Intro to Neuroscience - Chapter 1

motor system

A broad term used to describe all the central and peripheral structures that support motor behavior.

sympathetic nervous system

A division of the visceral motor system in vertebrates comprising, for the most part, adrenergic ganglion cells located relatively far from the related end organs.

parasympathetic nervous system

A division of the visceral motor system in which the effectors are cholinergic ganglion cells located near target organs.

myotatic reflex

A fundamental spinal reflex that is generated by the motor response to afferent sensory information arising from muscle spindles. The knee jerk reaction is a common example. Also called a "stretch" or "deep tendon" reflex.

white matter

A general term that refers to large axon tracts in the brain and spinal cord; the phrase derives from the fact that axonal tracts have a whitish cast when viewed in the freshly cut material.

Afferent

A neuron or axon that conducts action potentials from the periphery toward the central nervous system.

efferent

A neuron or axon that conducts information away from the central nervous system toward the periphery.

projection neuron

A neuron with long axons that project to distant targets.

Dendrite

A neuronal process arising from the nerve cell body that receives synaptic input.

gap junction

A specialized intercellular contact formed by channels that directly connect the cytoplasm of two cells.

enteric system

A subsystem of the visceral motor system, made up of small ganglia and individual neurons scattered throughout the wall of the gut; influences gastric motility and secretion.

peripheral nervous system (PNS)

All nerves and neurons that lie outside the brain and spinal cord.

Commissures

Axon tracts that cross the midline of the brain

motor neuron

By common usage, any nerve cell that innervates skeletal muscle.

Neurons

Cells specialized for the conduction and transmission of electrical signals in the nervous system. Also called nerve cells.

Computational mapping

Central process of assessing and integrating multiple stimulus attributes into an orderly representation that facilitates the extraction and processing of essential information (e.g., the number and configuration of odorant molecules in order to determine the source and nature of a smell).

ganglion (ganglia)

Collection of hundreds to thousands of neurons found outside the brain and spinal cord along the course of peripheral nerves.

Nucleus (pl. nuclei)

Collection of nerve cells in the brain that are anatomically discrete, and which typically serve a particular function.

local circuit neuron

General term referring to a neuron whose activity mediates interactions between sensory systems and motor systems. Interneuron is often used as a synonym.

gray matter

General term that describes regions of the central nervous system rich in neuronal cell bodies and neuropil; includes the cerebral and cerebellar cortices, the nuclei of the brain, and the central portion of the spinal cord.

Schwann cells

Glial cells in the peripheral nervous system that lay down myelin (named after the nineteenth-century anatomist and physiologist Theodor Schwann).

gene

Hereditary unit located on the chromosomes; genetic information is carried by linear sequences of nucleotides in DNA that code for corresponding sequences of amino acids.

Convergence

Innervation of a target cell by axons from more than one neuron. In vision refers specifically to the convergence of both rod and cone photoreceptor cells onto retinal ganglion cells.

electrophysiological recording

Measure of the electrical activity across the membrane of a nerve cell by use of electrodes. Extracellular recording places the electrode outside but nearby the cell of interest; intracellular recording places the electrode is placed inside the cell of interest.

associational systems

Neural cell circuits that are not part of the relatively defined sensory (input) and motor (output) systems; they mediate the most complex and least well defined brain functions.

glial stem cells

Neural precursor cells in the adult brain that retain the capacity to proliferate and generate both additional precursor cells and differentiated glial cells (and, in some cases, differentiated neurons).

microglial cells

One of the three major classes of glial cells found in the central nervous system; concerned primarily with repairing damage following neural injury.

astrocytes

One of the three major classes of glial cells found in the central nervous system; important in regulating the ionic milieu of nerve cells and, in some cases, transmitter reuptake.

oligodendrocytes

One of the three major classes of glial cells found in the central nervous system; their major function is to lay down myelin.

Axon hillock

Point at the cell body that is the site of an action potential's initiation

postsynaptic

Referring to the component of a synapse specialized for transmitter reception; downstream at a synapse.

presynaptic

Referring to the component of a synapse specialized for transmitter release; upstream at a synapse.

visceral

Referring to the internal organs of the body cavity, particularly the gut.

genomics

Scientific field focusing on the analysis of DNA sequences, including both protein-coding DNA (genes) and non-coding DNA

retrograde

Signals or impulses that travel "backward," e.g., from the axon terminal toward the cell body, or from the postsynaptic cell to the presynaptic terminal, or from the periphery to the CNS.

Anterograde

Signals or impulses that travel "forward," e.g., from the cell body to the axon terminal, from the presynaptic terminal to the postsynaptic cell, or from the CNS to the periphery.

synaptic vesicles

Spherical, membrane-bound organelles in presynaptic terminals that store neurotransmitter molecules.

Neurotransmitter

Substance released by synaptic terminals for the purpose of transmitting information from one cell (the presynaptic cell) to another (the postsynaptic cell).

electrical synapses

Synapses that transmit information via the direct flow of electrical current at gap junctions.

Chemical synapses

Synapses that transmit information via the secretion of chemical signals (neurotransmitters).

Interneuron

Technically, a neuron in the pathway between primary sensory and primary effector neurons; more generally, a neuron whose relatively short axons branch locally to innervate other neurons. Also known as local circuit neuron.

sensory system

Term sometimes used to describe all the components of the central and peripheral nervous system concerned with sensation.

Central nervous system (CNS)

The brain and spinal cord of vertebrates (by analogy, the central nerve cord and ganglia of invertebrates)

synaptic transmission

The chemical and electrical process by which the information encoded by action potentials is passed from a presynaptic (initiating) cell to a postsynaptic (target) cell.

Neurophil

The dense tangle of axonal and dendritic branches, and the synapses between them, that lies between neuronal cell bodies in the gray matter of the brain and spinal cord.

Action potential

The electrical signal conducted along axons (or muscle fibers) by which information is conveyed from one place to another in the nervous system

Cognitive neuroscience

The field of neuroscience devoted to studying and understanding cognitive functions

receptor potential

The membrane potential change elicited in receptor neurons during sensory transduction. Also called generator potential.

myelin

The multilaminated wrapping around many axons formed by oligodendrocytes or Schwann cells.

Axon

The neuronal process that carries the action potential from the nerve cell body to a target.

spinal cord

The portion of the central nervous system that extends from the lower end of the brainstem (the medulla) to the cauda equina.

receptive field

The region of a receptive surface (e.g., the body surface, or a specialized structure such as the retina) within which a specific stimulus elicits the greatest action potential response from sensory cells.

Dorsal root ganglia

The segmental sensory ganglia of the spinal cord; they contain the first-order neurons of the dorsal column/medial lemniscus and spinothalamic pathways.

Cranial nerve ganglia

The sensory ganglia associated with the cranial nerves; these correspond to the dorsal root ganglia of the segmental nerves of the spinal cord.

synaptic cleft

The space that separates pre- and postsynaptic neurons at chemical synapses.

cortex

The superficial mantle of gray matter (a sheet-like array of nerve cells) covering the cerebral hemispheres and cerebellum, where most of the neurons in the brain are located.

Divergence

the branching of a single axon to innervate multiple target cells

glia cells (glia)

the support cells associated with neurons (astrocytes, oligodendrocytes, and microglial cells in the central nervous system; Schwann cells in peripheral nerves; and satellite cells in ganglia).