| receptive field | That part of the retina whose photoreceptors (rods and cones) pertain to a single optic nerve fibre. The response of a neuron to stimulation of its receptive field depends on the type of neuron and the part of the field that is illuminated; an "on-centre" neuron is stimulated by light falling at the centre of its receptive field and inhibited by light falling at the periphery; an "off-centre" neuron reacts in exactly the opposite fashion; that is, it is inhibited by light falling at the centre of its receptive field. In either case, the net response depends on a complex switching action in the retina. When an entire receptive field is equally illuminated, the response of receptors at the centre of the field predominates. (05 Mar 2000) |
|---|---|
| receptoma | An obsolete term for chemodectoma. (05 Mar 2000) |
| receptor | 1. A molecular structure within a cell or on the surface characterised by selective binding of a specific substance and a specific physiologic effect that accompanies the binding, for example, cell surface receptors for peptide hormones, neurotransmitters, antigens, complement fragments and immunoglobulins and cytoplasmic receptors for steroid hormones. 2. A sensory nerve terminal that responds to stimuli of various kinds. (18 Nov 1997) |
| receptor aggregation | Chemically stimulated aggregation of cell surface receptors, which potentiates the action of the effector cell. (12 Dec 1998) |
| receptor agonist | A substance that mimics a specificneurotransmitter, is able to attach to that neurotransmitter's receptor and thereby produces the same action that theneurotransmitter usually produces. Drugs are often designed as receptor agonists to treat a variety of diseases and disorders whenthe original chemical substance is missing or depleted. (22 May 1997) |
| receptor downregulation | A phenomenon observed in many cells: following stimulation with a ligand the number of receptors for that ligand on the cell surface diminishes because internalisation exceeds replenishment. Often used very loosely, thus destroying the utility of the term. (18 Nov 1997) |
| receptor mediated endocytosis | Endocytosis of molecules by means of a specific receptor protein that normally resides in a coated pit, but may enter this structure after complex formation occurs. The structure then forms a coated vesicle that delivers its contents to the endosome whence it may enter the cytoplasm or the lysosomal compartment. Many bacterial toxins and viruses enter cells by this route. (18 Nov 1997) |
| receptor potential | The transmembrane potential difference of a sensory cell. Such cells are not generally excitable, but their response to stimulation is a gradual change in their resting potential. (18 Nov 1997) |
| receptor protein | An intracellular protein (or protein fraction) that has a high specific affinity for binding a known stimulus to cellular activity, such as a steroid hormone or adenosine 3',5'-cyclic phosphate. (05 Mar 2000) |
| receptor protein-tyrosine kinase | <enzyme> A catalytic protein-tyrosine kinase domain found on the cytoplasmic beta-portion of receptors. Many growth and differentiation factor receptors contain this domain. It is critical for the signal transduction pathways required for mitogenesis, transformation, and cell differentiation. Registry number: EC 2.7.1.- (12 Dec 1998) |
| receptor site | Point of attachment of viruses, hormones, or other activators to cell membranes. (05 Mar 2000) |
| receptor tyrosine kinase | Class of membrane receptors that phosphorylate tyrosine residues. Many play significant roles in development or cell division. Examples: insulin receptor family, c ros receptor, Drosophila sevenless, trk family. (18 Nov 1997) |
| receptor, chemokine | A molecule that receives a chemokine and acts as a dock for a chemokine. Several chemokine receptors are essential co-receptors for HIV. (12 Dec 1998) |
| receptor, visual | The layer of rods and cones, the visual cells, of the retina. (12 Dec 1998) |
| receptor-CD3 complex, antigen, T-cell | Molecule composed of the non-covalent association of the T-cell antigen receptor (receptors, antigen, T-cell) with the CD3 complex (antigens, CD3). This association is required for the surface expression and function of both components. The molecule consists of up to seven chains: either the alpha/beta or gamma/delta chains of the T-cell receptor, and four or five chains in the CD3 complex. (12 Dec 1998) |