Difficulty: Intermediate | Prerequisites: Research Methods notes
This section covers the biological machinery behind behaviour: the nervous system, the brain, neurons, and chemical signalling. It is the most anatomy-heavy portion of the midterm. You need to know structures by name, where they sit, and what happens when they are damaged. The endocrine system and neurotransmitter functions round out the picture. If you can trace a signal from dendrite to axon terminal and name what happens at the synapse, you are in good shape.
Behavioral neuroscience studies how the brain, nervous system, and chemical messengers produce behaviour. The central nervous system (brain and spinal cord) handles processing and decision-making; the peripheral nervous system relays information to and from the body; and the endocrine system uses hormones for slower, longer-lasting communication. At the cellular level, neurons transmit signals electrically within the cell and chemically across synapses, and knowing the major neurotransmitters and what they do is essential for this exam.
Histology
The microscopic study of tissue structure. In neuroscience, histology involves slicing and staining brain tissue to examine cells after death.
Electroencephalogram (EEG)
A non-invasive technique that records electrical activity across the scalp using electrodes. Excellent temporal resolution (millisecond-level), poor spatial resolution.
Event-related potential (ERP)
A measured brain response (derived from EEG) that is a direct result of a specific sensory, cognitive, or motor event. Think of it as the brain's electrical signature for a particular stimulus.
Positron emission tomography (PET)
An imaging technique in which a radioactive tracer is injected and its uptake is measured to show which brain areas are metabolically active. Decent spatial resolution, poor temporal resolution.
Functional magnetic resonance imaging (fMRI)
Measures brain activity by detecting changes in blood oxygenation (the BOLD signal). Good spatial resolution, but the signal lags a few seconds behind actual neural activity.
Transcranial magnetic stimulation (TMS)
Uses magnetic pulses to temporarily stimulate or disrupt activity in a specific brain region. Can establish causal links between brain areas and behaviour.
Lesion
Damage to brain tissue, whether from injury, surgery, or disease. Studying what functions are lost after a lesion reveals what that brain area normally does.
Cerebrospinal fluid (CSF)
Clear fluid that surrounds the brain and spinal cord, providing cushioning, nutrients, and waste removal.
Spinal reflex
An automatic response to a stimulus that is processed at the spinal cord level without input from the brain. Example: the knee-jerk reflex.
Thalamus
The brain's sensory relay station. Nearly all sensory information (except smell) passes through the thalamus on its way to the cerebral cortex.
Hypothalamus
A small structure below the thalamus that regulates basic drives: hunger, thirst, body temperature, sexual behaviour, and the endocrine system via the pituitary gland.
Hippocampus
Critical for forming new long-term memories, particularly declarative (explicit) memories. Damage to the hippocampus impairs the ability to create new memories.
Amygdala
Plays a central role in processing emotions, especially fear and threat detection. Also involved in emotional memory.
Basal ganglia
A group of subcortical structures involved in voluntary motor control, habit formation, and reward processing.
Nucleus accumbens
Part of the brain's reward circuit. Strongly associated with pleasure, motivation, and the reinforcing effects of drugs.
Corpus callosum
The thick bundle of nerve fibres connecting the left and right cerebral hemispheres, allowing them to communicate.
Broca's area
A region in the left frontal lobe involved in speech production. Damage leads to Broca's aphasia: difficulty producing fluent speech, though comprehension is largely intact.
Wernicke's area
A region in the left temporal lobe involved in language comprehension. Damage leads to Wernicke's aphasia: fluent but meaningless speech, with impaired comprehension.
Prefrontal cortex
The front-most part of the frontal lobe, responsible for executive functions: planning, decision-making, impulse control, and personality expression.
Hemispatial neglect (unilateral neglect)
A condition, usually following right parietal lobe damage, in which the patient fails to attend to or acknowledge stimuli on the left side of space.
Mirror neurons
Neurons that fire both when an individual performs an action and when they observe someone else performing the same action. Thought to support imitation and understanding others' intentions.
Sympathetic nervous system
The branch of the autonomic nervous system that activates the fight-or-flight response: increases heart rate, dilates pupils, diverts blood to muscles.
Parasympathetic nervous system
The branch that promotes "rest and digest" functions: slows heart rate, stimulates digestion, conserves energy.
Hormones
Chemical messengers released by endocrine glands into the bloodstream. They act more slowly than neurotransmitters but their effects last longer.
Dendrites
Branching extensions of the neuron that receive incoming signals from other neurons.
Axon
The long fibre extending from the cell body that carries electrical impulses away from the cell body toward other neurons, muscles, or glands.
Myelin sheath
A fatty insulating layer around the axon (produced by glial cells) that speeds up electrical transmission via saltatory conduction.
Action potential
A brief electrical charge that travels down the axon when the neuron fires. It is all-or-nothing: the neuron either fires at full strength or does not fire at all.
Resting potential
The electrical charge of a neuron when it is not firing (approximately -70 millivolts). The inside of the cell is negatively charged relative to the outside.
Synapse
The tiny gap between the axon terminal of one neuron and the dendrite (or cell body) of the next. Chemical neurotransmitters carry the signal across this gap.
Neurotransmitter
A chemical messenger released at the synapse that binds to receptors on the receiving neuron. Different neurotransmitters have different effects on the target cell.
Reuptake
The process by which a neurotransmitter is reabsorbed by the sending neuron after it has done its job. Many drugs work by blocking reuptake (e.g. SSRIs block serotonin reuptake).
Biological psychology (also called behavioural neuroscience) studies the links between the nervous system and behaviour. Early work relied on lesion studies and post-mortem histology; modern methods let researchers observe the living brain in action.
Histology: microscopic examination of stained brain slices. Useful for identifying cell types and structures, but requires tissue removal (typically post-mortem).
Skin conductance response: measures electrical conductance of the skin, which changes with sweat gland activity. Used as a proxy for arousal or emotional response.
EEG (electroencephalogram): records electrical activity via scalp electrodes. Superb time resolution, poor spatial resolution. Used to study sleep stages, seizures, and cognitive processing.
ERP (event-related potential): averaging many EEG trials time-locked to a stimulus to reveal a brain response specific to that event.
Single-cell recording: an electrode inserted into the brain records the firing of one neuron. Invasive, so primarily used in animal research.
Magnetoencephalography (MEG): measures the magnetic fields produced by neural activity. Better spatial resolution than EEG, still excellent temporal resolution.
PET (positron emission tomography): uses a radioactive tracer to map metabolic activity. Shows which regions are active during a task. Lower temporal and spatial resolution than fMRI.
fMRI (functional magnetic resonance imaging): detects changes in blood oxygen level (BOLD signal) to infer neural activity. Good spatial resolution, moderate temporal lag.
Electrical stimulation: applying a small current to a brain area during surgery to map functions (pioneered by Wilder Penfield).
TMS (transcranial magnetic stimulation): non-invasive magnetic pulses disrupt or stimulate a cortical region temporarily. Useful for establishing causal links.
Lesions: naturally occurring or experimentally produced brain damage. Observing what function is lost tells you what the area normally does.
Surrounds and cushions the brain and spinal cord. Delivers nutrients, removes waste, and maintains pressure.
Runs from the brainstem down the vertebral column.
Carries sensory information up to the brain and motor commands down to the body.
Handles spinal reflexes (e.g. withdrawal reflex) without waiting for brain input, which is why reflexes are so fast.
Medulla: controls vital automatic functions such as breathing, heart rate, and blood pressure. Damage here is often fatal.
Pons: involved in sleep, arousal, and relaying signals between the cerebellum and cortex.
Cerebellum: "little brain" at the back. Coordinates fine motor movements, balance, and motor learning. Damage produces clumsy, uncoordinated movement (ataxia).
Midbrain: processes auditory and visual information, and contains regions involved in movement and pain.
Reticular formation: a network running through the brainstem that regulates arousal, alertness, and sleep-wake transitions.
Thalamus: sensory relay station. Routes incoming sensory signals (except smell) to the appropriate cortical areas.
Basal ganglia: involved in initiating and regulating voluntary movement, procedural learning, and habit formation.
Hypothalamus: master regulator of basic drives (hunger, thirst, temperature, sex) and controls the endocrine system via the pituitary gland.
Hippocampus: essential for forming new explicit (declarative) memories. Damage does not erase old memories but prevents the formation of new ones.
Cingulate cortex: the anterior cingulate is involved in error detection, conflict monitoring, and emotional regulation. The posterior cingulate is part of the default mode network (active during rest and mind-wandering).
Amygdala: processes emotional information, particularly fear. Damage can reduce fear responses and impair emotional memory.
Nucleus accumbens: key node in the reward pathway. Activated by pleasurable stimuli and involved in motivation and addiction.
The corpus callosum is the massive fibre bundle connecting the two hemispheres.
In split-brain operations (corpus callosum severed, historically done to treat severe epilepsy), the hemispheres can no longer share information directly. Classic experiments by Sperry and Gazzaniga showed that each hemisphere has distinct capabilities.
Frontal lobe
Contains the primary motor cortex (controls voluntary movement) and the prefrontal cortex (executive function: planning, decision-making, impulse control).
Broca's area (left frontal lobe): speech production. Damage produces effortful, telegraphic speech with intact comprehension.
The case of Phineas Gage: an iron rod destroyed much of his prefrontal cortex (specifically the orbitofrontal cortex). He survived but his personality changed dramatically, becoming impulsive and socially inappropriate. This was early evidence that the frontal lobe is involved in personality and self-regulation.
Orbitofrontal cortex: involved in decision-making, reward evaluation, and social behaviour.
Occipital lobe
Located at the back of the brain. Houses the primary visual cortex. Damage can cause blindness even if the eyes are intact.
Temporal lobe
Involved in auditory processing, memory, and language comprehension.
Wernicke's area (left temporal lobe): language comprehension. Damage produces fluent but nonsensical speech and difficulty understanding language.
Parietal lobe
Processes sensory information (touch, temperature, pain) via the somatosensory cortex.
Hemispatial neglect / unilateral neglect: damage to the right parietal lobe can cause the patient to ignore everything on the left side of their visual field. They may eat food only from the right side of a plate or draw only the right half of a clock.
Mirror neurons fire both when performing an action and when watching someone else perform it. They may underlie empathy and imitation.
Lateralization refers to the tendency for certain functions to be more strongly represented in one hemisphere (e.g. language is typically left-lateralised).
Right brain / left brain myths: popular culture overstates hemispheric differences. While some specialisation exists, the two hemispheres work together on nearly every task. Nobody is purely a "right-brain" or "left-brain" thinker.
The PNS connects the CNS to the rest of the body. It has two main divisions.
Controls voluntary movements by carrying motor commands from the CNS to skeletal muscles.
Also carries sensory information from the body back to the CNS.
Controls involuntary functions (heart rate, digestion, breathing). It has three branches:
Sympathetic nervous system: the "accelerator." Activates the fight-or-flight response: heart rate up, pupils dilated, digestion suppressed, glucose released, blood routed to muscles. Prepares you for action.
Parasympathetic nervous system: the "brake." Promotes rest-and-digest: slows heart rate, stimulates digestion, conserves energy. Returns the body to homeostasis after the threat passes.
Enteric nervous system: a mesh of neurons lining the gastrointestinal tract. Sometimes called the "second brain" because it can operate somewhat independently of the CNS, managing digestion locally.
The endocrine system communicates through hormones, chemical messengers secreted by glands into the bloodstream. Compared with the nervous system, hormonal signalling is slower to start but longer-lasting.
Pineal gland: secretes melatonin, which helps regulate sleep-wake cycles (circadian rhythms).
Pituitary gland: the "master gland." Controlled by the hypothalamus, it releases hormones that direct other glands (growth hormone, oxytocin, vasopressin, and others).
Thyroid gland: secretes thyroid hormones that regulate metabolism, energy levels, and growth.
Adrenal glands: sit atop the kidneys. The adrenal medulla releases adrenaline (epinephrine) and noradrenaline during fight-or-flight. The adrenal cortex releases cortisol (a stress hormone).
Ovaries and testes: produce sex hormones (oestrogen, progesterone, testosterone) that influence sexual development, reproduction, and some behaviours.
Islets of Langerhans (in the pancreas): produce insulin and glucagon, regulating blood sugar levels.
Dendrites: receive incoming signals from other neurons.
Cell body (soma): contains the nucleus and keeps the cell alive. Integrates incoming signals.
Axon: carries the electrical impulse (action potential) away from the cell body toward the axon terminals.
Axon terminals: the endpoints of the axon, where neurotransmitters are released into the synapse.
Myelin sheath: a fatty insulating layer wrapped around the axon in segments. Produced by glial cells (oligodendrocytes in the CNS, Schwann cells in the PNS). Speeds up signal transmission by allowing the impulse to jump between gaps in the myelin (nodes of Ranvier), a process called saltatory conduction.
Sensory neurons (afferent): carry information from the senses toward the CNS.
Motor neurons (efferent): carry commands from the CNS to muscles and glands.
Interneurons: connect sensory and motor neurons within the CNS. The vast majority of neurons in the brain are interneurons.
Resting potential (~-70 mV): the neuron at rest is polarised, with the inside more negative than the outside.
Reaching threshold: when excitatory input pushes the membrane potential to about -55 mV, voltage-gated sodium channels open and an action potential fires.
Action potential: a rapid depolarisation (inside goes positive), followed by repolarisation. The signal travels down the axon in an all-or-nothing fashion.
Refractory period: a brief interval after firing during which the neuron cannot fire again (absolute) or requires a stronger-than-normal stimulus (relative). This prevents the signal from travelling backward.
Advantages of myelin: faster conduction speed, lower energy cost, and more efficient long-distance signalling.
When the action potential reaches the axon terminals, it triggers the release of neurotransmitters into the synapse.
Neurotransmitters cross the synaptic gap and bind to receptors on the receiving neuron.
Binding can produce an excitatory effect (making the receiving neuron more likely to fire) or an inhibitory effect (making it less likely to fire).
Summation: the receiving neuron adds up all excitatory and inhibitory inputs; if the net result reaches threshold, it fires.
Reuptake: unused neurotransmitter is taken back up by the sending neuron for recycling. Many psychoactive drugs work by altering reuptake (e.g. SSRIs block serotonin reuptake, leaving more serotonin in the synapse).
Acetylcholine (ACh): involved in muscle contraction, attention, and memory. Depletion is associated with Alzheimer's disease.
Norepinephrine (noradrenaline): regulates arousal, alertness, and the fight-or-flight response. Also plays a role in mood.
Dopamine: central to reward, motivation, movement, and pleasure. Implicated in Parkinson's disease (too little in motor pathways) and schizophrenia (too much in certain pathways).
Serotonin: influences mood, sleep, appetite, and impulse control. Low serotonin activity is linked to depression and anxiety.
Endorphins (endogenous morphine): the body's natural painkillers. Released during exercise, stress, and pain. Produce feelings of well-being.
Glutamate: the most abundant excitatory neurotransmitter in the brain. Essential for learning and memory. Excess glutamate can be toxic to neurons (excitotoxicity).
GABA (gamma-aminobutyric acid): the most abundant inhibitory neurotransmitter. Calms neural activity. Drugs that enhance GABA (e.g. benzodiazepines, alcohol) have sedating, anti-anxiety effects.
Students often believe you are either a "right-brain person" or a "left-brain person." In reality, both hemispheres collaborate on virtually every task. Lateralisation exists, but it is a matter of degree, not exclusivity.
The idea that "we only use 10% of our brain" is a myth. Imaging studies show that virtually all brain areas are active over the course of a day.
Students sometimes confuse the sympathetic and parasympathetic systems. A useful mnemonic: sympathetic = stress (fight or flight); parasympathetic = peace (rest and digest).
Neurotransmitters are not simply "good" or "bad." Dopamine, for instance, is involved in both the pleasure of eating and the hallucinations of schizophrenia, depending on which pathway is affected.
⚠️ Know the function of each major brain structure (especially thalamus, hypothalamus, hippocampus, amygdala, and prefrontal cortex).
⚠️ Be able to identify which lobe processes which type of information (occipital = vision, temporal = hearing/language comprehension, parietal = somatosensory, frontal = motor/executive).
⚠️ Understand the difference between Broca's aphasia and Wernicke's aphasia: production vs. comprehension.
⚠️ Know the steps of neural signalling: resting potential, threshold, action potential, neurotransmitter release, receptor binding, reuptake.
⚠️ Be able to match neurotransmitters to their primary functions (ACh and memory, dopamine and reward, serotonin and mood, GABA and inhibition, glutamate and excitation).
⚠️ Understand the difference between the sympathetic and parasympathetic divisions.
True or false: The hippocampus is primarily responsible for processing fear.
Fill in the blank: The ______ is the brain's sensory relay station.
True or false: An action potential is graded, meaning its strength varies with stimulus intensity.
Fill in the blank: ______ is the most common inhibitory neurotransmitter in the brain.
True or false: Damage to Broca's area produces fluent but meaningless speech.
Answers: 1. False (that is the amygdala; the hippocampus is involved in memory). 2. Thalamus. 3. False (action potentials are all-or-nothing). 4. GABA. 5. False (damage to Broca's area produces non-fluent, effortful speech; fluent meaningless speech is Wernicke's aphasia).
Q: A patient suffers a stroke that damages the right parietal lobe. What deficit would you expect, and why?
A: Hemispatial neglect (unilateral neglect) on the left side. The patient would fail to attend to objects and events in the left visual field, because the right parietal lobe processes spatial attention for the left side of space.
Q: Explain why severing the corpus callosum can cause a patient to be unable to name an object placed in their left hand (with eyes closed).
A: Touch information from the left hand goes to the right hemisphere. Language production (naming) is primarily a left-hemisphere function. With the corpus callosum cut, the right hemisphere cannot relay the tactile information to the left hemisphere for naming.
Q: How does reuptake influence the effect of a neurotransmitter, and how do SSRIs exploit this process?
A: Reuptake removes neurotransmitter from the synapse, ending its effect on the receiving neuron. SSRIs (selective serotonin reuptake inhibitors) block the reuptake of serotonin, leaving more serotonin available in the synapse for longer, which can improve mood in people with depression.
Q: What is the functional difference between the sympathetic and parasympathetic nervous systems? Give one example of each.
A: The sympathetic system activates the body for emergency action (e.g. increasing heart rate before a confrontation). The parasympathetic system calms the body and promotes maintenance functions (e.g. stimulating digestion after a meal).
Behavioural neuroscience connects directly to sensation and perception (the visual pathway runs from retina through the thalamus to the occipital cortex) and to consciousness (EEG wave patterns define sleep stages, the reticular formation regulates arousal, and the hypothalamus controls circadian rhythms). Understanding neural signalling also matters for the psychoactive drugs section in the consciousness unit, because most drugs work by altering neurotransmitter activity at the synapse.
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