Skeletal Muscle Structure and Function

Question 1

Name the 3 types of muscle in the body

Answer 1

Smooth, cardiac, skeletal

Question 2

Where is smooth muscle commonly found?

Answer 2

Lining hollow organs (e.g. gut, blood vessels)

Question 3

Where is cardiac muscle found in the body and what is its function?

Answer 3

In the heart, generates force to pump blood around the body

Question 4

What types of muscle are not under voluntary control?

Answer 4

smooth and cardiac muscle

Question 5

What is the function of skeletal muscle?

Answer 5

Applies force to bones to control posture and body movement

Question 6

When is skeletal muscle not under voluntary control?

Answer 6

In an emergency situation, when the brain takes over (e.g. eyes close involuntarily if something flies towards them)

Question 7

What is the primary function of skeletal muscle?

Answer 7

To develop force by contracting (shortening)

Question 8

What are muscle cells referred to as?

Answer 8

Muscle FIBRES

Question 9

Name 3 secondary roles of skeletal muscle

Answer 9

• Support and protection for soft internal organs (ab muscles)
• Provides voluntary control over major openings (toileting)
• Converts energy to heat which is used to maintain core temperature (shivering)

Question 10

Individual muscle cells (fibres) are gathered into…

Answer 10

…fascicles

Question 11

Fascicles are gathered into bundles called…

Answer 11

…muscles

Question 12

Why do muscles have parallel organisation?

Answer 12

Because it allows contraction in one axis, therefore movement in one axis
= most energy efficient

Question 13

How is the organisation of muscle fibres described?

Answer 13

Parallel organisation

Question 14

What 2 structures (not muscular) are found in high numbers within/around fibres, fascicles, and muscles?

Answer 14

Nerves and blood vessels

Question 15

What is the function of the blood vessels around muscle fibres?

Answer 15

Blood vessels allows for transport of nutrients and glucose into cells, and waste products out

Question 16

What is the function of the nerves around muscle fibres?

Answer 16

Nerves connect brain to muscles. There are lots so that the brain can interact with lots of parts of muscle at same time = greater control

Question 17

Name the connective tissue used to connect muscle to bone

Answer 17

Tendons

Question 18

What is the function of a tendon?

Answer 18

Connect muscles to bones and allows force to be transferred to bone = movement

Question 19

True or false:

Muscle fibres can contain more than one nuclei?

Answer 19

True - muscle fibres can contain hundreds or even thousands of nuclei!

Question 20

A muscle fibre is comprised of bundles of…

Answer 20

…myofibrils

Question 21

Myofibrils are made of repeating units known as…

Answer 21

…sarcomeres

Question 22

Describe what a sarcomere is

Answer 22

A sarcomere is one contractile unit within a muscle fibre

Question 23

What are sarcomeres made up of?

Answer 23

Contractile proteins/myofilaments

Question 24

Name 2 types of myofilaments

Answer 24

Actin and myosin

Question 25

True or false: myosin is the thinner of the myofilaments?

Answer 25

False: myosin is the thicker of the two types of microfilament

Question 26

What is the purpose of muscle signalling?

Answer 26

To regulate the activity of the force- producing elements

Question 27

What is the special name for the cell membrane of a muscle fibre?

Answer 27

The sarcolemma

Question 28

What are transverse (t-) tubules?

Answer 28

Tube-like extensions (invaginations) of the sarcolemma that extend deep into muscle fibre

Question 29

What is the role of t-tubules?

Answer 29

To conduct electrical signals (action potentials) deep into the core of the fibre

Question 30

What membrane network is associated with the T tubules?

Answer 30

The sarcoplasmic reticulum (SR)

Question 31

Describe the role of the SR

Answer 31

To take up and store calcium (Ca2+) while the muscle is relaxed, and then to release calcium into the cytoplasm when the muscle contracts

Question 32

Define Excitation-Contraction Coupling (EC-coupling)

Answer 32

The pairing of a signalling event (excitation of the muscle cell) with a mechanical event (contraction of the muscle cell)

Question 33

When a signalling event in the muscle cell is paired with a mechanical event, this is known as...

Answer 33

Excitation-Contraction Coupling (EC-coupling)

Question 34

What 3 proteins are involved in muscle cell excitation?

Answer 34

- Voltage-gated sensor (DHPR) - Ryanodine receptor (RyR) - SR Calcium-ATPase (SERCA)

Question 35

Where is the voltage-gated sensor (DHPR) found and what is its function?

Answer 35

The DHPR sits in and receives signals t-tubules and interacts with RyR

Question 36

Where is the ryanodine receptor (RyR) found and what is its function?

Answer 36

The RyR is a passive calcium channel on the SR that can open to allow Ca2+ out of the SR and into the cell

Question 37

Where is the SR Calcium-ATPase (SERCA) found and what is its function?

Answer 37

The SERCA is found on the surface of SR, further from t-tubule. It is an active calcium pump that uses ATP to move Ca2+ back into the SR against its concentration gradient, ending the excitation.

Question 38

What is the first step of the excitation process?

Answer 38

Signal moves along and down into t-tubules

Question 39

What is the second step of the excitation process?

Answer 39

DHPR is activated by electrical signal

Question 40

What is the third step of the excitation process?

Answer 40

DHPR interacts with RyR

Question 41

What is the fourth step of the excitation process?

Answer 41

RyR opens, Ca2+ moves out of SR

Question 42

What is the fifth step of the excitation process?

Answer 42

Calcium diffuses throughout cell, activating the myofilaments and causing a contraction

Question 43

What is the first step of the relaxation process?

Answer 43

SERCA senses rise in intracellular Ca2+

Question 44

What is the second step of the relaxation process? What is the effect of this?

Answer 44

SECRA burns ATP to produce energy, then pumps calcium back into SR (against conc. gradient. This removes calcium from the cell, stopping the signal and allowing the muscle to relax