Burger_082907 - Biosciences in the 21st century Lecture 1...

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Unformatted text preview: Biosciences in the 21st century Lecture 1: Neurons, Synapses, and Signaling Dr. Michael Burger Outline: 1. Why neuroscience? 2. The neuron 3. Action potentials 4. Synapses 5. Organization of the nervous system 6. Clinical approaches of today and tomorrow http://www.ritsumei.ac.jp/~akitaoka/index-e.html What did he say? What did he say? http://www.media.uio.no/personer/arntm/english.html Now close your eyes! Figure-ground illusions are well known for visual stimuli But they occur in the auditory system too! Alzheimer's Disease more than 5 million people in the United States living with Alzheimer's. The direct and indirect costs of Alzheimer's and other dementias amount to more than $148 billion annually. Parkinson's disease: 3% of population over 65: 1.5 million patients Hearing Impairment: Approximately 28 million Americans have a hearing impairment Approximately 314 in 1,000 people over age 65 have hearing loss and 40 to 50 percent of people 75 and older have a hearing loss. Paralysis: 2.4 million Americans are paralyzed Depression: over 20 million Americans suffer from depression The neuron is the "unit of processing" for the nervous system synapse (glia) The cell membrane is a phospholipid bilayer nucleus plasma membrane The cell membrane is a phospholipid bilayer nucleus plasma membrane Cell membranes store Voltage Positive Outside: Extracellular + + + + + Inside: Cytoplasmic _ _ _ Negative _ _ Vmembrane= -60 mV This "resting" voltage depends on ion distribution, and ions in general cannot cross the membrane Na+ Extracellular K+ Cl+ + + + Ca++ + Cytoplasmic _ Na+ _ _ _ _ K+ - (organic anions; An ie proteins) The cell membrane contains proteins, some of which are channels for charged particles Two (of many) membrane protein types: Ligand gated (chemically gated) Voltage gated How does an electrical signal occur in a neuron? Na+ Extracellular + + + + + + Na+ channel + + + Cytoplasmic _ _ _ _ _ K+ channel K+ + + + + Na+ Extracellular + + + + + + + + + Cytoplasmic _ _ _ _ _ K+ Na+ Extracellular + + + + + + + Cytoplasmic _ _ + _ + _ _ K+ Na+ Extracellular + + + + + + Cytoplasmic _ K+ _ + _ + + _ _ Voltage Na+ Extracellular + + + + + + + Voltage gated K+ channel Cytoplasmic _+ _ + _+ _ K+ + + + _ Voltage Na+ + Extracellular + + + + Cytoplasmic _ _ _ _ + _ K+ Voltage Voltage To the board! Action Potential Summary: 2 direction of travel 1 3 Membrane Voltage 1. Na+ channels open/Na flows into the cell 2. Na+ channels close while K+ channels are opening 3. K+ flow out of the cell dominates Synaptic Transmission 1 2 Ca++ axon terminal postsynaptic receptor axon vesicle+ transmitter dendrite Step 1: Depolarization of the axon terminal Step 2:Voltage dependent Ca++ entry Synaptic Transmission Ca++ 4 3 Step 3: Ca++ dependent vesicle fusion Step 4: transmitter release Synaptic Transmission Ca++ Na+ 5 ++ + 6 Step 5: Activation of ligand gated channel Step 6: Na+ flux/dendrite depolarization Synaptic Transmission Ca++ Na+ 7 ++ + 6 5 Step 5: Activation of ligand gated channel Step 6: Na+ flux/dendrite depolarization Step 7: Action Potential is regenerated postsynaptically Very large auditory synapse Stain in red marks postsynaptic receptor markers Evaluating Neural responses + neuron Evaluating Neural responses + neuron Evaluating Neural responses + neuron How do neurons encode information? Neurons signal in repeatable/predictable ways... no sound evoked 100 ms tone with action potential timing.... ...and Neurons signal by changing their firing rate Intensity (dB SPL) 10 20 30 40 50 60 70 100 ms tone 100 ms tone What we learned today: Neurons and glia: characteristics and function Ionic basis of electrical signaling Basics of chemical synaptic signaling How neural activity is recorded How neural activity relates to information processing Next time.... Brain organization New technology for therapy ...
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