Epilepsy & Membrane Potentials

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Epilepsy Membrane Potentials
EEG WAVEFORM
Ca2
Neural Recording
Excessive Calcium influx leads to a depolarized
Resting Membrane
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Neurophysiology
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Anatomy of the Neuron
Dendrites
Cell Body (organelles)
Axon Hillock Trigger Zone
Direction of Action Potential
Axon
Terminals
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Schwann cells and Nodes of Ranvier
Schwann cells make MYELIN MYELIN is an
electrical insulator
Action Potential jump down myelinated axons by
SALTATORY CONDUCTION
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• Peripheral Nervous System Support Cells

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CNS Support Cells Neuroglia
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Action potential propagation along neurons
How does the action potential move from the
terminal of neuron 1 to the dendrites
of neuron 2?
Direction of Action Potential
2 main types electrical and chemical
SYNAPSE
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Electrical SYNAPSE
Gap Junction
Action potential moves DIRECTLY between neurons
EXAMPLES Smooth Muscle Cardiac Muscle
Gap junction between adjacent cardiac cells
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Chemical SYNAPSE
Presynaptic Terminal
Synaptic CLEFT
Postsynaptic membrane
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Chemical SYNAPSE Function
1) Action potential down axon to terminal
2) Ca2 Channel open Ca2 influx
3) Vesicles of Neurotransmitters release into
synaptic cleft
- 4) Neurotransmitter diffuse into synaptic
cleft - Bind to LIGAND-gated ion channels on
post-synaptic membrane
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Chemical SYNAPSE Signal types on post-synaptic
membrane

• EPSP Excitatory post-synaptic potential

Mechanism Ligand-gated Na channels OPEN
Importance Increases likelihood of AP in
postsynaptic cell
If ENOUGH neurotransmitters are released.AP
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Local Anesthetics Novacain, Lidocaine, etc.
Lidocaine
Painful stimulus
Action potential
Sensory Neuron
Blocks LIGAND-gated NA channels
NO EPSPno Action potential on post-synaptic
cellno perception of PAIN
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Chemical SYNAPSE Signal types on post-synaptic
membrane

• 2) IPSP Inhibitory post-synaptic potential

Mechanism Ligand-gated K or CL- channels OPEN
on post-synaptic membrane
Importance Decreases likelihood of AP in
postsynaptic cell
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Presynaptic INHIBITION and FACILITATION
Neuromodulators
Can modulate the ability of a neuron to release
neurotransmitter
Neuron
Collateral Neuron
INHIBITION of neurotransmitter release at
POST-SYNAPTIC membrane
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Clinically important neurotransmitters
neuromodulators
Cocaine
Alcohol
Nicotine
Caffeine
Heroin
Viagara
Marijuana
Crystal Meth
Morphine
LSD
Anti-depressants Prozac
Strychnine
We will cover how some of these drugs work
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Neural Summation
Spatial
Axon hillock SUMS EPSP IPSP
Temporal
Spatial Temporal
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Functional Organization of Nervous System
Central Nervous System Brain Spinal Cord
Peripheral Nervous System Spinal Nerves all
other nerves
Motor
Sensory
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Sensory Physiology
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Sensory Physiology

• Perception of sensation involves
• 1) External physical signals
• 2) Converted by physiological process
• 3) To neural signals (graded action
  potentials)

Eye
Light
Phototransduction
Action Potential in Optic Nerve
1
3
2
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General senses

• Perceive touch, pressure, pain, heat, cold,
  stretch, vibration, changes in position
• Located on skin and in joints/muscles

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Cutaneous Somatic Receptors
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Muscle spindle stretch receptor
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Golgi Tendon Organ Tendon stretch receptor
Sensory Neurons
Collagen Fibers within Tendon
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Physiology of Cutaneous Receptors

• Stimulus (Vibration, Pressure, Temperature,
  Stretch, etc)?
• Mechanical and/or biomolecules cause
  opening/closing of ion channels (K, Ca2, Na)
  on receptor membrane
• Graded Receptor Potential
• 3. If receptor membrane depolarizes to threshold
  
• ACTION POTENTIAL

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Functional classifications of sensory receptors
Sustained Pressure Pain
Vibration
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General sensory neural pathways
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Dorsal Column
thalamus
Tertiary Neuron
Proprioreception, Vibration, Pressure
Secondary Neuron
Primary Neuron
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Anterolateral System
Tertiary Neuron
Touch, Itch, Pain, Temperature
Secondary Neuron
Primary Neuron
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Blocking Pain Perception
Pressure, Vibration
Pain
Dorsal Column
Anterolateral system
2) Triggered by BRAIN (endorphins) Heroin
Morphine can trigger
Via Blood
1) Collateral Branch

• Triggered by Massage, Exercise

Presynaptic inhibition of 2nd Neuron in
Anterolateral System
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Sensory Perception in Brain
Somatosensory Cortex (Postcentral Gyrus)
Area on cortex sensitivity of body part of
sensory receptors on that part of body
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Special senses (located in the head region)?

• Vision
• Hearing and equilibrium
• Olfaction
• Taste

We will ONLY cover Vision as an example of a
Special Sense!
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Eye Basic Anatomy
Lens
Optic Nerve
Pupil
Retina
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Retina
Pupil
Lens
Ganglion Cells
Rod Cones
Bipolar Cells
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Disk
Rhodopsin
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Rhodopsin
Transducin (G-protien)
cGMP-gated Na/Ca2 Channel
cGMP
K channel
Glutamate
DARK

• -Rhodopsin inactive
• -Transducin inactive
• Intracellular cGMP levels HIGH
• Ion channels are OPEN
• Membrane potential -40 mV
• Glutamate release high onto
• Bipolar cells!

Bipolar Cells
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Retinal
Activated Transducin (G-protien) decreases
Intracellular cGMP
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Opsin
Rhodopsin BLEACHES
cGMP-gated Na/Ca2 Channels CLOSE
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cGMP
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K channel
-40
LIGHT
Photoreceptor Membrane potential (mV)
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Glutamate decreases
-70
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HYPERPOLARIZATION
Time
Bipolar Cell
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Cones Color Day Vision
Rod Night Vision
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Neural pathway to optic nerve brain
Optic Nerve
Neural Layer of Retina
Ganglion Cells
Rod Cones
Bipolar Cells
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Neural Pathway in Brain
Optic Chiasm
Optic Cortex
Optic Nerve
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Neural Processing in Brain
V4
V3
Layers of signal processing
V2
V1
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V1 sends projections Dorsal Ventral
Dorsal Stream Where How Pathway
Ventral Stream What Pathway
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Color Vision 3 cone types
Retina
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Distribution of Rod vs. Cones
of photoreceptors
Position on Retina
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Processing Visual Stimuli
Retinal Processing Convergent Neural Network!
1 million ganglion cells!
2001
Amount of convergence
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125 million photoreceptors!
Position on Retina
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Neural Networks
Vision
Brain Commands to Muscle (Motor Output)
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Circadian RhythmsWhy you get tired when its
dark!
Suprachiasmatic Nucleus (SCN)
Melanopsin
Rhodopsin