5.5 Introduction to the Biological Bases of Behavior

The neuron: basic unit of the nervous system

A neuron has dendrites (receive signals), a cell body/soma (integrates signals), and an axon (sends signals), often insulated by myelin for faster conduction. Communication happens via an action potential, an electrical impulse triggered when the neuron reaches threshold, followed by neurotransmitter release across the synapse.

Neurotransmitters and neural communication

Neurotransmitters cross the synaptic gap and bind to receptors, causing excitatory or inhibitory effects. Key ones include dopamine (reward, movement), serotonin (mood, sleep), acetylcholine (muscle action, memory), norepinephrine (arousal), and GABA (inhibitory calming). Imbalances are linked to disorders like depression and Parkinson's disease.

Endocrine system and hormones

The endocrine system uses glands to release hormones into the bloodstream for slower, longer-lasting effects than neurons. The pituitary gland ('master gland') regulates other glands; the adrenal glands release cortisol/epinephrine for stress response; the hypothalamus links the nervous and endocrine systems, maintaining homeostasis.

Key terms

Neuron

The basic building block of the nervous system; transmits electrical and chemical signals via dendrites, soma, and axon.

Action potential

An electrical impulse that travels down the axon when the neuron's stimulation reaches threshold.

Neurotransmitter

A chemical messenger released at the synapse that binds to receptors on the next neuron, exciting or inhibiting it.

Endocrine system

A system of glands that release hormones into the bloodstream, producing slower, longer-lasting effects than neurons.

Hypothalamus

Brain structure that links the nervous and endocrine systems and regulates hunger, thirst, and body temperature to maintain homeostasis.

Try an AP-style question

Biological psychologists study…

1. only learned habits
2. only unconscious desires
3. links between biology and behavior
4. only social influences