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The Neuron
Dendrites: Branch-like structures that receive messages from other neurons.
Soma (Cell Body): The neuron's life-support center, containing the nucleus.
Nucleus: Houses the cell's genetic material and decides whether the neuron should fire.
Axon: The long, thin fiber that carries electrical messages away from the cell body.
Myelin Sheath: A fatty layer that insulates the axon and speeds up the electrical signal.
Nodes of Ranvier: Gaps in the myelin sheath that allow the signal to jump, further increasing speed.
Schwann Cells: Special cells that form the myelin sheath in the peripheral nervous system.
Axon Terminal: The end of the axon where it connects with other neurons or muscles.
Terminal Buttons: Located at the axon terminal, these store and release neurotransmitters.
Think of It Like This:
Imagine a neuron as a tiny messenger:
Dendrites receive a message like a mailbox.
The soma (cell body) reads the message.
The axon is like a delivery truck, carrying the message along a highway (myelin sheath).
The terminal buttons deliver the message to another neuron (or muscle) like a package.
Reuptake is like returning the delivery truck to the depot to pick up more packages.
Two common types of brain cells:
Neurons: Cells that transmit information.
Glial Cells: Cells that provide structure, insulation, communication, and help with waste transport.
These cells are the foundation of the nervous system and are essential for all behavior and mental processes.
Reflex Arc in the Spinal Cord:
The spinal cord controls reflexes, which are automatic responses to stimuli that don't require conscious thought.
Shows how neurons in the central and peripheral nervous systems work together to respond to stimuli.
Three types of neurons involved:
Sensory Neurons (Afferent): Carry messages from the senses to the central nervous system (CNS).
Interneurons: Found only in the CNS, act as messengers between sensory and motor neurons.
Motor Neurons (Efferent): Carry messages from the CNS to muscles and glands.
Neural Firing
The Action Potential: The Neuron's "Message"
Resting Potential (-70mV): The neuron is at rest, like a battery charged and ready.
Inside: Mostly potassium ions (K+)
Outside: Mostly sodium ions (Na+)
Threshold (-55mV): The trigger point – if enough stimulation reaches the neuron, it fires.
Action Potential: A brief electrical charge that travels down the axon, like a wave.
Depolarization: Sodium gates open, and Na+ ions rush in, making the inside of the neuron positive.
Repolarization: Potassium gates open, and K+ ions rush out, restoring the negative charge inside.
Refractory Period: A short "recharge" time where the neuron cannot fire again.
Note: The sodium potassium pump is outside the scope of AP Psychology so you don't need to know how it works, but understand these big ideas in neural firing.
Key Points About Neural Firing
All-or-None Principle: A neuron either fires completely or not at all. There are no partial fires.
Reuptake: The process where excess neurotransmitters are reabsorbed by the sending neuron to be used again.
Neurotransmitters: Chemical Messengers
Synapse: The tiny gap between neurons.
Receptor Sites: Specialized places on the receiving neuron's dendrites where neurotransmitters fit like keys in locks.
Excitatory Neurotransmitters: Increase the chance the next neuron will fire.
Inhibitory Neurotransmitters: Decrease the chance the next neuron will fire.
Neurotransmitters For AP Exam
Dopamine:
Functions: Mood, emotion, reward, arousal.
Too Much: Schizophrenia, addiction
Too Little: Parkinson's disease
Serotonin:
Functions: Mood regulation, appetite, sleep.
Too Much: Hallucinations
Too Little: Depression
Norepinephrine:
Functions: Alertness, arousal, "fight-or-flight" response, mood.
Too Much: Anxiety
Too Little: Depression
Glutamate:
Functions: Main excitatory neurotransmitter, learning, memory.
Too Much: Overstimulation, migraines, seizures
GABA:
Functions: Main inhibitory neurotransmitter, calming the brain, regulating sleep.
Too Much: Sleep and eating disorders
Too Little: Anxiety, epilepsy, insomnia
Endorphins:
Functions: Pain relief, pleasure, stress reduction.
Too Much: Artificial highs, reduced pain sensitivity
Too Little: Possible link to addiction
Acetylcholine (ACh):
Functions: Muscle movement, learning, memory, attention.
Too Much: Muscle spasms
Too Little: Alzheimer's disease
Substance P: A neurotransmitter present in the brain and spinal cord involved in transmitting pain signals.
Agonists vs. Antagonists: How Drugs Affect Neurotransmitters
Agonists: Mimic neurotransmitters, enhancing their effects.
Antagonists: Block neurotransmitters, inhibiting their effects.
The Endocrine System
Key Features:
A slow-acting but longer-lasting communication system.
Works with the nervous system to maintain balance (homeostasis).
Supports the "fight-or-flight" response during stress.
Major Glands and Hormones:
Pituitary Gland: The "master gland," controls other glands and releases growth hormone.
Pineal Gland: Secretes melatonin, which helps with the timing of your circadian rhythms which influences sleep-wake cycles.
Adrenal Glands: Located on top of the kidneys, these release:
Adrenaline (epinephrine): For quick bursts of energy in stressful situations preparing you to react.
Corticosteroids (cortisol): For longer-term stress responses and blood sugar regulation.
Other Important Hormones
Leptin: Hormone secreted by fat cells. When abundant, it causes the brain to increase metabolism and decrease hunger.
Orexin: Hunger-triggering hormone secreted by the hypothalamus.
Ghrelin: Hormone secreted by empty stomach signaling hunger to the brain.
PYY: Hormone secreted by the empty stomach signaling satiety (fullness) to the brain.
Oxytocin: Associated with bonding, empathy, and trust.
Psychoactive Drugs and Their Effects
Psychoactive Drugs: Chemicals that change perceptions, moods, and consciousness.
Tolerance: The diminishing effect of a drug with regular use, requiring larger doses to achieve the same effect.
Withdrawal: Unpleasant physical and psychological symptoms experienced when stopping or reducing drug use.
Dependence (Addiction): A compulsive craving for and use of a drug despite negative consequences.
Types of Psychoactive Drugs
Depressants: Slow down brain activity and bodily functions.
Alcohol: Reduces inhibitions, impairs judgment and memory, slows reaction time.
Barbiturates: Sedatives or tranquilizers that can be highly addictive and dangerous.
Opiates (e.g., heroin, morphine): Painkillers that are highly addictive and can cause overdose.
Stimulants: Increase brain activity and bodily functions.
Caffeine: Boosts alertness and energy.
Nicotine: Highly addictive, found in tobacco products.
Amphetamines: Suppress appetite, increase energy, but can lead to anxiety and dependence.
Methamphetamine: A powerful, illegal stimulant with severe side effects and high risk of addiction.
Stimulants and Hallucinogens
Cocaine:
Effect: Intense euphoria and energy by blocking dopamine reuptake.
Risks: Highly addictive, heart problems, paranoia.
Ecstasy (MDMA):
Effects: Increased empathy, euphoria, energy.
Risks: Dehydration, overheating, high blood pressure, long-term damage to serotonin neurons.
Hallucinogens (Psychedelics): Alter perceptions, causing hallucinations.
LSD: Powerful hallucinogen with unpredictable effects, can cause intense emotions and "bad trips."
Marijuana (THC):
Effects: Relaxation, altered perception, impaired coordination and memory.
Risks: Potential for addiction, impaired cognitive function, lung damage (if smoked).
Why People Use Drugs
Biological Factors: Genetic predisposition, changes in the brain's reward system.
Psychological Factors: Stress, trauma, mental health disorders.
Social-Cultural Factors: Peer pressure, cultural norms, media influence.
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