Skeletal Muscle Physiology 2

Question 1

what two factors does the gradation of skeletal muscle tension depend on

Answer 1

Number of muscle fibres contracting

Tension developed by each contracting muscle fibre

Question 2

how can you achieve a stronger muscle contraction

Answer 2

by stimulating more motor units: motor unit recruitment

Question 3

how is muscle fatigue prevented in sub maximal contractions

Answer 3

by asynchronous motor unit recruitment

Question 4

what factors make up the tension developed by each contracting muscle fibre

Answer 4

frequency of stimulation
summation of contractions
length of muscle fibre
thickness of muscle fibre

Question 5

why does a skeletal muscle twitch

Answer 5

the action potential is much shorter than the duration

Question 6

how can twitches be used to give a stronger contraction

Answer 6

summate twitches give repetitive fast stimulation

twitch after twitch after twitch not allowing a break

Question 7

what is tetanus

Answer 7

when the muscle fibre is stimulated so rapidly it is not allowed to rest it leads to a maximal sustained contraction

Question 8

Cardiac and skeletal muscle can be tetanised true/false

Answer 8

false

cardiac muscle has long refractory periods to prevent tetanic contraction

Question 9

what is it called when the skeletal muscle is stimulated once

Answer 9

twitch

Question 10

how can you increase muscle tension without increasing frequency of stimulation

Answer 10

twitches overlap as there is not time for the muscle to rest, the second twitch adds to the first creating greater muscle tension

eventually produces a much stronger sustained contraction

Question 11

what is an important mechanism for modulating the force of contraction in skeletal muscle

Answer 11

the frequency of stimulation

Question 12

when is the muscle capable of achieving maximum contraction

Answer 12

when it is at its optimum length before the onset of contraction

RESTING LENGTH

Question 13

how is muscle tension transmitted to bone

Answer 13

via the stretching and tightening of muscle connective tissue and tendon

Question 14

what are the two types of skeletal muscle contraction

Answer 14

isotonic

isometric

Question 15

what is isotonic contraction

Answer 15

used for body movements and moving objects

muscle tension remains constant ad the muscle length changes

Question 16

what is isometric contraction

Answer 16

used for supporting objects and maintaining body posture

muscle tension develops at constant muscle length

Question 17

what decreased the velocity of muscle shortening

Answer 17

the load eg. how heavy the object you’re picking up is

Question 18

what are the main differences between skeletal muscle fibres

Answer 18

enzyme pathways
resistance to fatigue
activity of myosin ATPase

Question 19

how many types of muscle fibre are in one muscle unit

Answer 19

two

Question 20

muscle fibres with greater capacity to synthesise ATP are more resistant to fatigue true/fasle

Answer 20

true

Question 21

what does the activity of myosin ATPase determine

Answer 21

the speed at which anergy is made available for cross bridge cycling
eg. speed of contraction

Question 22

what does ATPase in muscle do

Answer 22

splits ATP to power power cross-bridge stroking

Question 23

what is ATP needed in muscle relaxation

Answer 23

to pump calcium back into the lateral sacs of the sarcoplasmic reticulum

Question 24

what are the metabolic pathways that produce ATP for skeletal muscle

Answer 24

Creatine phosphate
oxidative phosphorylation
Glycolysis

Question 25

what does creatine phosphate do

Answer 25

transfers high energy phosphate from creatine phosphate to ADP to create an immediate source of ATP

Question 26

what is the main source of ATP to muscles when O2 is present

Answer 26

oxidative phosphorylation

Question 27

what is the main source of ATP to muscles when O2 isn't present

Answer 27

Glycolysis

Question 28

what are the three types of skeletal muscle fibre

Answer 28

slow-oxidative fast-oxidative fast- glyhcotic

Question 29

what are type 1 muscle fibres

Answer 29

slow (slow twitch) resistant to fatigue used for prolonged relatively low work aerobic activities eg. posture maintenance

Question 30

type 2 muscle fibres

Answer 30

(intermediate twitch) fast oxidative use aerobic and anaerobic useful in prolonged moderate activities eg. jogging

Question 31

type 2x muscle fibres

Answer 31

fast glycotic (fast twitch fibres) anaerobic metabolism short term, high intensity activities eg. jumping

Question 32

what inputs influence the motor units

Answer 32

brain inputs | inputs from a variety of receptors

Question 33

what is a reflex

Answer 33

a stereotyped response to a specific stimulus

Question 34

what makes reflexes important

Answer 34

they're important for localising lesions in the motor system

Question 35

what is the simplest monosynaptic spinal reflex

Answer 35

stretch reflex

Question 36

what is the sense receptor in the stretch reflex

Answer 36

the muscle spindle

Question 37

what does stretching of the muscle spindle cause

Answer 37

firing of afferent neurons

Question 38

where do the afferent neurons fired in the stretch reflex go and what do they synapse with

Answer 38

synapse in spinal cord with the alpha motor neurons which innervate the stretched muscles

Question 39

how do you elicit a stretch reflex

Answer 39

tapping a muscle tendon with a rubber hammer

Question 40

what are muscle spindles

Answer 40

a collection of specialised muscle fibres Intrafusal fibres

Question 41

what are extrafusal fibres

Answer 41

normal muscle fibres

Question 42

what are the sensory nerve endings of muscle spindles called

Answer 42

annulospiral

Question 43

the discharge from muscle spindle sensory nerve endings decrease as the muscle is stretch true/false

Answer 43

false | increase

Question 44

what are the efferent neurons that supply muscle spindles called

Answer 44

gamma motor neurons

Question 45

what do gamma motor neurons do

Answer 45

adjust the level of tension in the muscle spindles to maintain their sensitivity when the muscles shorten during contraction

Question 46

the contraction of intramural fibres doesn't contribute to overall strength of muscle true/false

Answer 46

true

Question 47

causes of intrinsic muscle disease

Answer 47

genetically determines myopathies acquired myopathies eg. inflammatory, non-inflammaroy, endocrine, toxic

Question 48

symptoms of muscle disease

Answer 48

muscle weakness/tiredness delayed relaxation after voluntary contraction (myotonia) muscle pain (myalgia) muscle stiffness

Question 49

investigations in neuromuscular disease

Answer 49

``` EMG (electromyography) -electrodes detect the presence of muscular activity nerve conduction studies muscle enzymes (eg. creatine kinase) inflammatory markers (CRP) muscle biopsy ```