Muscle Structure And Function Pt 2- Week 4

Question 1

What is isotonic contraction ?

Answer 1

Muscle tendon remains unchanged where muscle length decreases

Question 2

What is isokinetic contraction ?

Answer 2

Muscle length decreases with constant velocity

Question 3

What affects the oxidative capacity of muscle fibres ? (3)

Answer 3

Quantity of mitochondria, capillaries and myoglobin around fibre

More mitochondria, more energy

Question 4

What are the 3 types of muscle fibres and their use/characteristics ?

Answer 4

Type 1 slow twitch , slow oxidative glycolic fibres

Type 2a intermediate fibres, fast oxidative glycolytic fibres

Type 2 x fast twitch, glycolytic fibres

Question 5

What is the equation for maximal power output ?

Answer 5

Max power output = force x shortening velocity

Question 6

What muscle fibre type fatigue fastest?

Answer 6

Type 2

Type 1 are more fatigue resistant

Question 7

What does muscle contraction speed depend on ?

Answer 7

Rate of cross-bridge cycling
- myosin ATPase isoforms

Question 8

What does shortening of a muscle fibre change in terms of cross bridge bands ?

Answer 8

Changes in I band but not A band

Question 9

How are muscle fibres typed after biopsy ?

Answer 9

Immunohistochemical staining

Question 10

What happens/found during Immunohistochemical staining ? (2)

Answer 10

Selective antibody fluids are unique to myosin proteins

Fibre types are differentiated by colour difference

Question 11

What muscle type has the most mitochondria ?

Answer 11

Slow twitch

Question 12

What are the dominant energy systems used for each muscle fibre type ?

Answer 12

Type 1 - aerobic

Type 2a - both

Type 2 x - anaerobic

Question 13

What muscle fibre type has the highest ATPase activity ?

Answer 13

Type 2 x

Question 14

The more motor units the ….

Answer 14

Greater the force produced

Question 15

What is a motor unit ?

Answer 15

Each muscle fibre is innervated by a single axon , one alpha motor neuron supplies many fibres forming a motor to unit

Question 16

What are small motor units best for ?

Answer 16

Fine motor control

Question 17

What are large motor units used for ?

Answer 17

Large force production

Question 18

What do motorneurons supplying larger/faster motor units have ? (5)

Answer 18

Large cell bodies

Large diameters

More axonal branches

Sparse afferent innervation

More complex motor end plate of neuromuscular junction

Question 19

Which motor units are easily excited ?

Answer 19

Slow easy , fast are harder to excite

Question 20

How does muscle length affect force regulation ? (3)

Answer 20

If sarcomere is too small - less force produced

If sarcomere longer can have more fore

If too long then cross bridges can’t fully form

Question 21

What happens when a neuron is stimulated close to each impulse ?

Answer 21

Tetanus - muscle can’t produce any more force

Question 22

What is the force-velocity relationship?

Answer 22

At any given force, the velocity of the movement is greater in muscles with higher% of type 2

Same applied to any given velocity, power is greater in type 2