Muscle histology

Question 1

What do you see when you look at a muscle fibre under a microscope?

Answer 1

Light bands and dark bands
Light = Z lines (within I band)
Dark = A lines

Question 2

What is a sarcomere?

Answer 2

The repeating unit between two Z lines

Question 3

Where is the nucleus found?

Answer 3

Outside the fibre

Question 4

What makes up the muscle fibre?

Answer 4

Myofibrils

Question 5

What is the full name for the A band?

Answer 5

The anisotropic band

Question 6

What is the full name for the I band?

Answer 6

The isotropic band

Question 7

What is the M line?

Answer 7

The middle of the A band

The middle of the sarcomere

Question 8

What do thin filaments compose of?

Answer 8

Actin
Troponin
Tropomyosin

Question 9

What do thick filaments compose of?

Answer 9

Myosin

Titin

Question 10

What stops myosin binding to actin?

Answer 10

Tropomyosin

Troponin

Question 11

What activates binding of myosin to actin?

Answer 11

Calcium

Question 12

What is the I band?

Answer 12

It crosses two sarcomeres

The thin filaments between myosin

Question 13

What is the A band?

Answer 13

The length of the thick filament

Question 14

What is the H zone?

Answer 14

Variable
Where there is only myosin
It disappears in contraction

Question 15

Name the three types of muscle

Answer 15

Skeletal
Smooth
Cardiac

Question 16

Which muscle types are striated?

Answer 16

Skeletal muscle

Cardiac muscle

Question 17

What does skeletal muscle do?

Answer 17

Moves joints by strong and rapid contractions

Question 18

What makes up a skeletal muscle?

Answer 18

Bundles of muscle fibres, each of which is a long multinucleated cell

Question 19

How is a multinucleated cell formed?

Answer 19

The fusion of many mononucleated cells called myoblasts

Question 20

Describe the structure of cardiac muscle

Answer 20

Striated
Cells have a single central nucleus
Cells are branched
Intercalated disc joining adjacent cells

Question 21

Describe the intercalated disc

Answer 21

Contains gap junctions, adhering junctions and desmosomes

Allows muscle cells to be electrically coupled

Question 22

Describe the structure of smooth muscle

Answer 22

Not striated
Cells have a single nucleus
Gap junctions connect the cells
Cells are spindle shaped

Question 23

Why is smooth muscle not striated?

Answer 23

Actin and myosin arrangement is random

Question 24

Name some functions of smooth muscle

Answer 24

Erecting hairs
Moving food along the digestive tract
Surrounding ducts and blood vessels

Question 25

What is a myoepithelial cell?

Answer 25

The name given to smooth muscle found in the epithelia

Question 26

Does skeletal muscle have any cell-cell junctions?

Answer 26

No it has none

Question 27

What is the purpose of adhering junctions in cardiac muscle?

Answer 27

Actin filaments attach filaments of the sarcomere to the cell membrane

Question 28

What is the purpose of desmosomes in cardiac muscle?

Answer 28

They're sites of strong adhesion that keep the muscle cells together when they contract

Question 29

What is the purpose of gap junctions in cardiac muscle and smooth muscle?

Answer 29

Direct connection between cells Facilitates electrical communication Waves of depolarisation spread rapidly

Question 30

How does skeletal muscle repair itself?

Answer 30

It has satellite cells that are stimulated to divide when it is damaged

Question 31

How does cardiac muscle repair itself?

Answer 31

It cannot

Question 32

How does smooth muscle repair itself?

Answer 32

All smooth muscle cells retain the ability to divide

Question 33

How is skeletal muscle stimulated?

Answer 33

Via a nerve impulse | Depolarises the muscle

Question 34

What happens when muscle is stimulated?

Answer 34

Calcium ions are released from the sarcoplasmic reticulum | Calcium ions bind to troponin

Question 35

What connects muscle fibres to the sarcolemma?

Answer 35

The T-tubules

Question 36

What is a triad?

Answer 36

Two terminal cisternae of sarcoplasmic reticulum along with their associated T-tubule

Question 37

How is smooth muscle activated?

Answer 37

Thin filaments do not have troponin | Instead calcium binds to calmodulin, activating an enzyme that phosphorylates myosin allowing it to bind to actin