Muscle excitation

Question 1

When does muscle excitation occur?

Answer 1

When an action potential iss propagated across the neuromuscular junction

Question 2

Define the neuromuscular junction

Answer 2

The connection between a muscle and a neuron

Question 3

Where does muscle excitation occur?

Answer 3

The sarcoplasm

Question 4

What mediates muscle excitation

Answer 4

Calcium ions

Question 5

WHat is the neurotransmitter of the neuromuscular junction

Answer 5

Acetyl choline

Question 6

What does the neurotransmitter binging to the receptor result in haooening

Answer 6

Releasing sodium ions into the cell

Question 7

What is the synaptic cleft

Answer 7

The space between the muscle and the neuron

Question 8

Can electrical impulses pass over the synaptic cleft?

Answer 8

No - therefore the signal is transported to the neurotransmitter

Question 9

Where would you find many Ach. receptors?

Answer 9

The motor end plate

Question 10

What are released in response to an action potential?

Answer 10

Synaptic vesicles which are full of Ach neurotranmitters

Question 11

Explain the stages of muscle excitation

Answer 11

1. Nerve impulse reaches the neuromuscular junction
   2, Acetyl choline is released from the motor neuron
2. Ach. binds with receptor in the muscle membrane to allow sodium to enter
3. Sodium imflux creates an action potential in the sarcolemma
4. Action potential travels down t tubule
5. Sarcoplasmic reticulum releases calcium
6. Calcium binds with troponin to move the troponin tropomyosin complex
7. Binding sites in actin filaments are exposed

Question 12

Outline the stages of muscle contraction

Answer 12

1. ATP is hydrolysed on myosin head - it then bind to actOin to form a crossbridge
2. Myosin head pivots - actin moves to the centre of the sarcomere
3. Myosin detaches and binds to ATP, ready for a new contraction
4. If stimulation stops, Calcium channels cloe preventing further release of calcium
5. Calcium is restored to the resevoir in the sarcoplasmic reticulum by active transport
6. tROPONIN AND TROPOMYOSIN RETURN TO THEIR ORIGINAL POSITIONS PREVENTING THE BINDING OF MYSOSIN AND ACTIN
7. Muscle relaxes and recoils