| intraventricular block | Delayed conduction within the ventricular conducting system or myocardium, including bundle-branch, peri-infarction blocks, the fascicular blocks, excitation, and the W-P-W (pre-expectation) syndrome. (05 Mar 2000) |
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| entrance block | An incompletely understood mechanism whereby a pacemaker is protected from being discharged by the impulse from another centre; the mechanism, usually conceived as an encircling zone of unidirectionally refractory tissue permitting egress of impulses from the centre but preventing access to the centre, is seen in operation in ventricular parasystole where the parasystolic centre is protected from discharge by the sinus pacemaker and so is able to maintain its intrinsic rhythm undisturbed. Synonym: entrance block, protection. (05 Mar 2000) |
| epidural block | An obstruction in the epidural space; used inaccurately to refer to epidural anaesthesia. (05 Mar 2000) |
| exit block | Inability of an impulse to leave its point of origin, the mechanism for which is conceived as an encircling zone of refractory tissue denying passage to the emerging impulse. (05 Mar 2000) |
| fascicular block | A condition based on the concept that the left branch of the bundle of His provides two of three major fascicles of a system of conduction, of which the right bundle branch constitutes the third, for the transmission of the cardiac impulse from the atrium above to the ventricles below the A-V node; block may occur in any or all fascicles, all three together producing complete A-V block. See: hemiblock. (05 Mar 2000) |
| unidirectional block | Block that prevents passage of an impulse when it approaches from one direction but not from the other, as when block in the A-V node prevents anterograde conduction to the ventricles while retrograde conduction to the atria remains intact. (05 Mar 2000) |
| field block | Regional anaesthesia produced by infiltration of local anaesthetic solution into tissues surrounding an operative field. (05 Mar 2000) |
| field block anaesthesia | Conduction anaesthesia in which small nerves are not anaesthetised individually, as in nerve block anaesthesia, but instead are blocked en masse by local anaesthetic solution injected to form a barrier proximal to the operative site. (05 Mar 2000) |
| first degree A-V block | See: atrioventricular block. (05 Mar 2000) |
| fish-block | See Fish-tackle. Source: Websters Dictionary (01 Mar 1998) |
| abducens nerve | <anatomy, nerve> The 6th cranial nerve. The abducens nerve originates in the abducens nucleus of the pons and sends motor fibres to the lateral rectus muscles of the eye. Damage to the nerve or its nucleus disrupts horizontal eye movement control. (12 Dec 1998) |
| abducent nerve | <anatomy> The abducent nerve enervates a muscle which moves the eyeball. Lesions of the sixth cranial nerve result in deviation of the eyeball outward and double vision. Synonym: cranial nerve VI. (27 Sep 1997) |
| accessory nerve | <anatomy, nerve> The accessory nerve enervates the sternocleidomastoid muscles and the trapezius muscles. Lesions of the eleventh result in drooping of the shoulder and inability to rotate the head away from the affected side. Synonym: cranial nerve XI. (27 Sep 1997) |
| accessory nerve lymph nodes | The nodes of the lateral deep cervical group that are located along the accessory nerve; their efferent vessels pass to the supraclavicular lymph nodes. Synonym: companion lymph nodes of accessory nerve, nodi lymphatici comitantes nervi accessorii. (05 Mar 2000) |
| accessory nerve trunk | Part of the accessory nerve formed within the cranial cavity by the union of the cranial and spinal roots, which then divides within the jugular foramen into internal and external branches, the former uniting with the vagus, the latter exiting the foramen as in independent branch which is commonly considered to be the accessory nerve. (05 Mar 2000) |