Unit 2 Topic 1.3

The Neuron and Neural Firing

Neuron

A specialized nerve cell that processes and transmits electrical and chemical signals throughout the nervous system.

Sensory Neurons

Nerve cells that detect external and internal environmental stimuli and transmit that data to the central nervous system.

All-or-Nothing Principle

The rule stating that a neuron fires completely with an action potential of full strength or it does not fire at all.

Resting Potential

The stable, polarized electrical charge of a neuron when it is inactive, typically around -70 millivolts.

Multiple Sclerosis

A neurological disorder where the immune system destroys the protective myelin sheath surrounding axons, disrupting neural communication.

Inhibitory Neurotransmitter

A chemical messenger that blocks or prevents a target neuron from firing its message to the next cell.

Glial Cells

Support cells in the nervous system that nourish, protect, and insulate neurons while aiding in myelin formation.

Motor Neurons

Nerve cells that carry movement commands from the brain and spinal cord to muscles and glands.

Depolarization

The phase of neural firing where the internal charge of a neuron becomes more positive, triggering an action potential.

Reuptake

The process by which the sending neuron reabsorbs excess neurotransmitters from the synaptic gap.

Myasthenia Gravis

An autoimmune neuromuscular disorder that causes severe voluntary muscle weakness due to communication breakdowns at the neuromuscular junction.

Dopamine

A primary neurotransmitter involved in motor control, motivation, reward processing, and pleasure pathways.

Reflex Arc

A swift, involuntary neural pathway that controls an immediate reflex action by routing directly through the spinal cord, initially bypassing the brain.

Interneurons

Central nervous system neurons that act as internal intermediaries, communicating directly between sensory and motor neurons.

Refractory Period

The brief recovery period immediately following an action potential during which a neuron cannot fire again.

Threshold

The minimum level of electrical stimulation required to trigger an action potential in a neuron.

Excitatory Neurotransmitter

A chemical messenger that stimulates a neuron, increasing the likelihood that it will fire an action potential.

Serotonin

A neurotransmitter that plays a crucial role in regulating mood, sleep cycles, appetite, and emotional balance.

Norepinephrine

A neurotransmitter and hormone that increases alertness, fuels the fight-or-flight response, and helps regulate mood.

Glutamate

The primary excitatory neurotransmitter in the central nervous system, crucial for learning and memory formation.

GABA

The primary inhibitory neurotransmitter in the brain, essential for calming neural activity and reducing anxiety.

Substance p

A neurotransmitter involved in transmitting pain signals from the peripheral nervous system to the brain.

Endorphins

Neurotransmitters that act as natural painkillers and mood elevators, released in response to stress or vigorous exercise.

Acetylcholine

A neurotransmitter that triggers muscle contractions, stimulates hormone excretion, and plays a vital role in memory and attention.

Hormones

Chemical messengers produced by endocrine glands that travel through the bloodstream to regulate distant organs and tissues.

Adrenaline

A hormone released by the adrenal glands during stress that rapidly accelerates heart rate, breathing, and energy production.

Leptin

A hormone produced by fat cells that signals the brain to decrease appetite and increase energy expenditure when full.

Ghrelin

A hormone secreted by an empty stomach that signals the hypothalamus to trigger hunger and increase food intake.

Melatonin

A hormone produced by the pineal gland that regulates the body's circadian rhythms and signals the onset of sleep.

Oxytocin

A hormone and neurotransmitter involved in social bonding, trust, empathy, and child labor contraction.

Agonist drugs

Chemical substances that mimic or enhance the actions of a specific neurotransmitter by binding to its receptors.

Antagonist drugs

Chemical substances that block or inhibit the action of a neurotransmitter by clogging its receptor sites.

Reuptake

The cellular reabsorption of a neurotransmitter from the synaptic cleft back into the sending neuron after a signal has been transmitted.

Stimulants

A class of psychoactive drugs that excite central nervous system activity, accelerating bodily functions and increasing alertness.

Caffeine

A widely consumed stimulant drug that boosts alertness by blocking inhibitory adenosine receptors in the brain.

Cocaine

A powerful stimulant that produces intense euphoria by blocking the reuptake of dopamine in reward pathways.

Depressants

A class of psychoactive drugs that reduce neural activity and slow down essential body functions.

Alcohol

A central nervous system depressant that impairs motor coordination, slows reaction times, and decreases inhibitions by enhancing GABA activity.

Hallucinogens

A class of psychoactive drugs that distort sensory perceptions, alter thought processes, and evoke vivid sensory images without sensory input.

Marijuana

A psychoactive drug derived from the cannabis plant that acts as a mild hallucinogen, depressant, or stimulant by binding to cannabinoid receptors.

Opioids

A class of highly addictive drugs derived from or mimicking opium that relieve intense pain and induce feelings of euphoria.

Heroin

An illicit, highly addictive opioid drug that rapidly converts into morphine in the brain, blocking pain and flooding reward systems.

Addiction

A chronic, relapsing brain disorder characterized by compulsive drug seeking and use despite devastating harmful consequences.

Withdrawal

The painful physical and psychological symptoms that occur when an individual stops using a substance they have become dependent upon.

Tolerance

The reduced response to a drug after repeated use, requiring increasingly larger doses to achieve the initial desired effect.