VPT 321: Veterinary Neuropharmacology (2+1) copy 1

WRITING / RECORDING LEVERS

• They are used to record the contraction or relaxation of the isolated tissue preparation. The recording is done on smoked paper fixed on electrically operated cylinders/recording drums. The writing lever is connected through a thread to upper part of the tissue suspended in the inner tissue bath.
• The writing levers are made up of light aluminium, stainless steel, wood (straw) etc. They are usually light and fine but rigid so that while writing they do not bend thereby losing their sensitivity and efficiency.

On the basis of location of fulcrum, writing levers are of two types:

• Class I type: The fulcrum or pivot lies between the writing point and the point of attachment of the tissue.For example, frontal writing lever.
• Class II type: In this type, the fulcrum or pivot lies at one end beyond the point of attachment. For example, Starling’s heart lever.