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A rapid change in the membrane potential of an excitable cell, caused by stimulus-triggered, selective opening and closing of voltage-sensitive gates in sodium and potassium ion channels.
autonomic nervous system
A subdivision of the motor nervous system of vertebrates; regulates the internal environment; consists of the sympathetic, parasympathetic, and enteric divisions.
A typically long extension, or process, from a neuron that carries nerve impulses away from the cell body toward target cells.
One of usually numerous, short, highly branched processes of a neuron that convey nerve impulses toward the cell body.
An electrical state in an excitable cell whereby the inside of the cell is made less negative relative to the outside than at the resting membrane potential. A neuron membrane is depolarized if a stimulus decreases its voltage from the resting potential of -70 mV in the direction of zero voltage.
Hormone secreted from the adrenal medulla; mediates fight-or-flight responses to short-term stress; functions as a neurotransmitter.
gated ion channel
A gated channel for a specific ion. By opening and closing such channels, a cell alters its membrane potential.
An electrical state whereby the inside of the cell is made more negative relative to the outside than at the resting membrane potential. A neuron membrane is hyperpolarized if a stimulus increases its voltage from the resting potential of -70 mV, reducing the chance that the neuron will transmit a nerve impulse.
Part of the vertebrate forebrain; functions in maintaining homeostasis, especially in coordinating the endocrine and nervous systems; secretes hormones of the posterior pituitary and releasing factors that regulate the anterior pituitary.
In a neuron, an insulating coat of cell membrane from Schwann cells that is interrupted by nodes of Ranvier, where saltatory conduction occurs.
A ropelike bundle of neuron fibers (axons and dendrites) tightly wrapped in connective tissue.
A weblike system of neurons, characteristic of radially symmetrical animals, such as Hydra.
A nerve cell; the fundamental unit of the nervous system, having structure and properties that allow it to conduct signals by taking advantage of the electrical charge across its cell membrane.
A chemical messenger released from the synaptic terminal of a neuron at a chemical synapse that diffuses across the synaptic cleft and binds to and stimulates the postsynaptic cell.
peripheral nervous system (PNS)
The sensory and motor neurons that connect to the central nervous system.
The membrane potential characteristic of a nonconducting, excitable cell, with the inside of the cell more negative than the outside.
Rapid transmission of a nerve impulse along an axon, resulting from the action potential jumping from one node of Ranvier to another, skipping the myelin-sheathed regions of membrane.
A type of glial cells that forms insulating myelin sheaths around the axons of neurons in the peripheral nervous system.
Gap between synaptic terminal of an axon and a signal-receiving portion of another neuron or effector cell.
Membranous sac containing neurotransmitter molecules at the tip of the presynaptic axon.
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