Textbook Notes (367,974)
Canada (161,538)
Psychology (9,695)
PSYB64H3 (201)
Chapter 3

Chapter 3

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Janelle Leboutillier

Cells of the Nervous System Tetrodotoxincan cause death by blocking voltagedependent sodium channels in the membranes of nerve fibers OverviewNeurons and Glia Generation and Propagation of Action PotentialsSynapsesElectricalChemicalNeuromodulationNeurons and GliaThe Structure of neuronsNeuron membranes separate intracellular fluid from extracellular fluidThe neural cytoskeleton provides structural support that maintains the shape of the neuronall cells have membranes nuclei and small internal structures known as organelles many of these structures are found within the main mass of the neuron cellbodysoma Neurons differ structurally from other cells int hat they have specialized branches extending from the cell body known as axons and dendritesNeural Membraneprimary task is to form a boundary between the cell and its external environment in this case intracellular fluid from the extracellular fluidMembrane is a bilayer composed largely of phospholipids and other lipids studded with proteins and other large moleculesthis separates inner and extracellular fluid they do this inspite of being only two phospholipid molecules wide with a thickness of only 5 nanometers in the membrane are a number of protein structures that control its permeability 9movement of substances across the membrane these areIon Channels Allow ions to diffuse down concentration gradientSelective permeability to certain ionsDont require additional energy Ion PumpsActively move ions against concentration gradient Create ion concentration gradientsRequire Energy The amino acids or protein building blocks that make up the ion channel or pump determine which ions will be allowed to pass through the membraneIon channels have the ability to open and close in response to stimuli in their immediate vicinityvoltage dependent channelsopen and close in response to the electrical status of adjacent areas of membraneLigand gated Channels open when they come in contact with specific chemicalsThe Two most important pumps in neurons are Sodium Potassium Pumphhelp maintain the differences in chemical composition between the intracellular and extracellular fluid prisoner exchange send 3 sodium ions out and collect two potassium ions from the extracellular environment this is energy expensive and as much as 2040 percent of the energy required by the brain is used to run the sodium potassium pumps Calcium pumppump calcium outThree Fibre Types Compose the Cytoskeleton of Neurons Cytoskeleton ctructural support that maintains the shape of the neuron 3 types of filament which also move elements within the ceell and anchor the various channel and receptor proteins in their appropriate places on the neural membrane Microtubules largest of fibersresponsible for the movement of various materials within the cellmovement along the microtubules from the cell body to axon terminal is known as anterograde transportand movement back to the cell body from the periphery is known as retrograde transporthave been implicated in alzheimers tau levels become elevate and in response an affected neuron adds molecules of phosphate to the tau protein which causes it to disconnect from the microtubulesNeuroFilaments middle size most common about 10nm in diameter similar to that of a haira nd quite strong run parallel to the length of axon and provide structural support Microfilaments range from 35nm in diameter
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