1.3B Neurotransmitters and Hormones

Action Potential

Brief electrical charge traveling down axon when neuron reaches threshold, transmitting signal in all-or-nothing manner to communicate information.

All-Or-Nothing Principle

Law stating neuron either fires completely at full strength or does not fire at all, with no partial responses.

Depolarization

Process where neuron's internal charge becomes less negative, moving toward threshold and potentially triggering action potential firing.

Reuptake

Process where neurotransmitters are reabsorbed by sending neuron after crossing synapse, removing them from synaptic cleft and terminating signal.

Multiple Sclerosis (MS)

Disorder where myelin sheath deteriorates, slowing or blocking neural signal transmission and causing communication problems throughout nervous system.

Neurotransmitters

Chemical messengers released across synapse to transmit signals between neurons, changing from electrical to chemical communication at gaps.

Excitatory Neurotransmitters

Chemical messengers increasing likelihood of postsynaptic neuron firing action potential by promoting depolarization and neural activity.

Inhibitory Neurotransmitters

Chemical messengers decreasing likelihood of postsynaptic neuron firing action potential by preventing depolarization and reducing neural activity.

Dopamine

Excitatory neurotransmitter regulating reward, motivation, pleasure, and movement; low levels linked to Parkinson's, high levels to schizophrenia.

Norepinephrine (Noradrenaline)

Excitatory neurotransmitter promoting arousal, alertness, and activating sympathetic fight-or-flight response; also functions as stress hormone.

GABA (Gamma-Aminobutyric Acid)

Inhibitory neurotransmitter calming nervous system by reducing neural activity, promoting relaxation, regulating sleep, and managing mood.

Substance P

Excitatory neurotransmitter transmitting pain signals from sensory neurons to brain, contributing to inflammatory response and anxiety perception.

Hormones

Chemical messengers traveling through bloodstream affecting behavior and mood with slower, longer-lasting effects than neurotransmitters.

Leptin

Hormone released by fat cells regulating hunger sensation and fat storage by signaling satiety to brain.

Melatonin

Hormone secreted by pineal gland regulating sleep-wake cycles and circadian rhythms, increasing during darkness to promote sleep.

Refractory Period

Brief recovery time after action potential when neuron cannot fire again, requiring reset before generating another signal.

Resting Potential

Neuron's stable negative electrical charge when inactive and ready to fire but not currently transmitting signal.

Threshold

Minimum level of stimulation required to trigger action potential, representing critical voltage for neuron firing.

Myasthenia Gravis

Autoimmune disorder where acetylcholine receptors are attacked, disrupting neuromuscular transmission and causing progressive muscle weakness.

Serotonin

Inhibitory neurotransmitter regulating mood, emotion, and happiness; deficiency linked to depression and anxiety disorders.

Glutamate

Most abundant excitatory neurotransmitter in brain, essential for learning and memory formation through neural plasticity.

Endorphins

Inhibitory neurotransmitters serving as natural painkillers by blocking pain signals and producing euphoria, especially during exercise.

Acetylcholine (ACh)

Context-dependent neurotransmitter causing muscle contractions, facilitating memory formation; excitatory for muscles, inhibitory for heart; depletion linked to Alzheimer's.

Endocrine System

Slower communication network using glands releasing hormones into bloodstream to regulate long-term bodily functions and behaviors.

Adrenaline (Epinephrine)

Hormone and neurotransmitter increasing heart rate, energy, and blood pressure during fight-or-flight stress response.

Ghrelin

Hunger hormone released by stomach stimulating appetite and signaling brain to initiate eating behavior.

Oxytocin

Hormone influencing social bonding, trust, empathy, childbirth, and parent-child attachment through emotional connection processes.