LEWIS: Muscles Flashcards
Sarcolemma is the
Plasma membrane
Each muscle fibre contains:
- myofibrils
- mitochondria
- sarcoplasmic reticulum
- nuclei
Sarcoplasmic reticulum is the equivalent to the endoplasmic reticulum of cells. It forms a network of channels - acts as a store of
Calcium ions that when released initiate muscle contraction
Sarcoplasm is the
Liquor interior of a muscle fibre
Striated appearance or muscles is caused by alternating
Dark and light bands
Dark bands are called
A bands
Light bands are called
I bands
The I bands are bisected by the
Z line
The centre of A bands is divided by the
H zone
The reoccurring unit in a Myofibril is the
Sarcomere
The sarcomere goes from
One Z line to another
2 myofilaments:
Actin
Myosin
Actin filament is the
Thin, light band
The thin filament of actin extends in each direction from the
Z line
Myosin filament produces the
Dark, thick band
Shortening of the sarcomeres in a Myofibril produces the shortening of the Myofibril and in turn, of the
Muscle fibre of which it is a part
Where the myofilaments do not overlap is known as the
H zone
Step 1 of muscle contraction:
1) nerve impulse arrives at the end of motor neurone
Step 2 of muscle contraction:
2) acetylcholine is released
Step 3 of muscle contraction:
-acetylcholine binds to receptors on motor end plates
Step 4 of muscle contractions:
-sodium ions rush into muscle fibres
Step 5 of muscle contractions:
Muscle action potential sweeps into T tubules
Step 6 of muscle contractions:
-sarcoplasmic reticulum releases calcium ions
Step 7 of muscle contraction
Calcium binds to troponin, causing it to change shape
Step 8 of muscle contraction
When calcium binds to troponin, it causes tropomyosin to move and expose myosin binding site
Step 9 of muscle contraction
- myosin binds to actin, activating enzyme myosin-ATPase (energy released from ATP breakdown = causes change in shape of myosin head)
- cross bridge formed
Step 10 of muscle contraction
-Myosin pivots pulling actin filaments (ratchet mechanism/power stroke)
Step 11 of muscle contraction:
-myosin releases from actin
Step 12 of muscle contraction:
Myosin re-extends into ‘ready’ position