Force generation and energy usage

Question 1

describe the sliding filament mechanism

Answer 1

force generation produces shortening of a skeletal muscle fibre, the overlapping thick an thin filaments in each sarcomere move past each other, propelled by movements of the cross bridges
LENGTH DOES NOT CHANGE
Lines move in towards the m line

Question 2

what does a muscle fibres ability to generate force depend on

Answer 2

the interaction of the contractile proteins actin and myosin

Question 3

where does this overlap of actin and myosin occur

Answer 3

in the a band

Question 4

what are the steps in the cross bridge cycle

Answer 4

1. cross bridge binds to actin
2. cross bridge moves
3. ATP binds to myosin, causing cross-bridge to detach
4. hydrolysis of ATP energises cross-bridge

Question 5

what happens when there is no ATP after death

Answer 5

there is an accumulation of ca2+ there for myosin remains bound to actin in a state of rigor mortis
stiffening begins 3-4 hours after death and hits maximum at 12 hours

Question 6

what re the three ways a muscle fibre can form ATP

Answer 6

phosphorylation of ADP by creatine phosphate
oxidative phosphorylation of ADP in the mitochondria
Phosphorylation of ADP by the glycolytic pathway in the cystol

Question 7

fibres are classed on the basis of:

Answer 7

• their maximal velocities of shortening (fast or slow)

- the major pathway they use to form ATP - oxidative or glycolytic

Question 8

what can fibres also be classed by

Answer 8

the type of enzymatic machinery available for synthesising ATP
many mitochondria = high capacity for oxidative phosphorylation (oxidative fibres) (appear dark and for long term)
few mitochondria = glycolytic fibres as have high conc of glycolytic enzymes and a large store of glycogen. allowing for quick bursts of energy (white)

Question 9

what are the three types of skeletal muscle fibres

Answer 9

slow oxidative fibres (1)
Fast-oxidative-glycolytic fibres (2a)
Fast-glycolytic fibres (2b)

Question 10

slow oxidative fibres (1)

Answer 10

combine low myosin-ATPase activity with high oxidative capacity

Question 11

Fast-oxidative-glycolytic fibres (2a)

Answer 11

combine high myosin-ATPase activity with high oxidative capacity and intermediate glycolytic capacity

Question 12

Fast-glycolytic fibres (2b)

Answer 12

combine high myosin-ATPase activity with high glycolytic capacity

Question 13

what two factors does the total tension a muscle can develop depend on

Answer 13

- the amount of tension developed by each fibre 
AP frequency 
fibre length 
fibre diameter 
fatigue 
- the number of fibres contracting at any time
number of fibres per motor unit
number of active motor units

Question 14

what does the shortening velocity of a whole muscle depend on

Answer 14

the load of the muscle, the types of motor units in the muscle and the number of motor units recruited to work against the load

Question 15

what results from an increase in the amount of contractile activity

Answer 15

increases the size of the muscle fibres and increases their capacity for ATP production

Question 16

what are the two types of muscle atrophy

Answer 16

disuse atrophy (arm in a cast) 
denervation atrophy (nerve damage=loss of function)