voluntary muscle - skeletal muscle brief notes

• muscles attach to bones by tendons - which are made of collagen
• bones to bones = ligaments
• muscles work in pars - oppose each other - antagonistic 

complex joing e.g. wrist has whole range of movement you need a complex series of muscles = synergist
if a join does a lot of movement it needs to be lubricated - use synonial fluid - made by the synorial membrane

skeletal of voluntary muscle

muscle is made up of bundles of muscle fibre and each muscle fibre is a giant cell with many nuclei

each muscle fibre is made up of bundles of myofibrils each myofibril is made off bundles of myofilaments which are proteins, myosim and actin

became myofils are inside giant fibre they can be called organelles

how muscles contracts - sliding filament theory and power stroke

Actin = globular protein which join together like string of heads

2 actins twist around each other - they have binding sites to the myosin head

troponin has 3 binding sites: 1 to troponin and actin and ca^++

POWER STROKE

• nervous impulse arrives at the neuromuscular junction an releases acetyl-choline 
•  DEPOLARISES 
• sarcolemma going into the centre of cells to T tubes - releases calcium ions from sarcoplasmic reticulum
• calcium ions binds to the troponin 
• troponin moves tropomyosin exposing thebinding sites on the actin
• myosin head flips through 45 degrees = power stroke
• pulling the actin
• ATP binds to the head - head = ATPase - ATP > ADP + phosphate > eergy
• energy unbinds the head to the binding site in ATP - head flips back to bind to next binding site
• this continues to happen power stroke is the flipping of the head
• actin is made to slide over myosin
• sarcomere - Z - Z shortens from 2.5 um to 2 um
• after contraction calcium ions move back to sarcoplasmic reticulum by active transport

• when myosin head binds to the actin band is known as cross link
• as the muscle contracts the A band always stays at thesame length
• H band gets shorter and may disappear
• I band - actin on its own will get shorter
• Z-Z = sarcomere shortens

Fight - flight - scared

• e.g. heart rate increase, breathing rate increases, depth increases, pupils dilate
• release endorphins in brain (natural pain killers)
• stressor - stimulus that causes stress
• humans are intelligent - so we can percieve stress e.g. when OFSTED come we know theyre not going to kill you
• percieve by cererum
• sends mpulse to the hypathalamus
• sympathetic nervous system stimulated release of adrenaline from adrennal medulla
• hypathtlamus releases a hormone aka CORTICOTROPHIN RELEASING FACTOR into the pitutitary - pituitury release adrenocorticotrophic hormone
• this makes adrenal cortex release more corticotrophic hormones

Hypathalaus - nervous tissues - release hormones

• lots of ways to animal deals with threats/stress
• animals deal w/ stress in different ways
• e.g. snakes place dead so they wont be eaten by the eagle
• some reptiles camouflage
• stress/hurting/digestion - are interlinkes
• stress-stomach ulcer