Unit 1.1 - Nervous System & Drugs

Nature-Nurture

The long-standing debate over whether heredity (nature) or experience (nurture) most influences behavior and mental processes

Evolutionary Psychology

The study of the evolution of behavior and the mind, based on the principle of natural selection

Natural Selection

The principle that inherited traits enabling an organism to survive and reproduce in a specific environment are most likely to be passed to the next generation

Key steps in Natural Selection

1. Variation in offspring, 2. Competition for survival, 3. Adaptation of traits, 4. Selection of the fittest traits over time

Mutation

A random error in gene replication that leads to a change

Behavior Genetics

The study of the relative power and limits of genetic (nature) and environmental (nurture) influences on behavior

Heredity

The genetic transfer of characteristics from parents to offspring

Environment (in psychology)

All non-genetic influences, from external factors like people around us to pre-natal conditions like a mother's diet

Adaptive Flexibility

The human capacity to learn and adapt to varied environments, which gives us high fitness (ability to survive and reproduce)

The Human Genome

The complete set of genetic material in an organism; humans share around 95% of their genetics with each other

Monozygotic Twins

Identical twins resulting from one fertilized egg splitting; they are genetically identical and always the same sex

Dizygotic Twins

Fraternal twins resulting from two separate eggs fertilized by two different sperm; they are no more genetically alike than regular siblings

Findings from Twin Studies (Identical apart)

Identical twins raised separately show striking similarities in tastes, physical attributes, personality, abilities, interests, and fears

Adoption Studies Findings

Adopted children's personalities generally do not resemble their adoptive parents or adopted siblings; personality is more linked to biological parents

Epigenetics

The study of environmental influences on gene expression (phenotype) that occur without a change to the DNA sequence

Gene Expression

Whether a gene is active (expressed) or inactive (turned off)

Epigenetic Marks

Molecules attached to parts of DNA that signal whether a gene should be turned on or ignored (turned off), often created by environmental experiences

Genetic Determinism (Correction)

The belief that genes determine who you are (inaccurate); genes are probabilistic—they only give the probability of expressing a trait

Intergenerational Trauma

The concept that environmental influences (like trauma) can create epigenetic marks that are potentially passed down to the next generation

Nervous System

The body’s speedy, electrochemical communication network, made up of all the nerve cells of the peripheral and central nervous systems

Central Nervous System (CNS)

The division of the nervous system consisting of the Brain and Spinal Cord; coordinates incoming sensory and outgoing motor messages

Peripheral Nervous System (PNS)

The sensory and motor neurons that connect the CNS to the rest of the body; includes all the nerve endings not in the brain or spinal cord

Nerves

Bundled axons of many neurons that form neural cables connecting the CNS with muscles, glands, and sense organs

Sensory Neurons (Afferent)

Carry information from the peripheral (sense organs) to the CNS

Motor Neurons (Efferent)

Carry messages out of the CNS to the peripheral (muscles and glands)

Interneurons

Neurons within the CNS (brain and spinal cord) that internally communicate and intervene between sensory inputs and motor outputs

Somatic Nervous System

DIVISION OF PERIPHERAL NERVOUS SYSTEM that controls the body's voluntary movements of skeletal muscles

Autonomic Nervous System (ANS)

DIVISION OF PERIPHERAL NERVOUS SYSTEM: that controls the glands and muscles of the internal organs, managing functions you are not consciously thinking of

Broken into Sympathetic and Parasympathetic

Sympathetic Nervous System

The division of the Autonomic System that arouses the body, mobilizing energy for action (e.g., fight, flight, or freeze)

SIMP GETS AROUSED

Parasympathetic Nervous System

The division of the Autonomic System that calms the body, conserving its energy (e.g., rest and digest)

PARACHUTE SLOW DOWN

Homeostasis

The process by which the body's systems are kept in a state of balance (the sympathetic and parasympathetic systems work to maintain this)

Reflex Arc

A simple, fast pathway in the spinal cord that allows the body to respond very quickly to extreme situations without the information first reaching the brain

REFLEX HAPPEN ONLY INVOLVE SPINAL CORD

Neuron

A nerve cell; the basic building block of the nervous system

Cell Body (Soma)

The core of the neuron containing the nucleus; it produces genetic information and directs protein synthesis (the cell's life-support center)

Dendrites

Bushy, branching extensions of the neuron that receive and integrate messages and conduct impulses toward the cell body

Axon

The neuron extension that passes messages away from the cell body to other neurons, muscles, or glands

Myelin Sheath

A fatty tissue layer encasing the axons; it insulates the axon and increases the speed of neural impulse transmission

Terminal Branches (of the axon)

The end of the axon that contains synaptic vesicles (containers) that store and release neurotransmitters to enable communication across the synapse

Glial Cells

The "worker bees" of the nervous system; they support, nourish, and protect neurons and play a role in learning, thinking, memory, and creating the myelin sheath

Myelination Development

The process of creating the Myelin Sheath, which is not complete until about age 25; it's crucial for behavior, movement, and thought

Multiple Sclerosis (MS)

A condition caused by the deterioration of the myelin sheath, leading to motor impairments

Darwin's Theory and Evolutionary Psychology

It posits that behavioral traits (like mating or fears) that aided survival were naturally selected and passed down, explaining current human behavior.

Genetic Determinism vs. Probabilistic Traits

Genetic Determinism is the inaccurate idea that genes guarantee a trait; traits are Probabilistic—genes give a likelihood, and environment determines if they are expressed.

Ethical Issues with Past Twin Studies (1960s/70s)

Twins were sometimes forcibly separated at birth without parental informed consent for research purposes.

Adoption Studies: Nature vs. Nurture in Personality

Personality is more linked to biological parents (nature); the shared family environment (nurture) of the adoptive home has no measurable effect on personality.

Sympathetic Nervous System: Threat Response

It arouses the body by mobilizing energy for fight, flight, or freeze (e.g., accelerating heart, dilating pupils, inhibiting digestion).

Survival Importance of the Reflex Arc

It allows for an incredibly fast response to danger because the signal goes only to the spinal cord and immediately back out, bypassing the slower brain.

Myelin Sheath and Glial Cells: Neuron Function

Myelin Sheath insulates the axon and speeds up the signal; Glial Cells are the "worker bees" that support neurons and create the Myelin Sheath.

Action Potential

A brief electrical charge that travels down the axon; transmit information

ALL OR NONE RESPONSE: More stimulation does NOT mean more intense transmission

Resting Potential

The state of a neuron when it is not firing; the interior of the axon is negatively charged (polarized)

Negative in, positive out

Polarization

The electrical state of a resting neuron, where the outside is positive and the inside is negative

Depolarization

The process where an action potential causes the axon's interior to become momentarily positive as sodium ions (Na+) rush in

Repolarization

The process of the neuron returning to its resting potential as potassium ions (K+) flow out

Refractory Period

A brief pause after a neuron has fired, during which it cannot fire again until it restores the resting state

• Waiting for equilibrium with the environment → All Axon need to Repolarize

Threshold

The minimum level of stimulation required for excitatory signals to outweigh inhibitory signals and trigger a neural impulse

All-or-None Response

A neuron's reaction that either fires at full strength (if the threshold is met) or does not fire at all

Synapse

The small junction/gap between the sending neuron's terminal branches and the receiving neuron's dendrite

Neurotransmitters

Chemical messengers released by the terminal branches that travel across the synapse to bind to receptor sites on the receiving neuron

Reuptake

The process by which the sending neuron reabsorbs excess neurotransmitters from the synapse

• The sending neurons takes back the UNBOUND (non-absorbed) neurotransmitters

• DRUGS: Some drugs prevent reabsorption by blocking reuptake in the  dendrite of the sending

Inhibitory Neurotransmitter

A chemical messenger that slows down or stops the action potential from firing on the receiving neuron

Excitatory Neurotransmitter

A chemical messenger that pushes the receiving neuron past its threshold to trigger an action potential

Agonist

A drug molecule that mimics a neurotransmitter and excites a response (e.g., a pain pill mimicking endorphins)

Antagonist

A drug molecule that blocks a neurotransmitter's effect by occupying the receptor site (e.g., Botox blocking ACh for muscle movement)

Acetylcholine (ACh)

Enables role in Muscle action, learning, memory→ MAJOR role in communication between motor neurons and skeletal muscles

• Major part in voluntary movement

Deterioration linked to Alzheimer's disease.

Dopamine

Influences movement, learning, attention, and emotion. Oversupply → Schizophrenia; Undersupply → Parkinson's.

Serotonin

Affects mood, hunger, sleep, and arousal. Undersupply is linked to depression.

Norepinephrine

Helps control alertness and arousal. Undersupply can lead to a depressed mood.

Hormone and neurotransmitter

GABA (gamma-aminobutyric acid)

The major inhibitory neurotransmitter. Undersupply linked to seizures, tremors, and insomnia.

Glutamate

The major excitatory neurotransmitter; involved in memory. Oversupply can cause migraines.

The Firing of a Neuron (Steps)

1. Action Potential Begins: First Section Axon OPENS GATES where Na⁺ ions flood in 

2. Depolarization: The flood of Na ions leads to depolarization, and signals to the next axon section to open

3. Repolarization: Once the Na⁺ ions move to the second part, K⁺ ions on the OUTSIDE (not in the axon) repolarize

4. Depolarization and Repolarization repeat

5. Entering Refectory Period

Twi Jims

The "Two Jims" example (same name, same son's name, same smoking/divorce history). Case study illustrating striking similarities between identical twins raised apart

Two functional divisions of the Somatic Nervous System (PNS)

Sensory Input (incoming signals) and Motor Output (outgoing signals to muscles).

Roles of Glial Cells (Neuroglia)

They play a role in learning, thinking, and memory. They also form Myelin

Speed of communication: Nervous System vs. Endocrine System

Nervous System is fast (milliseconds); Endocrine System is slow (seconds to minutes).

Duration of effects: Nervous System vs. Endocrine System

Nervous System effects are brief/quick; Endocrine System effects are long-lasting.

Oxytocin

The "Hug Drug," involved in bonding, social trust, pleasure, pregnancy, and lactation.

Melatonin

Regulates the sleep/wake cycle (circadian rhythm).

Ghrelin

A digestive hormone that stimulates hunger (tells the brain you need food).

Leptin

A hormone produced by fat cells that decreases hunger (satiety signal).

Substance P

Involved in pain perception and immune response.

Result of an oversupply of Glutamate besides migraines

Can produce seizures.

Myasthenia Gravis

A condition where the body produces antibodies against Acetylcholine (ACh) receptors, causing muscle fatigue and temporary paralysis; an example of an ACh malfunction.

Divisions of the Nervous System

Sympathetic vs Parasympathetic

Sympathetic	Parasympathetic
Pupils Dilate Heartbeat accelerates Digestions are inhibited Bladder relaxes (hold) Adrenal glands release epinephrine and norepinephrine	Public contract Heartbeat slows Digestion is stimulated Bladder contracts (go pee)

2 Types of Neural Signals

• Excitatory Signal: Gas Pedal on Car → Trigger Action

• Inhibitory Signal: Brake on car → Depress action

More excitatory than inhibitory impulses → Reach THRESHOLD → ACTION POTENTIAL

Use Toilets to Explain Action Potential & Refectory Period

Action Potential: Pressing the toilet harder (after exceeding the minimum) does not make it flush faster

• For a more intense response, fire MORE neurons

Refectory Period: Neurons need Breaks → After FLUSH TOILET, need wait a bit before flush

Endorphins

 Morphine Within → Natural substance, opiate-like neurotransmitter and suppress pain and pleasure

• Help runners to push past a wall and keep going

• END PAI\n

Problem With Pain Suppression: Might not realize how badly injured they are → Lessen impact of pain

Adrenaline/ Epinephrine

Increases heart rate, blood pressure, blood sugar → Boosts energy in flight/ flight responses

• Secreted through adrenal glands 

When the fight or flight response, the adrenal glands release epinephrine and norepinephrine to energize the body

Endocrine System

Body’s SLOW chemical communication system → Glands and fat tissue that secrete hormones into blood stream

• If nervous system is sending a text, endocrine system is writing a letter

Hormones

Chemical messengers that are manufactured by the endocrine glands, and travel through the blood stream to affect other tissues

Pituitary Gland

Endocrine system’s most influential gland → Regulate growth and control other endocrine glands

• regulates hormone release for SOME glands

• Part of both the Central Nervous and Endocrine System → Near the Brain

Endocrine System vs Nervous System (BIG TABLE)

Endocrine System	Nervous System
Glands secrete hormones Hormones move through bloodstream Hormonal secretion is slow Message lasts longer	Neurons release neurotransmitters Neurotransmitters move across synapses Neural transmission is very fast Neuronal messages dissipate quickly

Ghrelin & Leptin

Ghrelin: Stimulates Hunger

Leptin: Decreases hunger, regulate food intake and fat storage

Psychoactive Drugs

Chemical substances that affect consciousness by altering perceptions and mood.

Depressants

Psychoactive drugs that calm neural activity and slow body functions.

Stimulants

Psychoactive drugs that temporarily excite neural activity and arouse body functions.

Hallucinogens

Psychoactive drugs that distort perceptions and evoke sensory images in the absence of sensory input (e.g., seeing or hearing things that aren't there).

Drug Action (Synaptic Level)

Psychoactive drugs all work at this level, influencing the reception, reuptake, and production of neurotransmitters.

Tolerance

The user requires larger and larger doses of a drug to experience the same effect.

Neuro-Adaptation

The brain's counteraction (adjustment) to the disruption of normal functioning caused by continued drug use; this is what produces tolerance.