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PSYB65 Ch 2

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Ted Petit

PSYB65 Ch 2 NeuroanatomyNeurons specialized cells in the nervous system responsible for commn and thus bhvr Glia specialized cells in the nervous system responsible for support and maintenance of neurons The neurons shape is closely related to its function to receive conduct and transmit signals The neuron consists of three main components 1 Dendrites the component of the neuron that received info for other neurons2 Soma the body of the neuron that contains the machinery for metabolic function 3 Axon the component of the neuron that transmits the action potential sending of info and releases neurotransmitters Action potential the primary means of commn within the neurons Action potentials are always the same size they are propagated and they are all or none they result in the release of neurotransmitters Info is passed f axon to the dendrite across a synapse gaps btwn neurons Events that occur in the axon referred to as presynaptic and events that happen in the dendrite referred to as postsynaptic Dendrites increase the surface area branching and retraction of tiny spines available for the reception of signals f the axons of other neurons After the dendrites receives the inputs this info is sent to the rest of the neuron in the form of an electrical changeaction potential The axon is the information sender it can divideits far end into many branches to increase the number of synapses it can form axons are covered w insulation called myelinMyelin insulation covering most axons in the CNS made by oligodendrocytes glia that makes myelinhelps speed the rate of info transfer and ensures the msg gets to the end of the axon Terminal buttons the end of the axon where neurotransmitters are released info is sent f the terminal button across the synapse to the dendriteInfo that passes f the axon across the synapse is in the form of a neurochemical msg by neurotransmitters chemicals that are released by the neuron in the axon that are used to commn btwn neurons over the synapse which may be transformed into an electrical msg within the dendriteAnatomy of the NeuronPlasma membrane covering of the neuron made of a lipid bilayer of sheets of phospholipids that separate two fluid envtone inside the cell cytoplasm and the other outside the cell Within this membrane are proteins and channels that allow the passage of materials into and out of the neuron Inside the cell main body are where the small components of the cell called organelles are found which perform the various processes that keep the neuron functioningNucleus contains and processes the info contained in the DNA Ribosomes responsible for manufacturing the proteins that are coded for in the DNAEndoplasmic reticulum responsible for making modifying and sending proteins for packaging Mitochondria responsible for providing the neuron w energy Structurally some common neurons are labeled as Unipolar having only one process leaving the cell body bipolar having two processes leaving the cell body and multipolar having numerous processes leaving the cell body Neurons w no axons or only very short axons are called interneurons and they tend to integrate info within a structure rather than sending info btwn structures Functionally neurons can be classified by the type of signals that they processEg the signals that motor neurons convey may represent muscle contraction Neurons can be classified as afferent moving info toward the nervous system or cell body or efferent sending info away f the nervous system or cell body Satellite cells cells in the PNS outside the brain and spinal cord that have functions similar to those of the glia Glia performs support functions and has three types1 Astrocytes the largest glia and are starshaped Involved in the bloodbrain barrier a protective system that keeps the brain separate f the rest of the bodyPerforms nutritive and metabolic functionsRegulates the chemical content of the extracelluar spaceStores neurotransmitters2 Oligodendrocytes one clear function to make myelin it wraps their processes around most axons in the brain and spinal cordthese processes are made of myelin which is fatty substance that acts to insulate axon Myelin are provided by Schwann cells cells in the PNS that make myelinA different is that Schwann cells provide only one segment to myelin to an axon whereas oligodendrocytes can contribute many segments to many axons 3 Microglia smallest of the glia are phagocytes that remove debris f the nervous system Different f other cells as they are made outside of the brain and spinal cord by macrophages Excessive activation of microglia has been implicated in neurodegenerative diseases such as multiple sclerosis and Alzheimers diseaseThe electrical events transmission of info by action potentials that underlie the transmission or inhibition of info rely on the balance of ions btwn the inside of the neuron intracellular and the outside of the neuron extracelluar When the neuron isrest it maintains an electrical charge of 70 millivolts mVthis initial state of the neuron is called the resting potential The resting potential of the neuron depends on the difference btwn the concentrations of ions across the neuron membrane rest the extracelluar fluid contains high concentration of Na sodium ions positive state and the intracellular fluid contains high concentrations of K potassium ions negative stateThe neuron has two properties that promote the uneven distribution of ionsthe first property relates to the permeability penetration of the cell membrane
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