6B Muscle Contraction

Question 1

How is skeletal muscle attached to bones

Answer 1

by tendons

Question 2

What attaches bones to other bones

Answer 2

Ligaments

Question 3

What are muscles that work together to move a bone called

Answer 3

Antagonist pairs

Question 4

What is a contracting muscle called

Answer 4

agonist

Question 5

What is a relaxed muscle called

Answer 5

antagonist

Question 6

What happens when the bicep contracts

Answer 6

triceps relax this pulls the bone so your arm bends at the elbow

The biceps is the agonist and the triceps is the antagonist

Question 7

What happens when the triceps contracts

Answer 7

biceps relax this pulls the bone so your arm straightens at the elbow

The triceps is the agonist and the biceps is the antagonist

Question 8

What are muscle cells made up of

Answer 8

muscle fibres

Question 9

What is the cell membrane of muscle cells called

Answer 9

the sarcolemma

Question 10

What is the cytoplasm of muscle cells called

Answer 10

sarcoplasm

Question 11

What are transverse tubules

Answer 11

folds of the sarcolemma that stick into the sarcoplasm

Question 12

What is the function of transverse tubules

Answer 12

To spread electrical impulses throughout the sarcoplasm so they reach all parts of the muscle fibres

Question 13

What is the sarcoplasmic reticulum

Answer 13

a network of internal membranes that run through the sarcoplasm

Question 14

What is function of the sarcoplasmic reticulum

Answer 14

It stores are releases calcium ions that are needed for muscle contraction

Question 15

What organelle does muscle fibres contain

Answer 15

myofibrils which are specialised for muscle contraction and mitochondria which provide ATP for the muscle contraction

Question 16

What are thick myofibrils made from

Answer 16

myosin

Question 17

What are thin myofibrils made from

Answer 17

actin

Question 18

Define multinucleate

Answer 18

Has many nuclei

Question 19

What do dark A bands in a myofibril contain

Answer 19

thick myosin filaments and some thin actin filaments which overlap

Question 20

What do light I bands in a myofibril contain

Answer 20

thin actin filaments

Question 21

What is a myofibril made up of

Answer 21

many sarcomeres

Question 22

Describe the sliding filament theory

Answer 22

thick myosin filaments and some thin actin filaments slide over each other to make the sarcomeres contract the simultaneous contraction of lots of sarcomeres means the myofibrils and muscle fibres contract

Sarcomeres return to their original length as the muscle relaxes

Question 23

Describe the structure of myosin filaments

Answer 23

They have hinged globular heads so that they can move back and forth and each head has a binding site for actin and one for ATP

Question 24

What are the binding sites on actin filaments called

Answer 24

actin-myosin binding sites

Question 25

What protein is found between actin filaments

Answer 25

tropomyosin

Question 26

In a resting muscle what happens to the actin-myosin binding sites

Answer 26

It is blocked by tropomyosin so the myosin head can't bind to the actin-myosin binding site on the actin filament so myofilaments can't slide past each other

Question 27

How is the sarcolemma depolarised

Answer 27

by an action potential the depolarisation spreads down the t tubules to the sarcoplasmic reticulum which causes it to release stored calcium ions into the sarcoplasm

Question 28

Where do the calcium ions from the sarcoplasmic reticulum bind to

Answer 28

They bind to a protein attached to tropomyosin causing the protein to change shape This pulls the attached tropomyosin out of the actin myosin filament on the actin filament this exposes the binding site which allows the myosin head to bind

Question 29

What is the bond called when a myosin head binds to the actin filament

Answer 29

actin-myosin cross bridge

Question 30

Which enzyme does calcium ions activate

Answer 30

ATP hydrolase

Question 31

What does the energy released from ATP in muscle contraction cause the myosin head to do

Answer 31

It causes it to bend, which pulls the actin filament along

Question 32

What provides the energy to break the actin-myosin cross bridge

Answer 32

ATP

Question 33

What happens after the actin-myosin cross bridge is broken

Answer 33

the myosin head detaches from the actin filament after its moved and then reattaches to a different binding site further along the actin filament and a new actin-myosin cross bridge is formed the cycle continues as long as calcium ions are present

Question 34

What happens when many cross bridges form and break very rapidly

Answer 34

the actin filament is pulled along, shortening the sarcomere and causing the muscle to contract

Question 35

What happens to calcium ions when the muscle stops being stimulated

Answer 35

calcium ions leave their binding sites and are moved by active transport back into the sarcoplasmic reticulum This causes tropomyosin to move back so the block the actin myosin sites again Muscles aren't contracted so no myosin heads are attached to actin filaments The actin filaments slide back to their relaxed position which lengths the sarcomere

Question 36

What type of exercise is aerobic respiration good for

Answer 36

Most ATP is generated by oxidative phosphorylation in the mitochondria It's only works when there is oxygen so it is good for long periods of low intensity exercise

Question 37

What type of exercise is anaerobic respiration good for

Answer 37

ATP is made rapidly by glycolysis and the end product is pyruvate which is converted to lactate by lactate fermentation Lactate can build up quickly and cause muscle fatigue so anaerobic respiration is good for short periods of hard exercise

Question 38

What type of exercise is the ATP phosphocreatine used for

Answer 38

ATP is made by phosphorylating ADP Pcr is stored in cells inside cells and the ATP-PCr system generates ATP very quickly Pcr runs out very quickly so is used during short burst of vigorous exercise The ATP-PCr system is anaerobic

Question 39

Describe the properties of slow twitch muscle fibres

Answer 39

Muscles fibres that contract slowly Muscle used for posture Good for endurance activities Can work for a long time without getting tired Energy is released slowly through aerobic respiration lots of mitochondria and blood vessels supply the muscles with oxygen Reddish in colour as they are rich in myoglobin

Question 40

Describe the properties of fast twitch muscle fibres

Answer 40

Muscles fibres that contract very quickly Muscle used for fast movement Good for short bursts of speed and power Get tired very quickly Energy is released slowly through anaerobic respiration there are mitochondria or blood vessels Whitish in colour as they don't contain much myoglobin