Muscle Structure

Question 1

Function and structure of smooth muscle

Answer 1

Unstriated
Spindle shaped cells
Uninucleated

Control artery contractions and processes such as peristalsis

Question 2

Function and structure of skeletal muscle

Answer 2

Striated
Cylindrical cells
Multinucleated
Lots of mitochondria

Move bones via contraction

Question 3

Function and structure of cardiac muscle

Answer 3

Striated
Branched cells
Uninucleated
Intercalated

Pump blood around the heart

Question 4

What is a myofibril a repeating unit of

Answer 4

Sarcomeres

Question 5

Make up of skeletal muscle

Answer 5

Muscle cells -> muscle fibres -> skeletal muscle

Question 6

Cytoplasm and cell membrane in a skeletal muscle

Answer 6

Sarcoplasm, sarcolemma

Question 7

Adaptation of sarcolemma

Answer 7

Contain foldings of T tubules which help spread electrical impulses quickly

Question 8

What are the 2 bundles within myofibrils and thickness

Answer 8

Myosin - Thick
Actin - Thin

Question 9

What is A band

Answer 9

Dark bands where actin and myosin overlap

Question 10

What is I band

Answer 10

Light band of just actin

Question 11

What is Z line

Answer 11

Centre of an I band which has a sarcomere inbetween

Question 12

What is H zone

Answer 12

Myosin filament with no actin overlap

Question 13

How does myofibril change during contraction

Answer 13

H zone and I band shortens as actin is pulled over myosin

A band remains the same length as myosin filament doesn’t shorten

Z lines get closer together because the sarcomere gets shorter

Question 14

What band and colour is actin and myosin within a sarcomere?

Answer 14

Actin - I & Light

Myosin - H & Dark

Question 15

Properties of slow twitch muscle fibres

Answer 15

Darker in colour due to higher concentrations of myoglobin

Contract slower

Slower to fatigue

Energy released slowly from aerobic respiration

Lots of mitochondria for ATP and blood vessels to reduce gas diffusion pathways

Question 16

Properties of fast twitch muscle fibres

Answer 16

Lighter in colour due to lower concentrations of myoglobin

Contains lots of glycogen to be broken down into glucose - this helps in the high rate of anaerobic respiration

Contract quickly

Fatigue quickly

Energy released quickly from anaerobic respiration

Few mitochondria and blood vessels

Question 17

Structure of myosin filaments

Answer 17

Globular heads hinged so can move with the addition of ATP

Each head has a binding for actin and ATP

Question 18

Structure of actin filaments

Answer 18

Has binding sites for myosin heads called actin-myosin

Tropomyosin are long chains which coil around actin filaments

Question 19

Why do both slow and fast muscle fibre contain ATPase? [2]

Answer 19

[1] Hydrolysis of ATP;

[2] (Muscle) contraction requires energy / ATP;

Question 20

What is ATPase two different functions in slow and fast twitch fibres?

Answer 20

Fast - (lots of) ATPase allows rapid hydrolysis of ATP

Slow - (lots of) ATPase allows rapid synthesis of ATP.