Muscles Flashcards
Gives the role of muscle in the body
- produces body movement
- stabilises body positions
- regulates organ volumes
- movement of sunstances in the body
- produces heat
Properties of Muscle
- excitability
- comductivity
- contractability
- extensibility
- elasticity
Describe skeletal muscle structure -
- multinuclear
- striated with ligh and dark bands
- voluntary control
- support soft or hard tissue
- cells are called fibres
- long and cylindrical
Give the order of muscle structure - outer to inner
muscle - covered in epimysium- fasicle - Permysium - Muscle Fibre- Endomysium- Sarcolemma - sarcoplasm, mitochonria - myofibril - action and myosin - surround each myofibirl - sarcoplamis reticulum - sarcomere.
What is a motor unit?
One motor nerve and the muscle fibres it supplies
Give the role of the sarcolemma -
- cell membrane of the muscle cell
- surrounds the sarcoplasm - cytoplasm of muscle fibre
- sacroplasm filled with myofibrils , myoglobin
- change in transmembrane potential begins contractions
Give the role of T tubercles -
- Invaginations of the sarcolemma into the centre of the cell
- Filled with extracellular fluid
- Carry muscle action potentials down into the cell
- allowing the entire muscle fibre to contract simultaneously.
Give the role of the Sarcoplasmic reticulum-
- membranous structure surrounding each myofibril
- System of tubular sacs similar to smooth endoplasmic reticulum in non-muscles cells
- help transmit action potentials to the myofibrils
- forms chambers at each end( terminal cisternae) , attached to T-tubules
Describe the Myosin molecule
- Head made of 2 globular proteins subunits which during contractions creates cross bridges , head pivot producing motion
Describe the Actin molecule -
-Myosin binding site on each actin molecule is covered by tropomyosin in relaxed muscle , during contraction these strands of tropomyosin needs to move away , this is initated by the binding of calcium=cross bridge formation.
Give the regulatory proteins -
Troponin and Tropomyosin
Outline the sliding filament mechanism-
- Myosin cross bridges pull on thin filaments
- Thin filaments slide inwards towards M line , between thick filaments
- z discs move closer together
- sarcomeres shorten , the muscle fibre shortens , the muscle shortens
- Thick and thin filaments do not change in length - width of A band stay the same
Outline skeletal muscle contraction-
- Nerve impulse reaches axon terminal
- Calcium ions(CA2+) are released from the terminal cistermae of SR
- CA2+ binds to the troponin causing a shirt of tropomyosin off the active sites on actin
- Activated myosin head binds to the active site on the actin
- Myosin head pivots and pulls the thin filament toward the M line
- ATP causes the myosin head to detach from the actin
- Myosin head spilts ATP providing energy to the myosin head.
- action potential ceases
- Active transport pumps CA2+ back into storage in the terminal cistermae
- Tropomyosin-Troponin complex recovers binding site on the actin molecules
- Contraction ends
Creatine Phosphate
- Formed from excess ATP
- Quick breakdown provides energy for creation of ATP
