15.8 - Contraction of skeletal muscles

Question 1

The contraction of skeletal muscle will move along a muscle

Answer 1

e.g For example a limb will move in one direction but same muscle cannot move into opposite direction

Muscles work antagonistically to the first one

Stretches partner muscle that relaxed returning to original state to work again

Question 2

What is the process of contraction?

Answer 2

Sliding filament theory

Question 3

What bands look like when contract:

Answer 3

1. I bands become narrow
2. Z ;omes move closer or sacromere shortens
3. H zones become narrower
4. A-band stays same width as determined by length of myosin filaments
5. This discounts the theory of muscle contraction

Question 4

Myosin is made up of two types of proteins:

Answer 4

1. Fibrous porteins arranged into a filament made up of several molecules
2. A golbular protein formed into bulbous structures at one end the head
3. Actin is a globular protein whose molecules arranged into long chains twisted - helical
4. Tropyomyosin from long thin threads wound around actin filament

Question 5

Muslce stimulation

Answer 5

• Action potential reaches neuromuscular junction simultaneously and cause calcium ion channels to open and calcium ions to diffuse into synaptic knob
• Calcium ions cause the synaptic vesicles to fuse with presynaptic membrane and release aceycholine into their synaptic cleft
• Acetlycholine diffuses across synaptic cleft and binds onto receptor of muscle-cell surface membrane to deploarise

Question 6

Muscle contraction

Answer 6

• Action potential travels deep into fibre of system of T tubules
• Tubules are in contact with endoplasmic muscle and actively transport calcium ions from cytoplasm leading low Calicum ions
• Action potential opnes calcium ions protein channels on endoplasmic recticulum and calicum ions diffuse into muscle
• Calcium cause tropomyosin molecules to block binding sites of actin flament
• ADP molecules attached on myosin heads to bind actin filament and form cross-bridge
• Once attached to actin filament myosin heads change angle pulling actin filament along release ADP
• ADP molecule attach to myosin heads causing it to detached from actin filament
• Calcium ions activate the enzyme ATPase to hyrolyse ATP into ADP
• Provides energy for myosin to return to original position

Question 7

Muscle relaxtion

Answer 7

• Nervous stimulation ceases calcium ions are actively transported back into the endoplasmicrecticulum using hydrolysis ATP
• Reabsorbption of calcium ions allows tropoymosint o block actin filament
• Myosin heads are unable to bind to actin filament ad contract ceases
• Antagonistic muscles pull actin filament out from between myosin

Question 8

What is ATP used for in muscle contraction?

Answer 8

1. Movement of myosin heads
2. Reabsorbption of calcium ions into the endoplasmic recticulum by active transport

Question 9

What is phodphocreatine?

Answer 9

• High demands
• Rapidly generating ATP anaerboically
• Partly more by glycosis
• Cannot supply energy directly to muscle and regenerates ATP
• Stored in muscle and combine ADP TO ATP