Psychology · Chapter 3

Biopsychology

Every thought you have ever had, every feeling, every memory, and every decision is, at bottom, a physical event — a pattern of electricity and chemistry playing out across cells. Biopsychology is the branch of the field that takes that idea seriously and asks how the nervous system and the glands that flavor it give rise to mind and behavior. This chapter starts with the single working unit, the neuron, and follows the signal outward: how one cell fires, how it whispers to the next across a synapse, how those cells are wired into the great trunk lines of the nervous system, how the brain organizes them into regions with jobs, and how a slower chemical messaging service — the endocrine system — sets the body's background mood. Understand these pieces and the rest of psychology stops feeling like magic and starts feeling like biology.

By the end of this chapter you can

Label the major parts of a neuron and explain what each part does.
Describe the resting potential and walk through the phases of the action potential.
Explain how a signal crosses the synapse and name the major neurotransmitters and their roles.
Distinguish drugs that act as agonists from those that act as antagonists.
Diagram the divisions of the nervous system: central vs peripheral, somatic vs autonomic, and sympathetic vs parasympathetic.
Identify the hindbrain, midbrain, and forebrain and the jobs of the four cortical lobes.
Explain how the endocrine system signals with hormones and how that differs from neural signaling.
Connect real cases and researchers — Phineas Gage, Broca, Wernicke, Selye — to the brain and body systems they illuminated.

Section 1The neuron

Anatomy of a neuron showing dendrites, cell body, axon, and myelin sheath — **Reference.** The neuron — dendrites receive, the cell body integrates, and the myelinated axon carries the signal to the terminals. OpenStax Anatomy & Physiology, CC BY 4.0 (via Wikimedia Commons)

The parts of a neuron

The neuron is the basic information-processing cell of the nervous system, and the whole of psychology — perception, memory, emotion, movement — runs on roughly 86 billion of them wired together. A neuron is built to do three things in sequence: receive a signal, decide whether to pass it on, and send it. The receiving end is a spray of branching fibers called dendrites. They funnel incoming signals toward the cell body (the soma), which holds the nucleus and tallies up everything arriving. If the total is large enough, the signal leaves down a single long fiber, the axon, and finishes at the swollen terminal buttons, where it will be handed off to the next cell.

Many axons are wrapped in a fatty white insulation called the myelin sheath, laid down by supporting cells. Myelin is not continuous; it comes in segments separated by bare gaps, the nodes of Ranvier, and this segmentation is precisely what makes myelinated axons fast. Neurons do not work alone, either. They are accompanied by an equally large population of glial cells (glia) — roughly 85 billion of them, about one glial cell for every neuron in the brain as a whole, though glia outnumber neurons several-fold within the cerebral cortex. Glia are the support staff that build myelin, feed neurons, clean up debris, and hold the whole structure in place. For a long time they were treated as mere packing material, and an old textbook figure of ten glia per neuron is still repeated; careful cell counts have retired both ideas, and we now know glia actively shape how signals travel.

Part	Job
Dendrites	Receive incoming signals from other neurons and carry them toward the cell body
Cell body (soma)	Holds the nucleus; integrates all incoming signals to decide whether to fire
Axon	Single long fiber that carries the outgoing signal away from the cell body
Myelin sheath	Fatty insulation that speeds conduction; gaps are the nodes of Ranvier
Terminal buttons	Axon tips that release neurotransmitter onto the next cell
Glial cells	Support cells that myelinate, nourish, and protect neurons

How a neuron fires: the action potential

At rest, a neuron is a tiny charged battery. It actively pumps ions across its membrane so that the inside sits at about −70 millivolts relative to the outside — a state called the resting potential. The cell is polarized, primed and waiting. Incoming signals nudge that voltage up or down. If enough excitatory input arrives to push the membrane past a tipping point of roughly −55 mV — the threshold — the neuron fires.

Firing is the action potential: a brief electrical spike that races down the axon. It unfolds in a fixed sequence. Voltage-gated channels fling open and positively charged sodium (Na⁺) ions rush in, flipping the inside briefly positive — this is depolarization. A heartbeat later those channels close and potassium (K⁺) ions flow out, dragging the voltage back down — repolarization — often overshooting into a short refractory period during which the cell cannot fire again. Then the ion pumps restore the resting balance and the neuron is ready to go once more. Crucially, the action potential is all-or-none: a neuron either fires a full spike or it does not fire at all, like a gun trigger. It cannot fire a “half” signal, so the brain codes the strength of a stimulus not in the size of each spike but in how fast and how many neurons fire.

In myelinated axons the spike does not crawl smoothly down the fiber — it leaps from one node of Ranvier to the next, a shortcut called saltatory conduction (from the Latin saltare, to jump). This is why myelin matters so much: it can multiply conduction speed many times over, letting a signal travel from your spinal cord to your toe in a fraction of a second.

Damaged myelin is a disease, not a metaphor. In multiple sclerosis the immune system strips myelin off central axons. With the insulation gone, saltatory conduction fails and signals slow, scatter, or die out — producing the numbness, weakness, and vision loss of the disorder. The lesson is direct: the physical health of a neuron's wiring is the health of the behavior it supports.

Interactive Trigger an action potential and step a neuron through its five phases — resting, threshold, depolarization, repolarization, and refractory recovery — watching the voltage climb and fall on a live membrane-potential graph. Open full ↑

Key points

A neuron receives at its dendrites, integrates in the cell body, and sends down its axon to the terminals.
The resting potential (about −70 mV) is a primed, polarized state; crossing threshold triggers firing.
The action potential is an all-or-none spike: Na⁺ in (depolarize), K⁺ out (repolarize).
Myelin enables fast saltatory conduction; when it is damaged, signaling and behavior suffer.

Section 2Neurotransmitters

A chemical synapse showing vesicles releasing neurotransmitter across the synaptic cleft to receptors — **Reference.** The chemical synapse — neurotransmitter is released from vesicles, crosses the cleft, and binds receptors on the next neuron. OpenStax Anatomy & Physiology, CC BY 4.0 (via Wikimedia Commons)

Crossing the synapse

Neurons almost never touch. Between the terminal of one and the dendrite of the next lies a microscopic gap, the synaptic cleft, and the whole junction is called the synapse. The electrical action potential cannot jump this gap, so the message is converted into a chemical one. When the spike reaches the terminal buttons, it triggers tiny sacs called vesicles to dump their cargo — molecules of neurotransmitter — into the cleft. Those molecules drift across and dock onto receptors on the receiving neuron, each receptor shaped to fit a particular transmitter like a lock fits a key.

The effect can be excitatory (nudging the next neuron toward firing) or inhibitory (nudging it away). Either way, the signal must be switched off promptly, or the receptor would keep firing. The body does this two ways: enzymes in the cleft chemically break the transmitter apart, or the sending neuron vacuums the leftover molecules back up to reuse them — a process called reuptake. Reuptake will matter enormously in a moment, because it is exactly the step that many psychiatric drugs target.

The major neurotransmitters

Dozens of neurotransmitters have been identified, but a handful do most of the work that intro psychology cares about. Each is loosely tied to particular functions and to particular disorders when it runs too high or too low.

Neurotransmitter	Associated with	When dysregulated
Acetylcholine (ACh)	Muscle movement, learning, memory	Loss is linked to Alzheimer's disease
Dopamine	Reward, motivation, movement, pleasure	Low in Parkinson's; overactivity linked to schizophrenia
Serotonin	Mood, sleep, appetite	Low levels linked to depression
Norepinephrine	Alertness, arousal, the stress response	Tied to anxiety and mood
GABA	The brain's main inhibitory transmitter; calming	Low activity linked to anxiety, seizures
Glutamate	The brain's main excitatory transmitter; learning	Excess can overexcite and damage neurons
Endorphins	Pain relief, pleasure (the body's natural opioids)	Mimicked by morphine and heroin

How drugs act: agonists and antagonists

Nearly every drug that changes mind or behavior does so by meddling with this chemical hand-off, and the effects sort into two broad camps. An agonist is any substance that increases a neurotransmitter's action — it might mimic the transmitter and bind its receptor directly, cause more of it to be released, or block reuptake so the transmitter lingers longer in the cleft. An antagonist does the opposite: it blocks or reduces a transmitter's action, often by plugging the receptor so the real transmitter cannot dock. The distinction is the heart of psychopharmacology. SSRIs, the most common antidepressants, are agonists that block the reuptake of serotonin, leaving more of it available at the synapse. Many antipsychotics are dopamine antagonists that dampen an overactive dopamine system. Caffeine, nicotine, opioids, and antihistamines all earn their effects by tilting one of these levers.

An agonist turns the volume up; an antagonist turns it down. Botox (a toxin) and curare (the arrow poison) both shut down acetylcholine at the muscle, but from opposite halves of the synapse. Botox works on the sending side: it stops the terminal from releasing acetylcholine at all, so the muscle relaxes and the wrinkle smooths. Curare works on the receiving side: it occupies the receptor on the muscle so acetylcholine that has been released cannot dock, and the result is paralysis. Same net direction — less acetylcholine action — by two different routes, which is a reminder that a drug's direction on a synapse, and the point at which it acts, is what predicts what it does.

Interactive Release a neurotransmitter across the synaptic cleft, then toggle agonist and antagonist drugs to see how each one activates or blocks the postsynaptic receptor. Open full ↑

Key points

Signals cross the synapse chemically: vesicles release neurotransmitter that binds receptors on the next neuron.
The signal is cleared by enzymatic breakdown or reuptake back into the sending neuron.
Key transmitters include dopamine, serotonin, acetylcholine, GABA, glutamate, and endorphins, each tied to specific functions and disorders.
Agonists increase a transmitter's action; antagonists block it — the basis of most psychiatric drugs.

Section 3The nervous system

Central and peripheral

All those neurons are organized into a two-part scheme. The central nervous system (CNS) is the brain and the spinal cord — the command center where information is integrated and decisions are made. Everything else — the vast web of nerves threading out to muscles, skin, and organs — is the peripheral nervous system (PNS), whose job is to carry messages back and forth between the CNS and the rest of the body. Sensory neurons run inward to the CNS; motor neurons run outward to muscles and glands. The spinal cord is not just a cable; it can run simple reflexes on its own, which is why your hand yanks off a hot stove before your brain has even registered the pain.

Somatic and autonomic

The peripheral system itself divides again by whether its actions are voluntary. The somatic nervous system handles the things you do on purpose: it carries sensory information in and sends commands out to the skeletal muscles you control — lifting a cup, typing, walking. The autonomic nervous system runs the housekeeping you never think about: heartbeat, digestion, breathing rate, pupil size, sweating. “Autonomic” and “automatic” are worth hearing as cousins, because this system manages the body on autopilot.

Sympathetic and parasympathetic

The autonomic system has two opposing branches that work like a gas pedal and a brake. The sympathetic nervous system is the accelerator — it mobilizes the body for action, the famous fight-or-flight response. Faced with a threat, it speeds the heart, dilates the pupils, dumps glucose into the blood, and shunts resources to the muscles, all in an instant. The parasympathetic nervous system is the brake, sometimes called rest-and-digest. Once the danger passes, it slows the heart, restarts digestion, and returns the body to a calm baseline. The two are almost always both active, and health is the balance between them; problems arise when the sympathetic accelerator is held down too long, as in chronic stress.

Organ	Sympathetic (“fight-or-flight”)	Parasympathetic (“rest-and-digest”)
Heart	Speeds up	Slows down
Pupils	Dilate (widen)	Constrict (narrow)
Digestion	Inhibited	Stimulated
Lungs	Airways widen	Airways narrow
Adrenal glands	Release stress hormones	—
Overall effect	Mobilize energy for action	Conserve energy, restore calm

The pounding heart before a test is your sympathetic system doing its job. The racing pulse, dry mouth, and shaky hands of stage fright are the fight-or-flight response firing at a threat that isn't physical. It evolved to help you outrun a predator; it doesn't know the difference between a lion and an audience. Understanding that the reaction is autonomic — not a character flaw — is often the first step to managing it.

Interactive A tap-to-explore branching tree of the nervous system — central vs. peripheral, somatic vs. autonomic, and sympathetic vs. parasympathetic — with a plain-language explainer, mnemonic, and breadcrumb path for each division. Open full ↑

Key points

The CNS (brain + spinal cord) integrates; the PNS carries signals to and from the body.
The somatic system controls voluntary skeletal muscle; the autonomic system runs involuntary organs.
The sympathetic branch mobilizes fight-or-flight; the parasympathetic branch restores rest-and-digest.
Health is the balance between the two; chronic sympathetic activation is the physiology of stress.

Section 4The brain

The four lobes of the cerebral cortex: frontal, parietal, temporal, and occipital — **Reference.** The four lobes of the cerebral cortex, each specialized for different functions. OpenStax Anatomy & Physiology, CC BY 4.0 (via Wikimedia Commons)

Hindbrain, midbrain, forebrain

One useful way to read the brain is from the bottom up, oldest structures first. The hindbrain sits where the spinal cord enters the skull and runs the machinery of staying alive. It includes the medulla (heartbeat and breathing), the pons (a relay involved in sleep and arousal), and the cerebellum (“little brain”), which coordinates balance, posture, and smooth, practiced movement. The small midbrain sits above it, handling reflexive orienting to sights and sounds and helping regulate movement and arousal. Together the midbrain and hindbrain — all but the cerebellum, which attaches behind it — make up the brainstem, the survival core.

The forebrain is the newest and largest region, and it is where the psychology lives. Deep inside sit structures we return to often: the thalamus, a sensory relay station routing incoming signals to the right places; the hypothalamus, which governs hunger, thirst, body temperature, and the endocrine system; and the limbic system — including the amygdala (emotion, especially fear) and the hippocampus (forming new memories). Draped over all of it is the wrinkled outer layer that makes us most human, the cerebral cortex.

The four cortical lobes

The cerebral cortex is the thin, folded sheet of neurons covering the brain, split into two hemispheres and divided into four lobes, each with characteristic jobs. The frontal lobe, at the front, is the seat of planning, judgment, personality, and voluntary movement (its rear strip is the motor cortex). It also holds Broca's area, essential for producing speech. The parietal lobe, just behind it, processes touch, temperature, and body position along its somatosensory cortex. The temporal lobe, at the side, handles hearing and language comprehension — home to Wernicke's area — and helps with memory. The occipital lobe, at the very back, is devoted almost entirely to vision.

Lobe	Location	Main functions
Frontal	Front	Planning, judgment, personality, voluntary movement (motor cortex), speech (Broca's area)
Parietal	Top rear	Touch, temperature, pain, body position (somatosensory cortex)
Temporal	Sides	Hearing, language comprehension (Wernicke's area), memory
Occipital	Back	Vision

The cortex also shows lateralization: the two hemispheres are not identical. For most people, language is concentrated in the left hemisphere, while the right leans toward spatial and holistic processing. And each hemisphere controls the opposite side of the body — the left motor cortex moves your right hand. None of this is rigidly fixed, though. The brain shows remarkable plasticity: after injury or with practice, healthy regions can take over lost functions, especially in the young.

Phineas Gage lost part of his frontal lobe and kept his intellect but lost himself. In 1848 an explosion drove an iron rod clean through the railroad foreman's frontal lobe. He survived, could still walk and talk and reason — yet the steady, responsible man became impulsive and profane. Friends said he was “no longer Gage.” The case became the founding evidence that the frontal lobe houses personality and self-control, and that damaging specific tissue changes specific parts of who a person is.

Interactive Tap the four cortical lobes and the deep structures beneath them — cerebellum, brainstem, thalamus, hypothalamus, hippocampus, and amygdala — to see what each brain region does. Open full ↑

Key points

The hindbrain (medulla, pons, cerebellum) and midbrain form the brain's survival core; the brainstem is that core apart from the cerebellum.
The forebrain holds the thalamus, hypothalamus, limbic system (amygdala, hippocampus), and cortex.
The four lobes are frontal (planning, movement, speech), parietal (touch), temporal (hearing, language), and occipital (vision).
Broca's area, Wernicke's area, and Phineas Gage each tie a specific function to specific cortical tissue; the brain remains plastic.

Section 5The endocrine system

The endocrine system showing major hormone-secreting glands throughout the body — **Reference.** The endocrine system — glands that release hormones into the bloodstream to signal distant organs. OpenStax Anatomy & Physiology, CC BY 4.0 (via Wikimedia Commons)

Glands and hormones

The nervous system is not the body's only messaging service. The endocrine system is a network of glands that release chemical messengers called hormones directly into the bloodstream, which then carries them to distant organs. Where a neuron speaks privately to the one cell across its synapse, a gland broadcasts to the whole body at once, and any cell with the right receptor will answer. The master gland is the pituitary, tucked under the brain and taking orders from the hypothalamus — the point where the nervous and endocrine systems shake hands. The pituitary in turn directs the others.

Gland	Key hormone(s)	Main effect
Pituitary	Growth hormone; releasing hormones	The “master gland” — directs other glands and controls growth
Thyroid	Thyroxine	Sets metabolic rate and energy level
Adrenal glands	Adrenaline (epinephrine), cortisol	Drive the stress response; arousal and energy
Pancreas	Insulin, glucagon	Regulate blood sugar
Gonads (ovaries/testes)	Estrogen, testosterone	Reproduction and sex characteristics
Pineal	Melatonin	Regulates sleep and the daily body clock

Hormones versus neural signaling

Both systems use chemical messengers — adrenaline is a hormone in the blood and a transmitter-like signal in the brain — but they operate on very different timescales, and the contrast is the point. Neural signaling is fast, precise, and brief: an action potential fires in a thousandth of a second, targets one specific cell, and is over almost as soon as it began. Hormonal signaling is slow, diffuse, and lasting: a hormone may take seconds to minutes to reach its target, it washes over the entire body, and its effects can persist for hours — think of how long it takes to calm down after a fright, long after the danger is gone. That lingering quality is what makes hormones the substrate of mood and long-running states rather than split-second reactions.

Feature	Neural signaling	Hormonal signaling
Messenger	Neurotransmitter	Hormone
Route	Across a synapse to one cell	Through the bloodstream to the whole body
Speed	Milliseconds	Seconds to minutes
Duration	Brief	Long-lasting
Precision	Targeted, private	Broadcast, diffuse

Hans Selye showed that chronic stress wears the body down through hormones. Studying how animals responded to prolonged stressors, Selye described the general adaptation syndrome — alarm, resistance, exhaustion — and put the adrenal glands at its center. When the hypothalamus signals the pituitary, which signals the adrenals to pour out cortisol, a short burst is protective, but weeks of it suppress immunity, disturb sleep, and erode health. It is the endocrine explanation for why long-term stress makes people sick.

Interactive Tap each gland on the body to reveal the hormone it releases and its effect on mood, sleep, stress, growth, and behavior. Open full ↑

Key points

The endocrine system is a network of glands that release hormones into the bloodstream.
The hypothalamus and pituitary gland link the nervous and endocrine systems and direct the other glands.
Compared with neural signals, hormones are slower, more diffuse, and longer-lasting — the chemistry of mood and stress.
Selye's work ties chronic stress and cortisol to real damage to health.

The chapter in one breath

The neuron receives at its dendrites, integrates in its cell body, and sends down its axon; myelin speeds the signal.
Crossing threshold triggers an all-or-none action potential — Na⁺ in to depolarize, K⁺ out to repolarize.
Signals cross the synapse as neurotransmitters that bind receptors and are then cleared by reuptake or enzymes.
Drugs are agonists (boost a transmitter) or antagonists (block it); SSRIs and antipsychotics work this way.
The nervous system divides into central vs peripheral, somatic vs autonomic, and sympathetic (fight-or-flight) vs parasympathetic (rest-and-digest).
The brain runs bottom-up from hindbrain and midbrain survival cores to the forebrain, whose cortex has four lobes: frontal, parietal, temporal, occipital.
The endocrine system signals with hormones through the blood — slower, more diffuse, and longer-lasting than neural signals — and drives the stress response.

ReferenceWords worth knowing

A quick reference for the terms in this chapter — skim it now, or circle back whenever a word trips you up.

Action potential: The brief, all-or-none electrical spike a neuron fires and sends down its axon.
Agonist: A drug or substance that increases a neurotransmitter's action — by mimicking it, boosting its release, or blocking reuptake.
Antagonist: A drug or substance that blocks or reduces a neurotransmitter's action, often by occupying its receptor.
Autonomic nervous system: The peripheral division that controls involuntary functions like heartbeat and digestion; split into sympathetic and parasympathetic branches.
Axon: The single long fiber that carries a neuron's outgoing signal away from the cell body.
Central nervous system (CNS): The brain and spinal cord, where information is integrated and decisions are made.
Cerebral cortex: The wrinkled outer sheet of the brain, divided into two hemispheres and four lobes, responsible for higher functions.
Dendrite: A branching fiber that receives incoming signals and carries them toward the cell body.
Endocrine system: The network of glands that release hormones into the bloodstream to signal distant organs.
Glial cell: A support cell of the nervous system that myelinates, nourishes, and protects neurons.
Hormone: A chemical messenger released by an endocrine gland into the bloodstream.
Myelin sheath: The fatty insulation around many axons that speeds conduction; its gaps are the nodes of Ranvier.
Neuron: The basic information-processing cell of the nervous system.
Neurotransmitter: A chemical released across a synapse to carry a signal to the next neuron.
Parasympathetic nervous system: The autonomic branch that calms the body and restores it — “rest-and-digest.”
Peripheral nervous system (PNS): All the nerves outside the brain and spinal cord that connect the CNS to the body.
Resting potential: The neuron's charged, polarized resting state, about −70 mV inside relative to outside.
Reuptake: The reabsorption of leftover neurotransmitter back into the sending neuron.
Somatic nervous system: The peripheral division that carries sensory input and controls voluntary skeletal muscle.
Sympathetic nervous system: The autonomic branch that mobilizes the body for action — “fight-or-flight.”
Synapse: The junction between two neurons, including the tiny synaptic cleft the signal crosses.
Threshold: The level of stimulation (about −55 mV) a neuron must reach to fire an action potential.

Check yourself

1. Trace an incoming signal through the three functional parts of a neuron, naming each part and its job.

Dendrites receive the signal, the cell body (soma) integrates all inputs to decide whether to fire, and the axon carries the outgoing signal to the terminal buttons. Myelin on the axon speeds that outgoing signal along.

2. What is the resting potential, and what has to happen for a neuron to fire?

The resting potential is the neuron's charged, polarized state (about −70 mV inside). Incoming excitatory input must push the membrane past threshold (about −55 mV); only then does an action potential fire.

3. Explain what “all-or-none” means, and how the brain then codes the strength of a stimulus.

All-or-none means a neuron either fires a full action potential or none at all — there is no partial spike. Because spike size is fixed, the brain signals a stronger stimulus by firing more neurons and firing them more frequently.

4. Why does damage to myelin, as in multiple sclerosis, impair function?

Myelin enables fast saltatory conduction, in which the action potential jumps between nodes of Ranvier. Strip the myelin and signals slow, scatter, or fail — producing numbness, weakness, and vision problems.

5. A signal reaches the end of an axon. Describe how it crosses to the next neuron and how it is then switched off.

Vesicles release neurotransmitter into the synaptic cleft; the molecules cross and bind receptors on the next neuron. The signal is cleared by enzymes that break the transmitter down or by reuptake back into the sending neuron.

6. Match each to its role: dopamine, serotonin, GABA, endorphins.

Dopamine — reward, motivation, and movement; serotonin — mood, sleep, appetite; GABA — the main inhibitory (calming) transmitter; endorphins — natural pain relief and pleasure. Low serotonin is linked to depression; low dopamine to Parkinson's.

7. Define agonist and antagonist, and explain which one an SSRI antidepressant is and why.

An agonist increases a neurotransmitter's action; an antagonist blocks or reduces it. An SSRI is an agonist for serotonin: it blocks reuptake, so serotonin lingers longer in the synapse and its effect is amplified.

8. Distinguish the central and peripheral nervous systems, then the somatic and autonomic subdivisions.

The CNS is the brain and spinal cord (integration and decisions); the PNS is all the nerves connecting the CNS to the body. Within the PNS, the somatic system controls voluntary skeletal muscle, while the autonomic system runs involuntary organs.

9. Your car swerves toward you and your heart pounds. Name the system responsible and three specific things it does; then name what returns you to calm.

The sympathetic nervous system drives fight-or-flight: it speeds the heart, dilates the pupils, and inhibits digestion (also releasing glucose and stress hormones). The parasympathetic system (“rest-and-digest”) then slows the heart and restores baseline.

10. Name the three major divisions of the brain from bottom to top, and one structure or job in each.

Hindbrain (medulla for heartbeat/breathing, or cerebellum for balance), midbrain (reflexive orienting and arousal), and forebrain (thalamus, hypothalamus, limbic system, and cortex). The brainstem is the midbrain plus the hindbrain, apart from the cerebellum.

11. Name the four cortical lobes and the primary function of each.

Frontal — planning, judgment, movement, and speech (Broca's area); parietal — touch and body position; temporal — hearing and language comprehension (Wernicke's area); occipital — vision. The case of Phineas Gage tied the frontal lobe to personality and self-control.

12. Give two ways hormonal signaling differs from neural signaling, and explain why hormones are better suited to mood and stress.

Hormones travel through the bloodstream to the whole body (diffuse) and act slowly and for a long time; neural signals are fast, brief, and targeted to one cell. Because hormone effects linger, they set long-running states like mood — and sustained cortisol, as Selye showed, wears the body down.

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