Epilepsy & Membrane Potentials Ca 2+ depolarized Excessive Calcium influx leads to a depolarized...
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Epilepsy & Membrane Potentials
Ca2+
Excessive Calcium influx leads to a depolarized depolarized Resting Membrane
EEG WAVEFORM
Neural Recording
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Neurophysiology
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Anatomy of the Neuron
Cell Body (organelles)
Axon
Terminals
Dendrites
Direction of Action Potential
Axon Hillock = Trigger Zone
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Schwann cells and Nodes of Ranvier
Schwann cells make MYELINMYELIN
MYELINMYELIN 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
Direction of Action Potential
How does the action potential move from the terminal of neuron 1 to the dendrites of neuron 2?
SYNAPSE2 main types:
electrical and chemical
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Electrical SYNAPSE
Action potential moves DIRECTLY between neurons
Gap Junction
EXAMPLES:
Smooth Muscle Cardiac Muscle
Gap junction between adjacent cardiac cells
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Chemical SYNAPSE
Presynaptic Terminal
Postsynaptic membrane
Synaptic CLEFT
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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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1) EPSP: Excitatory post-synaptic potential
Chemical SYNAPSE: Signal types on post-synaptic membrane
Mechanism Ligand-gated Na+ channels OPEN
ImportanceIncreases likelihood of AP in
postsynaptic cell
If ENOUGH neurotransmitters are
released….AP
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Local Anesthetics: Novacain, Lidocaine, etc.
Sensory Neuron
Painful stimulusAction potential
Lidocaine
Blocks LIGAND-gated NA+ channels
NO EPSP……no Action potential on post-synaptic cell……no perception of PAIN
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2) IPSP: Inhibitory post-synaptic potential
Chemical SYNAPSE: Signal types on post-synaptic membrane
Mechanism Ligand-gated K+ or CL- channels OPEN on post-synaptic membrane
ImportanceDecreases likelihood of AP in
postsynaptic cell
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Presynaptic INHIBITION and FACILITATION: Neuromodulators
INHIBITION of neurotransmitter release at POST-SYNAPTIC membrane
Can modulate the ability of a neuron to release neurotransmitter
Neuron
Collateral Neuron
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Clinically important neurotransmitters & neuromodulators
Cocaine
Heroin
Marijuana
Anti-depressants: Prozac
Crystal Meth
Alcohol
Strychnine
CaffeineNicotine
LSD
Morphine
Viagara
We will cover how some of these drugs work
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Neural SummationSpatial
Temporal
Spatial & Temporal
Axon hillock
SUMS EPSP & IPSP
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Functional Organization of Nervous System
Sensory Motor
Central Nervous SystemBrain & Spinal Cord
Peripheral Nervous SystemSpinal Nerves & all other nerves
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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)
LightLightPhototransductionPhototransduction Action Potential Action Potential
in Optic Nervein Optic Nerve
EyeEye
1122 33
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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 receptorMuscle spindle: stretch receptor
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Golgi Tendon Organ: Tendon stretch receptor
Collagen Fibers within Tendon
Sensory Neurons
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Physiology of Cutaneous Receptors
1. Stimulus (Vibration, Pressure, Temperature, Stretch, etc)
2. 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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VibrationVibration
Sustained PressureSustained PressurePainPain
Functional classifications of sensory receptors
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General sensory neural pathways
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Dorsal Column
Proprioreception,Vibration,Pressure
Primary Neuron
Secondary Neuron
Tertiary Neuronthalamus
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Anterolateral System
Touch,Itch,Pain,
Temperature
Primary Neuron
Secondary Neuron
Tertiary Neuron
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Blocking Pain Perception
Dorsal ColumnAnterolateral system
1) Collateral Branch
Pain
Presynaptic inhibition of 2nd Neuron in Anterolateral System
1) Triggered by Massage, Exercise:
2) Triggered by BRAIN (endorphins)
Heroin & Morphine can trigger
Pressure, Vibration
Via Blood
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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)
1) Vision
2) Hearing and equilibrium
3) Olfaction
4) Taste
We will ONLY cover Vision as an example of a Special Sense!
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Eye: Basic Anatomy
Lens
Retina
Optic NervePupil
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RetinaRetina
Ro
d &
Co
nes
Ro
d &
Co
nes
Bip
ola
r C
ells
Bip
ola
r C
ells
Gan
gli
on
Cel
lsG
ang
lio
n C
ells
Lens
Pupil
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RhodopsinRhodopsin
DiskDisk
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DARK
Rhodopsin Transducin (G-protien)
cGMP-gated Na+/Ca2+ Channel
K+ channel
Glutamate
Bipolar Cells
-Rhodopsin: inactive-Transducin: inactive-Intracellular cGMP levels HIGH-Ion channels are OPEN-Membrane potential = -40 mV
-Glutamate release high ontoBipolar cells!
cGMP
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LIGHT
RetinalActivated Transducin (G-protien)
decreases Intracellular cGMP
cGMP-gated Na+/Ca2+ Channels CLOSE
K+ channel
Glutamate decreases
RhodopsinBLEACHES
Opsin
cGMP
Ph
oto
rece
pto
rM
emb
ran
e p
ote
nti
al (
mV
)
Time
-40
-70
Bipolar Cell
1
2
3
4
5
6
HYPERPOLARIZATIONHYPERPOLARIZATION
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Rod: Night Vision
Cones: Color & Day Vision
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Neural pathway to optic nerve & brain
Ro
d &
Co
nes
Ro
d &
Co
nes
Bip
ola
r C
ells
Bip
ola
r C
ells
Gan
gli
on
Cel
lsG
ang
lio
n C
ells
Neural LayerNeural Layer of Retinaof Retina
Optic NerveOptic Nerve
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Neural Pathway in Brain
Optic Nerve
Optic Chiasm
Optic Cortex
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Neural Processing in Brain
V1
V2
V3
V4
Layers of signal processing
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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!
125 million photoreceptors!
1 million ganglion cells!
Position on Retina
Am
ount
of
conv
erge
nce
1:1
200:1
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Neural Networks
VisionBrain Commands to Muscle (Motor Output)
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Circadian Rhythms:Why you get tired when its dark!
Suprachiasmatic Nucleus (SCN) Melanopsin
Rhodopsin