Muscle Structure and Function Part 2 W4

Question 1

What is an isotonic contraction?

Answer 1

Muscle tension remains unchanged where muscle length decreases

Question 2

What is a concentric contraction?

Answer 2

Decrease in muscle length

Question 3

What is a eccentric contraction?

Answer 3

Increase in muscle length

Question 4

What is a isokinetic contraction?

Answer 4

Muscle length decreases with constant velocity

Question 5

What is a isometric contraction?

Answer 5

No change in muscle length

Question 6

How are different muscle fibre types distributed as?

Answer 6

Mosaic pattern

Question 7

What are the 3 key biochemical characteristics important to the 2 main types of fibres function?

Answer 7

Oxidative capacity
Type of myosin isoform expressed
Abundance of contractile protein within the fibre

Question 7

What is oxidative capacity?

Answer 7

Quantity of mitochondria, capillaries and myoglobin in and around fibre

Question 8

What is a type I muscle fibre?

Answer 8

Slow-twitch
Slow-oxidative fibres

Question 9

What is a type IIa muscle fibre?

Answer 9

Intermediate fibres
Fast-oxidative glycolytic fibres

Question 10

What is a type IIx muscle fibre?

Answer 10

Fast-twitch
Fast-glycolytic

Question 11

What are contractile properties?

Answer 11

Maximal force production
Speed of contraction (Vmax)
Maximal power output
Fatigue resistance
Muscle fibre efficiency

Question 12

What is muscle fibre efficiency?

Answer 12

Lower amount of ATP used to generate force

Question 13

What is speed of contraction (Vmax) regulated by?

Answer 13

Regulated by myosin ATPase activity

Question 14

What is the equation for maximal power output?

Answer 14

Maximal power output= force x shortening velocity

Question 14

What does muscle contraction speed depend on?

Answer 14

The rate of cross bridge cycling (depends on myosin ATPase isoform)

Question 15

How does shortening muscle contraction influence bands?

Answer 15

Changes the I band but not the A band

Question 16

What is gel electrophoresis?

Answer 16

Identify myosin isoforms specific to different fibre types

Question 17

How are muscle fibre typed?

Answer 17

Contractile properties
Muscle biopsy
Oxidative capacity
Staining for type of myosin ATPase
Immunohistochemical staining
Gel electrophoresis

Question 18

What is immunohistochemical staining?

Answer 18

Selective antibody binds to unique myosin proteins
Fibre types differentiated by colour difference

Question 19

What is a muscle biopsy?

Answer 19

Small piece of muscle removed <50g
May not be representative of entire body
Surface type II > I, deep type I > II

Question 20

Why is speed of shortening muscle contraction is greater in fast fibres?

Answer 20

SR releases Ca2+ at a faster rate
Higher ATPase activity

Question 21

What contributes to force regulation in muscle?

Answer 21

Number and types of motor units recruited
Muscle Length
Firing rate of motor neurons
Contractile history of muscle

Question 22

How is muscle force increased?

Answer 22

Recruiting more motor units

Question 23

What do motor neurons supplying larger faster motor units have?

Answer 23

Larger cell bodies
Larger diameter axons
Greater number of axonal branches
Sparse afferent innervation (less spindle excitatory input)
More complex and extensive motor end plate of neuromuscular junction

Question 24

What is the size principle of a slow motor units?

Answer 24

Have easily excited motor neurones

Question 25

What is the size principle of a fast motor units?

Answer 25

Have higher threshold motor neurons (harder to excite)

Question 26

What is the muscle force-velocity relationship?

Answer 26

At any absolute force exerted by the muscle, the speed of movement is greater in muscles with a higher percentage of fast-twitch fibres

Maximum velocity of shortening is greatest at the lowest force

Question 27

What is the muscle force-power relationship?

Answer 27

At any given velocity of movement, the peak power generated is greater in a muscle with a higher percentage of fast-twitch fibres