Question

1- Explain your understanding of the how the action potential (the electricity) passes from the motor neuron to the skeletal muscle. 2- In your own words, discuss the steps of how a skeletal muscle contracts. 3- If a muscle is not getting enough oxygen, which kind of cellular respiration w ill it use? 4- What is the oxygen debt?

Answer 1

1 & 2. A neuromuscular junction (or myoneural junction) is a chemical synapse formed by the contact between a motor neuron and a muscle fiber. It is at the neuromuscular junction that a motor neuron is able to transmit a signal to the muscle fiber, causing muscle contraction.

Synaptic transmission at the neuromuscular junction begins when an action potential reaches the presynaptic terminal of a motor neuron, which activates voltage-dependent calcium channels to allow calcium ions to enter the neuron. Calcium ions bind to sensor proteins (synaptotagmin) on synaptic vesicles, triggering vesicle fusion with the cell membrane and subsequent neurotransmitter release from the motor neuron into the synaptic cleft. In vertebrates, motor neurons release acetylcholine (ACh), a small molecule neurotransmitter, which diffuses across the synaptic cleft and binds to nicotinic acetylcholine receptors (nAChRs) on the cell membrane of the muscle fiber, also known as the sarcolemma. nAChRs are ionotropic receptors, meaning they serve as ligand-gated ion channels. The binding of ACh to the receptor can depolarize the muscle fiber, causing a cascade that eventually results in muscle contraction.

3. If not enough oxygen can reach your muscle cells, then aerobic respiration is replaced with anaerobic respiration. This does not need oxygen for it to happen. Anaerobic respiration produces much less energy than aerobic respiration.In anaerobic respiration, glucose breaks down without oxygen. Anaerobic respiration produces lactic acid, rather than carbon dioxide and water.

4.   Anaerobic respiration occurs when there is no oxygen available and so produces an oxygen debt. Oxygen debt is the amount of extra oxygen required by muscle tissue to oxidize lactic acid and replenish depleted ATP and phosphocreatine following vigorous exercise.