muscle

Question 1

explain the term antagonistic muscle action

Answer 1

muscles that work oppositely (one contracts while the other relaxes)

Question 2

describe and explain muscle fibres

Answer 2

-they have a cylinnder shape and are surrounded by a sarcomere (a cell surace membrane)
-they contain many nuclei and many myofibrils

Question 3

describe the structure of muscle fibres /myofibril

Answer 3

-thin filaments are made up of actin and thick filaments are made up of myosin
-thick filaments are present in A-band
-H-zone is the centre of A-band(dark band) and does not contain any myosin filaments
-I band contains only thin actin filaments

Question 4

describe what happens when muscles contract

Answer 4

-Ca2+ ions bind to tropomyosin on the actin filament
- This allows myosin heads to bind to the actin filament and pull it in
- this forms crossbridges
-ATP then binds to the myosin head which breaks the cross bridges and releases the myosin from the actin
-ATP is then hydrolysed back into ADP + Pi and this repeats

Question 5

describe the process of transmission across neuromuscular junction

Answer 5

-an action potential arrives at the pre-synaptic knob
-this causes calcium channels to open and Ca2+ ions to diffuse into synaptic knob
-the vesicles containig Ach fuses with the pre-synaptic membrane
-Ach is released and attactches onto specific protein receptors on the sarcolemma
-this causes Na+ channels to open and Na+ ions to diffuse in
-this causes action potentials to move along the muscle membrane
-this stimulates the release of Ca2+ ions