9 - Control of Organisms

Question 1

role of ATP in the sliding filament theory

Answer 1

• attachment / cross bridges between actin and myosin
• power stroke / movement of myosin heads to pull actin
• detachment of myosin heads due to addition of new ATP molecule
• recovery stroke / myosin heads moving back to original position
• reabsorb calcium ions into sarcoplasmic reticulum by active transport

Question 2

sliding filament theory

Answer 2

• tropomyosin blocks binding sites on actin molecule
• Ca2+ ions diffuse into myofibril from sarcoplasmic reticulum to move tropomyosin, exposing binding sites
• myosin heads bind to binding sites, forming actinomyosin cross bridge
• hydrolysis of ATP causes myosin heads to bend and pull actin molecules. This is the power stroke
• attachment of new ATP molecule to each myosin head causes them to move back to their original position - recovery stroke

Question 3

what is skeletal muscle made up of

Answer 3

• repeating units of myofibrils called sarcomeres

- each myofibril consists of myosin and actin with a tropomyosin molecule on it

Question 4

how does an action potential enter the myofibril

Answer 4

via T tubules

Question 5

role of phosphocreatine in muscle contraction

Answer 5

• generates ATP quickly by adding phosphate to a molecule of ADP released by the contracting muscle
• allows muscle contraction to continue for longer
• substrate level phosphorylation

Question 6

factors that affect speed of conductance through a neuron

Answer 6

• myelination
• saltatory conduction
• axon diameter
• temperature

Question 7

how does the Pacinian Corpuscle work

Answer 7

• Increase in pressure causes deformation of
  the concentric rings of the Pacinian corpuscle,
  opening stretch-mediated sodium channels in
  the membrane.
• Sodium ions enter the sensory neuron, causing a
  generator potential which can trigger an action potential