Muscles

Question 1

if the response needed is movement, the CNS sends

Answer 1

signals aling neurones to tell skeletal muscles to contract.

Question 2

skeletal muscle is made up of

Answer 2

large bundles of long cells called muscle fibres (cell membrane is called the sacrolemma)

Question 3

bits of the sacrolemma fold inwards acorss the muscle and stick into the sacroplasm - these folds are called?

Answer 3

transverse (T) tubules that help spread electrical impulsed throughout the sactoplasm so they reach all parts of the muscle fibre.

Question 4

a network of internal membranes called..

Answer 4

sacroplasmic reticulum runs through the sacroplasm which stores and releases calcium ions that are needed for muscle contraction.

Question 5

muscle fibres have lots of

Answer 5

long cylindrical organelles called myofibrils made up pf proteins and are highly specialised for contraction.

Question 5

muscle fibres have a lot of mitocondria to

Answer 5

provide ATP needed for muscle contraction

Question 6

under a microscope dark bands and light bands are visible which contain

Answer 6

dark bands contain the thick myosin filaments and some overlap with actin filaments - A bands
light bands contain thin actin filaments only - i bands

Question 6

myofibrils contain thick and thin myofilaments that move past eachother to make muscles contract:

Answer 6

thick: made up of the protein myosin
thin: made up of the protein actin

Question 7

the ends of each sacromere is marked with a

Answer 7

Z line.

Question 7

a myofibril is made up of many short units called

Answer 7

sacromeres

Question 8

the middle of each sacromere is an

Answer 8

M line - middle of myosin filaments

Question 9

around the M line is the

Answer 9

H zone - only contains myosin filaments

Question 10

actin filaments have binding sites bro

Answer 10

myosin heads called actin myosin binding sites

Question 11

myosin and actin filaments do what

Answer 11

slide over one another to make the sacromeres contract.

Question 12

the simultanious contraction of lots of sacromeres means

Answer 12

the myofibrils and muscle fibres contract

Question 13

contracted sacromeres:

what happens to the A , I and H zones

Answer 13

sacromere hets shorter - a bands stay the same length, I bands get shorter and H zones get shorter.

Question 14

myosin filaments have

Answer 14

globular heads and binding sites one for actin and one for ATP.

Question 15

2 other proteins called

Answer 15

tropomyosin and troponin between actin filaments - they are attached to eachother and help myofilaments move past each other.

Question 16

in a resting muscle, the actin myosin site

Answer 16

is blocked by tropomyosin which is held in place by troponin - myofilaments cant slide because the myosin heads cant bind to the actin filaments.

Question 17

when an action potential from a motor neurone stimulates a muscle cell, it

Answer 17

depolarises the sacrolemma and it spreads down the T-tubules to the sacroplasmic reticulum.

Question 18

1 - depolarisation causes the sacroplasmic reticulum to release

Answer 18

stored calcium ions into the sacroplasm

Question 19

2 - calcium ions bind to troponin, causing it

Answer 19

to change shape - pulls the attached tropomyosin out of the action-myosin binding site on the action filament

Question 20

3 - exposed binding site allows

Answer 20

myosin head to bind

Question 21

4 - the bond formd when a myosin head binds to an

Answer 21

actin filament is called action-myosin cross bridge.

Question 22

5 - calcium ions activate the enzyme

Answer 22

ATPase which breaks down ATP into ADP and Pi to provide the energy needed for muscle contraction.

Question 23

6 - the energy released from ATP moves the myosin head which

Answer 23

pulls the actin filament along in a kind of rowing action.

Question 24

7 - atp also provides the enrgy to

Answer 24

break the actin-myosin cross bridge so the myosin head detaches from the actin filament after its moved.

Question 25

8 - the myosin head then reattaches to

Answer 25

a different binding site further along the actin filament - a new actin-myosin cross bridge is formed and the cycle is repeated

Question 26

9 - many cross bridges form and break rapidly

Answer 26

pulls the actin filament along and shortens the sacromere causing the muscle to contract

Question 27

10 - the cycle continues as long as

Answer 27

calcium ions are present to bound to troponin

Question 28

when excitation stops…

1 - when the muscle stops being stimulated,

Answer 28

calcium ions leave their binding site on the troponin molecules and are moved by active transort back into the sacroplasmic reticulum

Question 29

when excitation stops…

2 - the troponin molecules return to their original shape,

Answer 29

pulling the attached troponin molecules with them - tropomyosin molecules block the actin-myosin cross briges.

Question 30

when excitation stops…

3 - muscles arent contracted because

Answer 30

no myosin heads are attached to action filaments

Question 31

when excitation stops…

4 - the actin filaments

Answer 31

slide back to their relaxed position which kengthens the sacromere.

Question 32

energy is needed for muscle contraction as ATP gets used up quickly - theres 3 ways it can be continually generated so excersize can continue

Answer 32

1 - aerobic respiration
2 - anareobic respiration
3 - ATP - Creatine Phosphate system

Question 33

aerobic respiration

most ATP is generated via

Answer 33

oxidative phosphorylation in the cells mitochondria - it only wors when theres oxygen so ita good for long periods of low intensity excersize

Question 34

anareobic respiration

4 points

Answer 34

ATP made rapidly by glycolysis
end product of glycolysis is pyruvate - converted to lactate by fermentation
lactate can quickly build uo in the muscles and cause muscle fatigue
good for short periods of hard excersize

Question 35

atp-creatine phosphate

4 points

Answer 35

ATP is made by phosphorylating ADP - adding a phosphate group taken from CP.
CP is stored inside cells and the ATP-CP system generates ATP quickly
CP runs out after a few seconds - used during short burts of vigorous excersize
ATP-CP system is anaerobic and alactic

Question 36

neuromuscular junctions

1 - neuromuscluar junction is…

Answer 36

a synapse between a motor neurone and a muscle cell.

Question 37

neuromuscular junctions

2 - neuromuscular junctions use the neurotransmitter

Answer 37

ACh - binds to receptors called nicotinic cholinergic receptors

Question 38

neuromuscular junctions

3 - neuromusclular junctions work in the same way as

Answer 38

synapses between neurones they release neurotransmitters which trigger depolarisation in thepost synaptic cell

Question 39

neuromuscular junctions

4 - depolarisation of a muscle cell always causes it to

Answer 39

contract if the treshold level is reached

Question 40

neuromuscular junctions

5 - acetylcholinesterase stored in the celfts of the post synaptic membrane is

Answer 40

released to break down acetlycholine after use

Question 41

neuromuscular junctions

sometimes a chemical may block the release of a neurotransmitter or affect the way it

Answer 41

binds to the receptirs on the postsynaptic membrane - prevents action potential from being passed onto the muscle so it wont contract.

Question 42

neuromuscular junctions

if muscles cant contract, ventilation cant take place

Answer 42

and the organism cant respire aerobically