6.3 Skeletal muscles

Question 1

what is the difference between a tendon and a ligament

Answer 1

tendon - muscle to bone
ligament - bone to bone

Question 2

3 functions of skeletal muscles

Answer 2

• produce a force for locomotion and breathing
• produce a force for postural support
• heat production during cold stress

Question 3

what is the cell membrane of the myofibril cells called

Answer 3

sarcolemma

Question 4

what are transverse tubules

Answer 4

bits of the sarcolemma folded inwards across the muscle tissue that stick to the sarcoplasm

Question 5

what is the sarcoplasmic reticulum

Answer 5

network of internal membranes which stores and releases calcium ions which are needed for muscle contraction

Question 6

what is the light (I) band made of

Answer 6

actin only

Question 7

what is the dark (A) band made of

Answer 7

myosin and actin

Question 8

what is the z line

Answer 8

the beginning and end of each sarcomere

Question 9

6 steps of neuromuscular junction

Answer 9

1. impulse arrives at the neurotransmitter junction causing vesicles to fuse with pre-synaptic membrane and release acetylcholine
2. Acetylcholine binds to receptors on the sarcolemma causing depolarisation
3. depolarisation wave travels down the T tubules
4. T tubules systems depolarisation leads to calcium release from stores in sarcoplasmic reticulum
5. calcium binds to proteins in the muscle, which leads to contraction
6. acetylcholine in the gap rapidly breaks down acetylcholine so the contraction only occurs when the impulse arrives continuously

Question 10

steps of muscle contraction

Answer 10

1. tropomyosin molecule prevents myosin head from attaching to the binding site on the actin molecule
2. calcium ions released from the endoplasmic reticulum cause the tropomyosin molecule to change shape so pull away from the binding site
3. myosin head now attaches to the binding site on the actin filament
4. head to myosin changes angle moving the actin filament. The ADP molecule is released
5. ATP molecule fixes to myosin head, causing it to detach from the actin filament
6. Hydrolysis of ATP to ADP by ATP synthase provides the energy for the myosin head to resume in normal position
7. head of myosin reattaches to a binding site further along the actin filament and cycle is repeated

Question 11

what are the 2 types of muscle fibres

Answer 11

slow twitch and fast twitch

Question 12

4 things about slow twitch fibres

Answer 12

• can sustain contractions over long periods of time without fatigue
• they are adapted for aerobic respiration and have a rich blood supply and prevents build-up of lactic acid
• they have many mitochondria and high concentrations of myoglobin for oxygen storage giving them a red colour
• a supply of glycogen as a source of metabolic energy

Question 13

7 things about fast twitch fibres

Answer 13

1. liable to fatigue and contract rapidly with powerful contractions
2. they use anaerobic respiration
3. they have fewer mitochondria and less myoglobin
4. thicker and more numerous
5. they have stored glycogen and a reduced vascular supply
6. can generate ATP very quickly using phosphocreatine store
7. a large number of enzymes for the release of energy from anaerobic respiration

Question 14

what is the formula of the phosphocreatine system

Answer 14

Pi + Cr + energy

Question 15

where does the energy go generated from the phosphocreatine system

Answer 15

to generate ATP