Question

1. When the neuron stops firing, what steps occur for the muscle to relax? Discuss the flow of ions in and out of the muscle and how that impacts relaxation.

2. Compare red and white muscles relative to their speed of action and endurance. Think about where you have mitochondria and myoglobin, think about aerobic and anaerobic respiration.

3. The spinal cord receives a stimulation, integrates the message, and then sends the signal out through the ventral spinal nerves. Describe the steps of excitation coupled with contraction, from the nerve to the muscle.

Answer 1

1. Steps.

Initially ca2+ move out of the cell. This is by the opening of ion channel the sodium moves out and the potassium moves in so the ca2+ is transported out.The ca2+ is actively transported to the sarcoplasmic reticulum. The. The myosin binding site on actin is blocked by restoring tropomyosin blockage. Now the muscle relaxes.

2. The red muscle fibres have myoglobin content more than the white.

For aerobic respiration the oxygen transported to the muscle needs to bind with the myoglobin. So this takes place in the red muscles. So they need myoglobin and the look red. They are slow twiching fibres.

For anaerobic respiration what we need is energy production the more. So there will be more mitochondria. These muscles are fast twiching fibres.

3. The message is formed in the spinal cord. The stimulus is formed. It is transferred to the cell body of the nerve which is then transported to the dendrites through axon. Now the dentrites will face the muscle fibres at the neuromuscular junction. Now the Voltage depended calcium channels open. Then the pre synaptic membrane gives out acetylcholine to the synaptic cleft when then fuses with the post synaptic membrane in the muscle fibre. Now ion channels open. Sodium moves in and potassium goes out. The muscle contraction occurs. After the stimulus is reverted the ion flow also reverts. The acetylcholine gets degraded.