Experiment 3: Varying the frequency of stimulus trains

We are smooth operators

Most of our skeletal muscle movements are smooth and fluid.

You could imagine how difficult it would be to drink a cup of coffee if all movements were done as a series of twitches. There probably wouldn’t be much liquid left in the cup by the time it reached your mouth!

Q. Which of the following do you think might contribute to making our movements occur smoothly?

Q. When you flex your biceps muscle, the required motor units recruited at the start of the contraction will remain active for the entire movement.

Experiment 3: Varying the frequency of stimulus trains

Tetanic Contractions in vivo

Which fibre type do you predict would produce a tetanic contraction with a lower frequency of input (action potentials) from its α motor neuron?

Experiment 2: Summation of contractions

You may recall the approximate time frame of the refractory periods from lectures or other learning activities. If not ask a friend or google it now.

• Do these seem similar to any of the ISI’s used in Experiment 2?
• It is very likely that at the lowest ISI (2 ms), the axons are still in their absolute refractory period.

What will this mean in terms of the skeletal muscle fibres?

Anatomy of the heart

Answer TRUE or FALSE to the following statements:

Q. Both the atrioventricular and semilunar valves have chordae tendineae.

Q. The tricuspid valve prevents back flow of blood from the left ventricle to the left atrium during ventricular contraction.

Q. The moderator band can only be seen in the right ventricle

Q. The primary function of the moderator band is to prevent over-distention of the right ventricle.

Q. The atrioventricular valves are open during diastole and close during systole.

Q. The right ventricle is thicker than the left ventricle.