Module 1.3: Neuron, Neural Firing, Neurotransmitters, and Psychoactive Drugs Flashcards
What is a neuron?
It is a nerve cell that is the basic building block of the nervous system
What are the parts of a neuron?
- Dendrites
- Cell body
- Axon
- Myelin Sheaths
- Terminal branches of axon
What are dendrites?
Branching extensions of neurons that receive messages from other neurons
What is the soma?
AKA cell body - contains the nucleus, the cell’s life-support center
What is the axon?
it passes electrical messages from the cell body to the axon terminals; attached to the soma
What is the myelin sheath?
It is a fatty layer that protects the axons of certain neurons and makes messages within a neuron travel faster
When does the myelin sheath begin to develop?
Before birth and continues into adulthood
What is myelination? When does it occur?
Myelination is the process of formation of myelin sheath - it helps with planning, logic, decision-making, and impulse control
It occurs during preteen years in the brain’s frontal lobes (which fully develop around age 25)
What is Multiple Sclerosis?
It is an autoimmune disease that results from myelin sheath deterioration, causing muscle control loss
What do terminal branches of the neuron do?
Contain terminal buttons, which hold vesicles ; found at the ends of each axon
What are vesicles?
The sacs that hold neurotransmitters
What do glial cells do?
Support, nourish and protect neurons; provide nutrients and myelin, guide neuron connections, and clean up ions and neurotransmitters
Why do glial cells provide nutrients to neurons?
Because neurons cannot feed themselves or do these functions for themselves
What is the synapse?
It is the gap or space between the tip of the sending (presynaptic) neuron and the dendrite of the receiving (postsynaptic) neuron
What is the synapse also known as?
Synaptic gap - synaptic cleft
What is a neurotransmitter?
It is the chemical messenger of the nervous system; it travels across the synapse and binds to receptor sites on the receiving (postsynaptic) neuron
What is a neural impulse?
It is the influx of the +ve ions moving like falling dominos in the axon of the neuron
How is a neural impulse generated?
If the combination of chemical signals received by a neuron’s dendrites exceed a minimum strength or threshold, the neuron fires, transmitting an action potential down its axon in a chemical-to-electrical process
What is a threshold?
It is the level of stimulation required to trigger a neural impulse
When is a threshold reached?
When the excitatory “go” messages overwhelm the inhibitory “stop” messages
What is the threshold value?
-55 mV (millivolts)
What is an all-or-none response mean?
Neural impulses are not “strong” or “weak” = action potentials have the same strength
therefore, neural firing happens at full response or not at all
What does a “strong” sensation equate to?
A large quantity of action potentials
What are neurotransmitters divided into?
Excitatory and Inhibitory Signals
What do excitatory signals do?
Provoke an action
What do inhibitory signals do?
Stop an action
What happens when excitatory signals greatly outnumber inhibitory?
The threshold is reached and action potential occurs
What is the resting potential?
Polarized state - no messages are sent; axon gates are closed
What happens in the neuron during resting potential?
Positive sodium (Na+) ions are on the outside of the cell; positive potassium (K+) ions are inside the cell along with many -ve charged protein ions
What is the resting potential value?
-70 mV
What does the axon membrane being selectively permeable mean?
It contains voltage-gated ion channels that either open to allow ion exchange (depolarization) or close to prevent it (polarization)
What is an action potential?
It is a brief electrical charge that travels down an axon (neural impulse, nerve firing, depolarization)
How is an action potential generated?
It is generated when positive sodium (Na+) ions move into the axon and potassium ions (K+) move out
When does an action potential start?
It starts when receptor sites of dendrites are stimulated
What are the steps of an action potential?
Step 1: The semipermeable axon opens its gates once threshold is met
Step 2: Na+ ions flood in through the channels -> inside becomes +ve
Step 3: Gates open in the 1st part of the axon, allowing K+ ions to flow out (repolarizes that section of the axon)
Step 4: Sodium/potassium pump continues to depolarize new sections of the axon and repolarize the previous ones
Step 5: Refractory period
What is a refractory period?
It is a resting pause after an action potential where subsequent action potentials cannot occur until the axon returns to resting state
What is a refractory period also known as?
Repolarization - reestablishing -ve charge in neuron -> Na+ is pushed out
What is an absolute refractory period?
It is a time when neural impulses CANNOT be sent, as +ve sodium ions are being pushed out of the cell
What is a relative refractory period?
It is when a neuron will only respond to a stronger than normal impulse; follows the absolute refractory period
What can happen when action potentials go wrong?
Multiple Sclerosis - a disease that leads the immune system to attack and destroy myelin sheath throughout the nervous system
- causes muscle weakness, vision changes, and numbness and memory issues
Myasthenia Gravis - a disease that leads to a weakening of voluntary muscles by destroying acetylcholine receptor sites
What can incorrect amounts of neurotransmitters do?
It can cause difficulties with movement, memory, and mood
What is the function of acetylcholine?
It enables muscle action, learning, and memory
What happens if there is an undersupply of acetylcholine? Oversupply?
Undersupply - Alzheimer’s
Oversupply - Paralysis (Black widow’s venom)
What is the function of dopamine?
It influences voluntary movement, learning, attention, and emotion
What happens if there is an undersupply of dopamine? Oversupply?
Undersupply - Parkinson’s disease
Oversupply - Schizophrenia
What is the function of serotonin?
It affects mood, hunger, sleep, and arousal
What happens if there is an undersupply of serotonin? Oversupply?
Undersupply - Depression
Oversupply - nervousness and insomnia
What is the function of norepinephrine?
It helps control alertness and arousal
What happens if there is an undersupply of norepinephrine? Oversupply?
Undersupply - depression
Oversupply - anxiety/mania
What is the function of GABA?
It is an inhibitory neurotransmitter, a natural tranquiller involved in calming you down
What happens if there is an undersupply of GABA? Oversupply?
Undersupply - seizures, tremors, insomnia
Oversupply - increase in anxiety
What is the function of Glutamate?
It is an excitatory neurotransmitter, involved in memory
What happens if there is an undersupply of Glutamate? Oversupply?
Undersupply - concentration problems
Oversupply - seizures and migranes
What is the function of endorphins?
It influences pleasure and pain
What happens if there is an undersupply of endorphins? Oversupply?
Undersupply - depression
Oversupply - anxiety/weirdness
What is the function of Substance P?
It is a potent neurotransmitter in the transmission of signals from pain receptors
What happens if there is an undersupply of Substance P? Oversupply?
Undersupply - reduced pain sensitivity
Oversupply - depression episode
What are agonists?
Psychoactive drugs that increase/mimic neurotransmitters’ actions
What are antagonists?
Psychoactive drugs that block receptor sites
What do reuptake inhibitors do?
They block the reuptake process, leaving the drug/neurotransmitter in the synaptic gap longer
What is the endocrine system?
It is the body’s slow chemical communication system, which consists of a series of glands that secrete hormones into the bloodstream
What are hormones?
They are the chemical messages of the endocrine system
Why is the pituitary gland the most influential gland?
It regulates growth and controls other endocrine glands. It also releases a growth hormone that stimulates physical growth, as well as releases oxytocin
What does oxytocin do?
It enables contractions during labor, milk flow during nursing, and orgasm. It also promotes pair bonding, group cohesion, and social trust.
What is the release point of adrenaline?
Adrenal glands
What is the function of adrenaline?
It prepares the body for emergencies - “fight or flight” response
What is the release point of cortisol?
Adrenal glands
What is the function of cortisol?
To maintain homeostasis - stress hormone
What is the release point of leptin?
white adipose tissue (body fat)
What is the function of leptin?
It regulates the long-term balance between your body’s food intake and energy use (decreases appetite)
What is the release point of ghrelin?
Pituitary Gland
What is the function of ghrelin?
It increases food intake, helps your body store fat, plays a role in controlling sugars and how your body releases insulin (increases appetite)
What is insulin?
The hormone responsible for processing sugar
What is the release point of melatonin?
Pineal glands
What is the function of melatonin?
It helps to synchronize circadian rhythms in different parts of your body (you sleep better with higher levels of melatonin)
What are psychoactive drugs?
They are chemical substances that alter perceptions and moods
When is drug use a disorder?
- diminished control and social functioning
- more is needed to get the desired effect
- hazardous to use
Why can psychoactive drugs be used in moderation?
To help with concentration or pain relief
What is substance use disorder?
It is a disorder characterized by continued substance craving and use despite significant life disruption and/or physical risk
What are the types of drugs?
Hallucinogens
Depressants
Stimulants
What are examples of hallucinogens?
Marijuana, mushrooms, LSD, ecstasy/MDMA
What do hallucinogens do?
They distort perception, causing false sensory hallucinations, impairing memory, and causing feelings of relaxation and/or euphoria
What do depressants do?
They reduce neural activity, increasing relaxation and pain relief, decreasing mood and arousal, and slowing down or depressing bodily processes
What are examples of depressants?
Alcohol, barbiturates, opiates (heroin)
What do stimulants do?
They excite neural activity, increasing energy, decreasing appetite, causing brief feelings of euphoria, and speeding up or stimulating bodily processes
What are examples of stimulants?
Caffeine, nicotine, cocaine, amphetamines (meth)
What is alcoholism/alcohol use disorder? What does it do?
It is prolonged and excessive use of alcohol - can shrink the brain, disrupt memory formation, reduce inhibitions, and slow functioning
How does smoking affect the body?
- Arouses the brain to a state of increased alertness
- Increases heart rate and blood pressure
- At high levels, relaxes muscles and triggers the release of neurotransmitters that may reduce stress
- Reduces circulation to extremities
- Suppresses appetite for carbohydrates
What are the pleasurable effects of alcohol? The negative aftereffects?
Pleasurable - initial high follow by relaxation and disinhibition
Negative - depression, memory loss, organ damage, impaired reactions
What are the pleasurable effects of heroin? The negative aftereffects?
Pleasurable - Rush of euphoria, relief from pain
Negative - depressed physiology, agonizing withdrawal
What are the pleasurable effects of caffeine? The negative aftereffects?
Pleasurable - increased alertness and wakefulness
Negative - anxiety, restless, and insomnia in high doses, uncomfortable withdrawal
What are the pleasurable effects of nicotine? The negative aftereffects?
Pleasurable - arousal and relaxation, sense of well-being
Negative - heart disease, cancer
What are the pleasurable effects of cocaine? The negative aftereffects?
Pleasurable - Rush of euphoria, confidence, energy
Negative - Cardiovascular stress, suspiciousness, depressive crash
What are the pleasurable effects of methamphetamine? The negative aftereffects?
Pleasurable - euphoria, alertness, and energy
Negative - irritability, insomnia, hypertension, seizures
What are the pleasurable effects of ecstasy (MDMA)? The negative aftereffects?
Pleasurable - emotional elevation, disinhibition
Negative - dehydration, overheating, depressed mood, impaired cognitive and immune functioning
What are the pleasurable effects of LSD? The negative aftereffects?
Pleasurable - visual “trip”
Negative - risk of panic
What are the pleasurable effects of marijuana? The negative aftereffects?
Pleasurable - enhanced sensation, relief of pain, distortion of time, relaxation
Negative - impaired learning and memory, increased risk of psychological disorders
What is addiction?
It is a complex condition characterized by compulsive drug use or behaviors despite harmful consequences
What is tolerance?
It is diminished psychoactive effects after repeated use of drugs (need a higher dose to achieve the same high)
What is withdrawal?
It is the painful symptoms of the body readjusting to the absence of the drug
What is near-death experience?
When individuals report strange sensations or vivid visions following a close brush with death (similar to drug-induced hallucinations)
