AP Psych p Neurons

Questions and Fun Facts Repeat the definition of psychology. The science of behavior and mental processes. What mental process is done without the brain or the nervous system? Our brain contains 100 billion neurons and 10,000 times as many connections. In a human, there are more than 125 trillion synapses just in the cerebral cortex alone. There are are more connections in the brain than there are stars in the Milky Way.

Neurons Neurons = Nerve Cells. Sensory Neurons carry messages from the bodies sensory organs and tissues inward to the brain and spinal cord. Inbound Motor Neurons carry outgoing messages from the brain and spinal cord to the muscles and glands. Outbound Interneuron's are neurons that process information in the brain.

Parts of the Neuron: Dendrite Dendrite Branching extensions of a neuron that receive messages. (Then sends it to the cell body, which is the cell’s life support center) Dendrite Cell Body or Soma

Parts of the Neuron: Axon Axon The extension of the Neuron that passes messages to other neurons, muscles, or glands. May be short or long and if axons are longer it takes more time for the brain to send a signal (Circle example) Axon Dendrite Cell Body or Soma

Parts of the Neuron: Myelin Sheath Myelin Sheath A layer of fatty tissue that may encase some axons of neurons (not all) Helps to speed up neural transmissions (up to 200 miles an hour) If I am driving across Nebraska do I want to go fast? If I am driving across Road Island do I want to go fast? Myelin continues to develop up to about age 25. (correlations with judgements and self control) Axon Dendrite Cell Body or Soma Myelin Sheath

Parts of the Neuron: Terminal Branches Terminal Branches Branch like connections at the end of the axon that forms connections with other cells. Passes the message to other neurons or cells. Axon Dendrite Cell Body/ Soma Myelin Sheath Terminal Branches

Resting Potential Resting Potential is the axon's electrical state during the period between action potentials. The fluid inside the axon membrane is electrically negative compared to the fluid outside the axon. Like a phone its charged and ready to go Here the axon is selectively permeable because it is not letting the positive ions into the axon.

Action Potential A brief electrical charge that travels down an axon. Triggered by a chemical reaction. Positive ions are rushing into the negatively charged axon and moving down the axon toward the terminal branches. We call this depolarization.

Refractory Period (Recovery Time) The time after the action potential (depolarization) when the axon is sending the positively charged ions back outside of the axon. A axon can not fire again until the refractory period is over and the axon is back at the resting potential.

Neuron Signals and Absolute Threshold Neurons can receive two types of signals. Excitatory Signals tell the neuron to go Inhibitory Signals tell the neuron to stop If the excitatory signals minus the inhibitory signals exceeds a minimum intensity or THRESHOLD, then the combined signals trigger an action potential. Threshold = the level of stimulation required to trigger a neural impulse. ALL OR NOTHING RESPONSE It either fires or it does not fire…like a gun.

How do Neurons Communicate? Synapse The meeting point between the terminal branches of one neuron and the dendrite or cell body of another neuron. They do not touch each other there is a tiny gap called the synaptic gap.

Neurotransmitters! When the action potential reaches synapse it triggers the release of chemicals called neurotransmitters. These neurotransmitters then cross the synaptic gap binds to the dendrite of the new neuron at receptor cites. If there are any neurotransmitters left in the synaptic gap the neuron that sent them will reabsorbed them back into the neuron. Lets look at the diagram on the next page an watch a short video clip.

Drugs and Neurotransmitters Drugs and other chemicals can boost or block neurotransmitters. We call the boosting drugs or chemicals agonist We call the blocking drugs or chemicals antagonist

Neurotransmitters and what they do to us! Endorphins Pain control and pleasure Runners High Morphine - Agonist

Neurotransmitters and what they do to us! Acetylcholine (Ach) Enabled muscle action (makes our muscles contract) and has something to do with learning and memory. Ach the the neurotransmitter found at every synapse between a motor neuron and a muscle. Curare (drug) - on the tip of a blow dart causes paralysis An Antagonist because it blocks the Ach Black Widow spider venom – produces convulsions An agonist because it boots ach

Neurotransmitters and what they do to us! Dopamine Does a lot – pleasure and addiction or mood…cravings When present in very high levels it is associated with schizophrenia Low amounts of dopamine in other areas of the brain is associated with Parkinson’s

Meth and Dopamine meth/body/faces.html

Neurotransmitters and what they do to us! Serotonin Mood, hunger, sleep, and arousal Depression is correlated with low serotonin Prozac –Agonist (boost serotonin) SSRI (Selective serotonin reuptake inhibitor) - a shield that blocks the reuptake of serotonin takes 6–8 weeks for the drug to begin reaching its full potential

Neurotransmitters and what they do to us! GABA Always Inhibitory – primary NT for keeping your brain under control, usually associated with anxiety Undersupply linked to seizures. Alcohol – agonist

Neurotransmitters and what they do to us! Glutamate Excitatory NT Can cause overstimulation of the brain, producing migraines or seizures. Alcohol – antagonist

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