| cardiac gating | Using an electronic signal from the cardiac cycle to trigger an event, such as in imaging separate phases of cardiac contraction. (05 Mar 2000) |
|---|---|
| gating | 1. In a biological membrane, the opening and closing of a channel, believed to be associated with changes in integral membrane proteins. 2. A process in which electrical signals are selected by a gate, which passes such signals only when the gate pulse is present to act as a control signal, or passes only the signals that have certain characteristics. See: gate. (05 Mar 2000) |
| gating current | <physiology> Small currents in the membrane just prior to the increase in ionic permeability, due to the movement of charged particles within the membrane. So called because they open the gates for current flow through ion channels. (20 Mar 1998) |
| gating mechanism | Occurrence of the maximum refractory period among cardiac conducting cells approximately 2 mm proximal to the terminal Purkinje fibres in the ventricular muscle, beyond which the refractory period is shortened through a sequence of Purkinje cells, transitional cells, and muscular cells; gating mechanism may be a cause of ventricular aberration, bidirectional tachycardia, and concealed extrasystoles, a mechanism by which painful impulses may be blocked from entering the spinal cord. Compare: gate-control theory. (05 Mar 2000) |
| channel gating | <physiology> Small currents in the membrane just prior to the increase in ionic permeability, due to the movement of charged particles within the membrane. So called because they open the gates for current flow through ion channels. (20 Mar 1998) |
| ion channel gating | The opening and closing of ion channels due to a stimulus. The stimulus can be a change in membrane potential (voltage-gated), drugs or chemical transmitters (ligand-gated), or a mechanical deformation. Gating is thought to involve conformational changes of the ion channel which alters selective permeability. (12 Dec 1998) |
| systolic/diastolic ratio | A calculation from pulsed Doppler ultrasound determinations of blood flow velocities that reflects intrinsic resistance in an arterial blood vessel. (05 Mar 2000) |
| diastolic | Of or pertaining to the diastole. (18 Nov 1997) |
| diastolic afterpotential | In the heart, a transmembrane potential change following repolarization, which may reach threshold magnitude and cause a rhythm disturbance; often recorded in poisoning, as by digitalis overdosage. (05 Mar 2000) |
| diastolic blood pressure | The pressure exerted on the walls of the arteries when the heart is in the relaxation phase (diastole). Considered abnormally elevated if consistently over 90 mmhg. (27 Sep 1997) |
| diastolic murmur | A murmur heard during diastole. (05 Mar 2000) |
| diastolic pressure | The intracardiac pressure during or resulting from diastolic relaxation of a cardiac chamber; the lowest arterial blood pressure reached during any given ventricular cycle. (05 Mar 2000) |
| diastolic shock | The abnormally palpable impact, appreciated by a hand on the chest wall, of an accentuated third heart sound. (05 Mar 2000) |
| diastolic thrill | A thrill felt over the precordium or over a blood vessel during ventricular diastole. (05 Mar 2000) |
| early diastolic murmur | A murmur that begins with the second heart sound, as the murmur of aortic insufficiency. (05 Mar 2000) |