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