B3.3 Muscle and Motility HL

skeleton (2)

• exoskeleton ( chitin )

• endoskeleton ( bones)

joint (2)

• hinge joint ( elbow and knee)

  • one plant of movement

  • bend & straight

• ball and socket joint ( hips, shoulder)

  • large range of movement

  • protraction, retraction , abduction, adduction , rotation

measure joint

goniometer

most allowing movement joint

synovial joint - human hip joint 

 

Bone (Femur & Pelvis)

Cartilage

Synovial fluid

Ligaments

Muscles

Tendons

function

bone- anchorage for muscle & ligants, guide movement 

muscle - provide force for movemet 

cartilage - smooth connective tissuet that covers the end of bone to reduce friction 

synovial fluid - lubricate joint reduce friction

ligaments - slight elastic tissue - attaches bones to bones 

tendons - non elastic tissue - attaches muscle to bone

skeletal muscle

• attacth bones - cause movement of animal body 

• It consists of large multinucleated cells called muscle fibers.

• There are also mitochondria between the myofibrils.

level of organisation 

muscle fibres → myofibris → microfillaments → sacromere 

wra around myofibrils

sacroplamatic reticulum

skeletal muscle & electrical impluse

Skeletal muscles are voluntary muscles that requires electrical impulse from the brain.

• Electrical impulse sent from brain through motor neuron → neuromuscular junction.

Each motor neuron has a set number of muscle fibers that it control called a motor unit.

motor unit + function

• contraction of skeletal muscle 

• include single motor neuron & muscle fibres

• muscle fibre contract when stimulated by motor neuron

• stimulus pass through neuron , through synapse- neuromuscular junction to muscle fibre

• require neurotransmitter : acetylcholine ( basically just the normal neurotransmitter process) 

sacromere

• two protein filaments

• subunit of myofibrils 

• between two Z-lines

• myosin 

  • thick , dark bands 

  • head that forms cross bridge by binding to actin 

• actin 

  • thin, light bands 

  • lengthening and shortening of sarcomere

  • attach at the end of Z lines

crose bridge cycle

1. When a nerve impulse arrives at the neuromuscular junction,calcium ions are released from the sarcoplasmic reticulum

2. calcium bind with troponin, change shape, move tropomyosin to expose the myosin-binding site on actin

3. Myosin heads bind to actin, forming crossbridges 

4. Myosin releases ADP and P_i, causing the power stroke - pulls the actin filament towards the centre of the sarcomere

5. ATP binds to myosin, breaking the crossbridges

6. ATP is hydrolysed to ADP and P_i, provide energy that “cock” the myosin head away from the center

7. Myosin heads bind to actin at a new binding site further along the sarcomere

The cycle continues until Calcium is pumped back into the sarcoplasmic reticulum, or there is no ATP available

titin

contraction of antagonistic muscle → creates energy →  needed to lengthen a muscle, which stretches titin. titin recoils → release energy → adds to the force of contraction in that muscle (provide supplemental force)

• prevent overstretching of sacromere 

• holds myosin filaments in place 

Explain how a skeletal muscle contracts