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Nerves and Coordination (Myelinated Motor Neurone (Schwann cells create…
Nerves and Coordination
Myelinated Motor Neurone
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Myelinated neurons can transmit action potential more quickly than non-myelinated neurons (100-120 m/s)
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Refractory Period
Almost immediately after the cell becomes depolarised, it begins to repolarise
When sodium channels open, potassium ion channels open as well
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Acetylcholine esterase
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Stops the transmission of signals, with the ethanoic acid and choline being recycled
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Synapses
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It then binds to the receptor sites on the Na+ channels in the postsynaptic membrane, making the Na channels open
Na+ diffuse across the post synaptic membrane into postsynaptic neuron, Excitatory Postsynaptic Potential is created, these combine and reach the threshold + AP is formed
Skeletal Muscles
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Sarcoplasms contain many mitochondria, extensive sarcoplasmic reticulum and myofibrils - Called striated muscle
Myofibrils are contractile elements that contain smaller units called saecomeres, with actin and myosin filaments
I band = Thin actin filaments, Z line = Region where actin is anchored, A band = Region containing the whole length of the myosin, M band = Region where sarcomere connects to skeleton, H band = Thick myosin only
Muscle Contraction
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When muscle is stimulated - impulse reaches the muscle and causes the release of Ca+, increasing conc of Ca+
Ca+ binds to troposmyosin causing it to change shape and move away from the myosin binding site on actin
Actin is now 'on', ATP binds to the myosin and is hydrolysed, Pi is released, changing the shape of myosin head, allowing cross bridges
ADP is released and causes the myosin head to tilt and pull the actin filaments over the myosin filament - Power Stroke
End of power stroke - ATP binds to myosin head and the X bridges are broken, if Ca+ conc remains high, repeat cycle
Neuron Pathway
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Sensory neurons send Action Potential (AP) from sensory receptor to Central Nervous System (CNS), has a long dendron and a short axon
Relay neurons connect the sensory and motor neurons, has many short dendrites and a short axon
Motor neurons carry AP from CNS to effectors (muscles and glands) its cell body is within the CNS and has a long axon
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Resting potential
Resting potential = electrical gradient across cell membrane when there is no action potential passing through it
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