Neuroscience Lecture: Cellular Components, Neural Circuits, and Organization

A vocabulary set covering genetic/genomic concepts, cellular components of the nervous system (neurons and glia), neural circuits, and organizational principles discussed in the lecture notes.

Gene expression

Process by which a gene's information is used to synthesize a functional product (RNA or protein); in the nervous system, about 14,000 of ~20,000 genes are expressed (roughly 70%).

Coding gene

Gene sequences that are transcribed and translated into proteins.

Non-coding gene

Genes that are transcribed but not translated into proteins; regulate levels and timing of expression.

Introns

Non-coding segments within genes that are removed during RNA processing.

5' region

Regulatory region at the 5' end of a gene that can influence expression.

3' region

Regulatory region at the 3' end of a gene that can influence expression.

ASPM (Abnormal Spindle-like Microcephaly-associated)

Gene whose mutation affects mitotic spindles and is linked to microcephaly (reduced brain size).

Microcephaly

Condition in which the brain is smaller than normal.

Neuron

Fundamental cell of the nervous system with diverse morphologies.

Golgi stain

Silver staining method that labels the entire neuron; used by Golgi and Cajal.

Camillo Golgi

Physician-scientist who developed the Golgi staining method (1843–1926).

Santiago Ramón y Cajal

Neuroscientist known as the father of modern neuroscience; contributed to neuron doctrine.

Golgi apparatus

Cell organelle involved in modifying, sorting, and shipping proteins.

Soma (cell body)

Neuron cell body containing nucleus, Golgi apparatus, ribosomes, and mitochondria.

Dendrite

Neuron processes that receive synaptic input.

Axon

Neuron process that transmits electrical impulses away from the soma.

Axon hillock

Region where the axon originates from the soma; site of action potential initiation.

Initial segment

First portion of the axon where action potentials commonly begin.

Myelination

Insulation of axons by glial cells to speed conduction.

Node of Ranvier

Gaps in the myelin sheath where action potentials are regenerated.

Internode

Myelinated segment between successive Nodes of Ranvier.

Synaptic endings (boutons)

Presynaptic terminals where neurotransmitters are released.

Presynaptic

Relating to the transmitting side of a synapse.

Postsynaptic

Relating to the receiving side of a synapse.

Unipolar neuron

Neuron with a single process that typically divides into two branches.

Pseudounipolar neuron

Neuron with a single process that splits into two axons; common in dorsal root ganglia.

Bipolar neuron

Neuron with two processes (one dendrite, one axon), typical of some sensory pathways.

Multipolar neuron

Neuron with multiple dendrites and a single axon; most CNS neurons.

Basal dendrite

Dendrite located at the base of the cell body.

Apical dendrite

Dendrite extending from the apex of the cell body.

Receptive field

Region of sensory space where a stimulus will affect the neuron’s firing.

Center-surround

Receptive field organization with excitatory center and inhibitory/distant surround.

Projection neuron

Neuron that sends signals to distant areas of the brain or CNS.

Local interneuron

Interneuron that connects neurons within a local region.

Interneuron

Neuron that connects other neurons; can be local or projection.

Sensory neuron

Neuron that carries information from sensory receptors toward the CNS.

Motor neuron

Neuron that carries signals from the CNS to muscles or glands.

Neuroendocrine cell

Neuron that releases hormones into the bloodstream.

Glial cell

Non-neuronal support cells in the nervous system (astrocytes, oligodendrocytes, microglia, etc.).

Astrocyte

Star-shaped glial cell that maintains the neural microenvironment, the blood-brain barrier, and synaptogenesis; some astrocytes retain stem cell properties in adulthood.

Blood-brain barrier

Specialized barrier formed by astrocytes and endothelial cells that protects the CNS.

Oligodendrocyte

Glial cell that myelinates axons in the CNS.

Schwann cell

Glial cell that myelinates axons in the PNS.

Myelin

Insulating sheath around axons (CNS by oligodendrocytes; PNS by Schwann cells) that speeds conduction.

Microglial cell

Innate immune cells of the CNS; sentinels that secrete cytokines and respond to injury.

Cytokines

Signaling proteins released by immune cells to communicate and coordinate responses.

Glial stem cell

Subset of astrocytes capable of self-renewal and generation of multiple CNS cell types.

Subventricular zone

Region near ventricles where glial stem cells reside.

Oligodendrocyte precursor

Cell that can give rise to oligodendrocytes but is not a stem cell.

Ependymal cells

Line the ventricles; produce and help move cerebrospinal fluid (CSF).

Choroid plexus

Specialized ependymal region that produces most CSF.

Satellite cells

Support cells in the peripheral nervous system, located in dorsal root ganglia.

Dorsal root ganglion (DRG)

Cluster of sensory neuron cell bodies in the dorsal root of spinal nerves.

White matter

Myelinated nerve fibers that transmit signals between brain regions.

Grey matter

Neuron cell bodies and unmyelinated regions involved in local processing.

Central nervous system (CNS)

Brain and spinal cord; integrates motor and sensory information.

Peripheral nervous system (PNS)

All neural tissue outside the CNS; includes sensory and motor nerves.

Somatic motor nerves

Nerves that control voluntary skeletal muscles.

Autonomic nervous system

Motor system for visceral functions; includes sympathetic and parasympathetic divisions.

Sympathetic division

Autonomic division that generally stimulates the body ('fight or flight').

Parasympathetic division

Autonomic division that generally promotes rest and digest functions.

Topographic map

Point-to-point neural representation preserving peripheral receptor layout from periphery to cortex.

Homunculus

Topographic brain map representing body parts; a 'miniature man' illustrating cortical body maps.

Decussation

Crossing of nerve fibers from one side of the body to the opposite side of the CNS.

Contralateral

Mediated by the opposite side of the brain or body.

Afferent

Nerve fibers carrying sensory information toward the CNS.

Efferent

Nerve fibers carrying motor information away from the CNS.

Thalamus

Relay nucleus in the brain that forwards sensory information to the cortex.

Primary sensory cortex

First cortical region to process sensory input.

Secondary (association) cortex

Cortical areas that integrate information from primary regions for higher-order processing.

Lateral geniculate nucleus

Thalamic nucleus in the visual pathway that relays data to the visual cortex.

Visual cortex

Cortical region that processes visual information; organized by orientation and features.

Convergence

Many inputs onto a single neuron, allowing integration of information.

Conscious processing hierarchy

Functional systems are organized hierarchically, with information flowing through successive processing stages.