AP Psychology

AP Psychology Unit 1: Biological Bases of Behavior

AP Psychology: Biological Bases of Behavior

🧠 1.1 Interaction of Heredity and Environment

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🔑 Key Concepts:

  • Nature vs. Nurture Debate: Are we shaped more by genes (nature) or environment (nurture)?
  • Behavior Genetics: Studies how genes and environment influence behavior.
  • Twin Studies:
    • Identical (monozygotic) twins share 100% genes.
    • Fraternal (dizygotic) twins share ~50%.
  • Heritability: Measures how much variation in a trait is due to genes.

✅ Example:

If intelligence has a heritability of 70%, 70% of the variation within a population (not one person!) is due to genetic differences.

🧠 1.2 Overview of the Nervous System

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🔑 Key Concepts:

  • Central Nervous System (CNS): Brain + spinal cord.
  • Peripheral Nervous System (PNS):
    • Somatic: Voluntary control (e.g., moving muscles).
    • Autonomic: Involuntary functions (heartbeat, digestion).
      • Sympathetic: "Fight or flight"
      • Parasympathetic: "Rest and digest"

🧠 Metaphor:

CNS = Command Center   PNS = Delivery Routes

⚡ 1.3 The Neuron and Neural Firing

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🧬 Structure of a Neuron:

  • Dendrites – receive messages
  • Cell body (soma) – keeps cell alive
  • Axon – sends messages
  • Myelin sheath – speeds up transmission
  • Axon terminal – releases neurotransmitters

🔥 Neural Firing:

  • Resting potential: Neuron is ready (-70mV).
  • Action potential: "All-or-nothing" electrical signal down the axon.
  • Refractory period: Time needed to reset.
  • Synapse: Gap between neurons; where neurotransmitters are released.

🧪 Important Neurotransmitters:

  • Dopamine: Movement, reward → low = Parkinson's
  • Serotonin: Mood → low = Depression
  • Acetylcholine (ACh): Memory & muscle → low = Alzheimer's
  • GABA: Inhibitory → low = seizures
  • Endorphins: Pain relief

🧠 1.4 The Brain

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🧠 Brain Structures:

Brainstem (basic survival):

  • Medulla – heartbeat & breathing
  • Pons – sleep & coordination
  • Reticular Formation – arousal
  • Cerebellum – balance & movement

Limbic System (emotion & memory):

  • Amygdala – fear/aggression
  • Hippocampus – memory
  • Hypothalamus – hunger, thirst, temperature, sexual behavior

Cerebral Cortex (higher thinking):

  • Frontal lobe – decision making, speaking, motor cortex
  • Parietal lobe – touch, spatial reasoning
  • Occipital lobe – vision
  • Temporal lobe – hearing

🧠 Split Brain:

  • Corpus callosum connects left & right hemispheres.
  • Left brain: language & logic.
  • Right brain: creativity & spatial skills.

😴 1.5 Sleep

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💤 Sleep Stages:

  • Stage 1: Light sleep (theta waves)
  • Stage 2: Sleep spindles
  • Stage 3 & 4: Deep sleep (delta waves)
  • REM Sleep: Dreams, brain active, body paralyzed

Why Sleep?

Restores body & brain, consolidates memory, releases growth hormone.

🧠 Sleep Disorders:

  • Insomnia: Trouble falling asleep
  • Narcolepsy: Sudden REM sleep
  • Sleep apnea: Breathing stops
  • Night terrors: During Stage 4, not REM

👁️ 1.6 Sensation

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🧠 Sensation vs. Perception:

  • Sensation = detecting stimulus
  • Perception = interpreting stimulus

🔑 Principles:

  • Transduction: Converting sensory info into neural signals.
  • Thresholds:
    • Absolute threshold: Smallest detectable stimulus.
    • Difference threshold (JND): Smallest detectable difference.

Vision:

  • Rods: Light/dark (night vision)
  • Cones: Color (daytime vision)
  • Path: Retina → Optic Nerve → Thalamus → Occipital Lobe

Hearing:

  • Cochlea: Transduces sound
  • Path: Ear → Auditory nerve → Temporal lobe

Content adapted from HeLovestMath: AP Psychology

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