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Nervous System Maddie Picher, Rachel Quigley, Lisa Waddell
Structures of a Motor Neuron • dendrites (processes) [dendrite spine] • conducts impulses from other neurons down to the axon • cell body (soma) • the nucleus • cell membrane • other parts of a normal cell • where protein synthesis occurs • axon • myelin sheath • nodes of ranvier • where the chemical reactions occur • synaptic terminal • where the neurotransmitters are released to bind with the dendrites of neighboring neuron
Myelin Sheath • Comprised of fat • Insulates the axon from electrical activity: maintains resting potential and aids action potential • The nodes of ranvier between the myelin sheath on the axon cause rapid saltatory conduction of impulses across the nodes resulting in a faster transmitted impulse • Demyelination (deterioration of the myelin sheath) is known to be a contributor to lack of muscle and speech control (parkinson's disease)
Ions in the Neuron at Rest: • Electric currents disturb the trigger region, that has gated channels • Protein Channels between cytoplasm (-) (NA) and interstitial fluid (+) (K) • Charge difference is maintained through active transport of the Sodium-Potassium pumps (use of ATP) • Sodium out, Potassium in at ratio of 3:2 • Result: (+) outside (-) inside of neutron • Resting Membrane Potential: difference of charges (-70mV)
The Nerve Impulse • As a reaction to a stimulus, rapid depolarization happens, causing a change in charge causing the impulse • Depolarized: inside of cell (+) and outside (-) • Action Potential: Moving depolarization; one transport effects neighboring channels • To bring back to resting state, active transport takes place again, balancing the cell– the inside of the plasma membrane becomes negative once again and repolarizes the membrane
Action Potential • occurs when a portion of the membrane rapidly depolarizes then repolarizes again to the original resting state • initiated by stimulus • reversal in voltage difference across plasma membrane (about +30mV)
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