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148 Cards in this Set
- Front
- Back
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what are the two major classes of cells in the nervous system?
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neurons
glia |
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what role do neurons play?
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receive and transmit electrochemical messages
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what role do glia play?
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supporting cells, providing structural and nutritional support for neurons
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what are the other names for a neuron cell body?
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soma
perikaryon |
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which are larger, neurons or glial cells?
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neurons
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what is the "stuff" surrounding neurons and glia? what is it composed of?
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neuropil
axons and dendrites |
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what is in the peripheral nervous system?
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all of the nerves and nerve endings
ganglia |
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where does nervous tissue originate?
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neuroectoderm
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what invaginates to form the neural groove?
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neural plate
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what closes to form a neural tube?
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neural plate
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what type of cells line the neural tube?
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pseudostratified columnar epithelium
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what develops from the neural tube?
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brain
spinal cord retina |
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what is formed by the pinching off of neuroectodermal cells along the lateral border of the neural plate?
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neural crest
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what does neural crest give rise to?
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entire peripheral nervous system
symp. and parasymp. neurons, Schwann cells, medullary cells of adrenal gland, sensory neurons in craniospinal ganglia |
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how does a typical neuron appear?
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has a large, pale-staining nucleus with a prominent nucleolus, and many Nissl bodies
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what is a Nissl body?
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a concentration of rough endoplasmic reticulum
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where is the well-defined golgi complex in a neuron? what is it for?
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near the nucleus
packages neurotransmitters into vesicles for release at synapse |
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why do neurons have a lot of Nissl bodies?
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they produce a lot of proteins or peptides
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what cytoskeletal elements are abundant in neurons?
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microtubules
neurofilaments (intermediate filaments) |
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where are neurotransmitter vesicles transported?
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along microtubules from soma to terminal bouton of axon
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what is the most common basic shape of neurons?
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multipolar (many dendrites)
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where are bipolar neurons found?
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olfactory bulb
retina |
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what is the structure of bipolar neurons?
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two dendrites
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where are pseudounipolar neurons found?
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sensory neurons in dorsal root ganglia
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what is the structure of pseudounipolar neurons?
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one dendrite
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what is the most common type of neuron in the cerebral cortex of the forebrain?
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pyramidal cell
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what basic shape of neurons do pyramidal cells have?
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multipolar neuron
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what are the functions that the cerebral cortex controls?
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higher functions such as thinking and speaking
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what is the axon hillock?
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the part of the soma leading into the axon
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what is evident in axon hillock, which makes it identifiable?
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lack of Nissl bodies
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what is the initial segment?
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the region of the axon between the axon hillock and the beginning of the myelin sheath
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where is the neuron action potential generated?
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initial segment
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what characterizes the initial segment of an axon?
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a thin layer of electron-dense material beneath the plasma membrane
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how can you tell the difference between axons and dendrites?
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axons show constant diameter, whereas dendrites taper
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what organelles are contained within axon proper?
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mitochondria
parallel bundles of microtubules and neurofilaments |
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what are branches from axon proper?
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collaterals
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what is the terminal end of an axon, which is bulb-like in shape?
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terminal bouton
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what is a myelin sheath composed of?
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several phospholipid bilayers stacked together around axon
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which direction does slow axonal transport travel? how fast?
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anterograde
0.2 - 4.0 mm/day |
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what is transported via slow axonal transport?
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structural elements
(tubulin, actin) |
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in what direction does fast axonal transport occur? how fast is it?
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both anterograde and retrograde
20 - 400 mm/day |
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what is transported via fast axonal transport?
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membrane bound organelles
(mitochondria, synaptic vesicles) |
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which type of axonal transport requires the use of ATP?
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fast axonal transport
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what is the advantage to having dendrites on a neuron?
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increasing surface area to permit greater number of synapses
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what is the purpose of a dendritic spine?
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to increase reserve for synaptic strength (interacts with a single axon of a single neuron)
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what are somatosensory nerves responsible for?
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touch
heat cold |
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what are somatomotor nerves responsible for?
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skeletal muscle movement
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what are visceral sensory nerves responsible for?
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smell
taste visceral pain |
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what are visceral motor nerves responsible for?
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smooth muscle contractions
glandular secretions |
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which type of nerves are responsible for sympathetic vs. parasympathetic reactions?
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visceral motor
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what is the degeneration of neurons distal to the site of an injury called?
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Wallerian degeneration
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what initially happens to crushed or severed axons?
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degenerates, both distal and proximal to the site of injury
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what causes Wallerian degeneration?
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macrophages phagocytose the dead tissue and the myelin sheath breaks down
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what type of axonal degeneration is limited in response to injury?
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proximal
(the axon is sealed) |
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how does the soma change in response to axonal injury?
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chromatolysis within 1-2 days
size increase nucleus moves to eccentric position |
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what is chromatolysis in the soma of a neuron which has been damaged?
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dispersion of Nissl substance
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what typically happens to target muscles which are deprived of innervation?
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they atrophy
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what is the first step in regeneration of a damaged axon?
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Schwann cells proliferate, forming a tube around degenerating axon, to guide the regenerating axon terminals
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what are neurites?
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small axonal processes developed from the proximal stump of a damaged axon
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what are endoneurial sheaths?
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Schwann cell tubes which guide neurites to the target muscle
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How long does axonal regeneration occur, assuming that the severed nerve is matched by fascicle size and arrangement and is sutured together?
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3-4 weeks
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what happens if reinnervation fails?
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neuroma
(painful swelling of neurites) |
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what mature nervous system cells can divide/replicate?
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neuroglial cells
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where is the presynaptic membrane typically found?
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in terminal boutons or boutons-in-passage
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what is the presynaptic density?
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the electron-dense thickening of the plasma membrane of a presynaptic membrane
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how big is the synaptic cleft?
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20-30 nm
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what shields synaptic cleft from the rest of the intercellular space?
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glial cell processes and basal lamina material
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what is the postsynaptic density?
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the electron-dense thickening of the plasma membrane in the postsynaptic membrane
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how can you tell the difference between axons and dendrites in an electron micrograph?
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dendrites don't have synaptic vesicles, whereas axons do
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what is the charge of inside of a neuron relative to the outside?
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-40 - -100 mV
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what helps to maintain the resting membrane potential?
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Na+/K+-ATPase pumps
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what is the resting membrane potential of a neuron?
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-70 mV
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what is the depolarization of the cell caused by an action potential?
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+35 mV
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what leads to the exocytosis of neurotransmitters into the synaptic cleft when an action potential arrives at an axon terminal?
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Ca2+
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what leads to the depolarization of the plasma membrane of a post-synaptic cell?
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binding of neurotransmitters, which causes ion channels to open
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what is contained in gray matter?
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neurons and glia
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what is contained in white matter?
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axons and glia
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where are gray matter and white matter found?
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brain and spinal cord
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what causes white matter to be white?
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abundance of myelin
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what are the very large neurons in the cerebellum with lots of dendrites?
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purkinje cells
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what are the neuroglial cells in the CNS?
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astrocytes
microglia oligodendrocytes |
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what are the neuroglial cells within the PNS?
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Schwann cells
satellite cells |
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which are the largest glia in the CNS?
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astrocytes
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how are astrocytes identified?
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by pale-staining nucleus with nucleolus
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where are protoplasmic astrocytes found?
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gray matter
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where are fibrous astrocytes found?
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white matter
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what are the intermediate filaments in astrocytes composed of?
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glial fibrillary acidic protein (GFAP)
(how you can tell if a tumor is of glial origin) |
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what glial cells regulate the microenvironment around neurons?
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astrocytes
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where are oligodendrocytes abundant?
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white matter of CNS
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what do oligodendrocytes do?
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myelinate axons (can be many)
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how are oligodendrocytes identified?
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small, round, dark-staining nuclei
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what are the smallest glia in the CNS?
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microglia
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How are microglia identified?
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small, elongate, very dark-staining nuclei
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which glial cells are phagocytic and are therefore found at sites of injury and disease, like Alzheimer's?
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microglia
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what are ependymal cells?
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remnants of the neural tube
(not glia) |
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where are ependymal cells found?
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lining cavities of brain and spinal cord that are filled with CSF
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what are the three protective meninges of the brain and spinal cord?
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layers of connective tissue
dura mater arachnoid mater pia mater |
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what type of tissue does the dura mater consist of?
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dense connective tissue
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where is the dura mater found?
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tightly bound to periosteum of skull and along spinal cord
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which layer of meninges forms the dural venous sinuses?
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dura mater
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what are the two components of the arachnoid mater?
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loose connective tissue
dense connective tissue strands (called trabeculae) |
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what is the purpose of the trabeculae in the arachnoid mater?
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to attach arachnoid mater to pia mater
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which layer of meninges contains the CSF?
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arachnoid mater
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what are the projections into the dural sinuses which transfer CSF to venous blood?
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arachnoid villi (granulations)
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what type of tissue composes the pia mater?
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thin, richly vascularized, loose connective tissue
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where can the pia mater be found?
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firmly attached to the brain
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what are the specialized projections of the pia mater into the brain ventricles?
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choroid plexus
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what composes the choroid plexus?
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pia mater and choroid epithelium with microvilli (derived from ependymal cells)
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what layer of meninges produces CSF?
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pia mater (choroid plexus)
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what is CSF?
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cerebrospinal fluid
a cell-free solution derived from blood |
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where is CSF synthesized in the choroid plexus?
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lateral and 4th ventricles
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what are the functions of the CSF?
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supports and cushions brain & spinal cord
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how does CSF return to circulation?
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superior sagittal sinus
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what are the purposes of the blood-brain barrier?
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protect brain from fluctuations in blood chem
prevents some antibiotics/pharmacologic agents from reaching neurons |
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what is the blood-brain barrier composed of?
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relatively impermeable capillaries
(endothelial cells linked by tight junctions) |
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what type of glial cell surrounds brain capillaries forming an additional barrier layer?
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astrocytic glial processes
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what are the components of the blood-brain barrier?
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continuous capillaries with tight junctions
basal lamina astrocytic foot processes |
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where are satellite cells found?
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surrounding neuronal cell bodies in craniospinal and autonomic ganglia
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where do satellite cells originate?
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neural crest cells
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where do Schwann cells originate?
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neural crest cells
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what is the function of satellite cells?
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to establish and maintain the microenvironment around ganglion neurons
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where are Schwann cells found?
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peripheral nervous system
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what is the function of Schwann cells?
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to protect and nourish peripheral nerves
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What are the two types of glia that produce myelin?
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oligodendrocytes (CNS)
Schwann cells (PNS) |
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what is the name for the process of a Schwann cell wrapping its cytoplasm around an axon?
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myelination
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what molecule is myelin rich in?
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sphingomyelin
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what causes saltatory conduction?
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depolarization only occuring at nodes of ranvier
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what is the name for the parts of the myelin sheath which contain cytoplasm?
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Schmidt-Lanterhan clefts
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how does Schwann cell also protect unmyelinated neurons?
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it embeds the axons in its cytoplasm but does not myelinate them (wraps only once)
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what is the name of a cluster of neurons in the PNS?
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ganglion
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what is the name for a cluster of neurons in the CNS that have similar structure and function?
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Nucleus
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what do peripheral nerves contain?
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myelinated axons
unmyelinated axons Schwann cells fibroblasts (no neuronal cell bodies) |
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what are the three components of the connective tissue sheath surrounding nerves?
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Endoneurium
Perineurium Epineurium |
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what does the endoneurium consist of?
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loose connective tissue
fine collagen fibrils blood capillaries |
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what is the perineurium composed of?
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several layers of squamous, fibroblast-like cells with tight junctions
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what is the most significant component of the nerve sheath, with regards to protecting the neuron?
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perineurium
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what is the epineurium composed of?
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dense connective tissue with adipose tissue
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what is a myoneural or neuromuscular junction?
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site of a nerve-muscle synapse
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which horn of the spinal cord do motor neurons originate in? which root do they send their axons through?
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ventral horn
ventral root |
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what are terminal aborizations?
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motor end-plates
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True or False: axons of motor neurons are myelinated by oligodendrocytes
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False - axons of motor neurons are myelinated by Schwann cells because they are in the PNS
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what neurotransmitter is contained in the terminal bouton at a myoneural junction?
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acetylcholine (ACh)
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what enzyme is contained within the synaptic cleft which degrades acetylcholine?
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acetylcholinesterase
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what is noticed in the sarcolemma of a muscle cell at the site of a neuromuscular junction?
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extensive folding
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what is the name for the specialized muscle fibers which compose muscle spindles?
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intrafusal fibers
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where are intrafusal fibers contained?
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enclosed in fluid-filled connective tissue capsule
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what do the sensory nerve fibers detect from the intrafusal fibers?
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changes in the length
provides information on degree of muscle tone |
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what is an example of a monosynaptic reflex arc?
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patellar reflex
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