AP PSYCH UNIT 1

AP Psychology Unit One: Biological Basis of Behavior

Overview of Psychology

  • Definition of Psychology: The study of the mind and behavior. Focuses on answering the question, "What causes our brain to act a certain way?"
      - Nature vs. Nurture: Key dilemma in understanding behavior.
        - Nature: Genetic and biological traits (DNA, brain chemistry, inherited tendencies) that influence physical, behavioral, and mental traits.
        - Nurture: Environmental factors (education, culture, family) that one experiences throughout life.
        - Question: Which has a greater impact on personality, behavior, or mental state? The answer remains uncertain.

Psychological Approaches

  • Evolutionary Perspective: Derived from Darwin's theories.
      - Natural Selection: Principle that organisms more adapted to their environment are more likely to survive and reproduce.
      - Social Darwinism: Misapplication of natural selection to social contexts, leading to discrimination.
        - Eugenics: Ideology aimed at improving the human race by selectively breeding individuals with "desirable" traits. Discredited and associated with historical injustices like those seen during World War II.
      - Supporting Evidence: Twin studies (e.g., Minnesota Twin Study) show identical twins raised apart often exhibit similarities in personality and intelligence, supporting genetic impacts on behavior.

The Nervous System

  • Function of the Nervous System: Receives messages (e.g., sensory input) and sends out instructions, maintaining bodily homeostasis.

  • Central Nervous System (CNS): Primarily consists of the brain and spinal cord; interprets information and controls bodily responses.

  • Peripheral Nervous System (PNS): Functions as a messenger system for the CNS. Divided into:
      - Somatic Nervous System: Controls voluntary muscle movements (e.g., typing, walking).
      - Autonomic Nervous System: Manages involuntary functions (e.g., heart rate, digestion).
        - Divisions of Autonomic Nervous System:
          - Sympathetic Nervous System: Prepares the body for action/stress (fight or flight response).
          - Parasympathetic Nervous System: Calms the body and restores homeostasis.

  • Example: When stubbing a toe, sensory neurons send a pain signal to the CNS, which processes the signal and sends motor signals back to the somatic system to react, while the autonomic system responds involuntarily.

  • Neurons: Two main types within the nervous system—neurons (info transmitting) and glial cells (supportive functions).
      - Action Potential: A threshold of positive ions entering a resting polarized neuron triggers a signal; follows a refractory period where another action potential cannot occur.
      - Neuron Structure:
        - Dendrites: Receive signals.
        - Soma: Contains the cell nucleus.
        - Axon: Transmits signals, insulated by myelin sheath (gaps called nodes of Ranvier).
        - Axon Terminal: Releases neurotransmitters into the synaptic cleft.

Neurotransmitters

  • Role of Neurotransmitters: Facilitate communication between neurons.

  • Key Neurotransmitters:
      - Dopamine: Involved in reward, motivation, and movement.
      - Serotonin: Regulates mood, sleep, and appetite.
      - Norepinephrine: Increases alertness and arousal.
      - Glutamate: Main excitatory neurotransmitter important for learning and memory.
      - GABA: Main inhibitory neurotransmitter that reduces neural activity.
      - Acetylcholine: Involved in muscle movement and memory.
      - Endorphins: Reduce pain and increase pleasure.
      - Substance P: Transmits pain messages to the brain.

Hormones vs. Neurotransmitters

  • Hormones: Travel through the bloodstream, slower and longer-lasting effects compared to neurotransmitters.

  • Key Hormones:
      - Adrenaline: Triggers fight or flight response.
      - Leptin: Signals satiety and lessens appetite.
      - Ghrelin: Stimulates hunger.
      - Melatonin: Regulates sleep-wake cycles.
      - Oxytocin: Promotes bonding, trust, and social connections.

Effects of Drugs on Neurons

  • Drug Interactions with Neurotransmitters:
      - Agonists: Mimic or enhance neurotransmitter effects.
      - Antagonists: Block receptor sites and impede neurotransmitter effects.
      - Reuptake Inhibitors: Block reabsorption, increasing neurotransmitter levels in the synaptic cleft.

  • Types of Drugs:
      - Stimulants: Increase neural activity (e.g., caffeine, nicotine, cocaine).
      - Depressants: Decrease neural activity (e.g., alcohol, barbiturates).
      - Hallucinogens: Distort perception and cognition (e.g., marijuana, LSD).
      - Opioids: Provide pain relief and a sense of euphoria (e.g., heroin, morphine).

Brain Structure and Function

  • Brainstem: Basic survival functions; includes the Medulla (regulates breathing and heart rate).

  • Reticular Activating System: Controls arousal and aspects of learning/cognition.

  • Cerebellum: Coordinates muscle movements and balance.

  • Cerebral Cortex:
      - Outer Layer: Divided into two hemispheres responsible for higher-level functions.
      - Limbic System: Includes structures important for memory and emotion.
        - Thalamus: Relay station for sensory information.
        - Hypothalamus: Regulates hunger, thirst, body temperature, and communicates with the pituitary gland.
        - Hippocampus: Involved in forming new memories.
        - Amygdala: Processes emotions like fear and aggression.
        - Corpus Callosum: Connects the two hemispheres for communication.

  • Hemispheres and Lobes:
      - Each hemisphere contains four lobes:
        - Occipital Lobe: Processes vision.
        - Temporal Lobe: Processes auditory information and language.
        - Parietal Lobe: Handles sensory input, containing the somatosensory cortex.
        - Frontal Lobe: Responsible for higher-order thinking and voluntary movement (prefrontal cortex).
          - Broca's Area: Produces speech (left hemisphere).
          - Wernicke's Area: Comprehends speech (left hemisphere).

  • Aphasia: Language impairments resulting from damage to Broca's or Wernicke's areas.

  • Brain Plasticity: The brain's ability to reorganize and form new connections, especially noted in early life.

Research Methods in Psychology

  • EEG (Electroencephalogram): Measures electrical brain activity.

  • fMRI (Functional Magnetic Resonance Imaging): Shows brain activity through blood flow.

  • Case Studies: Examine specific instances (e.g., Phineas Gage) to understand behavior changes resulting from brain damage.

  • Lesioning: Surgical methods to study functions of specific brain areas.

Sleep and Consciousness

  • Consciousness: Awareness of thoughts, feelings, behaviors, and the environment.

  • Circadian Rhythm: Biological clock with a 24-hour sleep-wake cycle; disrupted by factors like jet lag.

Stages of Sleep

  • Full night typically includes 4-6 sleep cycles, each about 90 minutes long.

  • Stages:
      - Non-REM 1: Light sleep with hypnagogic sensations (5-10 minutes).
      - Non-REM 2: Deeper sleep with sleep spindles (10-25 minutes).
      - Non-REM 3: Deep sleep, essential for physical restoration (20-40 minutes).
      - REM Sleep: Paradoxical sleep where dreaming occurs; brain activity similar to waking state; duration increases throughout the night.
      - REM Rebound: Increased REM sleep following deprivation.

  • Theories on Sleep:
      - Activation Synthesis Theory: Dreams stem from random neural activity.
      - Consolidation Theory: Sleep aids memory organization and storage.

  • Sleep Disorders:
      - Insomnia: Difficulty in falling/staying asleep.
      - Narcolepsy: Sudden, uncontrollable sleep episodes.
      - Sleep Apnea: Interrupted breathing during sleep.
      - REM Sleep Behavior Disorder: Acting out dreams due to lack of paralysis.
      - Somnambulism: Sleepwalking, often during non-REM 3.
      - Treatment: Emphasis on improved sleep hygiene and consistent sleep schedules.

Sensation and Perception

  • Sensation: Detection and processing of environmental stimuli that meet certain thresholds.
      - Absolute Threshold: Minimum stimulus intensity detectable 50% of the time.
      - Just Noticeable Difference (JND): Minimum change needed to notice a difference, expressed in Weber's Law (change must be proportional to original stimulus).
      - Sensory Adaptation: Decreased sensitivity to constant stimuli.
      - Sensory Interaction: How multiple senses work together (e.g., synesthesia).

Vision

  • Retina: Photosensitive surface converting light into neural messages.

  • Blind Spot: Area lacking photoreceptors where the optic nerve exits the retina.

  • Lens: Focuses light; errors cause nearsightedness or farsightedness.

  • Photoreceptors:
      - Rods: Detect shapes, movement, and low light (periphery).
      - Cones: Detect color and detail (fovea).

  • Color Vision Theories:
      - Trichromatic Theory: Color perception through three types of cones.
      - Opponent-Process Theory: Explains afterimages and color vision through contrasting pairs.

  • Color Vision Deficiency: Problems with cones or opponent cells (e.g., dichromatism, monochromatism).

  • Brain Damage Effects:
      - Prosopagnosia: Face blindness.
      - Blindsight: Responding to visual stimuli without conscious perception.

Hearing

  • Sound: Produced by vibrations of air, measured for wavelength (pitch) and amplitude (loudness).

  • Theories of Pitch:
      - Place Theory: Different frequencies stimulate different locations in the cochlea.
      - Frequency Theory: Firing rate of auditory neurons matches sound frequency.
      - Volley Theory: Neurons work in groups to handle sound frequencies.

  • Sound Localization: Determining the origin of sounds.

  • Types of Deafness:
      - Conduction Deafness: Damage to outer/middle ear.
      - Sensorineural Deafness: Damage to inner ear/auditory nerve.

Chemical Senses

  • Olfaction (Smell): Directly routes stimuli to the brain, bypassing the thalamus; pheromones can carry behavioral signals.

  • Gustation (Taste): Involves receptors for various basic tastes (sweet, sour, salty, bitter, umami).
      - Variations in Taste Sensitivity: Super tasters, medium tasters, non-tasters.
      - Interaction of Taste and Smell: Creates flavor perception.

Somatosensation

  • Touch: Detected by skin receptors responding to pressure, temperature, and pain.

  • Pain Theories:
      - Gate Control Theory: Pain signals can be modulated in the spinal cord.
      - Phantom Limb Sensation: Sensations of pain in a missing limb.

Balance and Movement

  • Vestibular Sense: Helps maintain balance through semi-circular canals and brain structures monitoring head movement.

  • Kinesthesis: Sense of body position and movement; coordination without visual feedback.

Conclusion

  • The study of the biological basis of behavior encompasses a broad range of topics, including the nervous system, neurotransmitters, the brain's structure, the mechanics of sleep, and sensory perception. Understanding these foundations is critical for a comprehensive grasp of psychology as a discipline.