Notes
Heredity and environment
Behavior comes from both nature (genes) and nurture (environment). Twin studies and adoption studies help separate them: identical twins raised apart who are still similar suggest a genetic influence. Evolutionary psychology asks how behaviors helped our ancestors survive and reproduce.
The nervous system
- Central nervous system (CNS): brain and spinal cord. Peripheral nervous system: everything else, split into somatic (voluntary muscles) and autonomic (automatic functions).
- Autonomic: sympathetic ("fight or flight," arousal) and parasympathetic ("rest and digest," calming).
- A reflex arc goes sensory neuron → interneuron in the spinal cord → motor neuron, without waiting for the brain.
Neurons and neurotransmitters
- A neuron receives signals at its dendrites, sends an action potential down the axon (sped up by the myelin sheath), and releases neurotransmitters from the terminal buttons across the synapse.
- All-or-nothing principle: a neuron fires completely or not at all once it reaches threshold.
- Reuptake pulls neurotransmitters back into the sending neuron. Agonists mimic or boost a neurotransmitter; antagonists block it.
| Neurotransmitter | Linked to |
|---|---|
| Dopamine | Reward, movement (low in Parkinson's) |
| Serotonin | Mood, sleep, appetite |
| Norepinephrine | Alertness, arousal |
| GABA | Main inhibitory ("calming") |
| Glutamate | Main excitatory; memory |
| Acetylcholine | Muscle movement, memory |
| Endorphins | Pain relief, pleasure |
- Hormones from the endocrine system travel in the blood and act more slowly: adrenaline, leptin and ghrelin (hunger), melatonin (sleep), oxytocin (bonding).
- Psychoactive drugs: stimulants (caffeine, cocaine), depressants (alcohol), hallucinogens, and opioids. Repeated use builds tolerance; stopping causes withdrawal.
The brain
- Brainstem: medulla (heartbeat, breathing), reticular activating system (arousal). Cerebellum: balance and coordination.
- Limbic system: amygdala (fear, emotion), hippocampus (forming new memories), hypothalamus (hunger, thirst, body temperature, hormones), thalamus (sensory relay, except smell).
- Cerebral cortex lobes: frontal (planning, decisions; motor cortex; Broca's area for speaking), parietal (touch; somatosensory cortex), occipital (vision), temporal (hearing; Wernicke's area for understanding language).
- Split-brain studies show the hemispheres specialize; the corpus callosum connects them. Plasticity lets the brain reorganize after damage, especially in children.
- Tools: EEG (electrical activity), fMRI (blood flow and activity), lesion studies.
Sleep, sensation
- Sleep stages: NREM 1–3 (stage 3 is deep sleep), then REM (dreaming, active brain, paralyzed body). Circadian rhythms run on about 24 hours.
- Sensation is detecting stimuli; transduction turns them into neural signals. Absolute threshold, difference threshold (Weber's law), and sensory adaptation. Rods see in dim light; cones see color.
Practice
Parasympathetic is "rest and digest."
More serotonin stays in the synapse, strengthening its effect.
The hippocampus helps encode new explicit memories.
Broca's area in the frontal lobe controls speech production.
Once threshold is reached, the action potential has the same strength.
The hypothalamus maintains homeostasis.
REM sleep has vivid dreams and an active brain.
Sensory receptors respond less to an unchanging stimulus.
Free response
Write your answer first, then open the scoring guide.
Free-response question
Jordan, a college student, drinks lots of coffee before an exam, feels his heart race, and has trouble sleeping that night.
(a) Explain how the sympathetic nervous system relates to Jordan's racing heart.
Show the answer and scoring guide
The sympathetic nervous system triggers arousal (fight or flight), increasing heart rate. Caffeine as a stimulant and exam stress both activate it.
Check off the points you earned:
(b) Explain how caffeine as a stimulant affects neural activity.
Show the answer and scoring guide
Stimulants increase nervous system activity. Caffeine blocks the receptors for adenosine, a chemical that builds up and makes us sleepy, so Jordan stays alert.
Check off the points you earned:
(c) Explain how Jordan's lack of sleep could affect his memory of what he studied.
Show the answer and scoring guide
Sleep helps consolidate memories, moving them into long-term storage. Missing sleep means less consolidation, so he may remember less.
Check off the points you earned: