Muscles and Movement

Question 1

Name the three types of muscle and their main characteristics.

Answer 1

Striated (skeletal),smooth and cardiac muscles

Striated- muscle attached to skeleton, involved in locomotion. Appears stripy. Contracts rapidly and fatigues quickly.
Smooth- Under control of involuntary nervous system.Found in gut and blood vessels. Contracts and fatigues slowly.
Cardiac - found in the heart. Striated, fibres joined by cross-connections. Contracts spontaneously and does not fatigue.

Question 2

What is a muscle fibre?

Answer 2

Striated muscle is made up of large bundles of long cells called muscle fibres.

Question 3

Explain the structure of a muscle fibre..

Answer 3

cell membrane of muscle fibre= sarcolemma
muscle cell cytoplasm= sarcoplasm
Bits of the sarcolemma fold inwards across the muscle fibre and stick into the sarcoplasm= transverse tubules
network of internal membranes= sarcoplasmic reticulum
contain lots of mitochondria, are multinucleate and myoglobin and long, cylindrical organelles called myofibrils

Question 4

What is the role of the transverse tubules and sarcoplasmic reticulum within the muscle fibres?

Answer 4

Transverse tubules= help spread electrical impulses

Sarcoplasmic reticulum= stores and releases calcium ions

Question 5

How are muscle fibres adapted for their function?

Answer 5

1) contain lots of mitochondria for aerobic respiration to provide ATP
2) contain myoglobin-readily accepts oxygen from the blood. Acts as an oxygen store in the muscles
3) long to extend full length of muscle

Question 6

Name the two proteins that make up myofibrils

Answer 6

Actin and myosin myofilaments

Question 7

Describe how myofilaments, muscle fibres, myofibrils and muscles and related

Answer 7

Muscles are made up of muscle fibres, which are made up of myofibrils which are made up of two types of myofilaments: actin and myosin.

Question 8

Explain the structure of a sarcomere and change in contracted sarcomere.

Answer 8

Sarcomere is made up of myoson and actin myofilaments. Sarcomere runs ‘z’ line to ‘z’ line. ‘H’ zone consists of myosin only. As myosin and actin slide each other to make the sarcomeres contract the I bands shorten, H zone shortens and Z lines become closer together so that the sarcomeres get shorter.

Question 9

What is actin and myosin made up of?

Answer 9

Actin= two chains of actin monomers joined like beads. contains tropomyosin and troponin. Troponin binds actin, tropomyosin and calcium ions.

Myosin= two polypeptide chains twisted together with globular heads

Question 10

What molecules must be present for muscle contraction?

Answer 10

Calcium ions and ATP must be present for contraction

Question 11

Explain how the process of muscle contraction occurs

Answer 11

1) stimulation at neuromuscular junction triggers release of ca2+ ions that bind to troponin, changing their shape moving the tropomyosin away from the myosin binding site
2) myosin heads bind to the actin, forming an actomyosin bridge
3) ADP and Pi released from myosin head. Myosin changes shape- head bends forward moving the actin filaments along the myosin, shortening the sarcomere.
4) Free ATP binds to head, actomyosin bridge breaks. In presence of calcium ions, ATPase in myosin head is activated. ATP is hydrolysed, providing energy to return myosin head to orginal position, primed with ADP and Pi to go again.
5) With continued stimulation calcium ions remain in sarcoplasm and cycle repeats. If no stimulation, ca2+ ions pumped back into the sarcoplasmic reticulum using energy from ATP. Troponin and tropomyosin return to original positions and muscle fibre relaxes.

Question 12

Explain the different properties of fast twitch and slow twitch fibres

Answer 12

Fast twitch: contract quickly, good for short bursts of energy, get tired quickly, energy released quickly through anaerobic respiration using glycogen. few mitochondria or blood vessels. whitish in colour as not much myoglobin.

slow twitch: contract slowly, good for endurance and use for posture, can work for a long time withput tiring. energy released slowly through aerobic respiration. lots of mitochondria and blood vessels supplying oxygen. Reddish colour as lots of myoglobin.

Question 13

Give examples of athletes that may have more fast twitch or slow twitch fibres

Answer 13

higher proportion slow twitch in long distance runners, cyclists and swimmers

higher proportion fast twitch in weightlifters and sprinters

Question 14

What is the ‘all or nothing’ rule?

Answer 14

If the stimulation threshold is not reached, stimulus does not cause a twitch of the muscle fibre. Size of twitch is always the same, but two stimuli can be given closer together.

Question 15

What is summation?

Answer 15

the addition of individual twitch contractions to increase the intensity of overall muscle contraction.

Question 16

What is tetanus?

Answer 16

If a muscle fiber is stimulated so rapidly that it does not relax at all between stimuli, a smooth, sustained contraction called tetanus occurs

Question 17

How does training of muscles affect muscle fibres?

Answer 17

Number of muscle fibres does not change but with training, size and type of fibre (slow/fast) can alter.

Genes also play a part in composition of fast and slow twitch.

Question 18

Compare bone and cartilage

Answer 18

Bone is strong, hard and light. Cartilage is hard and flexbile made up of chondrocytes cells. Both can withstand compression forces. Bone cells embedded in matrix of collagen and calcium salts. Cartilage contains elastic (collagen) fibres also. Cartilage a shock absorber-found between vertebrae.

Question 19

What are the two types of cartilage? How do they differ?

Answer 19

Hyaline cartilage and white fibrous cartilage. Hyaline-found at end of bones (and nose, air passageways and parts of ear). White fibrous bundles of densely packed collagen. Great tensile strength and less flexible.

Question 20

What are tendons and ligaments?

Answer 20

Tendons join muscle to bone. Ligaments bone to bone. Tendons almost entirely white fibrous tissue, collagen but inelastic. Ligaments are elastic, made up of elastic yellow tissue. Tendons make secure attachment and a little shock absorption. Ligaments structure varies at different joints: some loose and others very tight: dependent on their varying collagen and white fibrous tissue.

Question 21

Muscles work together in pairs called….

Answer 21

Antagonistic pairs- flexor and extensor muscles work antagonistically to operate the joint.

Question 22

Give examples of varying joint types:

Answer 22

Ball and socket = hip and shoulder (give free movement)

Hinge = fingers and knees (more restrictive)

Question 23

What is the purpose of synovial fluid in joints?

Answer 23

It is a liquid lubricant which fill the joint cavity and ensure easy friction free movement in most mobile joints (hip and shoulder)

Question 24

True or false…. MUSCLES DO NOT PUSH

Answer 24

TRUE

Question 25

How is the action of movement brought about?

Answer 25

By the action of muscle on bones. Muscles attached by tendons to two different bones and work in antagonistic pairs (flexor and extendor muscles).