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Unit 1
15–25% of examThis unit is about the body behind the mind. You'll see how your genes and your experiences work together, how neurons pass signals through your nervous system, what different parts of the brain do, why you sleep, and how your senses pick up information from the world. Almost everything later in the course, from memory to mental health, builds on this biology.
Longer videos that cover the whole unit. Good for a first pass or a final review.
Your behavior and mental processes come from both heredity (nature, the genes you inherit) and environment (nurture, everything you experience), and the two constantly shape each other. Psychologists use twin, family and adoption studies to sort out how much genes matter. The evolutionary perspective asks how behaviors may have helped our ancestors survive and reproduce, and some people have misused these ideas to justify discrimination, as in the eugenics movement.
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Your central nervous system is your brain and spinal cord, and the peripheral nervous system carries messages between it and the rest of your body. The peripheral system has a somatic part for voluntary movement and an autonomic part for automatic functions, whose sympathetic branch gears you up for "fight or flight" while the parasympathetic branch calms you back down.
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When a neuron gets enough input to pass its threshold, it fires an electrical signal called an action potential all the way down its axon (the all-or-none principle). It then releases chemical messengers called neurotransmitters, such as dopamine, serotonin and GABA, across the synapse, while hormones like adrenaline and melatonin carry slower messages through the blood. Psychoactive drugs such as stimulants, depressants, hallucinogens and opioids change this signaling, and repeated use can lead to tolerance, addiction and withdrawal.
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Different brain areas have different jobs. The brainstem keeps you breathing, the cerebellum coordinates movement and balance, the hippocampus and amygdala help with memory and emotion, and the lobes of the cortex handle vision, hearing, touch, movement and planning. Split-brain studies show the two hemispheres specialize (language usually sits in the left), and plasticity lets the brain rewire itself as you learn or after an injury.
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Your sleep and waking follow a roughly 24-hour circadian rhythm, and each night you cycle several times through NREM stages 1 to 3 and REM sleep, when most vivid dreaming happens. Leading theories say sleep helps you consolidate memories and restore your body, and sleep disorders such as insomnia, narcolepsy and sleep apnea show how much poor sleep affects you during the day.
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Sensation is how your sense organs detect energy such as light, sound waves and chemicals and transduce it into neural signals your brain can use. You'll learn about thresholds, how the eye and ear work, the theories that explain color vision and pitch, and the senses of smell, taste, touch, pain, balance and body position.
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