Unit 4

• Nervous System: it starts with an individual nerve cell called a NEURON
• How does a Neuron fire?
• Resting potential: slightly negative charge
• Reach the threshold when enough neurotransmitters reach dendrites.
• Go into Action Potential (firing)
• The All-or-None Response: the idea that either the neuron fires or it does not-no part way firing. Like a gun.
• Steps of Action Potential
• Dendrites receive neurotransmitter from another neuron across the synapse.
• Reached its threshold- then fires based on the all-or-none response.
• Opens up a portal in axon, and lets in positive ions (Sodium) which mix with negative ions (Potassium) that is already inside the axon (thus Neurons at rest have a slightly negative charge).
• The mixing of + and - ions causes an electrical charge that opens up the next portal (letting in more K) while closing the original portal.
• Process continues down axon to the axon terminal.
• Terminal buttons turns electrical charge into chemical (neurotransmitter) and shoots message to next neuron across the synapse.
• Types of Neurotransmitter
• Acetylcholine (ACH): deals with motor movement and memory. Lack of ACH has been linked to Alzheimer's disease.
• Dopamine: deals with motor movements and alertness. Lack of dopamine has been linked to Parkinson's disease. Too much has been linked to schizophrenia.
• Serotonin: involved in mood control. Lack of serotonin has been linked to clinical depression.
• Endorphins: involve in pain control. Many of our most addictive drugs deal with endorphins.
• Norepinephrine: helps control alertness and arousal. An undersupply can lead to depression. An oversupply can lead to manic symptoms
• GABA (gamma-aminobutytic acid): major inhibitory neurotransmitters. An undersupply can lead to tremor.
• Glutamate: major excitatory neurotransmitter; involved in memory. Oversupply can overstimulate the brain leading to migraines (this is why some people avoid MSG in food).
• Drugs can be...
• Agonist- make neuron fire
• Antagonists- stop neural firing
• Reuptake Inhibitors- block neurotransmitters from entering the neuron.
• Types of Neurons
• Sensory Neurons (Afferent Neurons): take information from the senses to the brain.
• Inter Neurons: take messages from Sensory Neurons to other parts of the brain or to Motor Neurons.
• Motor Neurons (Efferent Neurons): take information from the brain to the rest of the body.