Muscles Flashcards
skeletal muscle:
the muscle that causes our bodies to move (is attached to the skeleton), also called striated muscle.
myofibril:
part of a muscle fibre, contains sarcomeres and the contractile proteins actin ans myosin.
muscles are made up of thousands of _______________
cylindrical muscle fibres
what do the muscle fibres contain?
Numerous thin thread-like MYOFIBRILS (arranged like a cable and run the entire length of the fibre)
Many MITOCHONDRIA
An extensive network of interconnective tubes called SARCOPLASMIC RETICULUM
Many NUCLEI
does training increase the number of muscle fibres within a muscle?
No. normally a fixed number early on in life.
In adults, increased strength and muscle mass come about through increases in the thickness of the individual fibres and in the amount of connective tissues.
A band:
the dark band in a myofibril
I band:
the light band in a myofibril
H zone:
the lighter region in the centre of the A band
Z line:
the darker region in the centre of the I band
sarcomere:
the repeating unit of a myofibril, goes from one Z line to another
how is the striated appearance of the muscle created?
by a pattern of alternating light and dark bands. (dark bands=A band ///// light bands= I bands)
what is the name of the protein in the THICK filament in each myofibril?
MYOSIN
what is the name of the protein in the THIN filament in each myofibril?
ACTIN - troponin & tropomyosin(which are two even smaller proteins)
what is the name and the use of the round head on a myosin molecule?
myosin head = have binding sites on them for the actin molecules in the thin filaments and ATP.
routine= ATTACH TO ACTIN, PIVOT, DETATCH, RESET.
as a muscle CONTRACTS:
the Z lines come CLOSER together
the WIDTH of the I bands DECREASES
the WIDTH of the H zones DECREASES
no change in the width of the A bands
as a muscle is STRETCHED:
the WIDTH of the I bands and H zones INCREASES
still no change in the width of the A bands
describe in step by step guide the SLIDING FILAMENT THEORY:
1) Nerve impulse arrive at the Neuromuscular Junction.
2) Release of Acetyl Choline
3) Acetyl Choline causes depolarisation of Neuromuscular Junction (Motor End Plate)
4) Depolarisation causes a release of Ca+ ions from the sarcoplasmic reticuclum
5) In high Ca+ concentrations, Ca+ BINDS to TROPONIN changing its shape and therefore moving tropomyosin from the active actin site.
6) Myosin heads can bind to the actin forming a ‘cross bridge’
7) When myosin heads can bind to the actin , enzyme Myosin-ATPase is ativated to break down ATP.
8) ATP is broken down to release energy which changes shape of myosin head –> this moves the actin filament,
9) Once myosin head has changed shape and moved the actin it relocates on another active site further along the actin molecule.
10) More Myosin-ATPase is released to break down ATP and release energy = causes myosin head to change shape and power stroke to occur.
11) This process can last for as long as there’s adequate ATP + Ca+ stores.
12) Once the contraction has stopped the Ca+ is actively transported back into the sarcoplasmic reticulum.
when resting, do myofibrils have large or small stores of Ca+ in the sarcoplasmic reticulum??
LARGE stores of Ca+ at resting
Transverse tubules:
a network of folds/tubes from the membrane of a myofibril that provide access for electrical activity to the inside of the myofibril.
Slow-twitch muscle fibres:
contract up to 10 times slower than fast-twitch fibres but have greater endurance.
(names according to how quickly they reach peak tension)
Also known as Type I.
Fast-twitch muscle fibres type IIa: (FOG)
characteristics are fast contraction, large force, fatigues easily.
FOG= fast oxidative glycolytic
used mainly in short high intensity sports such as a 1 mile run/400m swim.
Fast-twitch muscle fibres type IIb : (FG)
characteristics are very rapid contractions, very large force, fatigues very easily.
FG= fast glycolytive
used mainly in highly explosive events such as 50m swim, 100m sprints.
motor unit:
a motor neurone and its muscle fibres.
also the name for the minimum unit of contraction
All or nothing law:
muscle fibres either contract or do not contract, there is no inbetween.
Spatial Summation:
changes in strength of contraction are brought about by altering the number and size of motor units involved.
what is a Neuromuscular junction?
the point at which a motor neurone meets a muscle fibre.
