AP Psychology Unit 1: Biological Basis of Behavior
Overview of Biological Basis of Behavior
Definition: This unit examines how the biological system impacts physical and mental actions and responses.
The Central Question: Behavioral study has moved from "Nature vs. Nurture" to "Nature AND Nurture."
Nature (Heredity): The passing of physical and mental traits from one generation to another.
Nurture (Environment): Includes factors such as family life, social groups, education, and societal influences.
Evolutionary and Genetic Perspectives
The Evolutionary Approach: Based on Charles Darwin’s theory of evolution. It leans heavily toward the nature side of the debate. - Natural Selection: Beneficial traits survive and are passed on, while undesirable traits die off. - Darwin's Background: While not a psychologist, his work is a fundamental pillar of evolutionary psychology. - Misuse of Principles: Some have used these ideas to support Eugenics, the belief in improving human genetic quality through selective breeding.
Epigenetics: The study of how environment and behavior affect how a person's genes work/express themselves. - Key Mechanism: Body reads a sequence differently; the sequence itself does not change. Genes are "turned on or off" due to sustained environmental pressures. - Twin Studies: Explains why identical twins with nearly shared genes develop different characteristics. - Named Studies: - Minnesota Study of Twins Reared Apart: Examined similarities/differences in identical twins separated at birth. - Colorado Adoption Project (est. 1975): A longitudinal study following biological and adoptive families to understand genetic vs. environmental impact on identity and cognitive abilities.
Neuroplasticity (Plasticity): The brain's ability to change and adapt via experiences by strengthening or weakening neural connections.
The Nervous System Architecture
Central Nervous System (CNS): Composed of the brain and spinal cord; sends orders to the body.
Peripheral Nervous System (PNS): Nerves branching from the brain and spine; connects the to organs and muscles.
Neuron Types: - Afferent Neurons (Sensory Neurons): Signal from sensory receptors to the ("Approaches" the brain). - Efferent Neurons (Motor Neurons): Signal from the to the ("Exits" the brain).
Subsystems of the PNS
Somatic Nervous System (Skeletal): Controls voluntary skeletal muscle movements and the five senses.
Autonomic Nervous System: Controls involuntary activities (heartbeat, digestion, breathing). - Sympathetic Division: Mobilizes the body for action (heart rate increases, eyes dilate). Known as "Fight or Flight." - Parasympathetic Division: Relaxing the body (slows heart rate, increases digestion). Known as "Rest and Digest." - Mnemonic: Think of a parachute; it slows you down before landing on the ground.
Neural Anatomy and Firing
Glial Cells: Provide structure, insulation, communication, and waste transportation. Most abundant cells. They support neurons but do not process/send information.
Neurons: The basic functional unit of the nervous system. Communicate via electrical impulses and chemical signals.
The Reflex Arc: A nerve pathway allowing a response to stimulus without conscious thought. Path: Sensory Receptor -> Sensory Neuron -> Interneuron (spinal cord) -> Motor Neuron -> Muscle.
Process of Neural Transmission (Action Potential)
Resting Potential: The state when a neuron is not sending a signal; it has more negative ions inside than outside.
Depolarization: Occurs when an outside stimulus meets the threshold, causing the neuron to fire an Action Potential.
All-or-Nothing Principle: A neuron only fires if the threshold is met; strength of stimulus does not change the impulse size.
Repolarization: Channels open to rebalance charges, letting positive ions back outside.
Refractory Period: A brief time post-firing when the cell cannot fire again until it returns to resting potential.
The Synapse and Neurotransmitters
Synapse: The tiny space between the axon terminal of one neuron and the dendrite of another.
Chemical vs. Electrical Synapses: Chemical use neurotransmitters; electrical are for immediate/fast messages.
Transmission Steps: - reaches the Pre-synaptic Terminal. - Neurotransmitters are released into the Synaptic Gap. - Neurotransmitters bind to receptor sites on the Post-synaptic Terminal. - Reuptake: The sending neuron reabsorbs extra neurotransmitters.
Effects: - Excitatory: Increases the likelihood of firing (depolarization). - Inhibitory: Decreases the likelihood (hyperpolarization/inside becoming more negative).
Specific Neurotransmitters
Acetylcholine (ACh): Enables muscle action, learning, and memory.
Substance P: Transmits pain signals to the .
Dopamine: Movement, learning, attention, and emotion.
Serotonin: Hunger, sleep, arousal, and mood.
Endorphins: Pain control and tolerance.
Epinephrine: High emotional response; memory formation.
Norepinephrine: Increases blood pressure, heart rate, and alertness (Fight or Flight).
Glutamate: Long-term memory and learning.
GABA: Sleep, movement, and slowing the nervous system.
Associated Disorders
Multiple Sclerosis: Damaged myelin sheath disrupts electrical signals; results in muscle weakness and fatigue.
Myasthenia Gravis (Mosia Gravis): Autoimmune disorder blocking Acoline (Acetylcholine) receptors, preventing muscle contraction.
The Endocrine System
Function: Slower-moving system that sends hormones through blood to target larger areas.
Key Hormones: - Adrenaline (Epinephrine): Expands air passages, redistributes blood to muscles. - Leptin: Inhibits hunger (signals stored fat is sufficient). - Ghrelin: "Hunger hormone" signals search for food. - Melatonin: Regulated by the pineal gland; controls Circadian Rhythms (released in response to darkness). - Oxytocin: "Love hormone" produced in the hypothalamus; promotes emotional bonding.
Pituitary Gland: The "Master Gland"; regulates bodily functions and other endocrine glands.
Psychoactive Drugs
Agonists: Increase neurotransmitter effectiveness (mimic, increase production, or block reuptake). - Examples: Xanax (GABA), Prozac (Serotonin), Opioids.
Antagonists: Decrease effectiveness (block release or block receptors). - Examples: Schizophrenia medication (blocks Dopamine), Alcohol (blocks Glutamate).
Drug Categories
Stimulants: Excite neural activity, give energy, reduce appetite (Caffeine, Nicotine, Cocaine).
Depressants: Reduce neural activity, cause drowsiness, lower breathing (Alcohol, Sleeping pills).
Hallucinogens: Distort perceptions (Marijuana, Peyote, LSD).
Opioids: Depressant-like effects; highly addictive pain relief (Morphine, Heroin, Oxycontin).
Physiological effects: Sustained use leads to Tolerance, Addiction, and Withdrawal.
Brain Structures
The Hindbrain (Bottom)
Brainstem: Base of brain; damage often results in death. - Medulla Oblongata: Regulates cardiovascular and respiratory systems. - Pons: Bridge connecting medulla/cerebellum; coordinates movement, sleep, and dreams.
Reticular Activating System (RAS): Part of the reticular formation; regulates arousal, alertness, and attention.
Cerebellum: "Little brain"; coordinates voluntary movement, posture, balance, and motor skills.
The Forebrain (Top)
Cerebrum: Largest part; deals with complex thoughts. Divided into two hemispheres and four lobes.
Cerebral Cortex: Thin outer layer of billions of nerve cells.
Corpus Callosum: Thick band of fibers connecting the hemispheres.
Frontal Lobe: Higher thinking. - Prefrontal Cortex: Judgment, foresight, speech. - Motor Cortex: Voluntary movement. Contralateral organization (Left motor controls right body). - Broca’s Area: Left hemisphere; language production. Damage causes Broca’s Aphasia (cannot speak fluently but understands).
Parietal Lobe: Sensory info (touch, temperature, spatial orientation). - Somatosensory Cortex: Processes touch Sensations.
Temporal Lobe: Above ears; auditory processing, face recognition. - Hippocampus: Learning and forming memories (not storage). - Amygdala: Emotional reaction (fear, aggression). - Wernicke’s Area: Left hemisphere; creates meaningful speech. Damage causes Wernicke’s Aphasia (meaningless speech).
Occipital Lobe: Back of brain; visual processing via the Primary Visual Cortex.
Thalamus: Relay station for all senses except smell.
Hypothalamus: Homeostasis (hunger, thirst, temperature, sex); controls pituitary gland.
Specialized Brain Research and Imaging
Brain Lateralization: Hemispheric specialization. Left = language, logic. Right = faces, spatial, direction.
Phineas Gage Case: Railroad rod through head severed the limbic system; personality changed, but cognition remained.
Split Brain Research: Patients with severed Corpus Callosum (to treat epilepsy). - Result: Hemispheres cannot communicate. Example: Word in left visual field (right brain) allows drawing but not speaking the word until drawn.
Imaging Techniques: - EEG: Electrodes on scalp; records electrical signals (sleep/seizure research). - fMRI: Shows metabolic functions and brain activity in high detail.
Sleep and Consciousness
Consciousness: Awareness of self and environment. Includes Wakefulness and Sleep.
Circadian Rhythm: biological cycle; impacts alertness and body temp. - Jet Leg: Internal clock out of sync with local time.
Sleep Stages and Waves
Waves: - Beta: Fast, low amplitude (active engagement). - Alpha: Slower, high amplitude (relaxation/Step 1). - Theta: Slow frequency (Stage 2). - Delta: Slowest frequency, greatest amplitude (deep sleep/Stage 3).
Stages: - NREM Stage 1: Light sleep (); hypnogogic sensations. - NREM Stage 2: (); Sleep Spindles and K-complexes. - NREM Stage 3: Deep sleep (); growth hormones; sleepwalking occurs. - REM (Rapid Eye Movement): Paradoxical sleep; beta waves (brain active); external muscles paralyzed. Dreams occur.
REM Rebound: Entering REM faster/longer after deprivation.
Sleep Theories
Activation-Synthesis: Dreams are stories made to explain random neural firing.
Consolidation Theory: Dreams help process and strengthen memories.
Restoration Theory: Sleep restores energy and resources.
Sleep Disorders
Insomnia: Trouble falling/staying asleep.
Sleep Apnea: Breathing stops, preventing deep sleep.
REM Sleep Behavior Disorder (RBD): Acting out dreams due to lack of muscle paralysis.
Sambulism: Sleepwalking (Stage 3).
Narcolepsy: Uncontrollable daytime sleep attacks.
Sensation and Transduction
Sensation: Detecting info from the environment.
Sensory Transduction: Converting outside stimulus into neural impulses.
Thresholds: - Absolute Threshold: Minimum stimulus detected of time. - Difference Threshold: Minimum change needed to notice a difference. - Weber Fetcher Law: Difference must be a constant percent, not amount.
Adaptation vs. Habituation: - Sensory Adaptation: Decreased response to unchanging stimulus (candle smell). - Habituation: Reduced response from repeated exposure (drug tolerance).
Synesthesia: Seeing colors when hearing music (crossing senses).
The Visual System
Path: Cornea -> Pupil -> Lens -> Retina.
Photoreceptors: - Rods: Periphery, dim light, black and white. - Cones: Fovea (center), detail, color vision.
Color Theories: - Trichromatic: Three receptors (Red, Green, Blue). - Opponent Processing: Color pairings (Red-Green, Blue-Yellow, Black-White). Explains After Images.
Vision Disorders: - Myopia: Nearsightedness (focus in front of retina). - Hyperopia: Farsightedness (focus behind retina). - Prosopagnosia: Face blindness (damage to occipital/temporal lobes). - Blindsight: Responding to visual stimuli without conscious awareness.
The Auditory System
Frequency: Pitch (High frequency = high pitch; low frequency = low pitch).
Amplitude: Loudness (Greater amplitude = louder).
Theories of Pitch: - Place Theory: Hair cell location on cochlea (best for high pitch). - Frequency Theory: Auditory nerve matches wave frequency (best for low pitch). - Volley Theory: Neurons fire in staggered manners for high frequencies.
Deafness: - Sensory Neural: Damage to cilia or nerve. - Conductive: Blockage preventing sound travel through outer/middle ear.
Other Senses
Smell (Olfactory): Only sense that bypasses the thalamus; connected to the limbic system (memory/emotion).
Taste (Gustation): 6 tastes—Sweet, Sour, Bitter, Salty, Umami (savory/protein), and Oleogustus (fat).
Somatosensation (Touch): - Nociceptors: Pain receptors. - Gate Control Theory: Spinal cord has a "gate" that can block pain based on psychological state or distraction.
Body Positioning: - Vestibular Sense: Balance via fluid in semicircular canals. - Kinesthesis: Awareness of position and movement of body parts. - Proprioceptors: Receptors in muscles/tendons communicating position to the cerebellum.
Questions & Discussion
Audience Prompt: Mr. Sin asks the audience if the after-image exercise worked and prompts them to comment below.
Call to Action: Students are encouraged to use the Ultimate Review Packet study guides and answer keys for practice quizzes to ensure they get an "A" in class and a "5" on the national exam.