Neuroscience

~14 mins

Neuroscience is the study of the nervous system — the brain, spinal cord, and nerves that control our thoughts, movements, and senses. Think of it as the wiring and software of your body combined: it both carries signals (like an electrical system) and processes them (like a computer). Neuroscience connects deeply to everyday life — every laugh, memory, decision, and reflex is your nervous system at work. From the dopamine hit of seeing a like on social media, to the hippocampus recalling yesterday's chat, to the cerebellum balancing you as you climb stairs — neuroscience is not abstract. It's you, living moment to moment, powered by 86 billion neurons.

1) The nervous system has two main divisions that work together to control your body. The central nervous system (CNS) is the control centre, made up of the brain and spinal cord — think of it as your body's headquarters where all major decisions are made. The peripheral nervous system (PNS) is like the wiring that connects the CNS to the rest of your body — muscles, skin, and organs, carrying messages back and forth. For example, if you touch something hot, the PNS sends that danger signal to your CNS, which immediately tells your hand to pull back. This division allows for both centralised processing and distributed sensing throughout your entire body.

2) The brain, though it weighs only about 1.3–1.4 kg (roughly 2% of your body weight), uses 20% of your body's total energy consumption. That's why after long study sessions or deep conversations, you feel genuinely tired — your brain literally burns fuel in the form of glucose and oxygen while processing information. This massive energy requirement reflects the brain's incredible activity: even when you're "doing nothing," billions of neurons are constantly firing, maintaining consciousness, processing sensory input, and keeping vital functions running. The brain's energy demands are so high that it has priority access to glucose in your bloodstream.

3) The basic working unit of the nervous system is the neuron, or nerve cell. You have approximately 86 billion of them in your brain alone — more than there are stars in the Milky Way galaxy. Neurons don't look like ordinary cells: they have specialised structures including branch-like dendrites to receive information and long fibres called axons to send it out. Each neuron can connect to thousands of others, creating an incredibly complex network. The word "neuron" comes from Greek meaning "nerve," and these cells are uniquely designed for rapid communication across long distances in your body.

4) Each neuron has dendrites, the branch-like structures that receive incoming signals from other neurons. You can imagine dendrites as the "ears" of a neuron, constantly listening to chemical messages from neighbouring cells. Dendrites can be incredibly complex, with thousands of branches creating tree-like structures that maximise the surface area for receiving signals. For example, when you see your phone light up, photoreceptor neurons in your eyes send signals that are received by dendrites of visual-processing neurons in your brain. The more dendrites a neuron has, the more input it can integrate from other cells.

5) The cell body (or soma) of the neuron is the central hub that processes all incoming messages and decides what to do with them. It contains the nucleus with the cell's DNA and most organelles, making it like the "brain inside the brain cell." The cell body integrates all the signals coming in through dendrites — some excitatory (encouraging the neuron to fire) and some inhibitory (discouraging firing). If enough excitatory input accumulates and overcomes the inhibitory signals, reaching a critical threshold, the neuron will generate an action potential. This decision-making process happens in milliseconds and determines whether information gets passed along the neural network.

6) The axon is a long fibre that carries signals away from the cell body, functioning like the neuron's "mouth" or transmission cable. Axons vary dramatically in length: some are tiny (less than a millimetre long in your brain), while others stretch over a metre, carrying signals from your spinal cord all the way down to your toes. When you decide to kick a football, motor neurons send action potentials down axons that can be nearly a metre long to reach your leg muscles. The longest axons in your body belong to sensory neurons that carry touch information from your feet to your brain — they can be over a metre long in tall people.

Related: Axons | Motor Neurons | Sensory Neurons

7) Axons transmit information using electrical pulses called action potentials, which are not like lightning bolts but rather waves of charged particles (ions) moving in and out of the axon's membrane. These electrical signals travel at speeds up to 120 metres per second in the fastest axons. When you type on a keyboard, millions of action potentials zip through axons in your hands, arms, and brain every second, coordinating the precise finger movements needed for each keystroke. The action potential is an all-or-nothing event — it either happens completely or not at all, like a light switch that's either on or off.

8) To speed up signal transmission, many axons are wrapped in myelin, a fatty white substance that acts like insulation around electrical wires. Myelin allows action potentials to "jump" between gaps (called nodes of Ranvier) rather than travelling continuously, increasing speed by up to 100 times. This is why you can move your hand almost instantly after deciding to — the myelinated axons carry the signal from your brain to your muscles in milliseconds. In diseases like multiple sclerosis, the immune system attacks myelin, causing it to break down. This slows or blocks neural signals, leading to muscle weakness, coordination problems, and cognitive difficulties.

9) Neurons don't actually touch each other directly — they communicate across tiny gaps called synapses, which are about 20-40 nanometres wide (roughly 1/2000th the width of a human hair). When an action potential reaches the end of an axon (the axon terminal), it triggers the release of chemical messengers that cross this gap. Think of it like one person tossing a ball across a small space to another person — that "ball" is a neurotransmitter molecule crossing a synapse. Each neuron can have thousands of synapses, and your brain contains an estimated 100 trillion synaptic connections, making it the most complex network known to exist.

10) Neurotransmitters are the chemical messengers that allow neurons to communicate, and each type carries different "meanings" in the brain's language. Dopamine is linked to reward, motivation, and pleasure — when you check your phone and see a message from someone you love, dopamine is released in your brain's reward circuits. Serotonin helps stabilise mood and promote feelings of wellbeing; low serotonin levels are associated with depression. Acetylcholine plays crucial roles in both memory formation and muscle activation — without it, you couldn't form new memories or even blink your eyes. GABA is the brain's main inhibitory neurotransmitter, helping to calm neural activity and prevent overexcitation.

11) Synapses make the brain remarkably flexible through a process called synaptic plasticity — the ability of connections between neurons to strengthen or weaken based on activity. Each time you learn something new (a guitar chord, a math concept, a chess opening), the synapses involved in that learning become stronger and more efficient. This is the biological basis of the saying "practice makes perfect" — the more you repeat an activity, the stronger the neural wiring becomes. Conversely, unused connections weaken over time, which is why skills deteriorate without practice. This plasticity continues throughout life, allowing your brain to adapt and learn new things even in old age.

12) Neurons are supported by glial cells, which outnumber neurons by about 1:1 in the human brain. For centuries, scientists thought glial cells were just passive "glue" (glia means "glue" in Greek), but we now know they perform crucial active functions. Astrocytes regulate the chemical environment around synapses and help form the blood-brain barrier. Oligodendrocytes produce myelin in the brain and spinal cord. Microglia act as the brain's immune system, cleaning up cellular debris and fighting infections. Think of glial cells as the essential support staff that keep your brain's highways smooth and efficient — without them, neurons couldn't function properly.

13) The brain is divided into two hemispheres (left and right) connected by a thick bridge of nerve fibres called the corpus callosum, which contains about 200 million axons. While the "left brain logical, right brain creative" idea is oversimplified, there are some functional differences. The left hemisphere typically handles language processing, mathematical calculations, and sequential reasoning, while the right hemisphere is more involved in spatial awareness, music processing, and recognising faces. For example, when you're solving a math problem, your left hemisphere is more active; when you're drawing or listening to music, your right hemisphere takes more of the lead. However, most complex tasks require both hemispheres working together.

14) The outer layer of the brain is the cerebral cortex, a thin sheet of neural tissue (about 2-4mm thick) that's folded into ridges (gyri) and grooves (sulci) to maximise surface area. If you could unfold the cortex, it would cover about 2,500 square centimetres — roughly the size of a large pizza. These folds allow more neurons to fit into the limited space of your skull. The cortex contains about 16 billion neurons and is where higher-order thinking happens: planning your day, forming memories, solving problems, creating art, and having conversations. Every time you decide what to text someone or imagine what you'll have for dinner, you're using your cortex.

15) The cortex is divided into four main lobes, each with specialised functions. The frontal lobe (behind your forehead) controls executive functions like planning, decision-making, personality, and voluntary movement. The parietal lobe (top and back of head) processes touch, spatial awareness, and integrates sensory information. The temporal lobe (above your ears) handles hearing, language comprehension, and memory formation. The occipital lobe (back of head) is dedicated to visual processing. When you recognise your friend's voice on the phone, thank your temporal lobe; when you reach for your coffee cup without looking, thank your parietal lobe for knowing where your hand is in space.

16) The frontal lobe, particularly the prefrontal cortex, is crucial for personality and social behaviour. The famous case of Phineas Gage, a 19th-century railroad worker who survived an iron rod blasting through his skull and frontal lobe, demonstrated this dramatically. After his accident, Gage could still walk, talk, and remember things, but his personality changed completely — he became impulsive, rude, and unable to make good decisions. His case proved that the frontal lobe helps regulate social behaviour, emotional control, and long-term planning. The prefrontal cortex doesn't fully mature until around age 25, which explains why teenagers and young adults often struggle with impulse control and risk assessment.

17) The hippocampus, a seahorse-shaped structure deep in the temporal lobe, is essential for forming new long-term memories. Without functioning hippocampi, you can't convert short-term experiences into lasting memories. The famous patient H.M. (Henry Molaison) had both hippocampi surgically removed to treat severe epilepsy. Afterward, he could remember his childhood and hold conversations, but couldn't form new long-term memories — every day was like meeting people for the first time. When you remember a conversation from yesterday, a movie you watched last week, or where you put your keys, your hippocampus was involved in storing that information. The hippocampus is also one of the few brain regions where new neurons continue to be born throughout life.

18) The amygdala, an almond-shaped structure in the temporal lobe, is your brain's alarm system, specialising in detecting and responding to threats and emotional significance. It processes fear, anger, and other intense emotions, helping you react quickly to danger. If you jump when you see a spider, feel your heart race before giving a presentation, or instinctively step back from a cliff edge, your amygdala is firing. People with damaged amygdalas often struggle to recognise fear in others' facial expressions and may approach dangerous situations without appropriate caution. The amygdala can trigger emotional responses before your conscious mind even processes what you're seeing, which is why you might feel scared before you consciously realise what frightened you.

19) The basal ganglia are a group of structures deep in the brain that control movement initiation, coordination, and habit formation. They help you start and stop actions smoothly and learn automatic behaviours. Disorders affecting the basal ganglia include Parkinson's disease (causing tremors, stiffness, and slow movement) and Huntington's disease (causing uncontrolled movements and cognitive decline). When you tie your shoes, drive a familiar route, or brush your teeth without thinking about each movement, your basal ganglia are coordinating these well-learned motor sequences. The basal ganglia are also involved in motivation and reward processing, working closely with dopamine systems to reinforce behaviours that led to positive outcomes.

20) The cerebellum (meaning "little brain" in Latin) sits at the back of your skull and controls balance, coordination, and fine motor skills. Despite being only 10% of the brain's volume, it contains more than half of all neurons in the brain — about 50 billion neurons packed into its highly folded structure. The cerebellum allows you to ride a bike, play piano, or catch a ball without consciously thinking about each movement. It constantly receives information about your body's position and movement, making rapid adjustments to keep you balanced and coordinated. People with cerebellar damage often stagger when walking and have difficulty with precise movements, similar to appearing intoxicated.

21) The thalamus is the brain's central relay station, sitting at the top of the brainstem like a switchboard operator. All sensory information except smell passes through the thalamus before reaching the cortex for conscious processing. When you hear your phone's ringtone, sound signals travel from your ears to the thalamus, which then directs them to the appropriate areas of your auditory cortex to be processed as recognisable sound. The thalamus also plays roles in consciousness, sleep, and attention — damage to the thalamus can cause coma or altered states of consciousness. It acts like a gatekeeper, determining which sensory information gets through to conscious awareness and which gets filtered out.

22) The hypothalamus, though only about the size of an almond, regulates many of your body's most basic survival functions including hunger, thirst, body temperature, sleep-wake cycles, and hormone production. When you feel hungry, thirsty, tired, or too hot or cold, your hypothalamus is detecting these changes and initiating responses to restore balance (homeostasis). It controls the pituitary gland, often called the "master gland," which releases hormones that regulate growth, reproduction, stress response, and metabolism. The hypothalamus also contains your body's master clock, synchronising your circadian rhythms with the 24-hour day-night cycle based on light information from your eyes.

23) The brainstem (consisting of the midbrain, pons, and medulla oblongata) controls the automatic functions that keep you alive without conscious effort: breathing, heart rate, blood pressure, digestion, and arousal. You don't have to remember to breathe or tell your heart to beat — your brainstem handles these vital functions 24/7. The medulla contains centres that control breathing and heart rate; damage here is often fatal. The pons helps regulate sleep and arousal. The midbrain controls eye movements and reflexes. Even when you're in the deepest sleep, your brainstem continues working to keep you alive, which is why brainstem death is considered clinical death even if other brain areas might still show some activity.

Related: Brainstem | Medulla | Pons | Midbrain

24) The spinal cord is the major highway carrying messages between your brain and body, containing about 13.5 million neurons organised into specific pathways. Sensory pathways carry information up to the brain (like touch, pain, and position), while motor pathways carry commands down from the brain to muscles. The spinal cord also handles many reflexes independently — when you touch a hot stove, sensory neurons detect the heat, connect directly to motor neurons in the spinal cord, and cause your hand to pull back before your brain even processes the pain. This reflex arc can save you from serious injury by responding in milliseconds, much faster than if the signal had to travel all the way to your brain first.

25) Complex everyday actions depend on neural circuits that coordinate multiple brain areas working together seamlessly. When you walk across a room, your motor cortex initiates the movement, your cerebellum fine-tunes balance and coordination, your basal ganglia help sequence the movements automatically, your visual cortex processes what you see, and your somatosensory cortex provides feedback about your foot position and the ground beneath you. All of this happens without conscious effort because these neural circuits have been refined through years of practice. Similarly, having a conversation involves language areas (Broca's and Wernicke's areas), memory systems (hippocampus), emotional processing (amygdala), and executive control (prefrontal cortex) all working together.

26) Emotions are complex brain-body feedback loops that involve both neural processing and physical responses throughout your body. When you feel anxious before an exam, your amygdala detects the threat, your hypothalamus triggers stress hormones, your sympathetic nervous system increases heart rate and breathing, and your muscles tense up. This creates a feedback loop where physical sensations (racing heart, sweaty palms) can intensify the emotional experience. Nervous laughter, butterflies in your stomach, or feeling weak-kneed with fear all demonstrate how emotions involve your entire nervous system, not just your brain. Understanding this connection explains why physical techniques like deep breathing or exercise can help manage emotions.

27) Sleep is crucial for brain function and involves dramatic changes in neural activity patterns. During sleep, your brain doesn't just "turn off" — it actively strengthens important neural connections while pruning unused ones, consolidates memories from the day, and clears metabolic waste products. This is why you need adequate sleep to learn effectively and why all-night cramming sessions are generally ineffective. During REM (Rapid Eye Movement) sleep, your brain is nearly as active as when awake, which is when most vivid dreaming occurs. Sleep deprivation impairs attention, memory, decision-making, and emotional regulation, demonstrating that sleep is not optional but essential for optimal brain function.

28) Stress affects the brain through the activation of the hypothalamic-pituitary-adrenal (HPA) axis, your body's main stress response system. When you encounter a stressor (like an upcoming exam or work deadline), your amygdala signals danger to your hypothalamus, which triggers the release of stress hormones including cortisol and adrenaline. This fight-or-flight response was evolutionarily useful for avoiding predators, but modern stressors often can't be solved by fighting or fleeing. Chronic stress can damage the hippocampus (impairing memory), suppress immune function, and increase risk of anxiety and depression. However, moderate, short-term stress can actually enhance learning and performance by increasing focus and motivation.

29) Addiction involves the brain's reward system, particularly the mesolimbic dopamine pathway that evolved to reinforce behaviours necessary for survival like eating and reproduction. When you experience something pleasurable — whether it's food, social approval, exercise, or drugs — dopamine is released in brain areas like the nucleus accumbens, creating feelings of pleasure and motivation to repeat the behaviour. This system normally helps you learn what's good for you, but addictive substances and behaviours can hijack this pathway, creating unnaturally strong dopamine responses that train the brain to seek them compulsively. Over time, the brain adapts by reducing its natural dopamine response, requiring more of the addictive stimulus to achieve the same effect — this is tolerance.

30) Language processing involves several specialised brain regions working together, primarily in the left hemisphere for most people. Broca's area (in the frontal lobe) is crucial for speech production — damage here causes difficulty speaking fluently while comprehension remains intact. Wernicke's area (in the temporal lobe) is essential for language comprehension — damage here results in fluent but nonsensical speech. The arcuate fasciculus connects these areas, allowing coordination between understanding and producing speech. When you have a conversation, multiple brain networks activate simultaneously: auditory areas process the sounds, Wernicke's area extracts meaning, working memory holds information temporarily, and Broca's area formulates your response. Remarkably, bilingual people may use slightly different neural networks for each language.

31) Vision processing begins in the retina of your eyes but the real "seeing" happens in your brain, primarily in the occipital lobe at the back of your head. Light hitting your retina is converted into electrical signals by photoreceptor cells (rods and cones), which travel via the optic nerve to various brain areas. The primary visual cortex processes basic features like edges and movement, while higher visual areas recognise objects, faces, and spatial relationships. Remarkably, what you "see" is actually a construction created by your brain — it fills in blind spots, corrects for eye movements, and can even create visual experiences when no light is present (like in dreams or hallucinations). When you recognise your friend across the street, multiple visual processing streams work together to identify their face, judge distance, and track their movement.

32) Hearing involves converting sound waves (vibrations in air) into neural signals that your brain interprets as speech, music, or environmental sounds. Sound waves cause your eardrum to vibrate, which moves tiny bones in your middle ear, which in turn cause fluid in your inner ear (cochlea) to move. This movement stimulates hair cells that convert mechanical motion into electrical signals sent via the auditory nerve to your brainstem and then to your auditory cortex in the temporal lobe. Your brain can distinguish between thousands of different sounds, locate where sounds are coming from in 3D space, and separate meaningful sounds (like conversation) from background noise. The auditory system is so sensitive that it can detect movements smaller than the diameter of an atom.

33) The sense of touch is processed by the somatosensory cortex in the parietal lobe, where different body parts are represented in a "map" called the sensory homunculus. This map is distorted — body parts with more nerve endings (like hands, lips, and tongue) take up disproportionately more brain space than less sensitive areas (like your back or legs). This is why you can feel tiny textures with your fingertips but not with your elbow. Touch involves multiple types of receptors detecting pressure, vibration, temperature, and pain. Your brain integrates this information to create rich tactile experiences — like feeling the smooth coolness of a phone screen, the rough texture of sandpaper, or the gentle pressure of a handshake. Phantom limb sensations in amputees demonstrate how powerfully the brain's body map influences perception.

34) Smell (olfaction) is unique among the senses because it bypasses the thalamus and connects directly to brain regions involved in emotion and memory, including the amygdala and hippocampus. This direct connection explains why smells can instantly trigger vivid memories and strong emotions — like how your grandmother's perfume might immediately transport you back to childhood visits. Humans can distinguish between trillions of different odours using only about 400 types of olfactory receptors. Smell molecules dissolve in mucus in your nasal cavity and bind to these receptors, which send signals directly to the olfactory bulb and then to various brain areas. The close connection between smell, memory, and emotion is why certain scents can be so powerfully nostalgic or why loss of smell (anosmia) can significantly impact quality of life.

35) Taste involves much more than just your taste buds — it's actually a complex multisensory experience combining input from taste buds (detecting sweet, salty, sour, bitter, and umami), smell (which contributes most of what we call "flavour"), texture, temperature, and even sound. Your taste buds can only detect these five basic categories, but your brain combines this with smell information to create the rich variety of flavours you experience. This is why food tastes bland when you have a stuffy nose — you're missing the smell component. When you eat chocolate, multiple brain areas activate simultaneously: taste areas process sweetness, smell areas detect chocolate aroma, somatosensory areas feel texture and temperature, and reward areas release dopamine. The integration of these signals creates the complete experience of "chocolate flavour."

36) Mental health disorders often involve disruptions in brain chemistry, structure, or function, demonstrating the intimate connection between brain and mind. Depression is associated with imbalances in neurotransmitters like serotonin, dopamine, and norepinephrine, as well as changes in brain structure and connectivity. Anxiety disorders involve overactivity in the amygdala and altered communication between fear and control centres. Schizophrenia involves disrupted dopamine signalling and altered brain connectivity, affecting perception of reality. ADHD involves differences in prefrontal cortex function and dopamine systems that affect attention and impulse control. Understanding the neurobiological basis of mental health has led to more effective treatments and reduced stigma by showing these are medical conditions, not character flaws.

37) Brain plasticity (neuroplasticity) is the brain's remarkable ability to reorganise and adapt throughout life by forming new neural connections and even generating new neurons in certain areas. This plasticity allows stroke patients to recover function by training other brain areas to take over damaged regions. Musicians often show enlarged motor areas controlling their fingers, and London taxi drivers have enlarged hippocampi from navigating complex street layouts. Even in older adults, learning new skills like playing an instrument or speaking a language can create measurable brain changes. This plasticity is why rehabilitation after brain injury can be effective and why the saying "you can't teach an old dog new tricks" is neurobiologically false — your brain retains the capacity to learn and adapt throughout life.

38) Modern neuroscience technology allows us to observe the living brain in action, revolutionising our understanding of neural function. Functional MRI (fMRI) measures blood flow changes to show which brain areas are active during different tasks — you can literally watch your brain "light up" when you think about different things. EEG (electroencephalogram) measures electrical activity with millisecond precision, useful for studying sleep, epilepsy, and rapid cognitive processes. PET scans can track neurotransmitter activity and metabolism. Optogenetics allows researchers to control specific neurons with light, helping establish causal relationships between neural activity and behaviour. These tools have transformed neuroscience from a largely descriptive field to one that can test specific hypotheses about how the brain works.

Related: fMRI | EEG | Optogenetics

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