Glossary

Amygdala - part of the telencephalon, located in the temporal lobe. It is involved in memory, emotion, and fear, essentially acting as the brain's warning center. The fight-or-flight response originates with the amygdala. The amygdala is just beneath the surface of the front, medial part of the temporal lobe where it causes the bulge on the surface called the uncus. This is a component of the limbic system

Autonomic nervous system - part of the peripheral nervous system that supplies neural connection to glands and smooth muscles of internal organs; made of two divisions (sympathetic and parasympathetic), and sometimes is considered to have a third division called the enteric system

Axon - extension from the cell that carries nerve impulses from the cell body to other neurons

Basal ganglia - group of structures which coordinate movement; located in the forebrain (telencephalon)

Brain - a multi-layered structure containing billions of neurons and countless numbers of neuronal connections, thousands of specialized regions

Brainstem - also known as the hindbrain; region of the brain that consists of the midbrain (tectum, tegmentum), pons, and medulla; responsible for functions such as breathing, heart rate, and blood pressure

Cell Body - region of the neuron defined by the presence of a nucleus; also called the soma

Central nervous system (CNS) - portion of the nervous system that includes the brain and the spinal cord

Central sulcus - the major groove which divides the frontal lobe from the parietal lobe

Cerebellum - structure located in the back of the brain (dorsal to the pons) involved in central regulation of movement, such as basic movement, balance, and posture; comes from the Latin word meaning "little brain"; is divided into two hemispheres and has a cortex

Cerebral cortex - the outer covering of the cerebral hemispheres consisting mostly of nerve cell bodies and branches; involved in functions such as thought, voluntary movement, language, reasoning, and perception; the right and left sides of the cerebral cortex are connected by a thick band of nerve fibers (corpus callosum); highly grooved or "gyrencephalic" in mammals

Cerebral hemispheres - right and left halves of the forebrain

Corpus callosum - the large bundle of axons which connect the two cerebral hemispheres. It disseminates information from the cerebral cortex on one side of the brain to the same region on the other side

Dendrite - one of the extensions of the cell body that are reception surfaces of the neuron

Diencephalon - part of the midbrain; consists of the thalamus and hypothalamus

Dorsal - anatomical term referring to structures toward the back of the body or top of the brain

Encephalization factor - a measure of brain size relative to body size

Forebrain - the frontal division of the brain which contains cerebral hemispheres, the thalamus, and the hypothalamus

Frontal lobe - the most anterior portion of the cerebral cortex (in front of the central sulcus); it is involved in reasoning, planning, parts of speech, movement, emotions, and problem-solving

Glial cells - nonneuronal brain cells that provide structural, nutritional, and other supports to the brain

Gray matter - areas of the brain that are dominated by cell bodies and have no myelin covering (in contrast to white matter)

Gyrencephalic - when the cerebral cortex is highly folded and convoluted (due to gyri and sulci)

Gyrus - raised portion of convoluted brain surface

Hindbrain - the rear division of the brain, includes the cerebellum, ponds, and medulla (also called the rhombencephalon)

Hippocampus - the portion of the cerebral hemisphers in basal medial part of the temporal lobe. This part of the brain is important for learning and memory -- for converting short term memory to more permanent memory, and for recalling spatial relationships in the world about us

Hypothalamus - part of the diencephalon, ventral to the thalamus. The structure is involved in functions including homeostasis, emotion, thirst, hunger, circadian rhythms, and control of the autonomic nervous system. In addition, it controls the pituitary gland

Lateral - anatomical term meaning toward the side (versus medial)

Limbic system - a group of structures including the amygdala and hippocampus (and others); important for controlling emotions and memory

Lissencephalic - when the telencephalic hemispheres (i.e. cerebral cortex) are relatively smooth (as opposed to "gyrencephalic" when the cortex is highly folded); for example, the difference is apparent when comparing a human brain with a squirrel brain

Medulla Oblongata/Myelencephalon - this structure is the caudal-most part of the brain stem, between the pons and spinal cord. It is responsible for maintaining vital body functions, such as breathing and heartrate. See overall nervous system organization

Metencephalon - subdivision of the hindbrain, which includes the cerebellum and pons

Midbrain/Mesencephalon - middle division of the brain, which includes the tectum and tegmentum; involved in functions such as vision, hearing, eye movement, and body movement

Motor cortex - a region of the cerebral cortex that sends impulses to motor neurons; involved in coordination of movement; found in the frontal lobe

MRI - magnetic resonance imaging; noninvasive technique that uses magnetic energy to generate images that reveal some of the structural details in the living brain

Myelencephalon - caudal part of the hindbrain, includes the medulla oblongata

Myelin - fatty insulation around an axon which improves the speed of conduction of nerve impulses

Neocortex - recently evolved six-layered portions of the cerebral cortex (found in mammals); sometimes referred to as the "isocortex"; the neocortex occupies the bulk of the cerebral hemispheres

Nervous System - extends throughout the entire body and connects every organ to the brain; can be divided into the central nervous system (CNS) and the peripheral nervous system (PNS); the basic building blocks of the nervous system are nerve cells or neurons

Neural connectivity - estimated from length of dendritic trees of cortical neurons

Neuroanatomy - the structure of the nervous system

Neuron - the basic building block of the brain; these cells receive input from other nerve cells and distribute information to other neurons; the information integration underlies the simplest and most complex of our thoughts and behaviors

Neuroscience - the science of the nervous system

Neurotransmitter - chemical substance which is released by the presynaptic neuron at synapses that transmits information to the next neuron

Occipital lobe - the posterior lobe of the brain; involved with vision (the "occipital lobe" is also referred to as the "visual cortex")

Olfactory bulb - structure at the rostral end of the telencephalon that is involved in smell

Parasympathetic nervous system - one of the two systems that makes up the autonomic nervous system; a parasympathetic response constricts pupils, stimulates salivation, constricts airways, slows the heartbeat, stimulates digestion, etc.

Parietal lobe - located behind the frontal cortex (and central sulcus); involved in perception of stimuli related to touch, pressure, temperature, and pain

Peripheral nervous system (PNS) - portion of the nervous system that incluces all the nerves and neurons outside the brain and spinal cord

Pituitary gland - small gland which secretes hormones located at the base of the skull

Pons - part of the metencephalon in the hindbrain. It is involved in motor control and sensory analysis; for example, information from the ear first enters the brain in the pons. It has parts that are important for the level of consciousness and for sleep. Some structures within the pons are linked to the cerebellum, thus are involved in movement and posture

Prefrontal cortex - the most anterior region of the frontal cortex; involved in problem solving, emotion, and complex thought

Presynaptic - the region of a synapse that releases the neurotransmitter (in contrast to postsynaptic)

Primary motor cortex - region for initiation of voluntary movement

Primary somatosensory cortex - region which receives tactile information from the body

Primary visual cortex - the region of the occipital cortex where most visual information first arrives

Prosencephalon - the forebrain; lies rostral to the midbrain (mesencephalon); consists of the telencephalon (cerebral cortex & hippocampus), and diencephalon (thalamus and hypothalamus)

Putamen - another component of the limbic system. This part is responsible for familiar motor skills

Rhombencephalon - also known as the hindbrain; lies caudal to the midbrain (mesencephalon); composed of the metencephalon and myelencephalon

Sagittal - the plane that bisects the body or brain into right and left halves

Sulcus - a furrow of convoluted brain surface (opposite of gyrus)

Sympathetic nervous system - one of the two systems that compose the autonomic nervous system; a sympathetic response dilates pupils, inhibits salivation, relaxes airways, accelerates the heartbeat, inhibits digestion, etc.

Synapse - the area between one neuron and the next, through which neurotransmitters are passed which transmit neural messages

Tectum - the dorsal portion of the midbrain (mesencephalon)

Tegmentum - ventral part of the midbrain (mesencephalon)

Telencephalon - the frontal subdivision of the forebrain, includes the cerebral hemispheres and the hippocampus, basal ganglia, and amygdala

Temporal lobe - located below the frontal and parietal lobes; involved in perception and recognition of auditory stimuli and memory

Thalamus - a large mass of gray matter deeply situated in the forebrain at the topmost portion of the diencephalon. The structure has sensory and motor functions. Almost all sensory information enters this structure where neurons send that information to the overlying cortex. Axons from every sensory system (except olfaction) synapse here as the last relay site before the information reaches the cerebral cortex

Visual cortex - located in the occipital lobe; involved in detection of simple visual stimuli

White matter - the shiny layer underneath the cortex that consists mostly of axons with white myelin sheaths (in contrast to gray matter)