Epilepsy & Membrane Potentials

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

2. Neurophysiology

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

4. Schwann cells and Nodes of Ranvier Schwann cells make MYELIN MYELIN is an electrical insulator Action Potential “jump” down myelinated axons by SALTATORY CONDUCTION

5. Peripheral Nervous System: Support Cells

6. CNS Support Cells = Neuroglia

7. 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

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

9. Chemical SYNAPSE Presynaptic Terminal Synaptic CLEFT Postsynaptic membrane

10. 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

11. 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

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

13. 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

14. 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

15. 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

16. Neural Summation Spatial Axon hillock SUMS EPSP & IPSP Temporal Spatial & Temporal

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

18. Sensory Physiology

19. 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

20. General senses Perceive touch, pressure, pain, heat, cold, stretch, vibration, changes in position Located on skinand injoints/muscles

21. Cutaneous Somatic Receptors

22. Muscle spindle: stretch receptor

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

24. 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

25. Functional classifications of sensory receptors Sustained Pressure Pain Vibration

26. General sensory neural pathways

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

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

29. 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

30. Sensory Perception in Brain Somatosensory Cortex (Postcentral Gyrus) Area on cortex = sensitivity of body part = # of sensory receptors on that part of body

31. 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!

32. Eye: Basic Anatomy Lens Pupil Optic Nerve Retina

33. Retina Pupil Lens Ganglion Cells Rod & Cones Bipolar Cells

34. Disk Rhodopsin

35. 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

36. 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 Photoreceptor Membrane potential (mV) 5 Glutamate decreases -70 4 HYPERPOLARIZATION Time Bipolar Cell 6

37. Cones: Color & Day Vision Rod: Night Vision

38. Neural pathway to optic nerve & brain Optic Nerve Neural Layer of Retina Ganglion Cells Rod & Cones Bipolar Cells

39. Neural Pathway in Brain Optic Chiasm Optic Cortex Optic Nerve

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

41. V1 sends projections Dorsal & Ventral Dorsal Stream: “Where” & “How” Pathway Ventral Stream: “What” Pathway

42. Color Vision: 3 cone types Retina

43. Distribution of Rod vs. Cones # of photoreceptors Position on Retina

44. Processing Visual Stimuli Retinal Processing: Convergent Neural Network! 1 million ganglion cells! 200:1 Amount of convergence 1:1 125 million photoreceptors! Position on Retina

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

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