THE HISTORY OF NEUROSCIENCE
BIOLOGICAL ASPECTS OF BEHAVIOR: THE NEURON & NEURAL COMMUNICATION
NERVOUS SYSTEM Combined activity of the brain, spinal cord & other nerve fibers Acts as an information processing system Input (Sensory) Processing (In the brain) Output (Reaction)
NEURONS: 1. Cells that send & receive messages 2. Building Blocks of the Nervous System
PARTS OF THE NEURON Dendrites Terminal Branches Terminal Knob (Bulb) Nucleus Cell Body (Soma) Nodes of Ranvier Schwann Cells Axon Hillock Axon Myelin Sheath
PARTS OF THE NEURON Dendrites Receive Messages Extension of the cell body Several short branches Tapers in thickness Axon Sends Messages Added at the hillock A few long branches Constant thickness
Terminal knob (bulb) Close-up of axon terminal
Edible Neuron Model Fruit Roll Up: Shape to form the cell body (soma) Jelly Bean/Skittle: Nucleus Pull n Peel Twizzlers: Separate to form the dendrites, axon, and terminal branches. Red Vine Twizzlers: Separate into individual segments. Tear each segment down the middle and wrap each segment around the axon (pull & peel) to create the myelin sheath. Nerds: Use to represent the neurotransmitters at the end of the terminal branches (I will give these to your & your partner)
Review: PARTS OF THE NEURON Dendrites Terminal Branches Terminal Knob (Bulb) Nucleus Cell Body (Soma) Nodes of Ranvier Schwann Cells Axon Hillock Axon Myelin Sheath
Action Potential
ACTION POTENTIAL What is it? Communication between neurons (nerve impulse) Characteristics Neuron has a semi-permeable barrier. Molecules move in & out of the cell. Occurs in about 7 milliseconds
THE PROCESS OF AN ACTION POTENTIAL Polarization Outside of the membrane is positive while the electrical charge on the inside of the membrane is negative All-Or-None (Nothing) Principle Once the threshold is reached, the neuron will fire at full strength. If the threshold is not reached, the neuron will not fire. Refractory Period The period after a neuron fires, at which time it is less susceptible to stimulation from other neurons. The neuron must recharge itself electrically to reach polarization Resting Potential Negatively charged ions wait for stimulation w/in the axon. Point of inactivity Threshold A point of excitation on the neuron that must be reached for an action potential to occur It s like a toilet! Depolarization When stimulated channels along the axon allow NA+ & K+ ions to enter. This causes NA+ & K+ channels to open thus propelling the electrochemical process down the axon. Action Potential A change in the balance of the overall charge of the neuron causes the electrochemical signal to travel (it is fired) along the axon
THE PROCESS OF AN ACTION POTENTIAL
Action Potential
PRESYNAPTIC CELL POSTSYNAPTIC CELL
Excitatory & Inhibitory Signals Excitatory signals make the cell more likely to fire. Inhibitory signals make the neuron less likely to fire. It will depend on which messages predominate the neuron.
EXCITATORY & INHIBITORY SIGNALS When a neurotransmitter reaches the postsynaptic cell, the postsynaptic membrane becomes depolarized or hyperpolarized Depolarization Hyperpolarization Excitatory Postsynaptic Potential (EPSP) Inhibitory Postsynaptic Potential (IPSP)
GLIAL CELLS
GLIAL CELLS Direct neuron growth Keep chemical environment stable Provide energy Restore damage