Lectures3+4-Chapter_2-BiologicalFoundations

The number and layout of the dendrites are key

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Unformatted text preview: r it leaves the cell body). The number and layout of the dendrites are key distinguishing features among different types of neurons. A = axon; D = dendrites, S = soma 38 Functional Classification of Neurons Sensory (afferent) neurons are triggered by stimuli in the physical environment and transmit this information to the brain. Interneurons process the signals locally or transmit the information to other brain sites. This is the largest class and accounts for all of the neuronal processing in the cerebral cortex. Motor (efferent) neurons carry signals to the various muscles in the body. 39 The Other Cells of the Brain - Glia Outnumber neurons Not usually directly involved in signal processing Provide structural support for neurons, and also are key players in transferring energy from the vasculature to neurons Provide electrical insulation to axons (called myelin) that increases the speed of neural communication Peripheral nerve (crosssectional view) insulated by myelin from Schwann cell 40 Astrocytes A major type of glial cell that provides much of the brain’s structural support and firmness Astrocyte Maintains an adequate microenvironment for neurons Forms the blood-brain barrier Oligodendrocytes have processes that grow around axons, insulating them with myelin Blood vessel Astrocytes interact with blood vessels to form a tight seal, creating the bloodbrain barrier 41 Oligodendrocytes and Schwann Cells Both are glial cells that provide insulation to neurons by forming myelin sheaths: Oligodendrocytes: Insulating material in the CNS Schwann cells: Insulating material in the peripheral nervous system 42 Electrical activity in neurons The membrane potential: The fluids inside the neuron (intracellular fluid) and outside the neuron (extracellular fluid) are full of ions that have positive or negative charges. Channels and ion pumps in the nerve cell membrane determine which ions can move freely between the inside and outside of the cell. The balance of these ions determines the membrane potential across (between the inside and outside)...
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This document was uploaded on 02/16/2014.

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