M5 Topic 7: Skeletal Muscle Anatomy

Question 1

What are the two main parts of skeletal muscle?

Answer 1

• Muscle belly
• Tendons

Question 2

Muscle belly

Answer 2

Contains muscle fibres which are cells capable of activating

Arranged into structures called fascicles

Question 3

Tendons

Answer 3

Connective tissue structures that attach muscle belly to a bone

• Done by blending with the periosteum of a bone

Question 4

Fascicles

Answer 4

Layers of connective tissue sheaths which surround muscle cells/fibres

3 layers

• Epimysium
• Perimysium
• Endomysium

Converge to form the tendon at either end of the muscle bellow

Question 5

Epimysium

Answer 5

Surrounds the whole muscle

Question 6

Perimysium

Answer 6

Surrounds a fascicle

Question 7

Endomysium

Answer 7

Surrounds each individual muscle fibre

Question 8

Skeletal muscle fibres (cells)

Answer 8

Functional unit of a skeletal muscle

• Ability to generate pulling force when excited by motor neuron
• Multinucleated cells with lots of mitochondria

Question 9

What are the important elements of skeletal muscle fibres?

Answer 9

• Sarcolemma
• Transverse tubules
• Sarcoplasm
• Sarcoplasmic reticulum
• Terminal cisterns
• Triad
• Myofibrils

Question 10

Sacrolemma

Answer 10

The PM of muscle cell

• Penetrates through the cell to ensure that bits of the PM are in contact with all of the different contractile elements

Question 11

Transverse tubules (T-tubules)

Answer 11

Tube-like extensions of the PM that penetrate through the fibre

Question 12

Sarcoplasm

Answer 12

Cytoplasm of muscle fibre

Question 13

Sarcoplasmic reticulum

Answer 13

Fluid filled membranous sacs that store calcium ions (Ca2+)

Question 14

Terminal cisterns

Answer 14

Enlarged parts of the sarcoplasmic reticulum that are nestled against the transverse tubules

Question 15

Triad

Answer 15

A transverse tubule with a terminal cistern on either side

Question 16

Myofibrils

Answer 16

Microfilament components that move to generate the pulling force by changing the shape of a muscle fibre

Question 17

Structure of cylindrical myofibril

Answer 17

Contains lots of small protein filaments, two primary ones

• Thick filament
• Thin filament

which are arranged into repeating subunits called sarcomeres

Question 18

What creates the striated appearance of skeletal muscle tissue?

Answer 18

The overlapping and non-overlapping parts of protein filaments within a sarcomere

Question 19

Structure of a sarcomere

Answer 19

• Thin filament
• Thick filament
• Z-disc
• M-line

Question 20

Z-disc

Answer 20

Separates each sarcomere from its neighbours

• Narrow plate of dense protein material
• Attaches to thin filaments

Question 21

M-line

Answer 21

Protein plate in the centre of the sarcomere

• Attaches to thick filaments

Question 22

Thick filament

Answer 22

Primarily composed of long contractile proteins called myosin molecules

Question 23

Myosin

Answer 23

Ability to convert energy liberated from ATP hydrolysis into mechanical energy

• Actual structure that generates force when muscle activates

Question 24

Structure of myosin molecule

Answer 24

• Two myosin tails twisted together
• Head which extends outwards from the molecule (towards an adjacent thin filament)

Question 25

Thin filament

Answer 25

Has a contractile protein component called actin, as well as other parts including the troponin complex and tropomyosin

Question 26

What binding sites does actin have?

Answer 26

Myosin binding sites

Question 27

What binding sites does the troponin complex have?

Answer 27

Calcium binding sites

Question 28

Tropomyosin

Answer 28

Two strands of protein attached to the troponin complex - Any change in troponin complex will affect tropomyosin