One of the most common neurotransmitters; functions by binding to receptors and altering the permeability of the postsynaptic membrane to specific ions, either depolarizing or hyperpolarizing the membrane.
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 that 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.
Collection of structures in the adult brain, including the midbrain, the pons, and the medulla oblongata; functions in homeostasis, coordination of movement, and conduction of information to higher brain centers.
central nervous system (CNS)
In vertebrate animals, the brain and spinal cord.
Part of the vertebrate hindbrain located dorsally; functions in unconscious coordination of movement and balance.
The surface of the cerebrum; the largest and most complex part of the mammalian brain, containing sensory and motor nerve cell bodies of the cerebrum; the part of the vertebrate brain most changed through evolution.
The right or left side of the vertebrate brain.
The thick band of nerve fibers that connect the right and left cerebral hemispheres in placental mammals, enabling the hemispheres to process information together.
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.
A catecholamine hormone secreted from the adrenal medulla that mediates fight-or-flightresponses to short-term stress; also 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.
The ventral 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.
Segregation of functions in the cortex of the left and right hemispheres of the brain.
ligand-gated ion channel
A protein pore in the plasma membrane that opens or closes in response to a chemical signal, allowing or blocking the flow of specific ions.
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.
A hormone that is chemically and functionally similar to epinephrine.
One of three divisions of the autonomic nervous system; generally enhances body activities that gain and conserve energy, such as digestion and reduced heart rate.
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.
The locus where one neuron communicates with another neuron in a neural pathway; a narrow gap between a synaptic terminal of an axon and a signal-receiving portion (dendrite or cell body) of another neuron or effector cell. Neurotransmitter molecules released by synaptic terminals diffuse across the synapse, relaying messages to the dendrite or effector.
A narrow gap separating the synaptic knob of a transmitting neuron from a receiving neuron or an effector cell.
A bulb at the end of an axon in which neurotransmitter molecules are stored and released.
Membranous sac containing neurotransmitter molecules at the tip of the presynaptic axon.
voltage-gated ion channel
A specialized ion channel that opens or closes in response to changes in membrane potential.