muscles

Question 1

how do muscles work

Answer 1

work as antagonistic pairs
pull in opposite directions
one contracts pulling on bone
other relaxes
skeleton incompressible so muscle can transmit force to bone
this helps to remain posture

Question 2

skeletal muscles

Answer 2

made of many bundle of muscle fibres packaged together
attached to bones by tendons
muscle fibres
contain sarcomella which fold inwards to form transverse T tubules
sacroplasm
multiple nuclei
many myofibrils and mitochondria

Question 3

ultrastructure of a myofibril

Answer 3

2 long protein filaments arranged in parallel
myosin is the thick
actin Thin
arranged in sarcomeres
end Z line
middle M line
H zone contains only myosin

Question 4

banding patern in myofibrils

Answer 4

I bands are the light bands and are thin as only actin
a bands are dark bands that are thick contained myosin some actin
darkest regions are overlap
h zone only has myosin

Question 5

muscle contraction overview

Answer 5

myosin head slides actin along myosin which causes the sarcomere to contract
simultaneous contractions of many sarcomeres cause myofibrils and muscle fibres to contract
when sarcomeres contract
H and I shorter
A band the same
Z line gets closer

Question 6

myofibril contraction process

Answer 6

depol spread down sarcomella via t tubules causes calcium ions to be released from the sarcoplasmic reticulum which diffuse to the myofibrils
calcium ions bind to tropomyosin causing them to move and expose the binding sites on actin
allows myosin head with ads attached to bind to binding sites on actin forming actin myosin crossbridge
myosin head changes angle pulling actin along myosin using energy from atp hydrolysis
new atp binds to myosin head causing it to detach from binding site
hydrolysis of atp from atp hydrolase releases energy for myosin heads to original position
myosin reattaches to a different binding site further along actin
process repeated till ca2+ conc high

Question 7

during muscle contraction

Answer 7

calcium ions AT back into the endoplasmic reticulum using energy from ATP
Tropomyosin moves back to block myosin binding site on actin again → no actinomyosin cross bridges

Question 8

role of phosphocreatine in muscle contraction

Answer 8

source of pi phosphorylates adp rapidly to regen ATP
ADP+ phosphocreatine forms atp and creatine
runs out after a few seconds
short bursts of vigourous excercise
anaerobic and lactic

Question 9

slow twitch

Answer 9

specialised for slow sustained contraction
obtain atp from aerobic respiration
release energy slow and fatigue slow
high proportion In muscles for posture
legs of long distance runners
high conc of myoglobin store oxygen for aerobic respiration
Many mitochondria → high rate of aerobic respiration
Many capillaries → supply high conc. of oxygen / glucose for aerobic respiration and to prevent build-up of
lactic acid causing muscle fatigue

Question 10

fast twitch

Answer 10

brief intensive contraction
obtain atp for ana respiration release energy quick
fatigue quickly bc build of lactate
high prop in muscles for fast movement and in legs of sprinters
Low levels of myoglobin
Lots of glycogen → hydrolysed to provide glucose for glycolysis / anaerobic respiration which is inefficient so large quantities of glucose required
High conc. of enzymes involved in anaerobic respiration (in cytoplasm)
Store phosphocreatine