MDC BSC 2085 - Nervous System (39 pages)

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Nervous System



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Nervous System

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Pages:
39
School:
Miami Dade College
Course:
Bsc 2085 - Hum Anat & Phy 1
Hum Anat & Phy 1 Documents

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Nervous System Neurophysiology Neurophysiology Neurons are highly irritable Action potentials or nerve impulses are Electrical impulses carried along the length of axons Always the same regardless of stimulus The underlying functional feature of the nervous system Electricity Definitions 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 Conductor substance with low electrical resistance Electrical Current and the Body 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 Role of Ion Channels 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 Operation of a Gated Channel 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 Figure 11 6a Operation of a VoltageGated Channel 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 VoltageGated Channel Figure 11 6b Gated Channels 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 Electrochemical Gradient Ions flow



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