animal responses

• how is muscle contraction activated from depolarisation of the sarcolemma to movement of tropomyosin (4)

  • depolarisation spreads down t tubules to sarcoplasmic reticulum
  • sarcoplasmic reticulum releases Ca2+ ions into sarcoplasm
  • Ca2+ binds to troponin causing a conformational change
  • tropomyosin moves from actin-myosin binding sites
• what happens when there are no more Ca2+ ions / membrane is repolarised ?

  • no longer binding to troponin
  • tropomyosin covers binding sites
  • actin returns to original position
  • sarcomere becomes longer
• describe the effect of increased H+ concentration due to lactic acid on muscle contraction (6)

  • decrease in PH denatures troponin
  • Ca2+ can no longer bind to every troponin causing some actin-myosin sites to be covered
  • only some cross bridges form
  • not all actin filaments slide along
  • power of stroke reduced
• what is found in the H , I and A band ?

  H - only myosin

  I - only actin

  A - myosin and actin
• name three proteins involved in muscle contraction

  • actin
  • tropomyosin
  • troponin
• whats the purpose of z and m lines

  to hold myofibrils together
• describe how componants of the elbow joint interact to bring about bending of the arm

  • muscles contract in antagonistic pairs
  • tendons connect muscle to bone
  • ligaments hold bones together preventing dislocation
  • cartilage reduces friction
  • synovial membrane secretes fluid which acts as a lubricant
• what happens visually to muscle when it contracts

  • I band shortens
  • H zone shortens
  • sarcomere shortens
  • A band stays the same
• describe steps of the corneal reflex arc

  • specialised cells in the retina detect bright light
  • impulse sent along SN to RN in lower brain stem
  • to MN to facial muscles resulting in blinking
• role of ATP in muscle contraction

  • movement of myosin head
  • active transport of Ca2+ into sarcoplasmic reticulum
• compare the structure and function of all 3 muscle types

  • involuntary : lines blood vessels and glands , non - striated , uninucleated , spindle shaped , slow
  • skeletal : lines the skeleton , voluntary , striated , multinucleated , cylindrical , fast
  • cardiac : myogenic , striated , uninucleated , branched , fast
• describe the knee jerk reflex

  • if kneecap is hit it stretches the patellar tendon
  • this stimulus causes the extensor muscle to contract
  • a RN inhibits MN of the flexor muscle so it relaxes
  • leg kicks
• what are the differences and similarities of structure of the parasympathetic and sympathetic NS

  • similarities : smooth muscle , glands and cardiac muscle are the effectors , can be stimulatory or inhibitory , preganglionic neurones are lightly myelinated , postganglionic neuwornes are unmyelinated
  • sympathetic : noradrenaline , short preganglionic
  • parasympathetic : acetylcholine , long preganglionic