Inhibitory postsynaptic potentials (IPSPs)

Hyperpolarizations that move the membrane potential of the postsynaptic cell farther from the threshold for generating an action potential.

Summation

The process by which individual postsynaptic potentials combine to produce a larger postsynaptic potential, which can trigger an action potential.

Temporal summation

The summation of EPSPs produced in rapid succession.

Spatial summation

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