Chapter 11 Part 2 Fundamentals of CNS

Chapter 11 Part 2 Fundamentals of CNS - Chapter 11...

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Unformatted text preview: Chapter 11 Fundamentals of the Nervous System and Nervous Tissue Part 2 Angela Peterson-Ford, PhD E209 Voltage (V) measure of potential energy generated by separated charge Potential difference voltage measured between two points Current (I) the flow of electrical charge between two points Resistance (R) hindrance to charge flow Insulator substance with high electrical resistance Electricity Definitions Reflects the flow of ions rather than electrons There is a potential on either side of membranes when: The number of ions is different across the membrane The membrane provides a resistance to ion flow Electrical Current and the Body Types of plasma membrane ion channels: Passive, or leakage, channels always open Chemically gated channels open with binding of a specific neurotransmitter Voltage-gated channels open and close in response to membrane potential Mechanically gated channels open and close in response to physical deformation of receptors Role of Ion Channels Example: Na+-K+ gated channel Closed when a neurotransmitter is not bound to the extracellular receptor Na+ cannot enter the cell and K+ cannot exit the cell Open when a neurotransmitter is attached to the receptor Na+ enters the cell and K+ exits the cell Operation of a Gated Channel Operation of a Gated Channel Figure 11.6a Example: Na+ channel Closed when the intracellular environment is negative Na+ cannot enter the cell Open when the intracellular environment is positive Na+ can enter the cell Operation of a Voltage-Gated Channel Operation of a Voltage-Gated Channel Figure 11.6b When gated channels are open: Ions move quickly across the membrane Movement is along their electrochemical gradients An electrical current is created Voltage changes across the membrane Gated Channels Ions flow along their chemical gradient when they move from an area of high concentration to an area of low concentration Ions flow along their electrical gradient when they move toward an area of opposite charge Electrochemical gradient the electrical and chemical gradients taken together Electrochemical Gradient The potential difference (70 mV) across the...
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Chapter 11 Part 2 Fundamentals of CNS - Chapter 11...

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