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In animal behavior, a process involving transmission of, reception of, and response to signals. The term is also used in connection with other organisms, as well as individual cells of multicellular o
cyclic AMP (cAMP)
cyclic adenosine monophosphate, a ring-shaped molecule made from ATP that is a common intracellular signalling molecule (second messenger) in eukaryotic cells; regulator of some bacterial operons
G-protein linked receptor
When a neurotransmitter binds to this receptor it interacts with a GTP-binding protein, which in turn, interacts with enzymes or ion channels
a chemical messenger produced by an endocrine gland and carried by the bloodstream to another part of the body where it has a specific effect
ion channels
a transmembrane protein channel that allows a specific ion to diffuse across the membrane down its concentration or electrochemical gradient.
a molecule that binds specifically to another molecule, usually a larger one.
ligand-gated ion channel
a transmembrane protein containing a pore that opens or closes as it changes shape in response to a signalling molecule (lligand), allowing or blocking the flow of specific ions; ionotrophic receptor
signal transduction pathway
a series of steps linking a mechanical, chemical, or electrical stimulus to a specific cellular response
In animal behavior, transmission of a stimulus from one animal to another. The term is also used in the context of communication in other kinds of organisms and in cell-to-cell communication in all mu
Calcium ion in higher concentration outside the neuron. Voltage gated channels near the axon terminal, helps to depolarize the cell.
protein kinase
an enzyme that transfers phosphate groups from ATP to a protein, thus phosphorylating the protein
Receptor Protein
a protein with a particular shape allowing specific molecules to bind to it. Successful binding results in signals sent to the nucleus to use DNA to express certain physiological traits
second messenger
a small, nonprotein, water-soluble molecule or ion, such as a calcium ion (Ca2+) or cyclic AMP, that relays a signal to a cell's interior in response to a signaling molecule bound by a signal receptor
circadian rhythm
A physiological cycle of about 24 hours that is present in all eukaryotic organisms and that persists even in the absence of external cues.
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 relea
postsynaptic cell
The target cell at a synapse.
presynaptic cell
The transmitting cell at a synapse.
An automatic reaction to a stimulus, mediated by the spinal cord or lower brain.
refractory period
The short time immediately after an action potential in which the neuron cannot respond to another stimulus, owing to the inactivation of voltage-gated sodium channels.
A neurotransmitter that is a catecholamine, like epinephrine and norepinephrine.
electrochemical gradient
the diffusion gradient of an ion, which is affected by both the concentration difference of an ion across a membrane (a chemical force) and the ion's tendency to move relative to the membrane potentia
endocrine system
The internal system of communication involving hormones, the ductless glands that secrete hormones, and the molecular receptors on or in target cells that respond to hormones; functions in concert wit
motor neurons
neurons with axons that form synapses with muscle cells and command movements
myelin sheath
Around the axon of a neuron, an insulating coat of cell membranes from Schwann cells or oligodendrocytes. It is interrupted by nodes of Ranvier, where action potentials are generated.
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 plasma membrane.
Neuromuscular Junction (NMJ)
A chemical synapse between a spinal motor neuron axon and a skeletal muscle fiber. It is the localized site of Nicotinic Receptors in adults.
A molecule that is released from the synaptic terminal of a neuron at a chemical synapse, diffuses across the synaptic cleft, and binds to the postsynaptic cell, triggering a response.
nodes of ranvier
Gap in the myelin sheath of certain axons where an action potential may be generated. In saltatory conduction, an action potential is regenerated at each node, appearing to "jump" along the axon from
A physiological response to photoperiod, the relative lengths of night and day. An example of photoperiodism is flowering.
A type of light receptor in plants that mostly absorbs red light and regulates many plant responses, such as seed germination and shade avoidance.
resting potential
The membrane potential characteristic of a nonconducting excitable cell, with the inside of the cell more negative than the outside.
saltatory conduction
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.
Schwann Cells
Provides myelin that wraps around axons to increase the speed of the action potential. Located in the peripheral nervous system.
sensory neuron
A nerve cell that receives information from the internal or external environment and transmits signals to the central nervous system.
An association neuron; a nerve cell within the central nervous system that forms synapses with sensory and/or motor neurons and integrates sensory input and motor output.
sensory receptor
An organ, cell, or structure within a cell that responds to specific stimuli from an organism's external or internal environment.
The junction where one neuron communicates with another cell across a narrow gap. Neurotransmitter molecules released by the neuron diffuse across the synapse, relaying messages to the other cell.