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 NEUROBIOLOGY Molecules, Cells and Systems
Gary G. Matthews
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Glossary
[ A-E ] [ F-L ] [ M-R ] [ S-Z ]
Glossary
- F -
- fastigial nucleus
- One of the deep nuclei of the cerebellum, in the brainstem.
- filopodia (singular: filopodium)
- Part of a growth cone. Filopodia are finger-like amoeboid structures that interact with the external environment and propel the growth cone forward.
- forebrain
- The most anterior of the three brain vesicles that arise from the neural tube early in brain development. Also, the adult brain region that arises from the forebrain vesicle. The forebrain consists of the telencephalon and diencephalon.
- fornix
- A large fiber bundle that contains output axons leaving the hippocampus.
- fourth ventricle
- The part of the cerebral ventricles located in the hindbrain.
- fovea
- The part of the retina that receives light from the center of the visual field, at the normal fixation point of the eye.
- frontal eye field
- Part of the frontal lobe where neurons generate commands that trigger saccades of the eyes.
- G -
- G protein (GTP-binding protein)
- An important class of intracellular signaling molecules that provide the link between activated receptor molecules (such as hormone or neurotransmitter receptors that are not ligand-gated ion channels) and subsequent biochemical events inside target cells. G-proteins are activated when they bind GTP in response to receptor activation.
- GABA (gamma aminobutyric acid)
- A major inhibitory neurotransmitter in the brain. GABA is synthesized from glutamate by the enzyme glutamic acid decarboxylase.
- gamma motor neuron
- A special class of motor neurons that innervate the intrafusal muscle fibers within muscle spindles in skeletal muscles.
- ganglion (plural: ganglia)
- A cluster of neuronal cell bodies, usually located outside the central nervous system in vertebrates. Invertebrate central nervous systems consist of a series of ganglia connected by nerve bundles.
- gap junction
- A site of electrical connection between two cells, where gap junction channels bridge the gap between the insides of the two cells and allow small molecules such as ions to cross directly from one cell to the other.
- GDP
- Guanosine diphosphate, which is formed when GTP is hydrolyzed, releasing the terminal phosphate group.
- geniculostriate pathway
- The visual pathway leading from the lateral geniculate nucleus of the thalamus to the primary visual cortex (striate cortex).
- glial cell
- A non-neuronal cell in the nervous system that helps regulate the extracellular environment, including uptake of neurotransmitters released from synapses.
- globus pallidus
- One of the basal ganglia of the forebrain.
- glutamate
- An amino acid (glutamic acid) used as a neurotransmitter at many excitatory synapses in the central nervous system.
- glycosaminoglycans
- Large polysaccharide molecules of the extracellular matrix, which often combine with proteins to form proteoglycans.
- Golgi tendon organ
- A specialized sensory structure that provides an indication of the force applied to a tendon by active contraction of a skeletal muscle.
- gracile nucleus
- One of the dorsal column nuclei in the brainstem. The gracile nucleus receives somatosensory inputs from the medial portion of the dorsal columns in the spinal cord.
- gray matter
- A portion of the central nervous system containing predominantly neuronal cell bodies. The relative lack of myelinated axons makes gray matter less opaque than surround areas containing fewer cell bodies and more myelinated fibers (white matter).
- growth cone
- A motile structure at the leading edge of a growing neurite.
- GTP - Guanosine triphosphate
- A high energy phosphate compound formed by the combination of guanosine and a chain of three phosphate groups. GTP is an important signaling molecule because it is necessary for activation of G proteins.
- guanylyl cyclase
- The enzyme that synthesizes the second messenger, cyclic GMP, from GTP.
- gyrus (plural: gyri)
- An outfolding of the cerebral cortex in brains in which the cortex is highly folded (convoluted), such as the human brain.
- H -
- habituation
- Reduction in the strength of a reflexive response produced by repeated presentation of the eliciting stimulus.
- hair cell
- A ciliated sensory cell that produces changes in membrane potential in response to movements of the cilia induced by sensory stimuli.
- hair follicle receptor
- A type of sensory neuron that innervates hair follicles in the skin and is activated when the hair is deflected.
- heterologous expression
- An experimental technique in which DNA or mRNA for a protein is incorporated into a target cell that does not normally produce the protein.
- hindbrain
- The most posterior of the three brain vesicles that arise at the anterior end of the neural tube during embryonic development of the brain. Also, the most posterior part of the adult brain, which develops from the hindbrain vesicle, including the pons, medulla, and cerebellum.
- hippocampus
- A simplified form of cerebral cortex (archicortex) located under the lower lip of the neocortex at the medial border of the temporal lobe. The hippocampus is part of the limbic system and is thought to be involved in certain types of memory.
- homeostasis
- The maintenance of a relatively constant internal environment despite large changes in external conditions.
- horizontal cell
- A neuron type found in the retina. Horizontal cells are lateral interneurons that receive synaptic inputs from photoreceptors.
- hyperpolarization
- A change in membrane potential in the negative direction, making the cell interior more negative.
- hypothalamus
- A part of the diencephalon involved in a variety of homeostatic functions, in the control of the pituitary, and in motivation and drive. The hypothalamus is a major part of the limbic system.
- I -
- I band
- In a striated muscle cell, the part of the sarcomere corresponding the region occupied only by thin filaments, where thin and thick filaments do not overlap.
- immunocytochemistry
- An experimental technique in which an antibody specific for a particular protein is used to localize that protein in the cells or tissues.
- inferior colliculus
- The more posterior of the two colliculi, located on the dorsal surface of the midbrain. The inferior colliculus is a processing center for auditory information ascending from the cochlear nucleus and superior olivary nucleus in the brainstem.
- inhibitory postsynaptic potential (i.p.s.p.)
- A postsynaptic change in membrane potential that tends to prevent firing of an action potential in the postsynaptic cell, by bringing the membrane potential away from the threshold potential.
- initial segment
- The initial part of the axon as it leaves the cell body of a neuron. The initial segment is often the point at which action potentials are initiated in response to depolarization.
- inositol trisphosphate
- An intracellular second messenger, which is produced from membrane lipid by the enzyme phospholipase C.
- intermediolateral gray matter
- The part of the spinal cord gray matter containing the cell bodies of sympathetic preganglionic neurons.
- interneuron
- A neuron in the nervous system that receives inputs from other neurons and makes synaptic contact with other neurons.
- interoceptors
- Sensory receptor cells that detect stimuli arising within the organism. Muscle spindle receptors are an example of interoceptors.
- intrafusal muscle fibers
- The specialized subset of skeletal muscle cells found within the muscle spindle.
- inverse myotatic reflex
- The reflex stimulated by activation of sensory neurons of Golgi tendon organs (also called the tendon organ reflex). Activation of this reflex leads to inhibition of the motor neurons for the same muscle, causing a reduction in muscle tension.
- ion channel
- A membrane protein that forms an aqueous pore through which charged ions can cross the membrane.
- isometric contraction
- A muscle contraction in which muscle length does not change although muscle tension increases.
- isotonic contraction
- A muscle contraction in muscle tension remains constant during the contraction.
- L -
- labyrinth
- A collective term for the cochlea, semicircular canals, and otolith organs in the inner ear.
- lamellipodium
- Part of a growth cone, extending between successive filopodia. When filopodia adhere to the substrate, the lamellopodium fills in the space between the filopodia to bring the growth cone forward in the direction of growth.
- lateral column
- The lateral white matter of the spinal cord.
- lateral geniculate nucleus
- The part of the thalamus that receives synaptic inputs from retinal ganglion cells and projects to the primary visual cortex.
- lateral inhibition
- Inhibition mediated by lateral interneurons, in which sensory stimuli at a particular location on the sensory surface inhibits activity in sensory pathways originating from adjacent regions of the sensory surface.
- lateral intraparietal area
- A part of the parietal lobe of the cerebral cortex involved in integrating visual stimuli with the control of eye movements.
- lateral lemniscus
- An axon tract carrying auditory information from the cochlear nucleus and superior olivary nucleus in the brainstem to the inferior colliculus in the midbrain.
- lateral line organ
- A sensory system found in aquatic vertebrates, containing hair cells that respond to water movement.
- lateral sensory tract
- Part of the lateral white matter in the spinal cord, containing axons of interneurons that receive inputs from nociceptors and temperature-sensitive sensory neurons.
- lateral ventricles
- The portion of the cerebral ventricles found in the telencephalon.
- leptin
- A hormone synthesized by fat cells and thought to be involved in the regulation of feeding behavior.
- ligand-gated ion channel
- An ion channel in which channel gating is controlled by binding of a chemical signal (the ligand) to a specific binding site on the channel protein. The ACh-gated ion channel of the neuromuscular junction is an example.
- limbic system
- A brain system involved in the regulation of emotion, motivation, and homeostasis.
- Long-term depression (LTD)
- A reduction in the strength of a synaptic connection lasting for hours or days.
- Long-term potentiation (LTP)
- An enhancement of postsynaptic response amplitude lasting hours or days, produced by a burst of presynaptic activity. LTP is commonly studied as a cellular model of learning and memory.
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