Term
| What are the divisions of the nervous system? |
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Definition
Anatomical Divisions
-central nervous system (brain and spinal cord)
-peripheral nervous system (everything else)
Functional Divisions
-somatic nervous system (all nerve tissue not in ANS)
-autonomic nervous system (controls involuntary visceral functions, sympathetic and parasympathetic components) |
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Term
| What are the nervous system cell types? |
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Definition
Neurons
-Specialized to receive, integrate, & transmit electrochemical messages
-Unit structure for CNS
Composed of
•Soma or parikaryon: the body
•Variable number of dendrites (cytoplasmic processes that collect incoming messages & carry them towards the soma)
•Single Axons: cytoplasmic process that transmits messages to target cell
Glial Cells
-Structural & nutritional support of neurons
-Electrical insulation & enhancement of impulse conduction velocity |
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Term
| How are neurons classified by function? |
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Definition
Sensory - receive impulses generated by stimulation of peripheral sensory cells & organs carry them toward central nervous system
Motor - carry impulses to end organs and induce or inhibit muscle contraction & glandular secretion
Interneurons - carry signals between (1) motor neurons (2) sensory neurons (3) motor & sensory neurons |
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Term
| How are neurons classified by their cell processes? |
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Definition
Bipolar - single dendrite arising from pole of soma opposite the axon
Multipolar - most abundant, 2 or more dendrites which radiate in many directions
Unipolar - single short axon with NO dendrites
Pseudounipolar - single “T” shaped process |
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Term
| What filaments are in the cytoskeleton of neurons? |
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Definition
Microtubules (13 protofilaments) 25-28 nm
-microtubule-association proteins (MAPs)
-MAP2 in dendrites
-MAP3 in axons
Neurofilaments (intermediate) 10 nm
Microfilaments 3-5 nm |
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Term
| What is in the soma of a neuron? |
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Definition
The soma is the cell body
Cytosol
Membranous Organelles
mitochondria
rough endoplasmic reticulum
smooth endoplasmic reticulum
Golgi complex
secretory vesicles; endosomes
Nucleus |
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Term
| What are the components of the axon? |
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Definition
Axon hillock
Initial segment - where initial action potential is generated
Mitochondria
Smooth endoplasmic reticulum
Synaptic vesicles |
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Term
| What is myelination and what purpose does it serve? |
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Definition
| Wrapping of myelin (concentric layers of cell membrane) around an axon to increase the rate of action potential propagation (saltatory conduction) |
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Term
| What is gray matter? white matter? |
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Definition
Gray matter is unmyelinated material - soma, unmyelinated axons
White matter is myelinated material |
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Term
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Definition
Myelin sheath is missing
Conduction will eventually stop because there are NO ion channels below the myelin sheath |
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Term
| What are the different types of chemical synapses? |
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Definition
Axodendritic = axon connecting to dendrite
Axosomatic = axon connecting to soma
Axoaxonic = axon fusing with another axon
Dendrodendritic - synapse between two dendrites |
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Term
| What is axoplasmic transport? |
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Definition
Responsible for movement of mitochondria, lipids, synaptic vesicles, proteins and other cell parts to and from a neuron’s cell body through the cytoplasm of its axon.
Also responsible for moving molecules destined for degradation from the axon to lysosomes to be broken down.
two types - anterograde and retrograde |
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Term
| What is anterograde transport? |
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Definition
type of axoplasmic transport
-Mediated by kinesin
-Carries organelles and substances for making neurotransmitters away from the cell body toward the + (plus) end of microtubules
-Efferent Neurons work this way |
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Term
| What is retrograde transport? |
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Definition
type of axoplasmic transport
-Mediated by dynein
-Sends chemical messages and endocytosis products headed to endolysosomes from the axon back to the cell
-Afferent Neurons work this way |
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Term
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Definition
single neuron & all the corresponding muscle fibers it innervates
-Arm & Leg muscles have a LOT of fibers in each unit
-Eye muscles have relatively few fibers per unit
fewer fibers per unit allows faster & more accurate processing of signals |
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Term
| What is a neuromuscular junction? |
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Definition
The synapse or junction of the axon terminal of a motor neuron with the motor end plate
Responsible for initiation of action potentials across the muscle's surface, ultimately causing the muscle to contract |
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Term
| What are the different types of glial cells? |
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Definition
Oligodendrocytes
Astrocytes
Microglia
Ependyma |
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Term
| Characteristics of oligodendrocytes |
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Definition
Most numerous glial cell
Occur in both gray & white matter
Nuclei size is between astrocytes & microglia
Form myelin & occur in rows to myelinate entire axons
Can provide myelin for segments of several axons unlike a Schwann cell (only 1 segment myelinated per Schwann cell) |
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Term
| Characteristics of astrocytes |
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Definition
Largest glial cells
2 types
•Protoplasmic Astrocytes – common in gray matter
•Fibrous Astrocytes – more common in white matter and less branched than protoplasmic |
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Term
| Characteristics of microglia |
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Definition
Smallest & rarest of glia
Occur in both gray & white matter
Processes shorter than those of astrocytes
Very dense chromatin of nuclei
Have phagocytic capabilities
•If there is injury, there will be increase in size |
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Term
| Characteristics of ependymal cells |
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Definition
Derived from ciliated neuroepithelial cells
Lining resembles simple columnar
Have basal cell processes that extend deep into gray matter
Lines the ventricles |
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Term
| What are the components of a peripheral nerve? |
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Definition
Dorsal Root Ganglion
-nodule on a dorsal root that contains cell bodies of neurons in afferent spinal nerves
-Convey somatosensory information into the brain & spinal cord
-Neurons whose cell bodies are found outside CNS
Epineurium
-Connective tissue investment that surrounds the entire nerve & is thus the thickest layer
Perineurium
-A denser connective tissue that contains fibroblasts that appear to form septa as it divides the nerve into bundles termed fasicles
Endoneurium
-A basal lamina like extracellular matrix that surrounds the Schwann cells
-Composed of bundled myelinated axons |
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Term
| Characteristics of enteric nervous system |
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Definition
Responsible for peristalsis
Digestive tract is also innervated by the Autonomic Nervous System
-Parasympathetic – promotes digestion
-Sympathetic – shuts down digestion |
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Term
| What are the supporting cells of the peripheral nervous system? |
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Definition
Schwann Cells
-1 schwann cell may envelope segments of several unmyelinated axons or one segment of a single myelinated axon
-Schwann cell squeezes most of the cytoplasm out
-Myelin is the plasma membrane for Scwann cell & consists mainly of phospholipids (stains with osmium)
Satellite Cells
-Specialized Schwann cells in craniospinal & autonomic ganglia
-Nuclei appear as a “string of pearls” |
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Term
| What is the nissl stain used for? |
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Definition
To find axons because they lack RER and ribosomes.
The Nissl stains RER and ribosomes so the parts that remain unstained are the axons |
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