Neurons And Glia

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Neuron

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The information processing cell of the nervous system, also called nerve cell. Most neurons use action potentials to send signals over a distance, and all neurons communicate with one another using synaptic transmission.

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Glia/glial cells

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Contribute to brain function mainly by insulating, supporting, and nourishing neighboring neurons.

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Nissl Stain

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A class of basic dyes stains the nuclei of all cells and also stain clumps of material surrounding the nuclei of of neurons (Nissl bodies)

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Cytoarchitecture

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The arrangement of neurons in different parts of the brain

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Golgi Stain

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Silver chromate solution = revealed a small percentage of neurons in their entirety (more than Nissl bodies)

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Neurites

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2 types - dendrites/axons. Thin tubes that radiate away from the soma.

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The Neuron Doctrine

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The neuron adheres to cell theory = Communicate by contact not continuity (Santiago Ramon y Cajal).

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Cytosol

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Watery fluid inside the cell. Salty, potassium rich. Separated from outside by the neuronal membrane. Encapsulates organelles

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Ribosomes

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Measure about 25 nm, when in stacks = rough endoplasmic reticulum. Abounds in neurons (more than in glia). Synonym for Nissl bodies. Site of protein synthesis.

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Smooth ER and the Golgi Apparatus

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Rough ER minus the ribosomes = Smooth ER. Different functions in different locations. Golgi = post-translational chemical processing of proteins. Sort proteins for neurites.

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Mitochondrion

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Sausage-shaped. Site of cellular respiration. Pulls in pyruvic acid and oxygen. Makes ATP.

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Neuronal membrane

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Barrier to enclose cytoplasm inside neuron and exclude certain substances that float in the fluid that bathes the neuron. Membrane is 5nm thick and is studded with proteins.

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Axon hillock

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Beginning of the axon. No rough Er extends into the axon, and there are few, if any, free ribosomes.
The protein comp. of the axon is fundamentally different from that of the soma membrane.

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Axon collaterals

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Branches of an axon

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Axon terminal

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Where axon ends, comes into contact with other neurons and passes information to them.

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Synapse

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Point of contact between two neurons (occurs at axon terminal)

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Terminal arbor

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Many axon collaterals (branches) = arbor

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Innervation

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When a neuron makes synaptic contact with another cell, it is said to innervate that cell or provide innervation

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Synaptic vesicles

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Small bubbles of membrane in terminal. 50 nm in diameter.

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Synaptic cleft

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Space between the presynaptic and postsynaptic membranes

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Synaptic transmission

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Transfer of information at the synapse from one neuron to another

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Neurotransmitter

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Electrical signal converted to a chemical signal at synaptic cleft. Chemical signal = neurotransmitter.

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Axoplasmic transport

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Movement of material down the axon

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Anterograde transport

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Movement of material from soma --> axon

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Retrograde transport

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Axon --> Soma.

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Dendritic tree

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Dendrites of a signal neuron

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Receptors

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Specialized protein molecules. Detect neurotransmitters in the synaptic cleft.

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Dendritic spines

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Specialized structures that receive some types of synaptic input. Isolate various chemical reactions that are triggered by some types of synaptic activation.

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Stellate cells

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Star-shaped (dendrites)

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Pyramidal cells

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Pyramid-shaped (dendrites)

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Unipolar

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Neuron with a single neurite

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Bipolar

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Neuron with two neurites

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Multipolar

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Neuron with three ore more. Most cells in the brain are multipolar

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Spiny

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Dendrites that have spines

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Aspinous

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Dendrites w.o spines

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Primary sensory neurons

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Neurons that have neurites in the body's sensory areas e.g. skin

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Motor neurons

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Axons that form synapses with muscles and command movements

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Astrocytes

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Most numerous glia in the brain. Fill spaces between neurons. Influence whether a neurite can grow/retract. Regulate chemical content of extracellular space. Primary function unclear.

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Oligodendroglial and Schwann cells

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Provide layers of membrane that insulate axons. Make up the myelin.

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Myelin

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Made of oligodendroglial and Schwann cells. Wraps axon to encourage saltatory conduction.

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Nodes of Ranvier

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Interruptions on the myelin sheath where axon is exposed.

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Ependymal cells

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Provide lining of fluid-filled ventricles within the brain. Direct cell migration during brain development.

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Microglia

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Phagocytes, remove debris left by dead or degenerating neurons and glia.