muscular tissue part 2
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the basic functional units of a myofibril
narrow plate shaped regions of dense protein material separate of sarcomere from the next. thus a sarcomere extends from one of these to the next
the darker middle part of the sarcomere which extends the entire length of the thick filaments.
is a lighter, less dense area that contains the rest of the thin filaments but no thick filaments. A z-disc bases through the center of each of these bands.
in the centre of each band contains thick but no thin filaments
it is the middle of the sarcomere
one of two contractile proteins, it functions as a motor protein in all three types of muscle tissue. They push or pull various cellular structures. They form a single thick filament
the two projections of each myosin molecule. they extend towards the thin filaments.
thin filaments attached to z-discs have this protein. this type of molecules join together to forma filament that is twisted together into a helix. Each molecule has a myosine-binding site where a myosin head can attach
a regulating protein. It covers the myosin binding sites in relaxed muscles. they are held in place by troponin molecules. When bound with ca 2 troponin changes shape which causes this to move away from the myosin head binding site
sliding filament mechanism of muscle contraction
- 1. myosin heads hydrolyze atp and become reoriented and energized
- 2. myosin heads bind to actin, forming crossbridges
- 3.myosin crossbridges rotate toward center of sacromere
- 4. as myosin heads bind atp the crossbridges detach from actin
an increase in ca 2 concentration in the cytosol starts muscle contraction and a decrease stops it.
the synapses between a somatic motor neuron and a muscle fiber
somatic motor neuron
the neurons that stimulate muscle fiber contraction
at most synapses a small gap separates the two cells
because the cells do not physically touch the action potential cannot jump the gap. Instead the first cell communicates with the second by releasing a chemical called this
suspended in the cytosol within each synaptic end bulb are hundreds of membrane enclosed sacs
inside each synaptic vesicle are thousands of moleculesod this, a neurotransmitter released at the ends of axons
motor end plate
the region of the sarcolemma opposite the synaptic end bulbs. It is the muscle fiber part of the neuromuscular junction.
within each motor end plate are these. Integral transmembrane proteins bind specifically to Ach.
muscle action potential
the inflow on Na+ makes the inside of the muscle fiber more positively charged. This change in the membrane potential triggers this.
an enzyme that breaks down Ach. This enzymeis attached to collagen fibers in the extracellular matrix of the synaptic cleft
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