How does a Neuron fire? Resting potential The axon gets its energy from charged chemicals called ions. When the axon is waiting to be fired. Sodium on outside and Potassium on the inside. (SALTY BANANA) Action potential When the cell becomes excited, it triggers a NEURAL IMPULSE, which reverses the charge and causes the electrical signal to race along the axon.

Depolarization & Polarization describes an axon that is firing Positive ions enter the axon, and cause other positive ions to move into the axon in the form of a neural impulse down the axon. Polarization "Polarized" describes an axon that is not firing Outside Axon = + ions Inside Axon= - ions

Refractory Period Each action potential is followed by a brief recharging period known as the refractory period. After the refectory period, the neuron is capable of another action potential. Much like waiting for the flash to recharge on a disposable camera before you can take another picture.

All or Nothing Once the action potential is released, there is no going back. The axon either “fires” or it does not. This process is called the all-or-none principal. Squeezing a trigger harder wont make the bullet go faster.

Which theoretical perspective in psychology attempts to characterize the way in which humans store and process sensory information? Behavioral Psychodynamic Evolutionary Cognitive Sociocultural

Toilet Flushing

Neurons – How do they work? Neurons send messages to other neurons – this is what keeps every part of our body in communication with every other part. Neurons “fire” – send an impulse (message) down their length – or they don’t “fire”

So what, exactly, are neurons firing?

Neurotransmitters A chemical messenger that travels across the synapse from one neuron to the next Can influence whether the second neuron will generate an action potential or not (excite or inhibit) When released by the sending neuron, neuro-transmitters travel across the synapse and bind to receptor sites on the receiving neuron

NEUROTRANSMITTERS FIT LIKE A KEY IN A LOCK

2 CATEGORIES OF NEUROTRANSMITTERS: EXCITATORY and INHIBITORY The key fits and ‘opens’ the receiving neuron. Activation of the receptor causes depolarization of the membrane and promotes an action potential in the receiving neuron. Inhibitory The key fits in but only stops any other keys. Activation of the receptor causes hyperpolarization and depresses action potential generation.

Dopamine Deals with motor movement, alertness, and produces sensations of pleasure and rewards. 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

Acetylcholine (Ach) Alzheimer’s = less amount of Ach Enabled muscle action (makes our muscles contract) and has something to do with learning and memory. Curare (drug) - on the tip of a blow dart causes paralysis (it blocks the Ach) Black Widow spider venom – produces convulsions (boosts ach) Alzheimer’s = less amount of Ach

Serotonin Inhibitory in pain pathways Involved in sleep, mood, appetite, and sensory perception Too little== Depression Prozac –Agonist (boost serotonin) Too much== anxiety, limits dreaming, anorexia

Endorphins Endorphins Morphine – increases amount of endorphins Pain control and pleasure Runners High Morphine – increases amount of endorphins

Norepinephrine Controls alertness and arousal, Fight or flight response Under supply can lead to depression Too much can lead to hyperactivity

Glutamate Major excitatory neurotransmitter involved in information processing throughout the cortex and especially memory formation in the hippocampus. Oversupply can overstimulate the brain causing migraines and seizures

GABA Gamma-aminobutyric acid “nature’s VALIUM-like substance” is an inhibitory neurotransmitter Induces relaxation & sleep Balances the brain Too little = insomnia, anxiety, epilepsy Some drugs that increase the level of GABA in the brain are used to treat epilepsy and to calm the trembling of people suffering from Huntington’s disease. The disease destroys cells in the basal ganglia, the part of the brain that controls movement, emotion, and cognitive ability. What is Huntington's Disease? http://www.youtube.com/watch?v=hzKLNeYwbM8

Neurotransmitters Function Associated Disorders Acetylcholine Enables skeletal muscle movement; attention, arousal, memory and learning Alzheimer’s disease (decreased Ach) Black widow spider (increased Ach) Botox (decreased Ach) Curare (decreased Ach) Dopamine Voluntary movement, learning, attention, emotions, and rewards Parkinson’s disease (decreased dopamine) Muhamad Ali Schizophrenia (increased dopamine) Depression (decreased dopamine) Addictive Disorders Serotonin Sleep, mood, hunger, attention, arousal Depression (decreased serotonin) Anorexia (increased serotonin) Sleep disorders Norepinephrine Helps control alertness and arousal; Fight or flight response Depression (decreased NE) Agitation (increased NE) Endorphins (endogenous opiates) Pain, emotions; Mainly stimulate firing Mimicked by opiates (heroin, morphine, codeine) Runners high GABA (gamma amino-butyric acid) Hunger and sleep/arousal, Majorly inhibits Alcohol consumption causes an increase in GABA; Undersupply linked to seizures, tremors, and insomnia; Low levels linked to anxiety Glutamate Major excitatory; involved in learning and memory Oversupply overstimulates brain producing migraines or seizures

Agonists and Antagonists Agonists are chemicals that mimic the action of a particular neurotransmitter. They bind to receptors and generate postsynaptic potentials. Nicotine is an acetylcholine agonist, which means that it mimics acetylcholine closely enough to compete for acetylcholine receptors. When both nicotine and acetylcholine attach to a receptor site, the nerve fibers become highly stimulated, producing a feeling of alertness and elation. Antagonists are chemicals that block the action of a particular neurotransmitter. They bind to receptors but can’t produce postsynaptic potentials. Because they occupy the receptor site, they prevent neurotransmitters from acting. Curare is a drug that causes paralysis. As an acetylcholine antagonist, it binds to acetylcholine receptors at nerve-muscle junctions, preventing communication between nerves and muscles. Doctors sometimes use curare to immobilize patients during extremely delicate surgery. South American tribes have long used curare as an arrow poison.