Biological Psychology: The Neuron and The Brain

Phineas Gage

Railroad worker whose personality changed after a September 13, 1848 accident where a tamping iron ($3\,\text{feet } 7\,\text{inches}$ / $1.1\,\text{m}$ long and $13\frac{1}{4}\,\text{pounds}$) passed through his brain, demonstrating that different brain regions control different aspects of personality.

Representative Gabby Giffords

Arizona Democratic Congresswoman who survived a gunshot wound passing through the left side of her brain, an area that controls the right side of the body, logic, language, and mathematical skills.

Neuron

The basic nerve cell of the nervous system responsible for receiving, processing, and sending electrical and chemical signals.

Synapse

The tiny junction or gap between the axon tip of the sending neuron and the dendrite or cell body of the receiving neuron.

Nodes of Ranvier

Gaps in the myelin sheath along an axon that help speed up neural transmission.

Myelin Sheath

A layer of fatty tissue covering the axon of some neurons that speeds up neural impulses; its breakdown causes Multiple Sclerosis.

Glial Cells

Support cells in the brain that act as a maintenance crew by providing nutrients, cleaning up waste, protecting neurons, and repairing injuries.

Action Potential

An electrical charge or impulse generated when a neuron fires, caused by the movement of sodium ($\text{Na}^+$) and potassium ($\text{K}^+$) ions across the axon membrane.

Resting Potential

The electrical state of a neuron at rest, characterized by a slightly negative charge inside the neuron measured at $-70\,\text{mV}$.

All-or-None Response

The principle stating that a neuron either fires completely with full impulse strength or does not fire at all.

Absolute Refractory Period

The minimum time period of $1\,\text{ms}$ to $2\,\text{ms}$ after an action potential during which another action potential cannot begin.

Excitatory Neurotransmitter

A chemical messenger, such as Glutamate, that promotes the generation of an electrical signal (action potential) in a receiving neuron.

Inhibitory Neurotransmitter

A chemical messenger, such as GABA or Serotonin, that blocks or prevents a chemical message from being passed on to the receiving neuron.

Sensory Neurons

Afferent nerve cells that receive information from environmental stimuli (such as heat, light, pressure, muscle tension, and odor) and transmit it to the central nervous system.

Motor Neurons

Efferent nerve cells that transmit instructions from the central nervous system out to the body's muscles and glands.

Interneurons

Neurons located within the central nervous system that communicate internally and intervene between sensory inputs and motor outputs.

Reflex Arc

A neural pathway in the spinal cord that controls a rapid, involuntary reflexive action before conscious thought occurs in the brain.

Reuptake

The process by which a sending neuron reabsorbs excess neurotransmitter molecules from the synaptic gap.

Agonist

A drug or molecule structurally similar to a neurotransmitter that binds to its receptor and mimics its effects (e.g., Morphine, Heroin, Nicotine).

Antagonist

A drug or molecule structurally similar enough to occupy a receptor site and block neurotransmitter action without stimulating the receptor (e.g., Curare, Botox).

Acetylcholine (ACh)

Neurotransmitter enabling muscle action, learning, and memory; deterioration of this is linked to Alzheimer's disease.

Myasthenia Gravis

Chronic autoimmune disorder where antibodies destroy or block acetylcholine receptors at the neuromuscular junction, causing severe skeletal muscle weakness.

Curare

A poison historically used on hunting blowgun darts that acts as an ACh antagonist, causing muscle paralysis by blocking acetylcholine receptors.

Dopamine

Neurotransmitter influencing movement, learning, attention, alertness, and emotion; excess receptor activity is linked to schizophrenia, while scarcity produces Parkinson's disease tremors.

Substance P

A neuropeptide acting as a neurotransmitter in the nervous system involved in moderate pain, stress, anxiety, and inflammation.

Norepinephrine

Neurotransmitter helping control alertness, arousal, and the fight-or-flight response; an undersupply can depress mood.

Serotonin

Neurotransmitter affecting mood, hunger, sleep, and arousal; an undersupply is linked to clinical depression, OCD, and eating disorders.

Selective Serotonin Reuptake Inhibitors (SSRIs)

Medications (such as Prozac, Zoloft, and Paxil) that treat depression and anxiety by blocking the reuptake of serotonin in the synaptic cleft.

GABA (gamma-aminobutyric acid)

Major inhibitory neurotransmitter in the central nervous system; undersupply is linked to seizures, tremors, and insomnia.

Glutamate

Major excitatory neurotransmitter involved in memory; oversupply can overstimulate the brain, producing migraines or seizures.

Endorphins

Opiate-like neurotransmitters involved in pain control and pleasure sensations.

Central Nervous System (CNS)

Division of the nervous system comprising exclusively the brain and the spinal cord.

Peripheral Nervous System (PNS)

Division of the nervous system containing all nerves not encased in bone, categorized into somatic and autonomic systems.

Somatic Nervous System

Subdivision of the peripheral nervous system that controls voluntary muscle movements using motor (efferent) neurons.

Autonomic Nervous System

Subdivision of the peripheral nervous system controlling self-regulated, automatic functions of internal organs and glands.

Sympathetic Nervous System

Branch of the autonomic nervous system responsible for the fight-or-flight response by accelerating heartbeat, dilating pupils, and slowing digestion.

Parasympathetic Nervous System

Branch of the autonomic nervous system responsible for calming the body during rest-and-digest states by slowing heartbeat, constricting pupils, and stimulating digestion.

Endocrine System

The body's chemical communication system composed of glands that secrete hormones into the bloodstream, governed by the pituitary gland.

Leptin

A protein hormone secreted by fat cells that signals the hypothalamus to curb appetite and increase energy expenditure.

Ghrelin

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

Brain Lesions

The removal or deliberate destruction of a specific part of the brain used in research to observe functional changes.

Electroencephalogram (EEG)

Tool that records electrical wave activity across the brain's surface via scalp electrodes, primarily used in sleep research.

Computerized Axial Tomography (CAT Scan)

Brain imaging technique that takes a 3D X-ray structure of the brain; less expensive than an MRI scan.

Magnetic Resonance Imaging (MRI)

Imaging technique using magnetic fields to produce detailed pictures of soft tissues, brain tumors, strokes, and structural abnormalities.

Positron Emission Tomography (PET Scan)

Functional brain scan measuring chemical usage (such as glucose consumption) via a radioactive drug tracer.

Functional MRI (fMRI)

Neuroimaging technique combining PET and MRI principles to assess brain function and blood flow during specific tasks.

Brainstem

The oldest part and central core of the brain, starting where the spinal cord swells as it enters the skull, comprising structures like the medulla, pons, and reticular formation.

Medulla Oblongata

Structure located just above the spinal cord in the brainstem controlling vital autonomic functions: blood pressure, heart rate, and breathing.

Pons

Brainstem structure located above the medulla that connects the hindbrain with the midbrain and forebrain, involved in sleep and arousal.

Reticular Activating System (RAS)

A nerve network in the brainstem controlling arousal, sleep/wakefulness, fight-or-flight, and the ability to focus attention.

Cerebellum

Structure at the bottom rear of the brain ("little brain") responsible for coordinating fine voluntary muscle movements and balance.

Thalamus

The brain's sensory switchboard located atop the brainstem, receiving incoming sensory signals from the spinal cord (except smell) and routing them to the forebrain.

Limbic System

The emotional control center of the brain located at the border of the brainstem and cerebral hemispheres, composed of the hypothalamus, amygdala, and hippocampus.

Hypothalamus

Limbic system structure regulating basic drives (hunger, thirst, body temperature, sexual arousal) and governing the endocrine system through the pituitary gland.

Hippocampus

Structure in the limbic system essential for processing, organizing, and storing long-term explicit memories.

Amygdala

Limbic system structure involved in memory processing and handling volatile emotional responses such as anger and fear.