Muscles

Question 1

skeletal muscle:

Answer 1

the muscle that causes our bodies to move (is attached to the skeleton), also called striated muscle.

Question 2

myofibril:

Answer 2

part of a muscle fibre, contains sarcomeres and the contractile proteins actin ans myosin.

Question 3

muscles are made up of thousands of _______________

Answer 3

cylindrical muscle fibres

Question 4

what do the muscle fibres contain?

Answer 4

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

Question 5

does training increase the number of muscle fibres within a muscle?

Answer 5

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.

Question 6

A band:

Answer 6

the dark band in a myofibril

Question 7

I band:

Answer 7

the light band in a myofibril

Question 8

H zone:

Answer 8

the lighter region in the centre of the A band

Question 9

Z line:

Answer 9

the darker region in the centre of the I band

Question 10

sarcomere:

Answer 10

the repeating unit of a myofibril, goes from one Z line to another

Question 11

how is the striated appearance of the muscle created?

Answer 11

by a pattern of alternating light and dark bands. (dark bands=A band ///// light bands= I bands)

Question 12

what is the name of the protein in the THICK filament in each myofibril?

Answer 12

MYOSIN

Question 13

what is the name of the protein in the THIN filament in each myofibril?

Answer 13

ACTIN - troponin & tropomyosin(which are two even smaller proteins)

Question 14

what is the name and the use of the round head on a myosin molecule?

Answer 14

myosin head = have binding sites on them for the actin molecules in the thin filaments and ATP.

routine= ATTACH TO ACTIN, PIVOT, DETATCH, RESET.

Question 15

as a muscle CONTRACTS:

Answer 15

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

Question 16

as a muscle is STRETCHED:

Answer 16

the WIDTH of the I bands and H zones INCREASES

still no change in the width of the A bands

Question 17

describe in step by step guide the SLIDING FILAMENT THEORY:

Answer 17

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.

Question 18

when resting, do myofibrils have large or small stores of Ca+ in the sarcoplasmic reticulum??

Answer 18

LARGE stores of Ca+ at resting

Question 19

Transverse tubules:

Answer 19

a network of folds/tubes from the membrane of a myofibril that provide access for electrical activity to the inside of the myofibril.

Question 20

Slow-twitch muscle fibres:

Answer 20

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.

Question 21

Fast-twitch muscle fibres type IIa: (FOG)

Answer 21

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.

Question 22

Fast-twitch muscle fibres type IIb : (FG)

Answer 22

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.

Question 23

motor unit:

Answer 23

a motor neurone and its muscle fibres.

also the name for the minimum unit of contraction

Question 24

All or nothing law:

Answer 24

muscle fibres either contract or do not contract, there is no inbetween.

Question 25

Spatial Summation:

Answer 25

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

Question 26

what is a Neuromuscular junction?

Answer 26

the point at which a motor neurone meets a muscle fibre.