Muscle Physiology Structure and Function Part 2

Question 1

What is a synapse?

Answer 1

a place where neuromuscular connection takes place
- space between terminal axon and the motor end plate

Question 2

What is an action potential?

Answer 2

the signal from the brain that is driven by movement of depolarization.
- travel down our neuron and the neuron is a single cell in the nervous system

Question 3

What is a neuron?

Answer 3

a single cell in the nervous system

Question 4

What is the neurotransmitter primarily involved in muscle contraction

Answer 4

acetylcholine

Question 5

What are dendrites?

Answer 5

tiny hair-like RECEIVES around the nucleus that receives signals from other neurons and moves to the axon and then the axon terminal which connects to the neuromuscular junction

Question 6

what is myelin?

Answer 6

the coating around the cell or coating around the axon of the neuron and insulates the axons and allows the conduction of the signal and happen more efficiently. promotes good signal transmission

Question 7

what is the nodes of Ranvir?

Answer 7

tiny gaps in the myelin that allow the signal to jump down the axon faster

Question 8

where is the motor end plate?

Answer 8

between muscle fibers and the axon terminal

Question 9

Explain the steps of what happens after action potential arrives to the motor neuron axon? (the process of signal transmission) (neuromuscular junction)

Answer 9

1. action potential arrives at synapse via the axon terminal
2. neurotransmitter (acetylcholine) released into synaptic cleft (space between axon and muscle fiber (sarcolemma))
3. neurotransmitter triggers a cascade of events which lead the action potential (signal) to continue on the muscle fiber
4. action potential travels via the sarcolemma down the T-Tubules
5. action potential triggers the release of Calcium from the sarcoplasmic reticulum

Question 10

what does actin filaments look like?

Answer 10

balls in a spiral arrangement, around it is tropomyosin and troponin complexs

Question 11

what is tropomyosin?

Answer 11

• a purple band that wraps around the actin filament
• in relaxed muscle it blocks the myosin binding site on actin

Question 12

what is a troponin complex?

Answer 12

a complex that is attached to tropomyosin that is a binding site for calcium

Question 13

what is the role of calcium in muscle contraction?

Answer 13

causes tropomyosin to change shape and exposes the myosin binding site on actin for muscle contraction

Question 14

What is the sliding filament theory?

Answer 14

• systemic way that actin and myosin interact
• involves formation of “crossbridges”
• requires ATP
• repeats as long as Calcium and ATP remain present

Question 15

What are the steps of the sliding filament theory?

Answer 15

1. myosin heads hydrolyze ATP and become reoriented and energized
2. myosin heads bind to actin, forming crossbridges
3. myosin crossbridges rotate toward center of the sarcomere (power stroke)
4. as myosin heads bind ATP, the crossbridges detach from actin
5. repeat

• contraction cycle continues if ATP is available and Ca 2+ level in the sarcoplasm is high