Heart function in frogs 1 what is the temporal relationship

Heart function in frogs

1. what is the “temporal” relationship between the electrical activities (ECG) and the mechanical activities (ventricular contraction) in a frog heart?

In other words, do we expect to see the recordings of ventricular contraction preceded by the QRS complex on ECG recordings? Is there any other evidence that will show a cause-and-effect relationship between these two activities?)

2. why does the QRS complex appear first and then the ventricular contraction?)

3. what will happen to the heart rate and to the force of ventricular contraction when the temperature of the heart increases (20 to 30C) or decreases (20 to 10C)? What is the reasonable temperature coefficient (Q₁₀) for the heart rate or for the force of ventricular contraction?)

how does the temperature change affect these variables? Which chemical reactions are temperature-dependent during ventricular systole? For comparison, what is the temperature coefficient (Q₁₀) for a pure “physical” reaction?)

4. describe the expected changes in the heart rate and the contraction force when an electrical stimulation is applied to the S-V node.)

how does this change come about? Explain the mechanisms for the heart function in terms of neurotransmitters and its effect on ion channels.

Solution

Cardiac cycle in frog\'s heart begins with contraction of ‘sinus venosus’. With this contraction, a range of electrical signals are spread all over the heart. Electrical activity results in mechanical activity, i.e. contraction of auricles, and then ventricles.

QRS interval corresponds to depolarization of ventricles (both left and right). In frog\'s heart, only one ventricle is there, instead of mammalian heart, where two are there. Blood of both auricles come into the single ventricle; which is mixed over there.

So, depolarization of auricles will result in contraction of auricles first. This corresponds to P wave. Then the electrical wave reaches ventricles, where it causes depolarization; resulting in contraction of ventricles.

So, your answer is \'yes\'; contraction of ventricles should be preceded by QRS interval on ECG recording.