Muscles 1

Question 1

What are the functions of muscle?

Answer 1

The functions of muscle are:

Generate force and movement

Allow us to express and regulate ourselves

Question 2

What are the 3 types of muscle?

Answer 2

The 3 types of muscle are:

Skeletal

Smooth

Cardiac

Question 3

What kinds of muscle is striated?

Answer 3

Skeletal and cardiac muscle is striated

Question 4

What can you say about the nucleus of skeletal muscle?

Answer 4

Skeletal muscle is multinucleated

Question 5

What do myoblasts not do?

Answer 5

Myoblasts do not replace cells if they are damaged

Question 6

What does skeletal muscle form from?

Answer 6

Skeletal muscle forms in utero from mononucleate myoblasts

Question 7

What happens to skeletal muscle during growth?

Answer 7

During growth skeletal muscle increases fibre size

Question 8

What is muscle?

Answer 8

Muscle is bundles of fibres enclosed in connective tissue sheaths

Question 9

What are muscles attached to the bone by?

Answer 9

Muscles are attached to the bone by tendons

Question 10

What do satellite cells do?

Answer 10

Satellite cells replace cells during injury

Question 11

What cell replaces cells during injury?

Answer 11

Satellite cells replace cells during injury

Question 12

How do satellite cells replace cells during injury?

Answer 12

Satellite cells differentiate to form new muscle fibres

Question 13

What can muscle fibres that cannot completely recover undergo?

Answer 13

Muscle fibre that cannot completely recover can undergo hypertrophy to compensate

Question 14

What is hypertrophy?

Answer 14

Hypertrophy is the increase in size of skeletal muscles due to the growth of its component cells

Question 15

What is striated muscle?

Answer 15

Striated muscle is muscle tissue that is marked by transverse dark and light bands

Question 16

What does the structure of striated muscle look like?

Question 17

What are the compartments of myofibril?

Answer 17

Myofibril is split into:

I band

A band

Z line

Question 18

What is a sacromere?

Answer 18

A sacromere is the basic unit of striated muscle, between the Z lines

Question 19

What is the sarcomere composed of?

Answer 19

The sarcomere is composed of:

Myosin filament (thick)

Actin filament (thin)

Question 20

What does the structure of a sacromere look like?

Question 21

What are the thick myosin filaments surrounded by?

Answer 21

The thick myosin filaments are surrounded by a hexagon of thin actin filaments throughout the structure

Question 22

What is contraction caused by?

Answer 22

Contraction is caused by sliding filaments

Question 23

What happens when the muscle is shortened compared to relaxed?

Answer 23

When the muscle is shortened:

A band is unchanged

I band is reduced

H zone is reduced

Question 24

What causes the muscle to contract?

Answer 24

The cross bridge causes the muscle to contract

Question 25

What does the cross bridge contain?

Answer 25

The cross bridge contains:

Actin binding sites

ATP binding sites

Light chains

Heavy chains

Question 26

Describe the process of the cross chain cycle?

Answer 26

The process of the cross chain cycle is:

1. Cross bridge binds to actin
2. [Ca²⁺] rises
3. Cross bridge moves
4. ATP binds to myosin causing the cross bridge to detach
5. Hydrolysis of ATP energizes the cross bridge

Question 27

Why does an increase in [Ca²⁺] cause the cross bridge to move?

Answer 27

An increase in [Ca²⁺] causes the cross bridge to move because:

Tropomyosin partially covers myosin binding site, which is held in position by troponin

Calcium binds to troponin, changing conformation pulling tropomyosin away

ATP can bind to myosin

Question 28

What is tropomyosin partially covering myosin binding site and being held in position by troponin known as?

Answer 28

Cooperative blocking

Question 29

What happens when calcium is removed?

Answer 29

When calcium is removed the myosin binding site becomes blocked by tropomyosin again

Question 30

What is excitation/contraction coupling?

Answer 30

Excitation/contraction coupling is the conversion of electrical stimulis into a mechanical response

Question 31

What is the process of excitation/contraction coupling?

Answer 31

The process of excitation/contraction coupling is:

1. Muscle action potential propogated
2. Ca²⁺ released
3. Binds to troponin, removing blocking action by tropomyosin
4. ATP binds to the myosin of the cross bridge
5. Ca²⁺ taken up
6. Tropomyosin blocking action restored

Question 32

What is a motor unit?

Answer 32

A motor unit is a motor neuron and a collection of muscle fibres working together

Question 33

How may muscle fibres within a motor uni be arranged?

Answer 33

Muscle fibres within a motor unit may be scattered throughout the muscle

Question 34

What is tension?

Answer 34

Tension is the load exerted by a muscle

Question 35

What is load?

Answer 35

Load is the force exerted on a muscle

Question 36

What is isometric?

Answer 36

Isometric is a contraction with a constant contraction length

Question 37

What is an example of a sport that uses isometric contraction?

Answer 37

Weightlifting is an example of a sport that uses isometric contraction

Question 38

What is isotonic?

Answer 38

Isotonic is a contraction with a shortening muscle length

Question 39

What is an example of an isotonic contraction?

Answer 39

An example of an isotonic contraction is running

Question 40

What is lengthening?

Answer 40

Lengthening is a contraction with increasing length

Question 41

What is an example of a lengthening contraction?

Answer 41

An example of a lengthening contraction is sitting down

Question 42

What are twitch contractions shown by?

Answer 42

Twitch contractions are shown by:

Single AP → Muscle fibre → Twitch

Question 43

What is the latent period?

Answer 43

The latent period is the time before excitation contraction starts

Question 44

What is the contraction time?

Answer 44

Contraction time is the time between the start of tension and the peak of the tension

Question 45

What does muscle fibre contraction time depend on?

Answer 45

Muscle fibre contraction time depends on:

Fibre type

[Ca²⁺]

Question 46

Which type of contaction has the shorter latent period but the longer contraction event?

Answer 46

Isometric contraction has the shorter latent period by the longer contraction event

Question 47

What happens as load increases?

Answer 47

As load increases:

Contraction velocity decreases

Distance shortended decreases

Question 48

What is tetanus?

Answer 48

Tetanus is muscle spasms because AP is only 1-2ms long but the twitch lasts for up to 100ms so more APs may occur in this time, causing summation of APs

Question 49

Why is tetanus tension greater than twitch tension?

Answer 49

Tetanus tension is greater than twitch tension because [Ca²⁺] never gets low enough to allow reblocking of myolin binding sites

Question 50

What does the length-tension relationship look like?

Question 51

Why does the length-tension relationship look the way it does?

Answer 51

The length-tension relationship looks like this because:

Less overlap of filament is less tension

Too much overlap and filaments interfere with each other

Question 52

What is the optimal length (l_o)?

Answer 52

The optimal length is the muscle length for the greatest isometric tension

Question 53

What does movement around a limb require?

Answer 53

Movement around a limb requires 2 antagonistic groups of muscles:

One flexes

One extends

Question 54

Why are muscles arranged in a lever system?

Answer 54

Muscles are arranged in a lever system to amplify muscle shortening velocity to produce increases maneuverability

Question 55

Do muscles exert or support muscle force?

Answer 55

Muscles tend to exert more force than they support