Muscles

Question 1

Myosin

Answer 1

Thick protein filament. Point at which ATP is is transferred into energy. Myosin heads pull the actin to pull the unit inwards

Question 2

Sarcomere

Answer 2

Smallest part
Arranged in parallel
Each sarcomere contains actin and myosin

Question 3

Actin

Answer 3

thin protein filement
contains binding sites
on the binding sites are troponin which prevents the myosin from grabbing onto the actin

Question 4

Troponin

Answer 4

A complex of three proteins

attached to tropomyosin

Question 5

tropomyosin

Answer 5

an actin binding protein which regulates muscle contraction

holds troponin in place

Question 6

motor unit

Answer 6

nerve impulse and bunch of muscles fibres

Question 7

spatial summation

Answer 7

changes in strength of contraction brought about by altering the number and size of motor units involved

Question 8

sarcoplasmic reticulum

Answer 8

releases calcium

the calcium ions shifts the tropomyosin which also moves the troponin

Question 9

action potentials

Answer 9

in order for the skeletal muscles to contract, an action protential needs to be sent from the nervous system to the muscle fibres
this triggers the release of calcium

Question 10

perimysium

Answer 10

skeletal muscles are separated from their surroundings by a membranous layer of connective tssue

Question 11

tendons

Answer 11

tough relatively inelastic bands of tightly packed collagenous fibres that form connective tissue

Question 12

motor end plate

Answer 12

the specialised synapses separation the nerve and muscle cell membrances

Question 13

sarcolemma

Answer 13

each muscle fibre is surrounded by a hormogenous membrane that contains collagen fibres

Question 14

the contractile mechanism

Answer 14

a nerve impulse arrives at the neuromuscular junction which causes the release of acetylcholine which causes calcium to be released from th sarcoplasmic reticulum
Calcium binds to troponin changing itsshape and so moving tropomyosin from the active site
myosin filaments cannot attach to actin forming a cross bridge
the breakdown of ATP releases energy which enables the myosin to pull the actin filaments inwards and so shortening the muscle
the myosin detaches from the actin and the cross bridge is broken

Question 15

What are histochemical characteristics

Answer 15

Way of examining muscles

Question 16

Biopsy

Answer 16

Long hollow needle put into the muscle, pull a vacuum and you get a bulge of muscle tissue

Question 17

Type 1 slow twitch

Answer 17

Small in size 
fatigue resistant 
many mitochondria 
high capillary density 
slow contraction time 
red (myoglobin)
less force and takes longer to produce

Question 18

type 2a fast twitch

Answer 18

fast contraction time
fatigue resistance
used mainly during short high intensity events such as 400m
less red
can produce some amount of force but faster than slow twitch

Question 19

Type 2b fast twtich

Answer 19

fatiguable 
low oxidative capacity 
short sprints 
high velocity contraction 
few mitochondria 
high glycogen stores 
low myoglobin

Question 20

Muscle contractile mechanism (detailed)

Answer 20

• Sliding of the filaments begins when the myosin heads form cross bridges
• A nerve impulse from the motor nerve causes an action potential along the sarcolemma
• Action potential arriving at the motor end plate causes release of neurotransmitter acetylcholine which cause opening of sodium channels
• This causes action potential to be conducted along the muscle fibre
• Transmission of the action potential to the sites where the T tubules adjoin the sarcoplasmic reticulum which releases calcium
• This calcium binds to troponin, changing its shape and so moving tropomyosin from the active site of actin
• Myosin can now attach to actin forming a cross bridge
• Sequence of events repeated when another nerve impulse arrives at the motor end plate

Question 21

Biochemical characteristics

Answer 21

The maximum shortening velocity of a single fibre with its maximum ATP utilisation rate
If can’t use ATP quickly, won’t contract quickly
Mean Vmax of type 2 is 10 times greater than type 1

Question 22

Myosin head binding sites

Answer 22

One is a binding site for actin, second acts as ATPase

Question 23

Recruitment of fibre types factors

Answer 23

Genetic component
Ageing influences the mix
Detraining