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36 Cards in this Set
- Front
- Back
Behavior
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an output of the brain resulting from neural processing of external and internal information
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Neurons
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electrically active and responsive to chemical signals
Compute, communicate, transmit information |
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Information processing
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a product of electrical and chemical activity in the brain
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Parts of the neuron + how they function together
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Soma (5-50 micrometers)
Axon (axons can be few microns - centimeters in brain to spinal cord) Axon terminals (synaptic terminals = 1microm.) Input goes from soma, through axon, to axon terminals |
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3 key concepts about neurons
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1)Small
2) Terminate in thousands of branches 3) Vary in length |
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Approx how many neurons are there in the brain?
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More than 100 billion!
(1000 km laid side by side) |
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The adult human brain weighs...
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3 lbs
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3 different types of neurons
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Multipolar, bipolar (usually sensory, processing occurs in middle in soma), unipolar (also often sensory)
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Nissl stains of nucleus reveal
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dense packing of neurons (located in nucleus), white matter (contains axons), purple part/gray matter (contains cell bodies), holes in center = ventricles
dense packing in hippocampus |
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What is the function of glial cells? What are 2 main types?
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To support neurons, gather up/recycle NT . Astrocytes and oligodendrocytes
**Microglia clean up after neuron Astrocytes support neuron oligodendrocytes wrap axons with fatty sheath, myelin, to speed up conduction in CNS |
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Node of ranvier
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gap in the sheath that exposes bare axon
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Schwann cells
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also form myelin but only in PNS
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Multiple sclerosis
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a demyelinating disease - myelin lost = poor communication in neurons
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Axons
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transmit information from input to output w/ action potentials
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Dendrites/Soma
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Integrate information - gather information from other neurons, have a branched arborization pattern
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Axon hillock
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part connecting soma to axon, integrates electrical activity from the dendrites to trigger action potentials (if threshold met)
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Axon terminals
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Contain synapses that release neurotransmitters to transmit info to post-synaptic neuron, can both diverge and converge
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Key parts of the synapse
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1) Presynaptic membrane - on axon terminal of pre-synaptic neuron
2) Postsynaptic membrane - on dendrite/cell body of of postsynaptic neuron 3) Synaptic cleft - gap that separates the membranes |
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Electron microscopy can be used to look at...
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thin tissue samples (sliced like bread from large brain), high synaptic density, neurons
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Neurons transmit information how?
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Electrical and chemical activity across neuronal membrane
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The neuron membrane is..
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a impermeable lipid bilayer (hydrophobic tails, hydrophillic heads). Protein ion channels allow semipermiability
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Distribution of ions across membrane is tightly regulated. Ion balance depends on:
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Chemical concentration gradient
Electrical gradient State of protein ion channels (open/closed) |
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Describe neurons in resting state
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1) Extracellular [Na+] high
2) Intracellular [K+] high 3) Na+ permeability low 4) K+ permeability high **more positive outside, negative inside cell |
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Why doesn't all K+ ions leave to one side?
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because electrical/concentration gradients stay about balanced
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What are the two opposing forces that drive ion movement
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1) Diffusion - causes ions to flow from areas of high -> low concentration along a concentration gradient
2) Electrostatic pressure causes ions to flow towards oppositely charged areas Eventually a balance between the two is reached |
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Sodium potassium pump function
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Moves 3Na+ out, 2K+ in So that there are a lot of Na+ outside, a lot of K+ inside
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Function of K+/Na+ channels in resting state?
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K+ is open, K+ flows outward because of concentration gradient and inward due to voltage (electrostatic) gradient. K+ reaches equilibrium
Na+ (and large protein anions) does nothing since gates are closed Result = negative resting potential (more positive outside) of about -60V, as a consequence of K+ movement (which is why it's closer to Ek) |
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The voltage at equilibrium is called...
What is it a function of? What can it be calculated with? |
the Equilibrium potential of K+, which is a function of the concentration gradient, and can be calculated w/ Nernst equation
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Steps of action potential (lecture 3)
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SETUP (from resting state)
a) Sodium potassium pump moves 3Na+ out, 2K+ in b) There are lots of K+ inside and Na+ outside. More + charge outside cell. This is due to high permeability to K+ but NOT Na+ in resting state MAIN STEPS 1) Stimulus causes Na+ gate to open, Na+ floods into cell, potential increases, causing Na+ gate to close 2) K+ gate opens, K+ floods out of cell. Charge becomes too low, K+ gate closes 3) return to resting potential, action potential continues down axon |
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Need to study!
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1) Action potential voltage curve
2) What anatomy of neuron looks like (label) |
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Definitions from book to know
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All-or-none property (threshold)
Local potential Graded response Afterpotential Absolute/relative refractory Conduction velocity + size of axon Saltatory conduction Postsynaptic potential |
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Different neuron structures/shapes signify
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Different purposes. Large arborization = collecting info from a large area.
Locust/invertebrate neuron is large, no myelenation, small number of neurons, same neuron configuration for each locust in same spot. Used for experiments |
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Brain sizes
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Elephant/other animals
Do we need to know this??? |
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Brownian motion
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concentration goes from high to low
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How do you measure intracellular potentials?
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Insert electrodes (reference = outside, recording = inside) , use amplifier, read recording
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Current can be injected into neurons but they are...
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graded potentials (they dissipate) . If you can depolarize to threshold, an AP will occur. You can also hyperpolarize the neuron.
****AP LOOKS REVERSED! Due to...? |