paper 2: Muscles

Question 1

how do muscle act

Answer 1

in antagonsitic pairs

Question 2

what do muscle do

Answer 2

move bones at a joint and are attached to bones by tendons

Question 3

how do msucles produce a movement

Answer 3

muscle contract against incompressable skeleton

Question 4

what does antagonistic mean

Answer 4

when one muscle contracts the other of the pair relaxes

Question 5

draw a labelled diagram showing the gross structure of skeletal muscle, illustrating the arrangements of muscle fibres into many bundles surrounded by connectuve tissue

Answer 5

Question 6

draw and label a diagram to show the microscoping structure of skeletal muscle fibre including sarcolemma, sarcoplasmic reticulum, thick myosin, this myofillaments (actin), mitochondria and sarcomeres

Answer 6

Question 7

draw the ultrastructure of a myofibril, showing the arrangements of actin and myosin myofilaments in repeating sarcomere units

Answer 7

Question 8

draw a diagram showing a simple drawing of a repeating sarcomere unit

Answer 8

Question 9

what happens ot the H zone of a muscle fibre when the muscle contracts

Answer 9

gets shorter

Question 10

what heppens to the I band in a muscle fibre when the msucle contracts

Answer 10

gets shorter

Question 11

what happens to the A band of a muscle fibre when a muscle contracts

Answer 11

stays the same

Question 12

what theory describes when a muscle contracts

Answer 12

sliding filament theory

Question 13

what are thin filaments made out of

Answer 13

actin plus tropomyosin

Question 14

whar are thick filaments made from

Answer 14

myosin which have 2 heads and a tail

Question 15

what happens to the thick fillaments in muscle fibres when they contract

Answer 15

• myosin head attach to binding sites on the actin, forming actinmyosin bridges
• when relaxed the binding site on the actin is covered by tropomyosin

Question 16

describe the stages of myofibril contraction

Answer 16

• action potentials depolarise the sarcolemma and T-tubules
• voltage gated Ca2+ ion channels on the sarcoplasmic reticulum membrane open
• calcium ions diffuse from sarcoplasmic reticulum into the myofibril
• calcium ions cause the tropomyosin to move, exposing myosin bunding istes of the actin
• myosin heads bind actin forming actinmyosin bridges
• calcium ions also acitvate ATP hydrolase
• energy from hydrolysis of ATP cause myosin heads to bend and pull the actin
• attachment of ATP to the mysoin heads causes them to detach from actin
• myosin heads move back to thier original position ans reattach at binding sites further along the actin

Question 17

what is the role of phosphocreatine in providing energy during muscle contraction

Answer 17

it donates a phosphate to reform ATP quickly, from ADP + Pi, in anaerobic conditions

Question 18

what happens to phosphocreatine when muscle is relaxed

Answer 18

• creatine is phosphorylated back to phosphocreatine using Pi from ATP made in respiration

Question 19

what are slow twitch fibres adapted for

Answer 19

aerobic respiration (endurance)

Question 20

what are fast twitch fibres adapted for

Answer 20

anaerobic respiration (quick powerful contractions)

Question 21

what are the characteristics of slow twitch muscle fibres

Answer 21

• slow speed of contraction
• low force of contraction
• adapted for aerobic respiration to prevent lactic acid build up
• large myoglobin stores
• has many mitochondria
• adapted for endurance work such as standing and marathon running
• has a large number of capillaries (provide a shorter diffusion distance/ large surface area)

Question 22

what are the charcteristics of fast twitch muscle fibres

Answer 22

• have a high concentration of enzymes for anaerobic respiration
• contract rapidly with short powerful contractions
• have a store of phosphocreatine, to provide phosphate to genarate ATP
• have a large store of glycogen
• have thicker more numerous myosin fibres