Exam 2 Study Guide

This guide covers two chapters. First you will follow a signal from one neuron to the whole body. Then you will follow the mind through a full day and night, and see how drugs change it. Work one chapter at a time. Read the "what to know" part. Then cover the right side of each table and rebuild it from memory. Say each sequence out loud in order. End each chapter with its ten self-test items. The cram sheet at the end puts every name, number, and rule in one place.

Chapter 3Biopsychology

Read the full chapter: Chapter 3 · Biopsychology

What to know

Every thought and feeling is a physical event in living cells. The cell that does this work is the neuron. A neuron does three jobs in order. It receives, it decides, and it sends.

The dendrites receive signals. The cell body (soma) adds them up. If the total is big enough, the signal leaves down the axon. It ends at the terminal buttons, which pass it to the next cell. Many axons wear a fatty coat called myelin. The bare gaps in it are the nodes of Ranvier. The signal jumps from gap to gap. That jump is saltatory conduction, and it makes the signal fast. Helper cells called glial cells build myelin and care for neurons. There is about one glial cell per neuron in the brain overall.

At rest, the inside of a neuron sits at about −70 mV. This is the resting potential. Incoming signals push the voltage up or down. If they push it up to about −55 mV, the threshold, the neuron fires. Firing is the action potential. Sodium rushes in, and the inside turns positive. Then potassium flows out, and the voltage drops back. It dips a little below rest during the refractory period, when the cell cannot easily fire again.

The action potential is all-or-none. Every spike is the same size. So a strong stimulus does not make a bigger spike. It makes neurons fire more often, and it makes more neurons fire. Keep this rule close. Many exam questions test it.

At most junctions, neurons do not touch. The gap between them is the synaptic cleft, and the whole junction is the synapse. The spike makes vesicles spill neurotransmitter into the gap. The molecules bind to receptors on the next cell, like keys in locks. Then the signal is switched off. Enzymes break the neurotransmitter apart, or the sending cell takes it back. Taking it back is reuptake.

Drugs change this hand-off in two main ways. An agonist turns a neurotransmitter's action up. It may copy it, boost its release, or block its reuptake. An antagonist turns the action down, often by plugging the receptor. SSRIs block serotonin reuptake, so they are agonists. Many antipsychotics block dopamine receptors, so they are antagonists. Naloxone blocks opioid receptors and can reverse an overdose.

The nervous system splits in twos. The central nervous system is the brain and spinal cord. The peripheral nervous system is every other nerve. The peripheral side splits into the somatic system, for muscles you move on purpose, and the autonomic system, for automatic jobs. The autonomic side splits again. The sympathetic branch powers fight-or-flight. The parasympathetic branch brings back rest-and-digest.

Read the brain from the bottom up. The hindbrain holds the medulla (heartbeat and breathing), the pons (sleep and arousal), and the cerebellum (balance and smooth movement). The midbrain sits above it. The midbrain, pons, and medulla form the brainstem. The forebrain holds the thalamus (sense relay), the hypothalamus (hunger, thirst, temperature, hormones), the amygdala (fear), and the hippocampus (new memories). Over it all lies the cerebral cortex, with four lobes.

The two halves of the cortex differ in some jobs. This is lateralization. For most people, language sits mostly on the left. Each half controls the opposite side of the body. The corpus callosum links the halves. When it was cut to stop severe seizures, Sperry and Gazzaniga found that each half could know things the other did not. But the idea of "left-brained" and "right-brained" people is a myth. Healthy halves work as a team. The brain can also rewire itself, which is plasticity.

The endocrine system is the body's slower message service. Its glands release hormones into the blood. Hormones are slower than nerve signals, spread through the whole body, and last longer. The hypothalamus directs the pituitary, the "master gland." In stress, the chain runs from the hypothalamus to the pituitary to the adrenal glands, which release cortisol. Hans Selye showed that weeks of this wear the body down. He called the pattern the general adaptation syndrome: alarm, resistance, exhaustion.

The action potential, drawn

The parts worth memorizing

Neurotransmitters worth memorizing

The nervous system, drawn

The brain, drawn

The glands worth memorizing

Sequences, in order

A neuron fires.

1. The cell rests at about −70 mV.
2. Incoming signals push it up to threshold, about −55 mV.
3. Sodium gates open and sodium rushes in. The inside turns positive, up to about +30 mV.
4. Sodium gates shut. Potassium flows out, and the voltage falls.
5. The voltage dips a little below rest. The refractory period keeps the signal moving one way.
6. The cell settles back to rest, ready to fire again.

A signal crosses the synapse.

1. The spike reaches the terminal buttons.
2. Vesicles spill neurotransmitter into the synaptic cleft.
3. The molecules bind to receptors on the next neuron.
4. The signal is switched off by enzymes or by reuptake.

The stress chain (HPA axis).

1. The hypothalamus senses stress and signals the pituitary.
2. The pituitary sends a hormone (ACTH) through the blood.
3. The adrenal glands release cortisol.
4. A short burst helps. Weeks of it lead through alarm, resistance, and exhaustion.

How to reason through the question types

Chapter 4States of Consciousness

Read the full chapter: Chapter 4 · States of Consciousness

What to know

Consciousness is your awareness of what is going on inside you and around you. It is not on or off. It is a continuum. At the top is controlled processing, the effortful focus you use to learn something new. Lower down is automatic processing, the autopilot of a practiced skill. Sleep lowers awareness further, and anesthesia further still. Even then the brain keeps checking the world. Selective attention shows that awareness is a narrow spotlight.

The body runs on clocks called biological rhythms. A circadian rhythm lasts about 24 hours. An ultradian rhythm is shorter than a day, like the 90-minute sleep cycle. An infradian rhythm is longer than a day, like the menstrual cycle.

The master clock is the suprachiasmatic nucleus (SCN) in the hypothalamus. Light reaching the eyes keeps it on time. Cues that reset it are zeitgebers. The SCN tells the pineal gland when to release melatonin, the darkness hormone. Melatonin rises in the evening and peaks in the night. Light holds it back. That is why bright light late at night can delay sleep, and why jet lag happens after crossing time zones.

A second force also controls sleep. While you are awake, adenosine builds up in the brain. It creates sleep pressure. Sleep clears it. Borbély's two-process model puts the two forces together. Process S is sleep pressure. Process C is the clock's wake signal. Caffeine blocks adenosine receptors, so you feel less pressure until it wears off.

Why sleep at all? Three theories fit together. The restorative theory says sleep repairs the body and brain. The adaptive theory says sleep saves energy and keeps animals safe. The memory-consolidation theory says sleep stores what you learned.

The EEG shows the stages of sleep. Awake and alert, it shows beta waves. Relaxed with eyes closed, it shows alpha waves. N1 is light sleep with theta waves and the occasional hypnic jerk. N2 has sleep spindles and K-complexes and fills about half the night. N3 is deep sleep with slow delta waves. REM sleep has wake-like waves, rapid eye movements, and vivid dreams, while the body is paralyzed. That is why it is called paradoxical sleep. Aserinsky and Kleitman discovered REM in 1953.

One cycle takes about 90 minutes. You go through four to six a night. Deep N3 sleep fills the early cycles. REM periods get longer toward morning. So a short night takes away mostly REM. Waking out of deep N3 causes sleep inertia, a heavy fog.

Freud said dreams are hidden wishes. The story you remember is the manifest content. The hidden meaning is the latent content. His claims have little support today. The activation-synthesis hypothesis of Hobson and McCarley says the cortex builds a story from random signals during REM. The information-processing view says dreams help sort the day.

Sleep can go wrong in many ways. Insomnia is ongoing trouble falling or staying asleep. The first treatment to try is CBT-I. Sleep apnea means breathing stops again and again, often treated with CPAP. Narcolepsy brings sudden sleep attacks, often with cataplexy. Parasomnias are unusual events in sleep. Sleepwalking and night terrors come from deep N3. REM sleep behavior disorder means acting out dreams. Sleep paralysis means waking while REM paralysis lingers.

A psychoactive drug changes perception, mood, or awareness by acting at the synapse. Many misused drugs flood the dopamine reward pathway. There are four families. Depressants slow the nervous system. Stimulants speed it up. Opioids act on endorphin receptors and slow breathing. Hallucinogens change perception. With repeated use comes tolerance, where the same dose does less. Dependence can be physical, with withdrawal, or psychological, with craving. When use becomes compulsive despite harm, the DSM-5-TR calls it a substance use disorder. Mixing opioids with alcohol adds up the slowing of breathing. Naloxone can reverse an opioid overdose.

The rhythms worth memorizing

Two forces behind sleepiness, drawn

The stages of sleep

The sleep disorders worth memorizing

The drug families worth memorizing

Sequences, in order

Light sets the clock.

1. Light reaches special cells in the retina.
2. They signal the SCN in the hypothalamus.
3. The SCN signals the pineal gland.
4. In daylight, melatonin stays low. In darkness, it rises and you get sleepy.

One sleep cycle.

1. N1: drifting off, theta waves.
2. N2: true sleep, spindles and K-complexes.
3. N3: deep sleep, delta waves.
4. Back up through N2.
5. REM: dreams, eye movements, body paralyzed. Then the cycle repeats, about every 90 minutes.

How to reason through the question types