| A | B |
|---|
| Nervous system | A. rapid electrochemical communican = wire system B. discreste transmission--> targeted C. structurally complex |
| Neuron-structure | 1. soma (cell body) and denarites=input zone 2. initial segment (axon hillock)=triger zone 3. axon=conducting zone 4. axon terminals=output zone |
| Neuroglia | support nerve function by A. in CNS they outnumber the neurons 80:1, B. in spinal cord and periphery, Schwann cell-myelin sheath (lipid insulation) |
| Nerve Function-nerve plasma membrane separates ion chambers | ECF=high NA+ (high in sodium), ICF=high K+ and richin protiens |
| Nerve Function-action potential | eletrical response in an excitable cell, 1. membrane ion gates (for NAand K) are closed at rest (there is some leakiness to K), 2. excitatory stimulus--> depolarization (if depolarization-->threshold, then an AP is gnerated) 3. action potential (a. Na gates open-upstroke, b. K ates open (Na gates close)-downstroke, c. return to Em) |
| Nerve Function-propagation (conduction) of the AP | 1.directional, 2. from initial segment -->nerve terminals, AP is "all-or-none" (AP= action poential), saltartory in myelinated axons, AP jumps from node of Ranvier to node to node... |
| Nerve Function-synaptic transmission | 1. synapse=gap that seperates a neuron from target cell, 2. neurotransmitter=chemical messengers that diffuse across the snaptic deft (Neuron=presynaptic element, Target=postsynaptic element), 3. Characteristics (calcium dependent, quantal, neruotransmitter action is short lived (enzyme degrationk, reuptake)) |
| Nerve Function-post-synaptic responses | 1.EPSP=excitatory=postsynaptic potential depolarization, Em approches threshold, 2.IPSP=inhibitory postsynaptic potential=hyperpolarization, Em moves away from threshold, 3. in complex neural circuits hundres of synapes may converge on single target seuron (summation/adding together: temperal spatial) a. incoming messages (EPSPs and IPSPs) summate, b. if postsynaptic element is deppolarized to threshold -->AP |
| Nerve Function-After AP... | ...NaK ATPase works to re-establish resting membrane potential by pumping K back into the cell and pumping Na out of the cell across the plasma membrane |
