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23 Cards in this Set
- Front
- Back
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Glial Cells
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Small, numerous cells
Humans: 90% of brain cells, 50% brain mass |
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Glial Cells in the Central Nervous System
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Astroglia: support and other functions?
Microglia: immune cells Oligodendroglia: myelin sheaths |
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Glial Cells in the Peripheral Nervous System?
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Schwann cells: myelin sheaths
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Excitable Cells
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Muscles: generate force by contracting
Neurons: carry information (nerve signals) throughout body |
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Divisions of Nervous System
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Central
Peripheral One-way Flow of information! |
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Functional Types of Neurons:
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Afferent (sensory)
Efferent (motor) Interneuron |
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One-way flow of information
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-Dendrites
-Soma (cell body) -Axon Hillock (action potential initiation) -Axon (action potential) -Myelin Sheath -Axon (presynaptic) Terminals (neurotransmitter) |
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Voltage (potential):
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Charge difference (requires reference)
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Current:
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movement of charge
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Capacitance:
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storage of charge across an insulator
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Conductance:
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ease of current flow
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Resistance:
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inverse of conductance
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Resting Potential
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(-70 mV)
Inside of cell is negative with respect to outside Resting potential is due to an excess of positive charges outside the cell |
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Neurons at rest have the following properties:
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-Resting potential (voltage)
-High Capacitance across membrane -Excess Na+ outside the cell -Excess K+ inside the cell -Cell membrane has high permeability to K+ (high K+ conductance) -Low permeability to Na+ (low Na+ conductance) |
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Resting Potential the result of:
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1) Na+/K+ Pump creates concentration gradient (small charge difference)
Uses energy to move 3 Na+ ions out and 2 K+ions in 2) Large bidirectional permeability to K+ creates charge gradient (resting potential) |
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Ionic Basis of Resting Potential
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1. Outward K+ current because of concentration gradient
2. Charge gradient (Voltage) established by outward current of K+ 3. Inward current of K+ due to developing charge gradient (negative inside) 4. Steady state Equilibrium Potential is reached when these two currents balance |
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Resting Potential is -70 mV
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Resting Potential (-70 mV) does not equal K+ equilibrium potential (-90 mV) since it is opposed by small inward Na+ current (+20 mV)
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Resting membrane has high potential energy...
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(membrane capacitance) created by initial actions of Na+/K+ pump
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Potential energy in the form of both...
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concentration and charge gradients, especially for Na+, is stored across the membrane
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This potential energy will be released during the action potential due to...
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a change in the membrane’s conductance, especially the Na+ current
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Why are resting cells negative?
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Combination of
active pumping (creates concentration gradient) differential permeability to ions (creates charge gradient) |
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How is K+ concentration gradient maintained when membrane is permeable to K+?
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The charge gradient opposes the concentration gradient
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Is the resting cell in equilibrium?
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Yes (dynamic or steady state equilibrium)
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