muscles

Question 1

what are the 3 types of muscles

Answer 1

1. skeletal muscle- attached to the bone via inelastic tendons and is concerned with locomotion, contracts and fatigued rapidly
   2.smooth muscle- found in the walls of tubular organs such as arteries and the gut, contracts and fatigues slowly
2. cardiac muscle- found in the heart

Question 2

what are the features of skeletal muscle contraction

Answer 2

muscles act in antagonistic pairs against incompressible skelton. Skeletal muscle is used to move bones at joins. When muscles contract they usually shorten when the contact.

Question 3

what are muscles made up of

Answer 3

tiny muscle fibres which are elongated cells packed with myofibrils. The seperate cells have fused together into muscle fibres which share nuclei and a cytoplasm(sarcoplasm)

Question 4

what is within the sarcoplasm

Answer 4

a large concerntration of mitochondria and sarcoplasmic reticulum. mitochondria is the site of aerobic respiration hells supply atp needed to slide actin and myosin over eachother. sarcoplasmic reticula release calcium ions which initiate this sliding

Question 5

What is are thick filaments made up of ?

Answer 5

a protein myosin- it is shaped like a golf club and consists of a tail and a globular head. The tails of the myosin molecules are specifically shaped to bind to eachother and form thick filmaments

Question 6

what are the thin filaments made up of

Answer 6

actin- made up of two helical strands of globular actin molecules which twist around each other. They are associated with two regulatory proteins: tropomyosin and troponin.

Question 7

describe muscle stimulation

Answer 7

An action potential reaches a neuromuscular junction and triggers the release of acetylcholine from the motor neurone.
This causes an action potential in the cell membrane, this spreads through the muscles fibre via a system of tubules.
They are in contact with the ER which actively absorb calcium ions.
The action potential opens calcium ion channels so calcium ions flood into cytoplasm down the gradient.
The calcium ions cause the tropomyosin that was blocking the binding sites pulls away

Question 8

explain the mechanism of muscle contraction

Answer 8

1. The binding sites on the actin filaments are covered by tropomyosin
   2.muscle contraction is activated by calcium ions which diffuse from the ER
2. calcium ions bind to tropomyosin to move causing exposed binding sites
3. actin-myosin cross bridges form as myosin heads attach to binding sites on the actin
4. calcium ions stimulate the action of ATPase which hydrolyses ATP proving energy for the myosin head to bend pulling the actin filament along.
5. myosin attached to another new ATP molecule causing the myosin to become detached from the actin