Muscle 1

Question 1

What are the 2 subclasses of muscle?

Answer 1

• Striated

- Smooth

Question 2

What kind of muscles are striated?

Answer 2

• Skeletal (involuntary muscles)

- Cardiac

Question 3

Where would you find smooth muscle?

Answer 3

• Blood vessels
• Vas deferens
• Airways
• Uterus
• GI tract
• Bladder
• etc..

Question 4

What is a skeletal muscle cell?

Answer 4

• Muscle fibre

- Multinucleate

Question 5

Describe the growth and repair of skeletal muscle.

Answer 5

• Form in utero from mononucleate myoblasts
• Increase fibre size during growth
• Myoblasts do not replace cells if damaged
• Satellite cells replace cells after injuryWhat do sate

Question 6

What are muscles?

Answer 6

Bundles of fibres encased in connective tissue sheaths

Question 7

What do tendons do?

Answer 7

Attach muscle to bone

Question 8

What do satellite cells do?

Answer 8

Differentiate to from new muscle fibres

Question 9

What do other fibres do to compensate when muscle fibres are injured?

Answer 9

Undergo hypertrophy

Question 10

What is the A band?

Answer 10

Stretch of myosin filament

Question 11

What is the H zone?

Answer 11

Space between ends of actin filaments

Question 12

What happens during muscle contraction?

Answer 12

• Muscle shortens
• Myosin stays same length
• Space between actin filaments decrease
• Space between myosin filaments decrease

Question 13

What is the I band?

Answer 13

Space between ends of myosin filaments

Question 14

What is a cross bridge?

Answer 14

ATP binding site on myosin filament

Question 15

How does tension develop?

Answer 15

Through contraction of muscle

Question 16

What are the stages in the cross-bridge cycle?

Answer 16

• Cross bridge binds to actin
• It drags actin along the myosin filament
• ATP binds to Myosin
• Myosin detaches and cross bridge returns to original position

Question 17

Describe the role of troponin, tropomyosin and calcium ions in muscle contraction.

Answer 17

-Tropomyosin partially covers the myosin binding sites on actin.
Tropomyosin is held in this position by troponin which acts as a cooperative block.
-When calcium binds to troponin it causes a conformational change which pulls tropomyosin away and allows myosin to bind to actin.

Question 18

What is a motor unit

Answer 18

Motor neurons
+
muscle fibres

Question 19

Tension

Answer 19

Force exerted by muscle

Question 20

Load

Answer 20

Force exerted on muscle

Question 21

Isometric

Answer 21

Contraction with constant length

Question 22

Isotonic

Answer 22

Contraction with shortening length

Question 23

Lengthening

Answer 23

Contraction with increasing length

Question 24

What causes a twitch?

Answer 24

A single action potential sent to a muscle fibre

Question 25

What is the latent period?

Answer 25

The time before the excitation contraction starts

Question 26

When does the contraction time occur?

Answer 26

Between start of tension and time when we have peak tension

Question 27

What is contraction time dependent on?

Answer 27

Calcium ion concentration

Question 28

Describe the latent period and contraction event of isometric contraction?

Answer 28

- Shorter latent period | - Longer contraction event

Question 29

What happens as load increases?

Answer 29

-Contraction velocity and distance shortened decreases

Question 30

Summation

Answer 30

Addition of AP to give waves with greater amplitude

Question 31

Describe the AP of tetanus.

Answer 31

AP is 1-2 ms long but twitch can last up to 100ms

Question 32

Tetanus

Answer 32

Sustained level of tension in a given period of time

Question 33

Unfused tetanus

Answer 33

AP continue to rise and fall when recorded on graph

Question 34

Fused tetanus

Answer 34

APs are so frequent there is no repolarisation

Question 35

Why is tetanic tension greater than twitch tension?

Answer 35

[Ca] never gets low enough to allow troponin/ tropomyosin to re-block myosin binding sites

Question 36

What are the length tension relationships/

Answer 36

- Less overlap of filaments= less tension - Too much overlap of filaments=filaments interfere with each other - Muscle length for greatest isometric tension=optimal length

Question 37

What does movement around a limb require?

Answer 37

2 antagonistic groups of muscles (1 flexes, the other straightens)

Question 38

What does the lever system of muscles do?

Answer 38

Amplifies muscle shortening velocity producing increased manoeuvrability