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heart mechanics

Abstract:
The purpose of this experiment was to subject a rat cardiac muscle to different physiological situations and determine their effect on the twitch force and duration.Force-frequency relation show a positive trend suggesting that as frequency of stimulation increases (for the range of 0.2-0.8 Hz), the force increases.Also the extra cellular calcium concentration effects on the peak force were measured, showed an increasing trend when the [Ca2+ ]o was incrementally increased from 0.2 to 3mmolL-1.The rat cardiac muscle was also subjected to cardiac glycoside such as ouabain, which resulted in an increase in the diastolic force, inotropic agents such as isoprenaline, which increased the velocity of contractility, and finally the effects of caffeine were considered.
Method:

Experimental set up:

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We were provided with a ventricular strip of a rat heart muscle; it had the dimensions of (~20mm resting length, 5mm wide and 1mm thick). The strip was embedded in an oxygenated 1.5mM Ca2+ Tyrode solution (constant PH=7.4) with constant O2 partial pressure of oxygen is 760 mmHg, because the cell needs oxygen in order to survive, the strip mounted using threads to a force transducer and a stimulator (REF1), these were connected to power LAB (amplifier) which was connected to a computer, the Chart software was used to record the data.
Note that the temperature the experiment was performed at was 14 C, and specimen was field stimulate at a voltage of 60V in order to make the whole muscle contract.
Field stimulation is the stimulation of the specimen through a medium, so that the whole tissue is electrically stimulated, point stimulation is stimulating a single muscle cell.
Measurements of frequency-force relation:
We applied different stimulus frequencies to the muscle (ranges 0.1-0.8 Hz) and recorded the force response, each frequency stimulated the muscle for a short period of time (around 1 minute) until the force response …

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