Source: Exam 1 Study Guide | General Psychology, The Ohio State University
Difficulty: Introductory to Intermediate | Prerequisites: Unit 1 (Research Methods). Understanding how experiments work will help you evaluate the brain studies discussed here.
This unit zooms into the biological machinery behind behaviour. Everything you will study later, from perception to sleep to addiction, rests on how neurons communicate and how different brain regions contribute to different functions. You do not need a biology background, but you do need to learn the basic vocabulary: how a single neuron fires, how signals cross from one neuron to the next, and which brain structures are responsible for what. If someone asks "why does damage to the amygdala change emotional behaviour?", this unit gives you the answer.
Neurons communicate through electrical signals (action potentials) within the cell and chemical signals (neurotransmitters) between cells. The brain is organised into specialised regions: the amygdala handles fear and emotion, the four cortical lobes handle everything from movement to planning, and the spinal cord relays information between the brain and the body.
Neuron
A nerve cell that receives, processes, and transmits information through electrical and chemical signals. The basic building block of the nervous system.
Dendrites
Branching extensions of the neuron that receive incoming signals from other neurons. Think of them as antennae picking up messages.
Cell body (soma)
The central part of the neuron containing the nucleus. Integrates incoming signals and keeps the cell alive.
Axon
A long fibre extending from the cell body that carries electrical impulses (action potentials) away from the soma toward other neurons.
Myelin sheath
A fatty insulating layer around the axon that speeds up electrical transmission. Produced by glial cells. Gaps in the myelin are called nodes of Ranvier.
Terminal buttons (axon terminals)
Small structures at the end of the axon that release neurotransmitters into the synapse.
Action potential
A brief electrical charge that travels down the axon when a neuron fires. It follows an all-or-nothing principle: the neuron either fires completely or not at all. Think of it as a domino chain, once it starts, it goes all the way.
Resting potential
The electrical charge of a neuron when it is not firing, typically around -70 millivolts. The inside of the cell is negatively charged relative to the outside.
Refractory period
A brief interval after an action potential during which the neuron cannot fire again (absolute refractory period) or requires a stronger-than-normal stimulus to fire (relative refractory period). This ensures signals travel in one direction.
Synapse
The tiny gap between the terminal button of one neuron and the dendrite of the next. This is where chemical communication happens.
Neurotransmitter
A chemical messenger released from the terminal buttons into the synapse. It binds to receptors on the receiving neuron and either excites or inhibits it.
Reuptake
The process by which neurotransmitters are reabsorbed by the sending neuron after they have done their job. Many psychiatric drugs work by blocking reuptake (e.g. SSRIs block serotonin reuptake).
Spinal cord
A bundle of nerves running through the vertebral column that relays messages between the brain and the rest of the body. Also handles simple reflexes without input from the brain.
Amygdala
A small almond-shaped structure in the temporal lobe involved in processing fear, aggression, and other emotions. Damage to the amygdala impairs fear recognition.
Frontal lobe
The cortical lobe at the front of the brain. Responsible for planning, decision-making, personality, voluntary movement (motor cortex), and speech production (Broca's area).
Parietal lobe
Located behind the frontal lobe. Processes sensory information such as touch, temperature, and pain (somatosensory cortex). Also involved in spatial awareness.
Temporal lobe
Located on the sides of the brain, near the ears. Handles auditory processing, language comprehension (Wernicke's area), and memory.
Occipital lobe
Located at the back of the brain. The primary area for visual processing.
Dendrites receive signals from other neurons.
Cell body (soma) integrates those signals. If the combined input is strong enough, the neuron fires.
Axon carries the action potential away from the cell body toward the terminal buttons.
Myelin sheath insulates the axon and speeds transmission. The signal "jumps" between the gaps (nodes of Ranvier) in a process called saltatory conduction.
Terminal buttons release neurotransmitters into the synapse.
The direction of information flow is always: dendrites → cell body → axon → terminal buttons → synapse.
At rest, the neuron sits at about -70 mV (resting potential). The inside of the cell is negatively charged relative to the outside.
When a neuron receives enough excitatory input to reach its threshold (about -55 mV), an action potential fires.
The action potential is all-or-nothing: it either fires at full strength or does not fire at all. You cannot have a "half" action potential.
After firing, the neuron enters a refractory period during which it resets. The absolute refractory period means the neuron cannot fire no matter how strong the stimulus. The relative refractory period means it can fire, but only with a stronger-than-normal stimulus.
The refractory period ensures the action potential travels in one direction (from cell body to terminal buttons) and limits the rate of firing.
When the action potential reaches the terminal buttons, it triggers the release of neurotransmitters into the synapse.
Neurotransmitters cross the synapse and bind to receptors on the dendrites of the receiving neuron.
If the neurotransmitter is excitatory, it makes the receiving neuron more likely to fire. If it is inhibitory, it makes the receiving neuron less likely to fire.
After the signal is sent, neurotransmitters are cleared from the synapse. The main mechanism is reuptake, where the sending neuron reabsorbs the neurotransmitter.
Drugs that block reuptake (such as SSRIs for depression) increase the amount of neurotransmitter lingering in the synapse, amplifying its effect.
Acts as the main information highway between the brain and the peripheral nervous system.
Manages simple reflexes independently. When you touch a hot surface, the withdrawal reflex is handled by the spinal cord before the pain signal even reaches your brain.
Amygdala: fear, emotional processing, threat detection. Damage impairs the ability to recognise fear in facial expressions.
Hippocampus: formation of new long-term memories. Damage leads to anterograde amnesia (inability to form new memories).
Thalamus: relay station for sensory information (except smell). Routes incoming signals to the correct cortical area.
Hypothalamus: regulates basic drives such as hunger, thirst, body temperature, and the endocrine system.
Cerebellum: coordination, balance, motor learning. Located at the back of the brain, beneath the occipital lobe.
Brain stem: controls basic life functions (breathing, heart rate, arousal).
Frontal lobe (front): executive functions, planning, decision-making, personality, voluntary movement (primary motor cortex), speech production (Broca's area).
Parietal lobe (top-middle): somatosensory processing (touch, temperature, pain), spatial awareness.
Temporal lobe (sides): auditory processing, language comprehension (Wernicke's area), some memory functions. Houses the amygdala and hippocampus.
Occipital lobe (back): visual processing. Damage here can cause blindness even if the eyes are fine.
Students often think neurons "touch" each other. They do not. The synapse is a gap, and communication across it is chemical, not electrical.
Students confuse the myelin sheath with the axon itself. The myelin is a layer wrapped around the axon; it speeds up the signal but does not carry it.
Students sometimes believe a stronger stimulus produces a bigger action potential. It does not: the action potential is all-or-nothing. A stronger stimulus increases the rate of firing (how many action potentials per second), not the size of each one.
Students mix up the amygdala and the hippocampus. The amygdala is about fear and emotion; the hippocampus is about memory formation. Both are in the temporal lobe, which may be the source of the confusion.
⚠️ Be able to trace the path of a signal through a neuron: dendrites → cell body → axon → terminal buttons → synapse → next neuron.
⚠️ Know the all-or-nothing principle and what happens during the refractory period.
⚠️ Understand reuptake and how blocking it changes neural communication.
⚠️ Be able to match brain structures to their functions, especially the amygdala and the four cortical lobes.
⚠️ Know the difference between excitatory and inhibitory neurotransmitters.
The fatty insulating layer around the axon is called the __________.
True or False: A neuron can fire a "weak" action potential if the stimulus is small.
The process by which neurotransmitters are reabsorbed by the sending neuron is called __________.
Which brain structure is most associated with processing fear? __________
True or False: The occipital lobe is primarily responsible for hearing.
Q: Describe the sequence of events from when a neuron receives a signal to when it communicates with the next neuron.
A: Dendrites receive the signal. If excitatory input is strong enough, the cell body initiates an action potential. The action potential travels down the axon (sped up by the myelin sheath). At the terminal buttons, neurotransmitters are released into the synapse. They bind to receptors on the next neuron's dendrites.
Q: What is the all-or-nothing principle?
A: A neuron either fires a full-strength action potential or does not fire at all. There is no partial firing. The intensity of a stimulus is coded by how frequently the neuron fires, not by the size of the action potential.
Q: How do SSRIs work in terms of neurotransmitter activity?
A: SSRIs (selective serotonin reuptake inhibitors) block the reuptake of serotonin. This means serotonin stays in the synapse longer and continues to stimulate the receiving neuron, increasing serotonergic activity.
Q: A patient with damage to the occipital lobe has healthy eyes but cannot see. Explain why.
A: The eyes can still detect light, but the occipital lobe is the brain area that processes visual information. Without a functioning occipital lobe, the brain cannot interpret the signals from the eyes, resulting in cortical blindness.
Q: What is the function of the refractory period?
A: It ensures the action potential travels in one direction (away from the cell body) because the segment that just fired cannot fire again immediately. It also limits how rapidly the neuron can fire.
This connects directly to Unit 3 (Sensation and Perception): the photoreceptors in the eye are specialised neurons, and the process of transduction is really about converting external energy into action potentials. It also feeds into Unit 4 (Consciousness), where brain waves during sleep are patterns of neural electrical activity, and drug effects on consciousness work through the neurotransmitter systems covered here.
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