General Terminology - Neuroscience

Regional Neurobiology

study of the structure and function of anatomic parts of the nervous system (e.g, study of the brain stem)

Systems Neurobiology

study of the functional systems that involve the interaction of multiple regions of the nervous system (e.g., study of the motor system)

Terms of Relationship and Comparison

• Rostral: refers to the head of the organism; toward the face/nose (excluding brainstem)

• Caudal: refers to the tail of the organism; toward the buttocks/tail (excluding brainstem)

• Ventral/Anterior: refers to the front of the organism; toward the front or “belly”

• Dorsal/Posterior: refers to the back of an organism; toward the back

• Lateral & Medial: reference point is the midline of a structure – lateral: further from midline; medial: closer to midline

• Superior & Inferior: refers to spatial relationships in the vertical direction – superior: toward the top (with reference to the cortex of the brain the term dorsal is frequently used); inferior: toward the bottom (with reference to the cortex of the brain the term ventral is frequently used)

Terms of Laterality

• Ipsilateral: same side

• Contralateral: opposite side

• Unilateral: occurring on only one side of the body

• Bilateral: occurring on both sides of the body

Plans of the Brain Sections/Brain Slices

• Horizontal Slice: cut made in the horizontal plane: mid-horizontal section divides the brain into superior and inferior halves

• Coronal Slice: cut made in the coronal plane: mid-coronal section divides the brain into anterior and posterior halves

• Sagittal Slice: cut made in the sagittal plane: mid-sagittal section divides the brain into right and left halves

Structural Divisions of the Nervous System

• Central Nervous System: consists of the brain and spinal cord

• Peripheral Nervous System: consists of the spinal nerves, the cranial nerves, and the ganglia (collection of cell bodies located outside the CNS) associated with them

Functional Divisions of the Nervous System

• Somatic Nervous System: parts of the CNS and PNS that regulate skeletal muscle and that convey somatic sensory information coming from the periphery

• Autonomic Nervous System: parts of the CNS and PNS that regulate smooth muscle, cardiac muscle, glandular secretion, and that convey sensory information coming from the viscera

  • Parasympathetic Division: rest/digest

  • Sympathetic Division: fight/flight

Neuron: (aka nerve cell)

Basic structural and functional unit of the nervous system; responsible for receiving, integrating and transmitting electrical impulses that impact other neurons or target tissue (e.g., skeletal muscle)

Parts of a Neuron

• Dendrite: branching processes that conduct impulses toward the body of a neuron (receiving end of the neuron)

• Soma: cell body – contains all of the organelles that are required to keep the cell functioning

• Axon: branching processes that conduct impulses away from the body of the neuron (sending end of the neuron)

• Myelin: insulating lipoprotein that surround some axons

• Afferent: conduction toward a structure or incoming information (e.g., posterior or dorsal root of a spinal nerve)

• Efferent: conduction away from a structure of outgoing information (e.g., anterior or ventral root of a spinal nerve)

• Synapse: is the location where information from one neuron is transmitted to another neuron or to an effector target (e.g., muscle or gland)

• Neurotransmitter: chemical messenger

Glia: “glue” supporting cells in the CNS”

• Astrocytes

• Oligodendrocytes

• Microglial cells

Gray Matter

collection of neural cell bodies

Examples of terms that apply to gray matter

• Cortex: (pl. cortices) outer layer of gray matter that covers the surfaces of the cerebral hemispheres and cerebellum

• Nucleus: (pl. nuclei) a distinguishable mass of neuronal cell bodies in the CNS

• Lamina: (pl. laminae) a distinguishable layer of neuronal cell bodies in the CNS

• Posterior or Dorsal horn: gray matter in the spinal cord that contains second order sensory neurons

• Anterior or Ventral horn: gray matter in the spinal cord that contains somatic motor neurons

• Lateral horn: gray matter in the spinal cord that contains visceromotor neurons

• Ganglion: (pl. ganglia) a distinguishable mass of neuronal cell bodies in the PNS

White matter

collection of axons in the CNS

Examples of terms that apply to white matter

• Nerve: bundle of axons in the PNS

• Tract: collection of axons in the CNS that originate from a similar location and go to a similar destination

• Commissure: collection of axons that connect both hemispheres or both sides of the spinal cord

• Column: axonal tracts that carry information to and from the spinal cord

• Lemniscus: (pl. lemnisci) tract that travels through the brain resembling a ribbon

• Fasciculus: (pl. fasciculi) bundle or packet of nerve fibers traveling in the CNS (e.g., cuneate fasciculus)

• Funiculus: (pl. funiculi) cord – area of white matter that may consist of several functionally different fasciculi (e.g., lateral funiculus of the spinal cord) or tracts

• Decussation: point of crossing of paired tracts (e.g., left tract crosses to the right side and vis versa; decussations of the pyramids, the medial lemnisci, and superior cerebellar peduncles are examples

Regions of the Brain

• Telencephalon: consists of the cerebral hemispheres and related deep structures (e.g., insula, limbic structures (e.g., hippocampus and amygdala) and basal nuclei)

• Diencephalon

• Cerebellum: means “little brain” – plays a prominent role in motor control and motor learning

• Brainstem: mediates vegetative functions (e.g., control of respiration, blood pressure regulation), auditory and visual reflexes, arousal, sleep/wake patterns, modulation of pain signals, and it plays a role in motor control.

Telencephalon — Cerebral Structures

• Cerebrum: is divided by a fissure (deep groove) called the median longitudinal fissure into right and left hemispheres, and it has a folded appearance: the ridge or elevated area of the fold is called a gyrus (pl. gyri) and the groove or crease between folds is known as a sulcus (pl. sulci). Gyri and sulci have specific names and are associated with specific functions (e.g., the precentral gyrus is considered the primary motor cortex (M1) and it contributes to the control of voluntary movements).

• Each hemisphere consists of 4 main separate lobes, the insula, and deep structures.

  • Frontal Lobes: mediates motor planning and execution, expressive language, & mental functions (e.g., executive functions, social cognition & emotional regulation)

  • Parietal Lobes: detection of somatosensory information, and the integration, perception, and interpretation of sensory information (e.g., visuospatial processing, language comprehension, and self-processing operations)

  • Temporal Lobes: detection of auditory information and basic auditory processing, language comprehension, object identification, long-term memory formation, and social cognition

  • Occipital Lobes: detection of visual stimuli and basic visual processing

  • *Insula: considered a fifth lobe in some sources: related to basic survival mechanisms such as taste perception and the processing of visceral sensations; also thought to play a role in emotional processing

  • Deep Structures:

    • Basal Nuclei: caudate, putamen, and globus pallidus – involved with motor, cognitive and emotional functions.

    • Limbic Structures: hippocampus and amygdala – involved with memory formation and emotional processing

    • Internal capsule: large fiber bundle that connects the cerebral cortex with the diencephalon

Diencephalon Structures

• Thalamus: contains multiple nuclei and serves as a gateway for information traveling to/from the cortex, as such it is involved with multiple functions

• Hypothalamus: contains multiple nuclei and is instrumental in regulating visceromotor, viscerosensory, and endocrine functions

• Sub-thalamus: contains the subthalamic nucleus which plays a role in motor control

• Epithalamus: contains the pineal gland which plays a role in regulating circadian rhythms

Brainstem: consists of the following three structures from rostral to caudal

• Midbrain

• Pons

• Medulla

Additional terminology applied during development of the brain

• Mesencephalon: corresponds to the midbrain during development

• Metencephalon: corresponds to the pons and cerebellum during development

• Myelencephalon: corresponds to the medulla during development

• Prosencephalon: forebrain during development

• Rhombencephalon: hindbrain during development