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KIN 3600
Lec 16
| Term | Definition |
|---|---|
| Functions of nervous system | -Sensory -Motor -Inhibitory |
| What is electro-chemical equilibrium in a resting cell? | When the electrical & chemical force are equal in quantity. -Electrical ions pulling in & chemical pushing ions out |
| What happens when we stimulate cell / gets disturbed? | -Na+ gates open -Make cell membrane less negative -Results is overboard & becomes positive charge inside the cell (+30mV) -Na+ wants to get in equilibrium but the Na+ gates close before it can reach it -->Reversal potential |
| Electrical Activity of Neurons | What is sodium/potassium pump -ATP energy spent |
| Action Potential & its ionic bases | -Sodium gates closes preventing further influx -30mV -Cell is positive so it is pushing K+ out (0mV) -Cell becomes more negative and goes back to -70mV -Too much K+ gets out so it becomes hyperpolarized (-75mV) -K+ going back in (-70mV ) |
| 1 nerve impulse | 1 Action Potential |
| Na+ & K+ are voltage | regulated gates -Open & Closes based off voltage |
| Na+ & K+ pumps | chemically regulated |
| Overshoot | |
| What causes negativity in the cell? | Responsible ions: K+ outflux -Cell regains normal negativity |
| What ions cause hyper-polarization | Outflux of K+ -Why – membrane permeability is still higher than normal |
| Absolute refractory period | cell cannot be stimulated regardless of how strong -Time elapsed from beginning of stimulation during which another action potential cannot be generated in the cell regardless if stimulus strength. |
| Relative refractory period | cell may be stimulated if stronger than normal stimulation will trigger a reaction |
| Characteristics of AP | -ALL-or-none principle -Stimulation threshold -Hyper/Hypo polarization |
| ALL-or-none principle | -ALL way up or ALL way down -Stimulus intensity large enough to initiate AP it will trigger – even if you make it higher --->AP will be the same size |
| Stimulation threshold | -Causes trigger AP -Can change depend on what you’re doing |
| Hyperpolarization | -Cell is polarized more than normal (-75mv) -Drops membrane potential -Less excitable -Need intense stimulus to get AP |
| Hypo-polarized | -Drop membrane potential -Polarized less than normal -Easily excitable |
| Thicker fibers | faster propagation |
| Thinner fibers | Slower propagation |
| Saltatory Conduction | -Myelinated is 25x faster than regular conduction in fibers of same diameter (1msec – 130msec) -Myelination lowers energy expenditure |
| Larger diameter of an axon | greater is the propagation velocity |
| Schwan Cells (PNS) | -1mL -Warp around nerve fibers • Shiny white because myelination • Look like sausage links |
| Nodes of Ranvier | Gaps between Schwan cell • Only area that is exposed • AP inly happen here • Hopping from node to node |
| Lower energy expenditure | Fewer Na+ & K+ ions are exchanged during propagation of AP |
| Multiple Sclerosis | Demyelination of axons -Delays of transmission |
| Transmission of information through the nervous system – coding the stimulus intensity | Frequency of action potential |
Created by:
rmart11
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