Neurobiology of Neurons and Neuroglia

Neuron

Nerve cell specialized for impulse conduction.

Neurites

Processes projecting from a neuron's cell body.

Dendrites

Receive information and conduct it to cell body.

Axon

Single long neurite conducting impulses away from cell.

Unipolar Neuron

Single neurite dividing into two branches.

Bipolar Neuron

Two neurites emerging from an elongated cell body.

Multipolar Neuron

Multiple neurites arising from the cell body.

Golgi Type I

Long axon, may exceed 1 meter in length.

Golgi Type II

Short axon, often terminates near cell body.

Nerve Cell Body

Mass of cytoplasm containing the nucleus.

Nucleus

Stores genes, centrally located in cell body.

Cytoplasm

Contains organelles and structures for cellular function.

Nissl Substance

Granules synthesizing proteins in neuron cytoplasm.

Golgi Complex

Organelle involved in modifying and packaging proteins.

Mitochondria

Powerhouse of the cell, produces energy.

Microfilaments

Thin filaments providing structural support to cells.

Microtubules

Cylindrical structures aiding in cell shape and transport.

Lysosomes

Organelles containing enzymes for cellular digestion.

Centrioles

Cell structures involved in cell division.

Lipofuscin

Pigment granules indicating cellular aging.

Melanin

Pigment responsible for coloration in cells.

Glycogen

Stored form of glucose in cells.

Plasma Membrane

Boundary of the cell, regulates material transport.

Chromatolysis

Nissl substance disperses due to neuronal damage.

Neurofibrils

Main component of the neuron's cytoskeleton.

Kinesin

Motor protein for anterograde transport away from cell.

Dynein

Motor protein for retrograde transport towards cell.

Melanin Granules

Involved in dopamine formation.

Glycocalyx

Part of plasma membrane aiding in ion diffusion.

Resting Membrane Potential

Steady potential difference of about -80mV.

K+ Ion Permeability

Greater than Na+ ions in resting state.

Depolarization

Na+ influx changes membrane potential positively.

Action Potential

Rapid change in membrane potential to +40mV.

Duration of Action Potential

Lasts approximately 5 milliseconds.

Repolarization

K+ efflux returns membrane to resting state.

Self-Propagation of Impulse

Nerve impulse spreads without altering size or frequency.

Refractory Period

Period after impulse where another cannot occur.

Absolute Refractory Period

No further electrical change from second stimulus.

Relative Refractory Period

Strong stimulus can trigger action potential.

Axon Hillock

Site where action potential originates, lacks Nissl granules.

Axon Terminals

Distal ends of axon branches, often enlarged.

Axolemma

Plasma membrane surrounding the axon.

Axoplasm

Cytoplasm contained within the axon.

Initial Segment

First 50-100um of axon after axon hillock.

Axonal Transport

Transport of materials between cell body and axon terminals.

Anterograde Transport

Transport away from the cell body.

Retrograde Transport

Transport towards the cell body.

Synapses

Junctions for communication between two neurons.

Axoaxonic Synapse

Synapse between two axons.

Axodendritic Synapse

Synapse between an axon and a dendrite.

Axosomatic Synapse

Synapse between an axon and a cell body.

Bouton Terminal

Terminal expansion of a synapse.

Chemical Synapses

Involve presynaptic and postsynaptic clefts.

Synaptic Cleft

Space separating terminal axon and postsynaptic surface.

Neurotransmitters

Chemical messengers released at synapses.

Acetylcholine

Common neurotransmitter in central and peripheral nervous systems.

Dopamine

Neurotransmitter released by substantia nigra neurons.

Glycine

Neurotransmitter primarily in spinal cord synapses.

Vesicles

Contain neurotransmitters released into synaptic cleft.

Neurotransmitter

Chemical released to transmit signals between neurons.

Calcium Influx

Calcium entry that facilitates neurotransmitter release.

Synaptic Vesicles

Membrane-bound structures storing neurotransmitters.

Postsynaptic Membrane

Membrane receiving neurotransmitter signals.

Excitatory Postsynaptic Potential (EPSP)

Temporary depolarization of postsynaptic membrane.

Inhibitory Postsynaptic Potential (IPSP)

Temporary hyperpolarization of postsynaptic membrane.

Hyperpolarization

Increase in membrane potential, neuron inhibition.

Norepinephrine

Neurotransmitter at sympathetic nerve endings.

Neuromodulators

Substances modifying postsynaptic neuron activity.

Astrocytes

Supportive cells forming framework for neurons.

Oligodendrocytes

Cells forming myelin sheath in CNS.

Schwann Cells

Cells forming myelin sheath in PNS.

Microglia

Immune cells in CNS, perform phagocytosis.

Ependyma

Cells lining brain cavities and spinal canal.

Fibrous Astrocytes

Astrocytes providing structural support and insulation.

Protoplasmic Astrocytes

Astrocytes involved in nutrient storage and phagocytosis.

Neuroglia

Non-excitable cells supporting nervous system neurons.

Ion Channel

Protein allowing ions to flow across membranes.

Ependymocytes

Cells that circulate and absorb cerebrospinal fluid (CSF).

Tanycytes

Transport substances from CSF to hypophyseal-portal system.

Choroidal Epithelial Cells

Produce and secrete cerebrospinal fluid (CSF).

Extracellular Space

Gap between neurons and neuroglial cells.

Blood-Brain Barrier

Endothelial cells prevent chemical permeability.

Neuron Injury Reaction

First reaction is loss of function.

Morphologic Changes

Cell becomes swollen, nucleus displaced peripherally.

Nissl Granules

Dispersed toward cell periphery during injury.

Hyperchromatism

Cytoplasm stains dark with basic dyes.

Rabies

Viral disease transmitted via infected animal bites.

Incubation Period

Duration relates to peripheral nerve length.

Neuroblastoma

Malignant tumor associated with suprarenal gland.

Ganglioneuroma

Benign tumor in suprarenal medulla or ganglia.

Pheochromocytoma

Benign tumor secreting norepinephrine, causes hypertension.

Phenothiazines

Block dopamine receptors on postsynaptic neurons.

Procaine

Inhibits acetylcholine release from preganglionic fibers.

Nicotine

Mimics acetylcholine action on postsynaptic membrane.

Hexamethonium

Inhibits synaptic transmission resembling acetylcholine.

Multiple Sclerosis

Common CNS disease with demyelination patches.

Gliotic Scar

Formed by astrocyte proliferation after demyelination.

Cerebral Edema

Condition following head injuries or infections.

Vasogenic Edema

Fluid accumulation due to capillary wall damage.

Cytotoxic Edema

Fluid accumulation within nervous tissue cells.