Olivia Kern'S 4.1 Neuromuscular Function

Question 1

Draw and Label the diagram of a motor Unit

Answer 1

included had to be: Limit to dendrite, cell body, nucleus, axon, motor end plate, synapse and muscle.

(the red circles are muscle)

Question 2

Explain how skeletal muscle contracts by the sliding filament theory.

Answer 2

5. The Ca2+ binds to troponin located on the actin filament, causing tropomyosin to move and expose binding sites for myosin.
6. Once the binding site in the actin is exposed, The myosin head now binds to actin and forms a crossbridge.
7. ADP and P(i) are released from myosin, which causes the myosin to move. This movement is called the power stroke.
8. Once the impulse stops, Ca2+ is released from troponin causing tropomyosin to cover the binding sites and prevent contraction. Ca2+ returns to the SR and waits for another impulse. This is relaxation.

Question 3

Nr 1 of Muscular contraction

Answer 3

The brain or spinal cord sends an impulse to the muscle.

Question 4

Step 2 of Muscular contraction

Answer 4

The impulse travels down the motor neuron and reaches a neuromuscular junction where it releases acetylcholine, which triggers the impulse in the muscle.

Question 5

Step 3 of Muscular contraction

Answer 5

The impulse travels through the plasma membrane (sarcolemma) and down T tubules surrounding the myofibrils.

Question 6

Step 4 of muscle contraction

Answer 6

As the impulse passes through the T tubules, it causes the sarcoplasmic reticulum (SR) surrounding the T tubule to release calcium ions (Ca2+) into the sarcoplasm, eventually reaching the sarcomere.

Question 7

Explain the role of neurotransmitters in stimulating skeletal muscle contraction.

Answer 7

Acetylcholine: Signal from the brain is sent via motor neuron; the action potential arrives at the motor end plate where it enters vesicles containing Acetylcholine in the synaptic terminal; the vesicles release acetylcholine into the synapse; thereby creating a new action potential in the muscle; new action potential travels along the myofibril down the T-tubules into the sarcoplasmic reticulum reaching calcium ions whereby the calcium is released; the calcium binds to troponin causing tropomyosin to change position and expose the binding sites in the actin; this allows for the sliding filament theory to occur.

Acetylcholinesterase: When the nerve is no longer stimulated, acetylcholine is removed by acetylcholine esterase; calcium goes back into the sarcoplasmic reticulum and the myosin heads move back to their resting positions away from the actin.

Question 8

Explain how slow and fast twitch fibre types differ in structure and function.

Answer 8

There are 3 types of fibre based on how fast a muscle will twitch and the pathway used to generate energy (anaerobic or aerobic).

Type 1 Slow Oxidative Fibre: Maintains posture (anti-gravity muscles), endurance running; back and neck muscles.

Type 2a Fast Oxidative Fibre: Walking, sprinting; leg muscles.

Type 2b Fast Glycolic Fibre: Rapid, intense muscles for short duration; ball throwing, weight lifting; arm muscles.