Muscle Contraction

Question 1

What is involuntary muscle?

Answer 1

Smooth muscle found in the wall of tubular structures like blood vessels which is controlled unconsciously by the autonomic nervous system.

Question 2

What is cardiac muscle?

Answer 2

This from the muscular part of the heart which is myogenic meaning it contracts on its own

Question 3

What is skeletal muscle?

Answer 3

occurs at the joints in the skeleton and is composes of muscle fibres

Question 4

What do muscle fibres consist of?

Answer 4

they are fibres containing many nuclei and enclosed by a membrane called the sarcolemma. contain a cytoplasm called the sarcoplasm which is specialised with many mitochondria and a specialised endoplasmic reticulum.

Question 5

What are myofibrils?

Answer 5

Contained in muscle fibres and is divided into sarcomeres containing protein filaments , actin and myosin.

Question 6

What are light bands?

Answer 6

No overlap between actin and myosin

Question 7

What are dark bands?

Answer 7

An overlap between actin and myosin

Question 8

What is the Z line?

Answer 8

Line at the centre of s light band

Question 9

what is a sarcomere?

Answer 9

The distance between 2 Z lines

Question 10

What is the H zone?

Answer 10

The light section of the dark band

Question 11

What is the process at a neuromuscular junction?

Answer 11

1. Action potential arrives at the end of the axon and open the calcium channel which causes calcium to flood the axon
2. Vesicles of acetylcholine move towards and fuse with the end membrane
3. Molecules diffuse across gap and fuse with receptors on the sarcolemma
4. causes sodium ion channel to open and sodium enters the muscle fibre causing depolarisation of sarcolemma
5. wave of depolarisation spread along sarcolemma and down traverse tube in muscle fibre.

Question 12

What is the sliding filament hypothesis?

Answer 12

During contraction the light band and the H zone get shorter and the Z lines move closer together and the sarcomere shortens so the thick and thin slide over each other

Question 13

What is the process of muscle contraction?

Answer 13

1. the muscle is stimulated
2. action potential causes a release of calcium
3. calcium binds to troponin which alters its shape and pulls the tropomyosin to the side exposing the actin binding sites
4. myosin heads bind to the actin which forms cross bridges between the filaments
5. myosin head moves pulling actin past myosin
6. myosin then detaches and can bind again further up the actin filament.

Question 14

What is the role of ATP?

Answer 14

Supplies the energy for muscle contraction

Question 15

How is the supply of ATP maintained (3 ways)?

Answer 15

1. Aerobic respiration in mitochondria
2. anaerobic respiration in sarcoplasm
3. Creatine Phosphate in sarcoplasm

Question 16

How does creatine phosphate supply ATP and what is the enzyme involved?

Answer 16

It acts as a reserve store of phosphate groups which can be transferred to ADP molecules to create ATP. The enzyme involved is creatine phosphotransferase