Glossary
Acetylcholine
A neurotransmitter involved in muscle contraction, learning, memory, and attention.
Example:
When you recall a vivid memory or move your arm, acetylcholine is a key neurotransmitter facilitating these actions.
Addiction
A compulsive craving for and use of a drug or behavior despite adverse consequences, often involving a hijacked reward system in the brain.
Example:
Despite knowing the negative health effects, a person with a nicotine addiction may find it extremely difficult to stop smoking.
Adrenaline (Epinephrine)
A hormone and neurotransmitter that prepares the body for 'fight-or-flight' responses by increasing heart rate, blood pressure, and energy.
Example:
The sudden rush of energy and heightened senses you feel when narrowly avoiding an accident is due to the release of adrenaline.
Agonists
Drugs that mimic or enhance the effects of a particular neurotransmitter by binding to its receptors or increasing its production.
Example:
Pain relievers like morphine are agonists for endorphins, amplifying the body's natural pain-reducing system.
All-or-Nothing Principle
The rule that a neuron either fires completely once its threshold is reached, or it does not fire at all; there are no partial firings.
Example:
When you press a trigger on a water gun, it either sprays water fully or not at all, illustrating the all-or-nothing principle of neural firing.
Antagonists
Drugs that block or inhibit the effects of a particular neurotransmitter by occupying its receptor sites and preventing it from binding.
Example:
A drug used to treat schizophrenia might be an antagonist for dopamine, blocking its effects to reduce symptoms like hallucinations.
Depolarization
The process during an action potential when the inside of a neuron's cell membrane briefly becomes positive due to the influx of positive ions.
Example:
During depolarization, the neuron's internal charge rapidly flips from negative to positive, like a sudden surge of electricity.
Depressants
Psychoactive drugs that decrease neural activity and slow down bodily functions, often leading to relaxation and reduced inhibition.
Example:
Alcohol is a depressant that can impair judgment and coordination by slowing down the central nervous system.
Dopamine
A neurotransmitter associated with reward, motivation, pleasure, motor control, and attention.
Example:
The feeling of satisfaction you get after achieving a goal is often linked to the release of dopamine in your brain's reward pathways.
Endorphins
Natural opiate-like neurotransmitters produced by the brain that reduce pain and induce feelings of euphoria.
Example:
The 'runner's high' experienced after intense exercise is often attributed to the release of endorphins.
Excitatory Neurotransmitter
A type of neurotransmitter that increases the likelihood that the postsynaptic neuron will fire an action potential.
Example:
An excitatory neurotransmitter is like pressing the 'accelerate' button on a neuron, making it more likely to send its own signal.
GABA
The main inhibitory neurotransmitter in the brain, responsible for calming neural activity and reducing anxiety.
Example:
Medications for anxiety often work by increasing the effects of GABA, helping to quiet an overactive nervous system.
Ghrelin
A hormone produced by the stomach that stimulates hunger and promotes food intake.
Example:
When your stomach growls and you feel hungry, it's often because your body is releasing ghrelin.
Glial Cells
Support cells in the nervous system that provide structure, insulation, and protection for neurons, enhancing their function.
Example:
Think of glial cells as the support staff for a rock band, ensuring the main performers (neurons) can do their job effectively.
Glutamate
The primary excitatory neurotransmitter in the brain, crucial for learning, memory, and synaptic plasticity.
Example:
When you're actively learning new information, glutamate is highly active, helping to strengthen the connections between your brain cells.
Hallucinogens
Psychoactive drugs that cause profound distortions in perception, thought, and mood, often leading to vivid sensory experiences.
Example:
LSD is a powerful hallucinogen that can cause users to see, hear, or feel things that aren't actually present.
Hormones
Chemical messengers produced by endocrine glands that travel through the bloodstream to target organs, regulating various bodily functions.
Example:
During puberty, a surge of different hormones causes significant physical and emotional changes in the body.
Inhibitory Neurotransmitter
A type of neurotransmitter that decreases the likelihood that the postsynaptic neuron will fire an action potential.
Example:
An inhibitory neurotransmitter acts like a 'brake' on a neuron, making it less likely to fire and helping to calm neural activity.
Interneurons
Neurons located within the central nervous system that communicate between sensory and motor neurons, or between other interneurons.
Example:
In a reflex, interneurons act as the crucial middleman, quickly relaying the signal from your hand to your leg without needing to go all the way to the brain.
Leptin
A hormone produced by fat cells that signals satiety (fullness) to the brain, helping to regulate appetite and energy balance.
Example:
After eating a large meal, increased levels of leptin tell your brain that you are full and should stop eating.
Melatonin
A hormone primarily produced by the pineal gland that regulates sleep-wake cycles (circadian rhythm).
Example:
As evening approaches and light diminishes, your body starts producing more melatonin to prepare you for sleep.
Motor Neurons
Neurons that carry outgoing information from the central nervous system to muscles and glands, enabling movement and bodily functions.
Example:
When you decide to wave hello, your motor neurons transmit the command from your brain to your arm muscles.
Multiple Sclerosis
A neurological disorder caused by the damage to the myelin sheath surrounding neurons, impairing signal transmission.
Example:
In Multiple Sclerosis, the protective coating around nerve fibers is damaged, causing signals to slow down or get disrupted, much like a frayed electrical cord.
Myasthenia Gravis
An autoimmune disorder where antibodies attack acetylcholine receptors, leading to muscle weakness and fatigue.
Example:
Someone with Myasthenia Gravis might experience drooping eyelids or difficulty swallowing because their immune system blocks the signals needed for muscle contraction.
Neurons
Specialized cells that transmit information throughout the nervous system using electrical and chemical signals.
Example:
When you decide to pick up a pen, your brain's neurons send signals down to your hand muscles.
Neurotransmitters
Chemical messengers that cross the synaptic gaps between neurons to transmit signals from one neuron to another.
Example:
When you feel happy or sad, it's often due to the balance and activity of various neurotransmitters in your brain.
Norepinephrine
A neurotransmitter involved in arousal, alertness, attention, and the 'fight-or-flight' response.
Example:
When you're startled by a loud noise, a surge of norepinephrine helps to heighten your senses and prepare your body to react.
Opioids
A class of drugs that act on opioid receptors in the brain and body to produce pain relief, euphoria, and relaxation.
Example:
Prescription pain medications like OxyContin are opioids that are highly effective for severe pain but carry a risk of addiction.
Oxytocin
A hormone and neurotransmitter involved in social bonding, trust, empathy, and maternal behaviors.
Example:
The feeling of connection and warmth you might feel when hugging a loved one is partly influenced by the release of oxytocin.
Reflex Arc
A neural pathway that controls a reflex, allowing for an automatic, rapid response to a stimulus without direct brain involvement.
Example:
When a doctor taps your knee, the involuntary kick is a classic example of a reflex arc in action.
Refractory Period
A brief period immediately following an action potential during which a neuron cannot fire again, allowing it to reset.
Example:
After sending a text, your phone might have a tiny refractory period before you can send another, similar to how a neuron briefly rests.
Resting Potential
The stable, negative electrical charge of a neuron when it is inactive and not transmitting a signal.
Example:
A neuron at resting potential is like a loaded spring, ready to fire but currently in a stable, waiting state.
Reuptake
The process by which neurotransmitters are reabsorbed by the presynaptic neuron after transmitting a signal, clearing the synapse.
Example:
After delivering its message, a neurotransmitter is often 'recycled' back into the sending neuron through reuptake, like a delivery truck returning to its depot.
Reuptake Inhibitors
Drugs that block the reabsorption of neurotransmitters back into the presynaptic neuron, thereby prolonging their effects in the synapse.
Example:
Antidepressants like SSRIs are reuptake inhibitors for serotonin, allowing serotonin to remain active in the synapse for longer.
Sensory Neurons
Neurons that carry information from sensory receptors (like skin, eyes, ears) towards the central nervous system.
Example:
If you touch a cold ice cube, your sensory neurons are responsible for sending that 'cold' message to your spinal cord.
Serotonin
A neurotransmitter that plays a significant role in regulating mood, sleep, appetite, and digestion.
Example:
Low levels of serotonin are often linked to feelings of depression, which is why many antidepressant medications target its activity.
Stimulants
Psychoactive drugs that increase neural activity and arousal, leading to increased alertness, energy, and focus.
Example:
Caffeine is a common stimulant that helps people feel more awake and focused by boosting neural activity.
Substance P
A neurotransmitter involved in the transmission of pain signals from the peripheral nervous system to the central nervous system.
Example:
When you stub your toe, Substance P is one of the chemical messengers that helps your brain register the sensation of pain.
Threshold
The minimum level of stimulation required to trigger a neural impulse or action potential in a neuron.
Example:
For a neuron to fire, the incoming signals must reach a specific threshold, much like a light switch needing to be flipped fully to turn on the light.
Tolerance
A state in which a person needs increasingly larger doses of a drug to achieve the same effect, due to the brain adapting to its presence.
Example:
Someone who regularly drinks coffee might develop a tolerance, needing more cups to feel the same level of alertness.
Withdrawal
The uncomfortable and often painful physical and psychological symptoms experienced when a person stops using a drug they are dependent on.
Example:
Someone trying to quit caffeine might experience headaches and irritability as part of withdrawal symptoms.