Nervous Tissue

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central nervous system

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composed of brain and spinal cord. processing center for nervous system.

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CNS

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Central Nervous System

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peripheral nervous system

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consists of the nerves and ganglia outside of the brain and spinal cord. connects CNS to organs and limbs.

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PNS

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Peripheral Nervous System

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afferent

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carry nerve impulses from receptors or sense organs towards the central nervous system.

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efferent

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carry nerve impulses away from the central nervous system

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somatic

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of the body

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autonomic

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relating to or controlled by ANS

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ganglion

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mass of nerve cell bodies

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ganglia

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plural of ganglion

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preganglionic

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fibers from the CNS to the ganglion

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postganglionic

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fibers from the ganglion to the effector organ

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satellite cells

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type of glial cell that line the exterior surface of neurons in the PNS

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capsule cells

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One of the cells located around the bodies of the cerebrospinal and sympathetic ganglionic neurons.

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chromaffin cells

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are neuroendocrine cells found in the medulla of the adrenal gland; receive sympathetic input.

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somata

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plural of soma; cell bodies

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perikaryon

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aka soma. bulbous end of cell body containing nucleus.

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dendrite

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branched projections of a neuron that act to conduct the electrochemical stimulation received from other neural cells to the cell body, or soma, of the neuron

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axon

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a long, slender projection of a nerve cell, or neuron, that typically conducts electrical impulses away from the neuron's cell body or soma.

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axon hillock

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specialized part of the cell body (or soma) of a neuron that connects to the axon. site from which membrane potentials propagates

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synapse

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a structure that permits a neuron to pass an electrical or chemical signal to another cell

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axon terminal

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distal terminations of the branches of an axon.

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terminal boutons

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specialized junctions through which neurons signal to each other and to non-neuronal cells

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Nissl substance (bodies)

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large granular body found in neurons. These granules are rough endoplasmic reticulum (with free ribosomes) and are the site of protein synthesis

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neurofibril

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Any of the long, thin, microscopic fibrils that run through the body of a neuron and extend into the axon and dendrites, giving the neuron support and shape.

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neurofilament

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intermediate filaments found specifically in neurons. They are a major component of the cell's cytoskeleton, and provide support for normal axonal radial growth

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initial segment

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part of the axon between the hillock and the beginning of the myelin sheath

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spike trigger zone

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The axon hillock and initial segment give rise to propagated action potential and constitute this zone.

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white matter

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one of the two components of the central nervous system and consists mostly of glial cells and myelinated axons

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gray matter

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major component of the central nervous system, consisting of neuronal cell bodies

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anterograde transport

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movement of molecules/organelles outward, from the cell body or soma to the synapse or cell membrane.

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retrograde transport

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transport is movement of molecules/organelles inward, away from the synapse or plasma membrane toward the cell body or soma.

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unipolar

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neuron with a single neurite, round body and with different segments that serve as superficial receptors or terminals

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bipolar

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specialized neuron with two extensions. specialized sensory neurons for the transmission of special senses.

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pseudounipolar

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sensory neuron in the peripheral nervous system. This neuron contains an axon that has split into two branches; one branch runs to the periphery and the other to the spinal cord

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multipolar

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type of neuron that possesses a single (usually long) axon and many dendrites, allowing for the integration of a great deal of information from other neurons.

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sensory neurons

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neurons responsible for converting external stimuli from the environment into internal stimuli. They are activated by sensory input

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motor neurons

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neurons located in the CNS that project their axons outside the CNS and directly or indirectly control muscles. usually associated with efferent neuron.

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interneurons

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neuron that forms a connection between other neurons. can be motor or sensory.

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neuroglia

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Glial cells. non-neuronal cells that maintain homeostasis, form myelin, and provide support and protection for neurons in the brain, and for neurons in other parts of the nervous system such as in the autonomic nervous system

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astrocytes

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characteristic star-shaped glial cells in the brain and spinal cord. They perform many functions, including biochemical support of endothelial cells that form the blood–brain barrier, provision of nutrients to the nervous tissue, maintenance of extracellular ion balance, and a role in the repair and scarring process of the brain and spinal cord following traumatic injuries.

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protoplasmic astrocytes

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found in grey matter tissue, possess a larger quantity of organelles, and exhibit short and highly branched tertiary processes.

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fibrous astrocyte

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usually located within white matter, have relatively few organelles, and exhibit long unbranched cellular processes. This type often has "vascular feet" that physically connect the cells to the outside of capillary wall when they are in close proximity to them.

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Glial fibrillary acidic protein

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an intermediate filament protein that is expressed by numerous cell types of the CNS including astrocytes help to maintain astrocyte mechanical strength, as well as the shape of cells

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GFAP

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Glial fibrillary acidic protein

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oligodendrocyte

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type of brain cell. main function is the insulation of axons in the CNS of some vertebrates.

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interfascicular oligodendrocyte

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aligned in rows between the nerve fibres of the white matter of the central nervous system.

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satellite oligodendrocyte

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functionally distinct from most oligodendrocytes. They are not attached to neurons and, therefore, do not serve an insulating role. They remain apposed to neurons and regulate the extracellular fluid

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microglia

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type of glial cell that are the resident macrophages of the brain and spinal cord, and thus act as the first and main form of active immune defense in the CNS.

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Schwann cells

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principal glia in PNS. Partake in the conduction of nervous impulses along axons, nerve development and regeneration, trophic support for neurons, production of the nerve extracellular matrix, modulation of neuromuscular synaptic activity, and presentation of antigens to T-lymphocytes.

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myelin

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dielectric (electrically insulating) material that forms a layer, around the axon of a neuron. essential for the proper functioning of the nervous system. an outgrowth of a type of glial cell.

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sheath of Schwann

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outermost nucleated cytoplasmic layer of Schwann cells that surrounds the axon of the neuron. It forms the outermost layer of the nerve fiber in the PNS.

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neurilemma

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sheath of Schwann

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ependymal cells

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thin epithelial membrane lining the ventricular system of the brain and the spinal cord.

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node of Ranvier

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gaps in myelin sheath where the axonal membrane is uninsulated and therefore capable of generating electrical activity.

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internodal segment

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portion of a nerve fiber between two Nodes of Ranvier

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cleft of Schmidt-Lantermann

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Funnel-shaped interruptions in the regular structure of the myelin sheath of nerve fibres

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action potential

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short-lasting event in which the electrical membrane potential of a cell rapidly rises and falls, following a consistent trajectory.

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presynaptic cell

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cell membrane of an axon terminal that faces the receiving cell.

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postsynaptic cell

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membrane separated from the presynaptic membrane by the synaptic cleft.

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electrical synapse

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mechanical and electrically conductive link between two neurons that is formed at a narrow gap between the pre- and postsynaptic neurons known as a gap junction.

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chemical synapse

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specialized junctions through which neurons signal to each other and to non-neuronal cells

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boutons terminaux

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small, terminal enlargements of nerve fibers that are in contact with the dendrites or cell bodies of other nerve cells; the synaptic endings of nerve fibers.

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boutons en passage

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consecutive synapses along the course of an axon.

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neurotransmitter

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endogenous chemicals that transmit signals from a neuron to a target cell across a synapse

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neuromodulator

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a substance, other than a neurotransmitter, released by a neuron and transmitting information to other neurons, altering their activities

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neuropeptide

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small protein-like molecules used by neurons to communicate with each other, distinct from the larger neurotransmitters. They are neuronal signaling molecules, influence the activity of the brain in specific ways and are thus involved in particular brain functions, like analgesia, reward, food intake, learning and memory.

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fascicle

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a bundle of axons (nerve fibers) enclosed by the perineurium

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epineurium

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outermost layer of connective tissue surrounding a peripheral nerve. It is made of dense irregular connective tissue and usually contains multiple nerve fascicles as well as blood vessels which supply the nerve

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perineurium

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protective sheath that surrounds fascicles

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endoneurium

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layer of delicate connective tissue made up of endoneurial cells that encloses the myelin sheath of a spinal cord nerve fiber. bundled into fascicles

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saltatory conduction

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the propagation of action potentials along myelinated axons from one node of Ranvier to the next node, increasing the conduction velocity of action potentials without needing to increase the diameter of an axon.

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continuous conduction

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nerve impulse travels down the whole unmyelinated neuron.

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sympathetic

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nervous system responsible for fight-or-flight response

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parasympathetic

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nervous system responsible for rest-and-digest response

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blood-brain barrier

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a separation of circulating blood from the brain extracellular fluid in the CNS. Endothelial cells restrict the diffusion of microscopic objects (e.g. bacteria) and large or hydrophilic molecules into the cerebrospinal fluid (CSF), while allowing the diffusion of small hydrophobic molecules (O2, CO2, hormones).

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molecular layer

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the outer layer of the cortex of the cerebellum and cerebrum consisting of a mass of unmyelinated fibers rich in synapses

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granular layer

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the deep layer of the cortex of the cerebellum. densely packed with granule cells.

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cerebral cortex

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sheet of neural tissue that is outermost to the cerebrum of the mammalian brain. It plays a key role in memory, attention, perceptual awareness, thought, language, and consciousness.

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cerebellar cortex

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Tightly folded gray matter that makes up surface of cerebellum. Three layers: outer granular layer, middle Purkinje layer and innter granular layer.

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dura mater

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the outermost of the three layers of the meninges surrounding the brain and spinal cord. It is derived from mesoderm

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arachnoid

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one of the three meninges, the protective membranes that cover the brain and spinal cord. fine spider web-like appearance of the delicate fibres extend down through the subarachnoid space and attach to the pia mater.

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pia mater

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the delicate innermost layer of the meninges, the membranes surrounding the brain and spinal cord.

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choroid plexus

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structure in the ventricles of the brain where cerebrospinal fluid (CSF) is produced. consists of modified ependymal cells.

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cerebrospinal fluid

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clear, colorless, bodily fluid, that occupies the subarachnoid space and the ventricular system around and inside the brain and spinal cord.

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CSF

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cerebrospinal fluid