Muscles

Question 1

What are muscles made up of

Answer 1

Microfibrils

Question 2

What is actin

Answer 2

Thin two stranded layer twisted around eachother

Question 3

What is myosin

Answer 3

Thicker consists of long rod shapes tails with bulbous heads that project to the side

Question 4

What parts of myosin are important for muscle contraction

Answer 4

Myosin heads and tails

Question 5

What are the three bands

Answer 5

A I and H

Question 6

What is sarcoplasm

Answer 6

Surrounds muscles

Question 7

What is sarcomere

Answer 7

Plasma membrane

Question 8

What do myosin heads contain

Answer 8

Adp

Question 9

What moves out the way to allow myosin heads to bind to actin

Answer 9

Tropomyosin

Question 10

What colour are the bands

Answer 10

I = light
H = grey
A = dark

Question 11

What is contained in the different bands

Answer 11

I = only actin
H = part of A band (thats only myosin)
A = actin and myosin

Question 12

What happens when there is no action potential

Answer 12

Calcium channels close
NO more Ca diffuses in
Continues being actively transported out
No more calcium in sarcoplasm, troponin will move back into binding sites (no muscle contraction)

Question 13

What are thick filaments and thin filaments made up of

Answer 13

Thick = myosin
Thin = actin

Question 14

What protein molecules are myosin and actin made from

Answer 14

Myosin = fibrous protein molecules with globular heads
Actin = globular protein molecules

Question 15

What is tropomyosin made of

Answer 15

Two actin chains twisted together

Question 16

Describe the sliding filament model of muscle contraction process

Answer 16

1) Action potential arrives from the sarcoplasmic reticulum
2) Ca+ bind to troponin molecules stimulating them to change shape
3) Troponin and tropomyosin proteins to change position on actin filaments
4) Myosin binding sites are exposed on actin molecules
5) Globular heads on myosin bind with sites, forming cross-bridges between two types of filament
6) Cross bridge formation causes myosin heads to spontaneously bend releasing ADH pulling actin filaments towards the centre of the sarcomere
7) ATP binds to myosinn heads causing it to change shape so myosin heads release from actin filaments
8) Enzyme ATP hydrolase to hydrolyse ATP -> ADP, inorganic phosphate moves myosin heads back to their original position
9) Myosin heads bind to new binding sites on actin filament moving close to Z disc
10) Pulls the actin filaments closer to the centre of the sarcomere so the sarcomeres shorten
11) ATP binds to myosin heads to detach again

Question 17

Why is ATP needed for muscle contraction

Answer 17

To return myosin heads to their original position that causes actin filaments to slide
Return Ca+ back into sarcoplasmic reticulum (active transport)

Question 18

Explain the sliding filament model simply

Answer 18

1) Action potential reaches muscle cell
2) Ca+ diffuse in and bind to troponin
3) Troponin move out the way of myosin binding sites on actin
4) Myosin heads bind to the binding sites on action using ADP
5) Myosin heads change angle causing te actin and myosin to slide past each other
6) ADP is swapped out for ATP so myosin heads detach from the binding site
7) ATP hydrolysed into ADP releasing energy change the angle of myosin heads back to their original position
8) Cycle continues as long as there is an action potential

Question 19

When do muscles only have a small amount of atp

Answer 19

At rest

Question 20

Mitochondrisa function in muscle fibres

Answer 20

Aerobically respire to produce ATP but this is slow
Use phosphorylation to produce ATP from ADP + Pi

Question 21

What is phosphocreatines use

Answer 21

Stored by muscles used for rapid production of ATP

Question 22

Equation for the production of ATP from phosphocreatine

Answer 22

ADP + phosphocreatine -> ATP + creatine
Phosphate ion from phosphocreatine transferred to ADP

Question 23

Two types of muscle fibres

Answer 23

Fast and slow fibres

Question 24

Fast muscles contraction

Answer 24

-Contract rapidly
-Myosin heads bind and unbind from actin binding sites faster than slow
-Rapid contraction-relaxation cycle = need large amounts of Ca+ ti stimulate contraction

Question 25

Fast muscles ATP

Answer 25

Use a-naerobic respiration for ATP

Question 26

Fast muscles respiration

Answer 26

Suited for short bursts of high intensity activity because they fatigue quickly -> produce lactic acid from anaerobic respiration

Question 27

Fast muscles blood supply

Answer 27

Fewer capillaries Blood containing glucose and oxygen flow through capillaries So have slow O2 and glucose supply for aerobic resp

Question 28

Fast muscle fibres myoglobin and what myoglobin is

Answer 28

Lower amounts of myoglobin Myoglobin = similar to haemoglobin Myoglobin stores O2 in muscles and increases rate of O2 absoprtion in capillaries

Question 29

Slow muscles respiration

Answer 29

Aerobic respiration for ATP Fatigue less = less lactate produces so easier for endurance

Question 30

Muscle examples of slow fibres

Answer 30

Human back muscles = contract for long periods in order to keep skeleton erect when standing or sitting Wings in geese/ legs of wolves

Question 31

Slow muscle fibres blood supply

Answer 31

Denser network of capillaries Blood containing glucose and oxygen flow through capillaries Short diffusion distance and good supply of O2 and glucose for aerobic resp

Question 32

Myoglobin in slow muscle fibres

Answer 32

High amounts of myoglobin, haemoglobin and mitochondria Increase rate of O2 supply, O2 absorption and aerobic respiration

Question 33

Proportions of muscle fibres

Answer 33

Most have equal amount of slow and fast Some have higher of certain type enhancing performance on specific sport Athletes train for short burst high intensity activities = higher proportion of fast muscles than slow in arms and legs Endurance activities = high slow than fast fibres in arms and legs

Question 34

What gets larger when someone trains their muscles

Answer 34

Size of fibres increase not number of fibres

Question 35

What happens to calcium ions after long period of exercise

Answer 35

Decrease in availability of Ca+

Question 36

Why are Ca+ essential in exercise

Answer 36

Move tropomyosin away from actin-binding sites Activating ATPase

Question 37

When is lactate produced

Answer 37

After repeated contractions Anaerobic respiration provides supply of ATP for muscle contract, producing lactate as a waste

Question 38

What affect does lactate have on muscles

Answer 38

Lowers PH affecting contraction of fibres

Question 39

what microscope is used to observe skeletal muscles

Answer 39

Optical microscope

Question 40

How does an optical microscope work

Answer 40

Light directed through thin layer of biological material supported on a glass slide Light focused through several lenses so an image is visible Magnifying power of microscope can be increased by rotating the higher power objective lense into place

Question 41

What word is used to describe muscle action and why

Answer 41

Antagonistic = muscle pulls in one direction at a joint and the other muscle pulls in the opposite direction

Question 42

How do muscles maintain posture

Answer 42

By isometric contraction Antagonist muscles both contracting at joints to keep joint at a certain angle

Question 43

What is a striated muscle made of

Answer 43

Muscle fibres

Question 44

How are muscle fibres specialised

Answer 44

Each muscle fibre contains: -arrangement of contractile proteins in cytoplasm -surrounded by cell surface membrane -many nuclei

Question 45

Name the different parts of the muscle fibre

Answer 45

Cell surface membrane = sarcolemma Cytoplasm = sarcoplasm Endoplasmic reticulum = sarcoplasmic reticulum

Question 46

Name of sarcolemme that folds in from its outer surface

Answer 46

T-tubules that run close to the SR

Question 47

What does the sarcoplasm contain

Answer 47

Mitochondria = atp for contraction Myofibrils = bundles of actin

Question 48

Membrane of sarcoplasmic reticulum

Answer 48

Contain protein pumps to transport calcium ions into lumen of sr

Question 49

Adaptions of slow twitch fibres

Answer 49

-Large myoglobin store -Rich blood supply of blood vessels to deliver oxygen and glucose for aerobic respiration -Numerous mitochondria = atp

Question 50

Fast twitch fibres adaptations

Answer 50

-Thicker and more numerous myosin filaments -High concentration of enzymes = anaerobic respiration’s production of ATP -Store of phosphocreatine = ATP from ADP in anaerobic resp

Question 51

Whats a neuromuscular junction

Answer 51

Motor neurone meets skeletal muscle fibre

Question 52

What happens when a nerve impulse is received at the neuromuscular junction

Answer 52

1) Synaptic vesicles fuse with the presynaptic membrane and release acetylcholine 2) Acetylcholine diffuses into postsynaptic membrane (muscle fibre) altering its permeability to Na+ 3) Na+ enter rapidly depolarising the membrane

Question 53

What happens to the acetylcholine at neuromuscular junctions

Answer 53

1) ACh is released by synaptic vesicles and diffused into the postsynaptic membrane 2) Acetylcholine then broken down by acetylcholinesterase to ensure that the muscle is not over-stimulated 3) Resulting choline and ethanoic acid (acetyl) diffuses back into the neurone where its recombined into acetylcholine using ATP from mitochondria

Question 54

Similarities between neuromuscular junction and cholinergic synapse

Answer 54

Neurotransmitters transported by diffusion Receptors that on binding cause influx of Na+ Use sodium potassium pumps to repolarise axon Use enzymes to breakdown the neurotransmitter

Question 55

What changes to the sarcomere when muscles contract

Answer 55

I band = shorter Z line = move closer together H zone = shorter