PSY493H1 Lecture 1: Lecture 1 Intro Neurophysiology
Glia:
Oligodendroglia, microglia, ependyma, astrocytes
Central nervous system: astrocyte (blood vessel), oligodendrocyte (myelin) and
microglial
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Peripheral nervous system: Schwann cell (myelin)
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Astrocytes:
Supply nutrients to neurons and regulate firing
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Comprise the Blood-brain barrier
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Protects CNS from disease and toxins
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Role in healing from stroke and spinal cord injuries
Responsible for scar tissue from lesions
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Oligodendrocytes (CNS) and Schwann (PNS)
Fatty insulation forms white matter
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Microglia
Important for the brain's immune system
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Monitors cellular states around the brain to make sure there are no infected cells
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Cleans up any dead cells
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Homeostatic regulation and brain health
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Neurons:
Sensory, interneuron, motor
All have axon, cell body and dendritic tree
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Parts of neuron
Cell body
1.
Dendrites
2.
Axon hillock
3.
Myelin sheath
4.
Synaptic terminal
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Cell body
Contains vital items for functioning
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Nucleus, mitochondria, enzymes, proteins & DNA
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Cell bodies comprise the grey matter in the brain
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Dendrites
Receives signals (postsynaptic input) from all over the brain
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Different shapes for different areas and innervations
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Lecture 1
Wednesday, May 16, 2018
6:01 PM
Axon
Carries the electrical signal
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Wrapped in fatty insulation called myelin (white matter)
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Myelin sheath - glial cells
Oligodendrocytes - CNS
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Schwann cells - PNS
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Myelin insulates the electrical signal and prevents decay along with the Nodes of Ranvier
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Axon terminal
Electrical signal ends at axon terminals
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Presynaptic
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Terminal buttons
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Release neurotransmitters
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Action potentials!
Electrochemically generate from voltage difference in the cell membrane
Membrane potential = differences in charge across a membrane
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How?
Neurons are either on or off (resting or active)
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At rest: resting membrane potential (-70mV)
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The inside is relatively more negative than the outside
ACTIVE TRANSPORT
Moves Na+ out against concentration gradient
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Result in more K+ inside and more Na+ outside
ATP -> ADP
3 Na+ out, 2 K+ in
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Inside is negative relative to outside
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Definition: A rapid shift in the membrane potential of a neuron that occurs once a
neuron has been stimulated past a certain threshold!
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AP will occur IF the stimulation is strong enough
Dendrites are stimulated
AP starts at axon hillock
Resting:
-70 mV Neuron inactive
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With increased electrical summation -> reaches threshold -55mV -> Action potential
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Depolarization:
Once -55mV is reached -> neuron fires
Na+ rushes in, K+ leaves cell
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Stops at 40mV
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Hyperpolarization:
Overshoots to about -75mV
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Na+ rushes in until inside gets less negative
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Stops when back to -70mV (resting potential)
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During the refractory period, another action potential cannot be generated
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Ion channels in the axon are voltage-gated
Depolarization at one axon segment triggers the opening of ion channels in the next
segment. AP spreads as a "wave" of depolarization
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Document Summary
Central nervous system: astrocyte (blood vessel), oligodendrocyte (myelin) and microglial. Role in healing from stroke and spinal cord injuries. Monitors cellular states around the brain to make sure there are no infected cells. All have axon, cell body and dendritic tree. Cell bodies comprise the grey matter in the brain. Receives signals (postsynaptic input) from all over the brain. Wrapped in fatty insulation called myelin (white matter) Myelin insulates the electrical signal and prevents decay along with the nodes of ranvier. Electrochemically generate from voltage difference in the cell membrane. Membrane potential = differences in charge across a membrane. Neurons are either on or off (resting or active) The inside is relatively more negative than the outside. Result in more k+ inside and more na+ outside. Definition: a rapid shift in the membrane potential of a neuron that occurs once a neuron has been stimulated past a certain threshold! Ap will occur if the stimulation is strong enough.
