View
218
Download
0
Embed Size (px)
Citation preview
Epilepsy & Membrane Potentials
Ca2+
Excessive Calcium influx leads to a depolarized depolarized Resting Membrane
EEG WAVEFORM
Neural Recording
Neurophysiology
Anatomy of the Neuron
Cell Body (organelles)
Axon
Terminals
Dendrites
Direction of Action Potential
Axon Hillock = Trigger Zone
Schwann cells and Nodes of Ranvier
Schwann cells make MYELINMYELIN
MYELINMYELIN is an electrical insulator
Action Potential “jump” down myelinated axons by SALTATORY CONDUCTION
Peripheral Nervous System: Support Cells
CNS Support Cells = Neuroglia
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
Electrical SYNAPSE
Action potential moves DIRECTLY between neurons
Gap Junction
EXAMPLES:
Smooth Muscle Cardiac Muscle
Gap junction between adjacent cardiac cells
Chemical SYNAPSE
Presynaptic Terminal
Postsynaptic membrane
Synaptic CLEFT
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
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
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
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
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
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
Neural SummationSpatial
Temporal
Spatial & Temporal
Axon hillock
SUMS EPSP & IPSP
Functional Organization of Nervous System
Sensory Motor
Central Nervous SystemBrain & Spinal Cord
Peripheral Nervous SystemSpinal Nerves & all other nerves
Sensory Physiology
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
General senses
Perceive touch, pressure, pain, heat, cold, stretch, vibration, changes in position
Located on skin and in joints/muscles
Cutaneous Somatic Receptors
Muscle spindle: stretch receptorMuscle spindle: stretch receptor
Golgi Tendon Organ: Tendon stretch receptor
Collagen Fibers within Tendon
Sensory Neurons
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
VibrationVibration
Sustained PressureSustained PressurePainPain
Functional classifications of sensory receptors
General sensory neural pathways
Dorsal Column
Proprioreception,Vibration,Pressure
Primary Neuron
Secondary Neuron
Tertiary Neuronthalamus
Anterolateral System
Touch,Itch,Pain,
Temperature
Primary Neuron
Secondary Neuron
Tertiary Neuron
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
Sensory Perception in Brain
Somatosensory Cortex (Postcentral Gyrus)
Area on cortex = sensitivity of body part =
# of sensory receptors on that part of body
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!
Eye: Basic Anatomy
Lens
Retina
Optic NervePupil
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
RhodopsinRhodopsin
DiskDisk
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
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
Rod: Night Vision
Cones: Color & Day Vision
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
Neural Pathway in Brain
Optic Nerve
Optic Chiasm
Optic Cortex
Neural Processing in Brain
V1
V2
V3
V4
Layers of signal processing
V1 sends projections Dorsal & Ventral
Dorsal Stream: “Where” & “How” Pathway
Ventral Stream: “What” Pathway
Color Vision: 3 cone types
Retina
Distribution of Rod vs. Cones
# of photoreceptors
Position on Retina
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
Neural Networks
VisionBrain Commands to Muscle (Motor Output)
Circadian Rhythms:Why you get tired when its dark!
Suprachiasmatic Nucleus (SCN) Melanopsin
Rhodopsin