Muscles

Question 1

What is cardiac muscle?

Answer 1

Contracts without conscious control - only found in the heart

Question 2

What is smooth muslce?

Answer 2

Contracts without conscious control - found in the walls of internal organs e.g. stomach, intestine, blood vessels

Question 3

What is skeletal muscle?

Answer 3

Voluntary muscle, used to move e.g. biceps and triceps

Question 4

What is skeletal muscle also known as?

Answer 4

Striated, Striped, Voluntary muscle

Question 5

What is skeletal muscle made up of?

Answer 5

Long cells - called muscle fibres

Question 6

What is the cell membrane of the muscle fibre called?

Answer 6

Sarcolemma

Question 7

What are transverse (T) tubules?

Answer 7

Where parts of the sarcolemma fold inwards all across the muscle fibre - they stick into the sarcoplasm.

Question 8

What is the sarcoplasm?

Answer 8

The muscle fibres cytoplasm.

Question 9

What do T tubules help do?

Answer 9

They help spread electrical impulses throughout the sarcoplasm. This is so that they reach all parts of the muscle fibre.

Question 10

What is the sarcoplasmic reticulum?

Answer 10

It is a network of internal membranes which run through the sarcoplasm.

Question 11

What does the sarcoplasmic reticulum do?

Answer 11

It stores and releases calcium ions - needed for muscle contraction.

Question 12

What do muscle fibres have lots of and why?

Answer 12

Mitchondria - to provide the ATP needed for muscle contraction.

Question 13

What are multinucleate?

Answer 13

Muscle fibres

Question 13

Muscle fibres have lots of long cylindrical ORGANELLES… what are they called?

Answer 13

Myofibrils

Question 13

What are myofibrils made up of?

Answer 13

proteins

Question 13

Myofibrils are highly specialised for what?

Answer 13

Contraction

Question 14

What do myofibrils contain?

Answer 14

Bundles of thick and thin myofilaments

Question 15

What do the myofilaments do to make muscles contract?

Answer 15

The myofilaments move past each other

Question 16

What are the thick myofilaments made up of?

Answer 16

The protein - myosin

Question 17

What are the thin myofilaments made up of?

Answer 17

The protein - actin

Question 18

What can you see when looking at a myofibril under an electron microscope?

Answer 18

A pattern of alternating dark and light bands.

Question 19

What do the dark bands show in a myofibril - under an electron microscope?

Answer 19

The thick myosin filaments + some overlapping thin actin filaments
These are called A-bands
dArk bands

Question 20

What do the light bands show in a myofibril - under an electron microscope?

Answer 20

Contain only the thin actin filaments
These are called I-bands

Question 21

What is a myofibril made up of?

Answer 21

Many short units called - sarcomeres

Question 22

What marks the end of each sarcomere?

Answer 22

Z-line

Question 23

What is the middle of each sarcomere called?

Answer 23

M-line

Question 24

What is the H-zone?

Answer 24

Near the M-line, but only contains myosin filaments

Question 25

What are the A-bands?

Answer 25

thick myosin filaments + some overlapping thin actin filaments

Question 25

What are the I-bands?

Answer 25

Contains only the thin actin filaments

Question 25

What changes when the sarcomere is contracting?

Answer 25

The I-band gets shorter The H-zone gets shorter

Question 26

What is the only thing that stays the same when the sacromere contracts?

Answer 26

The A-band

Question 27

What is the sliding filament theory?

Answer 27

Where actin and myosin filaments slide over one another to make the sacromere contract

Question 28

How does the sliding filament theory result in muscle contraction?

Answer 28

The sacromeres contract --> the myofibrils contract --> the muscle fibres contract

Question 29

What happens to the sacromere when it relaxes?

Answer 29

It returns back to its original length.

Question 30

What do ligaments connect?

Answer 30

Bone to bone

Question 31

What do tendons connect?

Answer 31

Skeletal muscle to bone

Question 32

How do a pair of muscles act?

Answer 32

In antagonistic pairs against an incompressible skeleton.

Question 33

Describe the role of calcium ions in the contraction of a myofibril:

Answer 33

Ca ions diffuse from the sarcoplasmic reticulum into the myofibrils Ca ions cause the movement of tropomyosin This movement exposes the binding site on the actin Myosin heads attach to binding site on actin An actin-myosin cross-bridge forms

Question 34

DESCRIBE the role of ATP in the contraction of a myofibril:

Answer 34

Hydrolysis of ATP (on myosin heads) causes myosin heads to bend Pulling actin molecules Attachment of a new ATP molecule to each myosin head causes myosin heads to detach from actin sites.

Question 35

WHAT is the role of ATP in myofibril contraction?

Answer 35

Provides energy to move myosin heads Reaction with ATP breaks actin-myosin bridge and allows binding of myosin to actin.

Question 36

A fall in pH leads to a reduction in the ability of calcium ions to stimulate muscle contraction - how?

Answer 36

low pH changes shape of Ca2+ receptors, so fewer Ca2+ bind to tropomyosin, so fewer tropomyosin molecules move away, fewer binding sites on actin revealed, fewer myosin heads can bind and fewer actin-myosin cross bridges form.

Question 37

How is ATP a suitable energy sources for cells to use?

Answer 37

It phosphorylates other compounds, making them more reactive It can be rapidly re-synthesised Releases energy instaneously Releases relatviely small amounts of energy ATP is not lost from cells

Question 38

What are the 3 sources of energy for muscle contraction?

Answer 38

Aerobic respiration Anaerobic respiration ATP - PCr system

Question 39

What does PCr stand for?

Answer 39

Phosphocreatine

Question 40

How does the ATP-PCr system provide energy for muscle contraction?

Answer 40

ADP is phosphorylated using a phosphate group from PCr. The system geenrates ATP very quickly. The system is anaerobic and it's alactic

Question 41

Where is PCr stored?

Answer 41

insides cells

Question 42

When is the ATP-PCr system used?

Answer 42

During short bursts of vigorous exercise as PCr runs out very quickly

Question 43

What does alactic meaning?

Answer 43

Does not form lactate

Question 44

What does PCr get broken down into?

Answer 44

Creatinine

Question 45

Where can creatinine be removed from and to where?

Answer 45

From blood via kidneys

Question 46

How does aerobic repiration provide energy for muscle contraction?

Answer 46

Most ATP is generated via oxidative phsophorylation (in mitochondria) Long periods - low intensity

Question 47

How does anaerobic repiration provide energy for muscle contraction?

Answer 47

ATP made rapidly by glycolysis. End product is pyruvate --> converted into lactate (by lactate fermentation) Lactate quickly builds up on muscles causing fatigue - short periods/ high intensity

Question 48

Why is converting pyruvate to lactate essential for the continued production of ATP (during anaerobic respiration)?

Answer 48

Regenrates NAD So that glycolysis can continue

Question 49

What is myoglobin?

Answer 49

A single chain protein It has a high affinity for oxygen and can combine at very low partical pressures

Question 50

What is a slow twitch muscle fibre?

Answer 50

Found in muscles that carry out endurance exercise - adapted to carry out aerobic respiration

Question 51

How are slow twitch muscle adapted to aerobic respiration?

Answer 51

They are high in myoglobin

Question 52

What colour are slow and fast twitch muscle fibres?

Answer 52

Slow - red Fast - pale

Question 53

What is a fast twitch muscle fibre?

Answer 53

contract rapidly/powerfully for short periods. useful for intense exercise + adapted for anaerobic respiration (LOW in myoglobin)