1. Historically, how have neuroscientists determined the function of various brain regions? 2. Describe the impact of the Phineas Gage case on the field of neuroscience. 3. Explain neuron theory. THE HISTORY OF NEUROSCIENCE
BIOLOGICAL ASPECTS OF BEHAVIOR: THE NEURON
Everything psychological is simultaneously biological
NERVOUS SYSTEM Combined activity of the brain, spinal cord & other nerve fibers Acts as an information processing system Input Processing Output
GLIAL CELLS
GLIAL CELLS Direct neuron growth Keep chemical environment stable Provide energy Restore damage
NEURONS: Cells that send & receive messages.
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 DETECT messages Axon - Sends Messages - Long Branch - Constant thickness - Carry AWAY from cell body
PARTS OF THE NEURON Myelin Sheath Fatty Substance Wraps around axons Increases speed of action potential Terminal Button/Axon Terminal Releases messages into the synapse Synapse = the tiny gap b/w neurons where they communicate
Bellwork 9/9 B A C Identify the names and functions of each letter
Terminal knob (bulb) Close-up of axon terminal
ACTION POTENTIAL What is it? Transmission of a nerve impulse Communication between neurons 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 -55mv 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 Polarization Outside of the membrane is (+) while the electrical charge on the inside of the membrane is (-) Resting Potential (-) charged ions wait for stimulation w/in the axon. Point of inactivity
THE PROCESS OF AN ACTION POTENTIAL 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.
THE PROCESS OF AN ACTION POTENTIAL Threshold A point of excitation on the neuron that must be reached for an action potential to occur -55mv 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.
Crash Course Clip
THE PROCESS OF AN ACTION POTENTIAL 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 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
THE PROCESS OF AN ACTION POTENTIAL
Like a Toilet? depolarization - represented by the toilet flushing all-or-none principle - the toilet either flushes completely or not at all; it doesn't flush a little or a lot direction of impulse - the toilet only flushes one way, the impulse can't come the other direction (you hope!) refractory period - after you flush the toilet, it won't flush again for a certain period of time, even if you push the handle repeatedly threshold - you can push the handle a little bit, but it won't flush until you push the handle past a certain critical point - this corresponds to the level of excitatory neurotransmitters that a neuron must absorb before it will fire resting potential- if you are using a toilet with a tank, the water in the tank can represent Resting potential. The toilet is "waiting" to fire, and the water in the tank represents the overall negative charge nside the neuron waiting for depolarization
How is action potential like a row of dominoes? Action Potential affects one area of axon at a time refractory period= Laying dominoes- can not immediately fire again All or none principle Threshold
ROLE OF THE SYNAPSE
PRESYNAPTIC CELL POSTSYNAPTIC CELL
Normal
Depressed
Prozac
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. Its like a VOTE
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)