Epilepsy & Membrane Potentials EEG WAVEFORM Ca2+ Neural Recording Excessive Calcium influx leads to a depolarized Resting Membrane

Neurophysiology

Anatomy of the Neuron Dendrites Cell Body Axon Hillock (organelles) = Trigger Zone Direction of Action Potential Axon Terminals

Schwann cells and Nodes of Ranvier Schwann cells make MYELIN MYELIN 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 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

Electrical SYNAPSE Gap Junction Action potential moves DIRECTLY between neurons EXAMPLES: Smooth Muscle Cardiac Muscle Gap junction between adjacent cardiac cells

Chemical SYNAPSE Presynaptic Terminal Synaptic CLEFT Postsynaptic membrane

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

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

Local Anesthetics: Novacain, Lidocaine, etc. Painful stimulus Action potential Sensory Neuron Blocks LIGAND-gated NA+ channels NO EPSP……no Action potential on post-synaptic cell……no perception of PAIN

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

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

Clinically important neurotransmitters & neuromodulators Cocaine Alcohol Nicotine Caffeine Heroin Viagara Marijuana Morphine Crystal Meth LSD Anti-depressants: Prozac Strychnine We will cover how some of these drugs work

Neural Summation Spatial Axon hillock SUMS EPSP & IPSP Temporal

Functional Organization of Nervous System Central Nervous System Brain & Spinal Cord Peripheral Nervous System Spinal Nerves & all other nerves Motor Sensory

Sensory Physiology

Sensory Physiology Eye Light 1 3 2 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

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 receptor

Golgi Tendon Organ: Tendon stretch receptor Sensory Neurons Collagen Fibers within Tendon

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

Functional classifications of sensory receptors Sustained Pressure Pain Vibration

General sensory neural pathways

Dorsal Column thalamus Tertiary Neuron Proprioreception, Vibration, Pressure Secondary Neuron Primary Neuron

Anterolateral System Tertiary Neuron Touch, Itch, Pain, Temperature Secondary Neuron Primary Neuron

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

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)‏ Vision Hearing and equilibrium Olfaction Taste We will ONLY cover Vision as an example of a Special Sense!

Eye: Basic Anatomy Lens Pupil Optic Nerve Retina

Retina Pupil Lens Ganglion Cells Bipolar Cells Rod & Cones

Disk Rhodopsin

DARK cGMP Rhodopsin Transducin (G-protien) cGMP-gated Na+/Ca2+ Channel 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

LIGHT cGMP 2 Rhodopsin 1 BLEACHES 3 5 4 Time Bipolar Cell 6 Retinal Activated Transducin (G-protien) decreases Intracellular cGMP 2 Opsin Rhodopsin BLEACHES cGMP-gated Na+/Ca2+ Channels CLOSE 1 cGMP 3 K+ channel -40 LIGHT Membrane potential (mV) Photoreceptor 5 Glutamate decreases -70 4 HYPERPOLARIZATION Time Bipolar Cell 6

Cones: Color & Day Vision Rod: Night Vision

Neural pathway to optic nerve & brain Neural Layer of Retina Ganglion Cells Bipolar Cells Rod & Cones

Neural Pathway in Brain Optic Chiasm Optic Cortex Optic Nerve

Neural Processing in Brain V4 V3 Layers of signal processing V2 V1

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! 1 million ganglion cells! 200:1 Amount of convergence 125 million photoreceptors! 1:1 Position on Retina

Brain Commands to Muscle Neural Networks Brain Commands to Muscle (Motor Output) Vision

Circadian Rhythms: Why you get tired when its dark! Suprachiasmatic Nucleus (SCN) Melanopsin Rhodopsin