5.11 The Brain

Neurons and Neurotransmitters

The neuron is the basic unit of the nervous system, communicating via electrical impulses (action potentials) and chemical messengers (neurotransmitters) across the synapse. Key neurotransmitters include dopamine (movement, reward), serotonin (mood, sleep), acetylcholine (muscle action, memory), and GABA (inhibitory, calming). Imbalances in these chemicals are linked to disorders like depression and schizophrenia.

Brain Structures and Function

The hindbrain (medulla, pons, cerebellum) controls survival functions and balance. The midbrain relays sensory/motor info. The forebrain includes the limbic system (amygdala for emotion, hippocampus for memory, hypothalamus for drives) and the cerebral cortex, divided into frontal, parietal, temporal, and occipital lobes, responsible for higher-order thinking, sensation, and language.

Studying the Brain

Researchers use neuroimaging techniques to study brain activity: EEG measures electrical activity, fMRI shows structure and real-time function via blood flow, and PET scans track metabolic activity using radioactive tracers. Lesioning and studying brain-damaged patients (like Phineas Gage) also reveal structure-function links, showing how localized damage affects behavior and personality.

Key terms

Neuron

The basic building block of the nervous system; transmits information via electrical and chemical signals.

Dopamine

Neurotransmitter involved in movement, reward, and pleasure; linked to Parkinson's disease and schizophrenia.

Hippocampus

Limbic system structure critical for forming and storing new long-term memories.

fMRI

Functional MRI; shows brain structure and activity by measuring blood flow and oxygen use.

Cerebral cortex

The outer layer of the brain responsible for higher-order thinking, language, and sensory processing; divided into four lobes.

Try an AP-style question

What can they typically do?

1. Say the word aloud
2. Nothing at all
3. Write it with the right hand
4. Pick the object with the left hand