Comprehensive Neurobiology and Evolution: Brain Structures, Systems, and Disorders

Environment

All external (non-genetic) influences on behavior and traits (e.g. upbringing, culture, nutrition).

Eugenics

The (now widely discredited) idea of improving the human species by selective breeding or genetic control — often associated with unethical policies.

Evolutionary psychology

The approach that behavior and mental processes are shaped by natural selection and evolved adaptations.

Heredity

The transmission of genetic characteristics from parent to offspring (via genes).

Natural selection

The process by which heritable traits that increase survival or reproduction become more common in successive generations.

Autonomic Nervous System (ANS)

The branch of the peripheral nervous system that controls involuntary bodily processes (e.g. heartbeat, digestion).

Brain

The central organ of the nervous system housed in the skull; processes sensory information, initiates responses, stores memories, generates thought and emotion.

Central Nervous System (CNS)

The part of the nervous system comprising the brain and spinal cord.

Parasympathetic Nervous System

The branch of the autonomic system that calms the body and conserves energy ("rest and digest").

Peripheral Nervous System (PNS)

All the nerves outside the brain and spinal cord; it connects the CNS to the rest of the body.

Somatic Nervous System

The branch of the PNS that controls voluntary movements of skeletal muscles and relays sensory information to the CNS.

Spinal Cord

The cable of neural tissue running from the base of the brain through the vertebral canal; carries messages to/from the brain and also houses simple reflex arcs.

Sympathetic Nervous System

The branch of the autonomic system that readies the body for action (arousal, "fight-or-flight").

Myelin (or Myelin Sheath)

The fatty, insulating layer around many axons, enabling faster neural transmission.

Reflex Arc

A neural pathway that controls a reflex — typically involves a sensory neuron → interneuron → motor neuron; often bypasses the brain for faster reaction.

Glial Cell (or glia)

Non-neuron support cells in the nervous system; they maintain the chemical environment, provide nutrients, remove waste, guide neural development, etc.

Neuron

The basic cell of the nervous system specialized for sending and receiving signals (electrical & chemical).

Sensory Neuron (Afferent neuron)

Neurons that carry incoming information from sense receptors toward the CNS.

Interneuron

Neurons located within the CNS that process information between sensory and motor neurons.

Neurotransmitter

Chemical messengers released by neurons that travel across synapses to influence other neurons.

Synapse (Synaptic gap / cleft)

The junction (gap) between neurons where neurotransmitters pass signals.

Motor Neuron (Efferent neuron)

Neurons that carry outgoing instructions from the CNS to muscles or glands.

Acetylcholine (ACh)

A neurotransmitter involved in muscle action, memory, and learning.

GABA (Gamma-Aminobutyric Acid)

The primary inhibitory neurotransmitter in the brain (reduces neural excitability).

Multiple Sclerosis (MS)

A disorder in which the immune system attacks myelin sheaths in the CNS, impairing neural transmission.

Action Potential

The brief electrical charge (impulse) that travels down a neuron's axon when the neuron "fires."

Aminobutyric acid

Usually referring to GABA (gamma-aminobutyric acid).

Myasthenia Gravis (MG)

A neuromuscular disorder in which communication between nerves and muscles is impaired (e.g. via blocked ACh receptors).

Adrenaline (epinephrine)

A hormone and neurotransmitter that increases arousal, heart rate, blood flow, etc.

Ghrelin

A hormone produced in the stomach that stimulates hunger.

Norepinephrine

A neurotransmitter (and hormone) involved in arousal and alertness; also used by the sympathetic nervous system.

All-or-Nothing Principle

A neuron either fires fully or not at all; there is no partial firing.

Glutamate

The primary excitatory neurotransmitter in the brain (enhances neural activity).

Oxytocin

A hormone associated with bonding, social behavior, attachment, and childbirth/lactation.

Depolarization

The process during the action potential when the neuron's axon membrane becomes less negative (more positive) inside, triggering the impulse.

Hormone

Chemical messengers released by endocrine glands into the bloodstream, affecting target organs.

Pituitary Gland

A 'master' endocrine gland under the hypothalamus that regulates other endocrine glands.

Dopamine

A neurotransmitter associated with reward, movement, and motivation.

Hypothalamus

Brain region that regulates bodily maintenance (hunger, thirst, temperature), and controls the pituitary gland.

Refractory Period

The brief time after an action potential during which the neuron cannot fire again (or is less likely to).

Endorphin(s)

'Natural painkillers' (neuropeptides) produced by the brain; they inhibit pain signals and produce pleasure.

Inhibitory Neurotransmitter

A neurotransmitter that decreases the likelihood a neuron will fire (e.g. GABA).

Resting Potential

The electrical charge difference across the neuronal membrane when it is not firing (inside = negative relative to outside).

Excitatory Neurotransmitter

A neurotransmitter that increases the chance a neuron will fire (e.g. glutamate).

Leptin

A hormone produced by fat cells that signals satiety (fullness).

Reuptake

The process by which neurotransmitters are reabsorbed by the sending neuron after transmission.

Fight-Flight-or-Freeze

A response triggered by the sympathetic nervous system to prepare the body for threat or stress.

Long-Term Potentiation (LTP)

A lasting increase in synaptic strength between neurons, considered a neural basis of learning and memory.

Threshold

The level of excitatory stimulus that must be reached for a neuron to fire (trigger an action potential).

Serotonin

A neurotransmitter involved in mood regulation, appetite, and sleep.

Melatonin

A hormone produced by the pineal gland that helps regulate circadian rhythms (sleep/wake).

Substance P

A neurotransmitter involved in the transmission of pain signals.

Amygdala

A limbic structure involved in emotion, especially fear, aggression, and emotional memory.

Hemisphere

One half of the brain; we talk of the left and right cerebral hemispheres.

Prefrontal Cortex

The area at the front of the frontal lobe involved in planning, decision-making, impulse control, and executive functions.

Aphasia

Impairment in language (speaking, understanding, reading, writing) due to brain damage (often to Broca's or Wernicke's areas).

Procedural Learning

Learning of skills, habits, or tasks (motor or perceptual) that become automatic (e.g. riding a bike).

Association Area

Regions of the cortex that integrate information from various modalities (not primary sensory or motor).

Hippocampus

A brain structure in the limbic system critical for forming new declarative (explicit) memories.

Reticular Activating System (RAS)

A network in the brainstem that regulates arousal, attention, and sleep-wake transitions.

Brain Stem

The lower extension of the brain connecting to the spinal cord; controls basic life functions.

Broca's Area

Region in the frontal lobe (typically left hemisphere) essential for speech production.

Limbic System

A system of brain structures (including amygdala, hippocampus, hypothalamus) involved in emotion, motivation, and memory.

Cerebellum

A hindbrain structure that coordinates voluntary movement, balance, and fine motor skills; also implicated in some cognitive processes.

Lobe

A major subdivision of the cerebral cortex (frontal, parietal, occipital, temporal).

Reward Center

Neural circuits (often involving dopamine in the nucleus accumbens and related areas) that reinforce behaviors by producing pleasurable feelings.

Cerebral Cortex

The outermost layer of the brain (gray matter) responsible for higher-order processes (thinking, perception, language).

Medulla Oblongata (Medulla)

The base of the brainstem, controlling vital functions like breathing and heartbeat.

Contralateral Hemispheric Organization

The concept that each hemisphere of the brain controls the opposite side of the body (e.g. left hemisphere controls right side).

Somatosensory Cortex

Located in the parietal lobe, this area receives and processes bodily sensory information (touch, pressure, temperature).

Motor Cortex

Located in the frontal lobe (just anterior to the central sulcus), this region controls voluntary muscle movements.

Split Brain

A condition resulting from severing the corpus callosum, disrupting communication between hemispheres.

Corpus Callosum

The large band of neural fibers connecting the two cerebral hemispheres, allowing communication between them.

Nucleus (in neuroscience)

A cluster of neurons in the brain that function together (not to be confused with cell nucleus).

Temporal Lobe

The lobe involved in auditory processing, language comprehension (Wernicke's area), and memory.

Cortex Specialization

The idea that different parts of the cortex are specialized for different functions (e.g. visual cortex, auditory cortex).

Occipital Lobe

The lobe at the rear of the brain dedicated mainly to visual processing.

Thalamus

The brain's "relay station" — directs incoming sensory information (except smell) to appropriate areas of the cortex, and relays motor signals.

Epilepsy

A neurological disorder characterized by recurrent, uncontrolled electrical disturbances (seizures) in the brain.

Parietal Lobe

The lobe that processes spatial information, touch, and somatosensory input.

Wernicke's Area

Region in the temporal lobe (typically left hemisphere) critical for language comprehension.

Executive Function

Higher-order cognitive processes such as planning, decision-making, inhibiting impulses, working memory (often associated with prefrontal cortex).

Electroencephalography / Electroencephalogram (EEG)

A noninvasive method that records electrical activity (brain waves) of the cortex via electrodes on the scalp.

Functional Magnetic Resonance Imaging (fMRI)

A neuroimaging technique that measures brain activity by detecting changes in blood flow (oxygenation) in active brain regions.

Lesion / Lesioning

A research or clinical method involving damage (intentional or accidental) to a specific brain region to study its function (e.g. animal lesion studies or observing human brain injuries).