Skeletal muscles

Question 1

What are smooth muscles? Where are smooth muscles found?

Answer 1

Muscles that contract involuntarily and are usually found in organs.

Question 2

What are cardiac muscles? Where are cardiac muscles found?

Answer 2

Muscles that contract involuntarily and are usually found in the heart.

Question 3

What are skeletal muscles? Where are skeletal muscles found?

Answer 3

Muscles that contract voluntarily

Question 4

What attaches muscles and bones?

Answer 4

tendons

Question 5

What attaches bones to bones?

Answer 5

ligaments

Question 6

What are antagonistic pairs?

Answer 6

Muscles that work together to move a bone. The contracting muscle is the agonist muscle and the relaxing muscle is called the antagonist muscle.

Question 7

Draw the structure of a muscle fibre.

Question 8

What are myofibrils made up of?

Answer 8

sarcomeres

Question 9

Draw and label the structure of a sarcomere.

Question 10

What is the structure of the myosin filaments?

Answer 10

They have globular heads that have an actin-binding site and an ATP-binding site.

Question 11

What is the structure of the actin filaments?

Answer 11

They have a myosin-binding site which is blocked by proteins called tropomyosin.

Question 12

Describe the sliding filament theory.

Answer 12

1. An action potential arrives at the muscle fibres and polarises the sarcoplasm reticulum. This causes the reticulum to release calcium ions into the sarcoplasm.
2. The calcium ions bind to troponin and cause it to change shape. This pulls the tropomyosin attached to it away from the myosin-binding site.
3. The globular head of the myosin filaments can now bind to the binding site and form a cross bridge.
   4 The calcium ions also activate ATP hydrolase. The hydrolase breaks down the AT to release energy which is used to bend the myosin head. This pulls the actin filament along in a rowing motion.
4. Another ATP molecule is broken down to break the cross-bridge, this means the myosin head can bind to another binding site and pull the actin filament further along.
5. This causes the sarcomeres to shorten and the muscles to contract.
6. When the muscle sto[s being stimulated no more calcium ions bind to the troponin meaning the tropomyosin once again blocks the myosin binding site the sarcomere lengthens and the muscle stops contracting.

Question 13

How ATP is produced so it can be used to provide energy for muscle movement?

Answer 13

1. Aerobic respiration.
2. Anaerobic respiration
3. ATP-phosphocreatine system

Question 14

How is ATP produced in Aerobic respiration?

Answer 14

Produced during oxidative phosphorylation and glycolysis.

Question 15

How is ATP produced in anaerobic respiration?

Answer 15

produced in glycolysis

Question 16

Why is using anaerobic respiration to make ATP only good for short periods of hard exercise?

Answer 16

It produces ATP quickly through glycolysis. However, the end product of aerobic respiration is lactate which causes muscle fatigue.

Question 17

How does ATP get produced in the PCr system?

Answer 17

ADP + PCr - ATP + Cr (creatine)

Question 18

Why is using the PCr system to make ATP only good for short periods of hard exercise?

Answer 18

The PCr runs out after a few seconds.

Question 19

What are slow-twitch fibres?

Answer 19

Muscle fibres that contract slowly and can work for long periods.

Question 20

What adaptations do slow-twitch fibres have that aid them in their function?

Answer 20

1. They have a lot of mitochondria where aerobic respiration happens.
2. They have a high number of blood vessels which supply them with oxygen, needed for aerobic respiration.
3. The mitochondria are usually found on the edge of the muscle fibres so there is a short diffusion distance for the oxygen.
4. They are rich in myoglobin, which stores oxygen. This gives them their red colour.

Question 21

What are fast-twitch fibres?

Answer 21

Muscle fibres that contract quickly and get tired quickly.

Question 22

Why do fast-twitch muscle fibres have low amounts of mitochondria and blood vessels?

Answer 22

They make their ATP using anaerobic respiration and the PCr system meaning they don’t need oxygen or many mitochondria.