Muscles Flashcards
Why does skeletal muscle contract
Contracts in response to the release of acetylcholine from a motor neuron
Structure of muscle fibre
Each muscle fibre surrounded by sarcolemma membrane
Cell contains sarcoplasm cytoplasm
W lots of mitochondria
Each muscle fibre contains large number of myofibrils
Each myofibril surrounded by sarcoplasmic reticulum
Each myofibril made of myofilaments
Actin (thin) myosin (thick)
What are myofilaments arranged into
Sarcomeres
A-band=?
Dark
I-band= ?
Light
Actin anchored to what
Z-discs
Myosin anchored to what
M-line
Fall in ph leads to a reduction in ability of Ca2+ to stimulate muscle contraction
Low Ph changes shape of Ca2+ receptors
Less Ca2+ bind to troponin
Fewer tropomyosin moves away
Fewer binding sites on actin revealed
Less myosin heads bind
So less cross bridges for
Less activation of Atp hydrolase
What is the role of atp in myofibril contraction
Allows binding of myosin to actin
Atp provides energy which changes shape of myosin head
(Atp hydrolysed into Adp + Pi by Atp hydrolase) this provides the energy
Tropomyosin
Moves out of the way when Ca2+ bind
Allowing myosin to bind to actin forming crossbridge
Myosin in myofibril contractions
Head of myosin binds to actin
Myosin detaches from actin and resets
This uses atp
ATP provides energy which changes shape of myosin head
advantage of high glycogen content of fast muscle fibres
Glycogen hydrolysed into glucose for glycolysis
Glycolysis only yields 2 Atp per glucose
Advantage of capillaries in supplying slow muscle fibres
Many capillaries provide large SA for oxygen diffusion
Allows higher rate of aerobic respiration
Preventing build up of lactic acid
Describe the role of calcium ions and ATP in contraction of myofibril
Role of PC in providing energy during muscle contraction
Pc provides a phosphate
To make atp
