Psychology - Biological Bases of Behaviour

Neuron

A specialized nerve cell that receives and sends information

86 billion in the human brain

Dendrites

THE KEYBOARD

RECEIVES signals from other neurons

Cell body (soma)

Contains nucleus and keeps the neuron functioning

Axon (The Wire)

THE WIRE → AWAY

A long, slender nerve fiber extending from the cell body

Carry signals AWAY from the body

Myelin sheath

The fatty protective covering made of myelin around the axon

Axons with fastest impulses

Axon terminals

The specialized, button-shaped endings at the distal tip of an axon

Release neurotransmitters into the synaptic gap.

Glial cells

A cell that supports and protects neurons

metabolic nourishment, myelin insulation, and clearance of cellular debris.

1:1 with neurons

Resting potential

Neuron is at Rest.

Measuring around $-70\,\text{mV}$.

Threshold

The voltage a neuron must reach to fire an action potential.

Impulse typically around $-55\,\text{mV}$.

Action potential

An electrical impulse that travels down the axon

All-or-none law

A neuron fires a full action potential or none at all, once threshold is reached

Refractory period

The short period after firing when a neuron cannot fire normally again

Absolute refractory period

The neuron cannot fire another action potential

Synapse

The tiny gap where neurons communicate

100 trillion in the human brain

Presynaptic neuron

The nerve cell positioned upstream from a junction that initiates and transmits chemical signals into the cleft.

Postsynaptic neuron

The receiving cell positioned downstream from a junction whose surface receptors bind released chemical messengers.

Neurotransmitters

Chemical messengers that transmit signals between cells

Synaptic vesicles

Where neurotransmitters are stored

Receptors

Specialized transmembrane protein complexes located on receiving cells that selectively bind specific signaling molecules to trigger a downstream response.

Lock-and-key principle

The structural specificity concept describing how a signaling molecule binds selectively only to receptor sites possessing a complementary geometric shape.

Excitatory postsynaptic potential (EPSP)

A graded, local depolarization of the postsynaptic membrane that shifts the electrical potential closer to threshold, increasing the probability of firing.

Inhibitory postsynaptic potential (IPSP)

A graded, local hyperpolarization of the postsynaptic membrane that shifts the electrical potential farther from threshold, reducing the probability of firing.

Reuptake

The sending neuron reabsorbs released neurotransmitters from the synapse

Neurotransmitter degradation

The rapid enzymatic inactivation and breakdown of chemical messengers within the synaptic cleft.

Autoreceptor

A receptor on the sending neuron that detects its own neurotransmitter and helps regulate further release

Agonist

A chemical or drug that binds to a receptor site and activates it, mimicking or amplifying the action of an endogenous signaling molecule.

Antagonist

A chemical or drug that binds to a receptor site without activating it, effectively blocking or dampening the action of endogenous signaling molecules.

Local anesthetics (-caine)

Pharmacological agents that reversibly block voltage-gated sodium channels, preventing the initiation and conduction of sensory impulses.

Channelopathy

A clinical disease or pathological condition arising from structural or functional abnormalities in ion channel proteins.

Acetylcholine (ACh)

Twitches and spasms

TRIGGERS skeletal muscle contraction

Dopamine

A monoamine messenger involved in movement, reinforcement learning, reward processing, and motivation.

Serotonin

modulates MOOD, emotional stability, sleep-wake cycles, and APPETITE, and is directly influenced by hallucinogens.

Norepinephrine

A monoamine that helps regulate ALERTNESS, attention and arrousal

GABA (gamma-aminobutyric acid)

“The brains brakes”

MAIN inhibitory neurotransmitter

Slows down brain activity

Reduced = increased anxiety

Glutamate

The primary excitatory chemical messenger of the central nervous system, critical for long-term potentiation, synaptic plasticity, and learning.

Glycine

An amino acid that acts as a primary inhibitory chemical messenger within the brainstem and spinal cord.

Endorphins

Endogenous opioid peptides that bind to opioid receptors to blunt pain perception and induce sensations of pleasure.

Alcohol and GABA

Enhances inhibitory tone by binding as an allosteric modulator on $\text{GABA}_A$ receptor complexes, thereby depressing central nervous system excitability.

Valium (Diazepam)

A prescription benzodiazepine medication that acts as an allosteric enhancer of inhibitory $\text{GABA}_A$ receptor activity to produce anxiolytic and sedative effects.

Opioids

A class of analgesics that bind to selective receptor sites to mimic endogenous endorphins, producing pain relief and euphoria.

Naloxone (Narcan)

A rapid-acting competitive antagonist that binds opioid receptors with high affinity to displace narcotics and reverse life-threatening respiratory depression.

Stimulants

A broad pharmacological class of psychoactive agents that elevate central nervous system activity, alertness, cardiovascular output, and monoaminergic signaling.

Caffeine

A widely consumed psychoactive stimulant that promotes wakefulness and alertness primarily by competitively blocking adenosine receptors.

Nicotine

A potent psychoactive stimulant found in tobacco that acts as a direct agonist at ionotropic nicotinic acetylcholine receptors.

Cocaine

A powerful stimulant drug that amplifies synaptic monoamine transmission primarily by blocking dopamine transporter reuptake mechanisms.

Amphetamines

Sympathomimetic stimulant compounds that stimulate reverse transport and inhibit reuptake, markedly elevating synaptic dopamine and norepinephrine.

Methylphenidate (Ritalin) and lisdexamfetamine (Vyvanse)

Prescription stimulant formulations commonly used for ADHD that increase cognitive focus primarily by inhibiting the reuptake of dopamine and norepinephrine.

Methamphetamine

A potent synthetic stimulant that both massively stimulates reverse-transport dopamine release and impedes its reuptake, resulting in prolonged neurochemical surges.

Hallucinogens

A diverse category of psychoactive compounds (e.g., LSD, psilocybin, ketamine) that significantly alter sensory processing, subjective perception, and thought patterns.

Neuromodulators

Chemical substances that diffuse across neural populations without directly transmitting fast signals, instead modulating baseline excitability and circuit sensitivity.

Endocannabinoids

Naturally produced lipid-based retrograde messengers synthesized on demand by the body to regulate synaptic transmission.

Anandamide

A prominent endogenous cannabinoid neurotransmitter named from the Sanskrit word for bliss that participates in mood, appetite, and nociceptive regulation.

$\text{CB}_1$ receptors

Mainly in the CNS/brain

Involved in effects on memory, mood and movement

$\text{CB}_2$ receptors

Mainly associated with immune cells and peripheral tissues

Involved in immune responses and inflammation

THC (Tetrahydrocannabinol)

The principal psychoactive component of cannabis that binds as a partial agonist to central $\text{CB}_1$ receptors.

CBD (Cannabidiol)

A non-intoxicating constituent of cannabis that displays low direct affinity for $\text{CB}_1$ receptors and interacts predominantly with $\text{CB}_2$ and non-cannabinoid targets.

Placebo effect

A beneficial physical or cognitive change attributable purely to a subject's expectations, beliefs, and positive anticipation of a simulated therapeutic intervention.

Nocebo effect

When negative expectations or beliefs cause negative symptoms or effects

Central nervous system (CNS)

consisting of the brain and the spinal cord.

Peripheral nervous system (PNS)

The network of cranial and spinal nerves that lies outside the skull and spine

Connects CNS to the rest of the body

Somatic nervous system

Controls vuluntary SKELETAL MUSCLES

Autonomic nervous system

Controls automatic functions like heart rate and digestion

Sympathetic division

Fight or Flight

increases heart rate and alertness

Parasympathetic division

REST and DIGEST

Slows cardiac rate

Conserves metabolic energy

Afferent neurons (SENSORY)

Arrives → carries sensory info to the CNS

Efferent neurons (Motor)

Exits→ carries motor commands away from the CNS

Reflex

A rapid, involuntary, and stereotypic functional response to a specific sensory stimulus, typically coordinated through a localized spinal arc.

Endocrine system

Glands that produce and release hormones

An integrated communication system composed of ductless glands that secrete long-distance chemical messengers directly into the bloodstream.

Hormones

Circulating biochemical messengers produced by endocrine glands that travel through the cardiovascular system to alter distant target tissue physiology.

Hypothalamus

SWEATING, HUNGER, thirst, BODY TEMP and maintain homeostasis

helps regulate hormone release from the PITUITARY GLAND

🍔 Hypothalamus = hunger and body balance

Pituitary gland

The 'master' endocrine gland

Releases hormones and helps control other endocrine glans

helped by the hypothalamus with hormone release

Thyroid gland

A butterfly-shaped endocrine organ in the anterior neck that secretes thyroxine to modulate the basal metabolic rate and protein synthesis.

Parathyroid glands

Small endocrine structures embedded on the posterior thyroid surface that produce hormones controlling systemic calcium and phosphate homeostasis.

Adrenal glands

Endocrine organs positioned superior to the kidneys that release corticosteroids and catecholamines (epinephrine and norepinephrine) during stress responses.

Pancreas

A dual endocrine-exocrine abdominal organ that secretes insulin and glucagon to tightly control systemic glucose concentration.

Gonads (ovaries and testes)

Primary reproductive organs that secrete sex steroids (such as estrogens, progesterone, and testosterone) to guide sexual differentiation, development, and gametogenesis.

Biological psychology

The scientific branch that investigates how biological foundations, neural circuitry, genetics, and physiological mechanisms govern behavior and mental processes.

Biopsychosocial approach

A multi-layered conceptual model explaining health, mental processes, and behavior through the reciprocal interaction of biological, psychological, and sociocultural factors.

Neuroplasticity

The capacity of the nervous system to dynamically modify its synaptic connections, structural architecture, and functional pathways in response to experience, learning, or injury.

Neurogenesis

The developmental and biological process by which new, functional neurons are generated from neural stem or progenitor cells.

Lesioning

A neuroscientific research method that deduces functional brain localization by observing behavioral or cognitive deficits following natural trauma or surgical tissue destruction.

Electroencephalography (EEG)

A non-invasive diagnostic technique

Records ELECTRICAL activity in the brain

Magnetoencephalography (MEG)

A functional mapping technique that measures minute magnetic fields generated by synchronized neuronal electrical currents with high temporal precision.

Computed tomography (CT/CAT scan)

Uses XRAY SLICES to create images of the brain structures

Positron emission tomography (PET scan)

Measures brain activity by measuring METABOLIC ACTIVITY using a radioactive tracer

Can be consumed or injected

Magnetic resonance imaging (MRI)

A non-invasive diagnostic

Detailed and High Resolution images of brain structures using magnets

Functional magnetic resonance imaging (fMRI)

Measures changes in blood oxygenation to estimate brain activity.

Electrical stimulation of the brain (ESB)

An experimental technique applying micro-currents through inserted electrodes to depolarize specific neural substrates and observe resulting motor or experiential effects.

Transcranial magnetic stimulation (TMS)

A non-invasive technique

Uses magnetic pulses to temporarily disrupt activity in a targeted brain region.

Brainstem

comprising the medulla, pons, and midbrain

Medulla

Controls breathing, heart rate and blood pressure

Pons

relays motor signals between the cortex and cerebellum

while participating in sleep architecture and arousal

Reticular formation

ALERTNESS and wakefulness

Cerebellum

The hindbrain structure positioned dorsal to the brainstem

Controls balance, coordination and smooth movements

Hindbrain (Rhombencephalon)

composed of the medulla, pons, and cerebellum.

BASIC survival functions

Midbrain (Mesencephalon)

Movement, Senses and Reflex

Forebrain (Prosencephalon)

The largest, most rostral division of the brain

containing thalamus, hypothalamus and cerebral cortex and limbic structures.

Thalamus

Relays most sensory information to the cerebral cortex

The brains sensory relay station

Limbic system

Pleasure, Emotions, motivation and memory

KEY STRUCTURES including the amygdala and hippocampus

🧠 Hippocampus = memories

😨 Amygdala = emotions

🍔 Hypothalamus = hunger and body balance

📡 Thalamus = relays sensory information

Hippocampus

🧠 Hippocampus = memories

Helps form NEW MEMORIES and supports LEARNING