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Cell Body Also Called SOMA and CYTON – Has all the normal cell parts. Has dendrites and an axon sticking off in all directions
Dendrite Receive stimuli and conduct them toward the cell body A nerve cell has many dendrites Thin branches
Axon Extend from cell body Carries impulses AWAY from a cell body Transmits impulses to other neurons. Surrounded by cells called: SCHWANN CELLS Schwann Cells produce a fatty substance: MYELIN – Myelin insulates the axon
Sensory Neurons – receive information from external or internal environment. – Signals go to brain or spinal cord. Motor Neurons – transmit signals that originate in the brain or spinal cord. – Signals go to muscles or glands. MOTOR AND SENSORY NEURONS FORM THE “PERIPHERAL N.S.” Relay Neuron (Interneuron) – transmit signals from one neuron to another within the CNS.
Sensory and Motor Be able to draw – sensory and motor
Pathway of an Impulse (Stimuli) -- Receptors ---- Sense organs TO….. CNS through SENSORY NEURONS…............. Within CNS in RELAY NEURONS TO……………. MOTOR NEURONS take RESPONSE to Effectors (muscles or glands)
Resting Potential Occurs when a neuron is NOT conducting an impulse! Electrochemical gradient Inside membrane is negative relative to outside Protein Channel – Sodium/Potassium Pump Actively transport Na+ out and K+ in 3 Na+ out & 2 K+ in Membrane is more permeable to K+ Resting potential is -70mV (difference in charges)
Action Potential Rapid change from – to + to – in response to stimuli – Stimuli >>> causes membrane to become less negative. – Threshold Potential (-50mV) >>> triggers action potential >>>> Depolarization >>> Na+ channels open >>> Na+ enters cell ( + inside, - outside)…….. +30 to 60 mV inside the cell >>> – Peak Potential >>> K+ channels open >>> K+ flow out of cell>>> Na+ channels close; >>> (- inside, + outside) >>> Repolarization – K+ channels remain open >>> lowers membrane potential (- 90mV) >>> K+ channels close >>> Na+/K+ pump resumes
Synapse Junction between 2 neurons Axon of one neuron --- dendrite of another! Neurotransmitter – closes the “gap” between neurons. Acetylcholine
Synapse Impulse causes Ca+ to diffuse through membrane channels >>> Vesicles containing neurotransmitters fuse with “ pre-synaptic” membrane >>>> NeuroT released into the SYNAPTIC CLEFT --- Exocytosis! NeuroT binds to “post-synaptic” membrane >>> allows adjacent ion channels to open >>> depolarization of new neuron NeuroT – generally recycled