AMPHIBIAN CHARTS

HELPFUL IN PRACTICALS

1. AMPHIBIAN charts -KAVYA MATTA

2. Effect of ions and drugs on frogs heart. Calcium chloride and adrenaline stimulate the heart whereas potassium and acetylcholine depresses the heart. Sodium chloride increases the heart rate but decreases the force of contraction.

3. The heart of the contraction remains the same irrespective of the strength of the stimulus,that is the amplitude of the threshold stimulus is sameas the amplitude of the contraction recorded with stimuli of the highest threshold. No recordings occur with the subthreshold stimulus.

4. The frequency of the heart rate after placing the first stannous ligature is significantly less than the normal rhythm. The frequency is much lower after placing the second stannous ligature.

5. The first few contractions show a successive increase in amplitude , which is known as the stair case phenomenon.

6. When the subliminal stimulus are applied repeatedly with the interval between the consective stimuli being less than one second, the stimuli summate and produce a response.

7. Stimulus applied during systole produces no extrasystole but stimulus applied during diastole produces an extrasystole which is followed by an compensatory pause called post extrasystole potentiation .

8. The effect of temperature on the sinus venosus and the ventricles. On sinus venosus : Cold ringers solution decreases the heart rate but increases the force of contraction . Warm ringers solution increases the heart rate but decreases the force of contraction. on venticles : amplitude of contraction is decreased by cold riger & increased by warm riger .

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