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339 Cards in this Set
- Front
- Back
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2 major cell types of nervous tissue
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neurons and glial cells
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glial cell names
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astrocytes, oligodendrocytes/Schwann cells, microglia, ependymal
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nervous tissue could be considered an organ system due to:
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integration of cells
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primary fxn of nervous tissue
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rapidly relay info from periphery and to integrate organ systems
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how does nervous tissue integrate organ systems
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by regulating: smooth muscle contraction (gut motility & vascular tone), cardiac muscle contration (only rate & intensity), glandular epithelium (regulation of secretion)
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supporting cells AKA
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neuroglia
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fxn of neurons
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generate and conduct bio-electric impulses
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fxn of supporting cells
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support, nourish and protect neurons
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how does cationic stains allow visualization of nervous microstructure
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binds nucleic acids like Nissl substance (RNA of neurons)
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examples of cationic dyes
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thionine, neutral red, cresyl violet
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how does reduced silver methods stain nervous tissue
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deposit colloidal silver on proteinaceous components in axons
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what is reduced silver methods used by
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cajal
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how do you stain for myelin
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use stain that dyes protein-bound phospholipids
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example of myelin stain
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Weigert
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how does golgi method stain nervous tissue
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utilizes potassium and silver, in series, to stain fine neuronal structure
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what does golgi method especially stain
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dendrites
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what stain technique can be used to trace individual neuronal connections
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neuronal filling
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how does neuronal filling stain work
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individual neurons "injected" w/ ions (cobalt), dyes (lucifer yellow) or enzymes (peroxidase)
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how does immunohistochemical methods work to see nervous tissue
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utilizes antibodies generated against epitopes specific to nervous tissue
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what is immunohisochemical methods for nervous tissue common in and when was it developed
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experiemental neurobiology, 1940's
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2 components of somatic nervous system
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sensory and motor
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what does somatic nervous system innervate
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entire body except viscera, smooth muscle and glands
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somatic nervous system contains ______fibers and innervate ________ _____ muscle
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motor, voluntary skeletal
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autonomic nervous system is predominantly ______ but some _________
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motor but some sensory
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ANS regulates _______ control of _________ fxns
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homeostatic, visceral
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2 systems of ANS
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sysmpathetic and parasympathetic
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2 fxns divisons of nervous system
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autonomic and somatic
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what comprises CNS
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brain and spinal cord w/in skull and vertebral column
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what is the CNS derived from
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neural tube
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what is the PNS comprised of
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nerves and ganglia outside CNS
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what are PNS ganglia derived from
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neural crest (exceptions: olfactory neurons and spiral ganglia of cochlea)
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neurons carrying infor TO CNS are _________
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afferent (sensory)
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neurons carrying ifo from CNS are _______
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efferent (motor)
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are any two neurons alike (microanatomy)
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NO!
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w/ very few exceptions where are adult neurons in cell cycle
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post-mitotic
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3 components of neuron
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cell body, dendrites, axon
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how is size of neurons compared to other cells
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largest and smallest cells in body (5-150 microns in diameter, up to 75 ft in length)
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longest neuron
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75 ft, whale corticospinal neuron
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describe unipolar neuron, how common?
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single process, very rare in vertebrates
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describe pseudounipolar neurons and where are they located
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sensory neurons in spinal and cranial ganglia, have a single process at soma which branches
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describe bipolar neuron and where is it located
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assoc mostly w/ receptor for special senses (taste, smell, hearing, equilibrium), have single axon and dendrite
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what is the most common type of neuron in vertebrates
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multipolar
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describe multipolar neurons
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motor neurons and interneurons, have a single axon and multiple dendrites (dendritic tree)
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3 fxnal classes of neurons
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sensory, intergrative (interneurons) and motor
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what 2 types of stimuli does sensory neurons receive
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internal and external
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what do interneurons integrate
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sensory and motor neurons
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what do interneurons regulate
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signals transmitted to neurons (volume/gain control)
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motor neurons transmit info from ______ to other ____, ______ and __________ (__)
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transmit info from CNS to neurons, muscles and glands (ANS)
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morphology of neurons relate to ______
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fxn
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ie. of how sensory neuron morpohology relates to fxn
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round b/c only one process and no sensory input
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large diameter/length of axon=______ conduction
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fast
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large soma=____ axon
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large
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small soma=_____axon=_____conduction
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small axon, slow conduction
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neuron cell body AKA
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perikaryon, soma
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cell body has nucleus w/ prominent ______ and abundant ________
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nucelolus, euchromatin
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dominant cytoplasmic organelle in neurons
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rER
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neurons have prominent ______ and numerous _____ due to high metabolic rate and lots of vesicular transport
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Golgi apparati (enriched near nucleus), mitochondria
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2 significant components of neuron cytoskeleton
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neurofilaments, microtubules
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size of neurofilaments and what do they stain w/
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10nm stain w/ silver and gold
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size of microtubules
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25nm
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what accumulates w/ advancing age in neuron cell body
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lipofuscin (age pigment)
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what direction is impulse transmitted in dendrites
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toward soma
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proximal features of dendrites
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same cytological features of perikaryon
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distal features of dendrites
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no Golgi apparati, Nissl substance decreases, many microtubules
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dendrite form?
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taper and branch, branching pattern distinguishes neuronal type and fxn
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what are dendritic spines
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small extensions which serve to increase receptive synaptic surface area)
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do impulses get weak as they travel away from the soma down the axon
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no
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what does the axon begin and what does that are lack
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axon hillock, Nissl bodies
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axoplams contains abundant ___ and _____ with no _______ or _______
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abundant microtubules and neurofilaments, no ribosomes or rER
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what is axon limited by
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plasma membrane (axolemma)
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unlike dendrites, axons have a constant ______
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diameter
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do axons have branches
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yes- many
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what may branch at right angles from main trunk of axon
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collaterals
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what are the swellings at the axon's end that contacts other neurons
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axon terminals AKA boutons
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how many axonal contacts may one neuron ahve
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10,000
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what do axons transport to/from the perikaryon and terminals
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proteins, organells and vesicles
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what is anterograde transport
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movement of material away from soma
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what speed is anterograde transport
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fast or slow
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fast speed is used for what
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synaptic vesicles and mitochondria (up to 400mm/day)
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slow speed is used for what
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proteins, enzymes, and observed regeneration )1-2mm.day
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what is retrograde transport
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movement of material toward soma
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how fast is retrograde transport
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intermediate rate (pretty fast) 200-300 mm/day
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purpose of retrograde transport
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recycling and viral transport
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what protein does retrograde transport use
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dynein
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what protein does anterograde transport use
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kinesin
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where are neuroglial cells located
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in CNS (although homologues are in PNS)
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are glial cells or neurons more common
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glial -outnumber neurons 10:1
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do glial cells have impulses and synapses
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no
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do glial cells generate throughout life
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yes(unlike neurons)
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what are the 4 types of neuroglial cells
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astrocytes,oligodendrocytes, microglia,ependymal cells
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what is the largest glial cell
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astrocytes
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astrocytes = ____ shaped, ____ nucleus, ____cytoplasm
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star, euchromatic, light
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what are the perivascular endfeet that astrocytes have
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ramified processes that expand to contact blood vessels
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what glial cell contributes to blood-brain/spinal cord barrier
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astrocytes- control passage of substances to CNS
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astrocytes form ____ support for CNS and proliferate to form a _____ after injury to the CNS
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structural support, glial scar
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where are protoplasmic astrocytes
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gray matter
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protoplasmic astrocytes have processes that envelop _______, ______, and _____
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blood vessels, neurons and synapses
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protoplasmic astrocytes have _____ filaments composes of _________
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intermediate, GFAP (glial fibrillar acidic protein)
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how are fibrous astrocytes diff than protoplasmic astrocytes
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fibrous are in white matter and have long, slender process w/ fewer branches
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do fibrous astrocytes have GFAP
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yes
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where are oligodendrocytes found
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white & gray matter
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oligodendrocytes= _____ cytoplasm, _______nucleus, _____processes
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dark cytoplasm, small dark nucleus, few processes
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oligocytes require ______ for survival and vice versa
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neurons (symbiotic)
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what do oligodendrocytes produce
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CNS myelin
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can each oligodendrocyte cell produce myelin for several axons
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yes
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fxnal homologues of oligodendrocytes in PNS
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Schwanna cells -derived from neural crest
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Microglia are ____ in size, _____ in fxn and are of ______ lineage
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small, phagocytic, monocytic
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microglia have _____ soma, ______ nuclei, ______ cytoplasm, soma and processes that may have many _______
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small, elongated, dark, spikes
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what is the smallest glial cell
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microglia
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fxn of microglia
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proliferate/infiltrate rgions of CNS injury or disease and phagocytize
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shape and size of ependymal cells
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small,cuboidal to columnar epithelial cells
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what do ependymal cells line
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ventricles and central canal of spinal cord
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where is the nucleus in ependymal cells located
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basally
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are ependymal cells ciliated? why?
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yes, to move CSF
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what type of transport are ependymal cells capable of
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fluid
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what is the choroid plexus composed of
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specialized ependymal cells and associated capillaries that produce CSF
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what does white matter contain
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predominately myelinated fibers (although some unmyelinated nerve fibers are also present) and assoc. neuroglial cells
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what does gray matter contain
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neuronal cell bodies, many unmyelinated fibers, and assoc neuroglial cells
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what makes the H at center of spinal cord
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spinal cord gray matter
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what is the small central canal in spinal cord gray matter
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continuation of ventricles of brain lined by ependymal cells
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name of dorsal portion of spinal H
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dorsal horns
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what are dorsal horns
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sensory fibers from dorsal root ganglion neurons and interneuronal cell bodies
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what are ventral horns
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fibers and large perikaria of multipolar motor neurons
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where is brain gray matter located
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at the periphery of cerebrum and cerebellum (NOT CENTER)
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what is the majority of core of brain made of
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what matter (collection of mylelinated fibers and tracts)
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Meninges are __________ membranes that surround the ___________ & __________
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connective tissue, brain & spinal cord
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3 definitive layers of meninges
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Dura mater (tough mother), Arachnoid mater, Pia mater
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Dura mater is the ________ layer, composed of _________, continuous w/ the _________ of __________ which are seperated by the __________ at the spinal level
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outermost layer, dense fibrous CT, periosteum of skull/vertebral column which is separated by the epidural space at the spinal level
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what is dura mater lined by
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simple squamous epithelium of skull, both surface at spinal level
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where is the arachnoid mater
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middle minengeal lauer
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arachnoid mater is a delicate _______ loosely connected to_____
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sheet, dura mater
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what is arachnoid mater covered on both sides by
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simple squamous epithelium
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arachnoid mater demonstrates _________ which bridge the ________ to connect loosely with the ________
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trabeculae, subarachnoid space, pia mater
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what space is filled w/ CSF
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subarachnoid
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arachnoid mater exhibits ________ which are specialized proturusion in the ________ that return CSF to the ______
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arachnoid villi, dura mater, venous sinuses
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which meninge layer is highly vascularized
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pia mater
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what is the innermost meningeal layer
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pia mater
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the pia mater is covered by:
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simple squamous epithelium
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what is the pia mater separated from the unerlying nervous tissue by
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neuroglial elements (pia mater is initimately assoc, w/ CNS tissue
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what is the choroid plexus
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folds of pia mater that extend into ventricles of brain
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what is the choroid plexus made of
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connective tissue core covered by simple cuboidal (ependymal) epithelium w/ microvilli
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the connective tissue core of the choroid plexus is high vascularized w/ ________
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fenestrated capillaries
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Function of choroid plexus
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secrete CSF
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purpose of CSF
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fills and surround brain and spinal cord and bathes, nourishes and ushions the CNS
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what is the cerebral cortex and where is it located
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thin layer of gray matter on survace of the cerebral hemisphere
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the cerebral cortex is folded into______ with much of its surface buried in_______
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gyri, fissures
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functions of cerebral cortex
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-initiate motor responses,- integrate sensory signal from internal/external enviro,-assoc., analysis, and consolidation of information to memories
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the cerebral cortex is microanatomical divided in ___ layers all containing ______ and ______
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6, neuroglia and specialized neurons
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6 layers of cerebral cortex
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molecular layer, external granular layer, external pyramidal layer, internal granular layer, internal pyramidal layer, multiform layer
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the molecular layer is the _____ layer just beneath the _____ and contain few _____
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superficial, pia mater, somata
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the molecular layer is essentially the _____ of the cortex
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synaptic field
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what is the external granular layer composed of
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primarily granule cells (interneurons)
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what is the external pyramidal layer composed of
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interneurons and pyramidal cells
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what is the internal granular layer composed of
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narrow band of small and large interneurons
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what is the internal pyramidal layer composed of
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medium and large pyramidal cells
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what is the multiform layer composed of
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cells of various shapes including fusiforms (Marinotti Cells)
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What is the cerebellar cortex
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thin layer of gray matter on the surface of cerebellar hemispheres
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the cerebellar cortex is foled into ____
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folia
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fxns of cerebelar cortex
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-coordination of skeletal muscle activity
-maintenance of muscle tone -maintenance of equilaibrium and balance |
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3 layers of cerebellar cortex
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molecular layer, purkinje cell layer, granular layer
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where is the molecular layer of cerebellar cortex
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most superficial un the pia
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what does the molecular later of cerebellar cortex contain
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unmyelinated fibers from the granular layer, dendritic elaboration of Purkinje cells, stellate and basket cells (both are types of specialized neurons)
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contents of Purkinje cell layer
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purkinhe cells predominate (they are unique to cerebellar cortex
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Purkinhe cells have an extensive _____ that may receive several hundred thousand excitatory and inhibitory synapes
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dendritic tree
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What is the granular layer of the cerebellar cortex made of
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small,densely packed granule cells w/ regions devoid of cells (cerebellar island/glomeruli)
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What are cerebellar islands/glomeruli
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areas of synapses between axons entering the cerebellum and granule cell dendrites
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cerebral cortex aka
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neocortex
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Fxn of PNS
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connect body w/ CNS
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nerve definition
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collections of myelinated and unmyelinated axons held together in CT
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dorsal roots of the spinal cord- _____ axons from _____ entering the _____
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sensory axons from DRG entering the spinal cord
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ventral roots of the spianl cord- _____ axons from ______ in the ________ exiting to the _____
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motor axons from motor neurons in the ventral horn exiting to the periphery
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cranial nerves- _________- axons entering and exiting the ______
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sensory and/or motor axons entering and exiting the brain
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peripheral nerves- from from the union of ____ and _____ roots
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ventral and dorsal roots
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what are ganglia
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encapsulated colections of neuronal cell bodies located ouside the CNS
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what are the two types of peripheral ganglia
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autonomis and craniospinal
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auntonomic ganglia are _____ ganglia where _________-ganglionic neuonrs of the______ synapse
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motor, pre/post gangionic neurons, ANS
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where are autonomic ganglia located
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near the organsy they innervate of in the organs themselves
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examples of autonomic ganglia near the organs they innervate
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sympathetic chaing ganglia, celiac
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examples of autonomic ganglia in the organs themselves
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parasympathetic ganglia, submucosal plexus of Meissner
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describe autonomic ganglia cells appearance
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multipolar cell bodies with eccentric nucleus surrounded by satellite cells
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function of autonomic ganglia
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visceral motility, glandular secretion, control of smooth and cardiac musculature
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Craniospinal ganglia are ______ ganglia assoc w/ most ____ nerves and the _ of spinal nerves (i.e., ___,____
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sensory, cranial, dorsal roots (i.e. dorsal root ganglia and trigeminal)
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describe appearance of craniospinal nerves
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round, psuedounipolar cell bodies with a central nucleus
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craniospinal ganglia containt the cell bodies of ________ neurons which transmit info from _______ to the ____ without _______ in the ganglia
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sensory, peripheral receptors,CNS, synapsing
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craniospinal ganglia have process w/ morphology of _____ (i.e.______)
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axons- myelinated, lack Nissl substance, contain neurofilaments/microtubules
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the ANS has motor fibers that control what
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smooth muscle, cardiac muscle and some glands
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the ANS also conveys _______ info from organs to ______
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sensory (afferent) CNS
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the ANS establishes ________ of visceral fxns
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homeostasis
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3 division of ANS
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sympathetic, parasympathetic, enteric
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what is the sympathetic division referred to as and why
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thorcolumbar outflow b/c preganglionic cell bodies are located in the thoracic first 2 lumbar of spinal cord
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sympathetic division includes the _________ neurons whoch cell bodies are located in the __________ ganglia
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post-ganglionic, paravertebral chain
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sympathetic division causes vasoconstriction how?
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contraction of smooth muscle
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Parasympathetic division aka and why
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cranoosacral outflow b/c preganglionic cell bodies are located in cranial nerve nucli within the brain and in some sacral segments of spinal cord
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primary fxn of parasympathetic system
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stimulate secretion (secretomotor fxn)
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what does Parasymapthetic due to blood vessels to antagonize sympathetic
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dilation
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what is the enteric division of ANS
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ganglia and post ganglionic neuronal networks of the alimantary canal
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what does the enteric division contain
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intramural ganglia located in the walls of viscera and in Meissner's and Auerbach;s plexi
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enteric division fxn independently of _____ input as there are millions of neuron than are not innevervated by incoming fibers
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pre-ganglionic
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what is the site of functional contact between neurons
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synapses
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how many synapses does a neuron have
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a few or a thousand
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most common type of communication in synapses
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chemical synapses where neurotransmitters stimulate neurons receiving input
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how are synapses classified
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according to site of synaptic contact on receptive neuron and by the method of signal transmission
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2 types of synapses
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exitatory, inhibitory
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what does excititory synapses cause
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membrane depolarization initiating impulse
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what does inhibitory synapses cause
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membrane hyperpolarization preventing impulse
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what is the contact between the axon and a dendrite
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axodendritic synapse
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what is the contact between an axon and cell some
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axosomatic synapse
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what are the 2 most common synapses
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axodendritic and axosomatic
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what is contact between axons
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axoaxonic synapse
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what is contact between dendrites
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dendrodentritic synapse
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chemical synases generate a _________ in the postsynaptic neuron
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action potention (activation)
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what causes the slight dely in signal transmission (0.5 millisec) in chemical synapses
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time required for the secretion and diffusion of neurotransmitters
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electrical synapses utilize movemnt of _____ from one neuron to another by _____
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ions, gap junctions
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what do electrical synapses result in
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direct propagation of the action potential from the presynaptic neuron to the post synpatic neuron
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does elctrical synapses have neurotransmitters
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no
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are electrical synapses instantaneous
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yes-no delay
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2 main types of axon terminals
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boutons terminaux, and bouton en passage
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what are boutons terminaux
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single bulbous expansions at end of axons
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what are boutons en passage
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swellings that occur aong an axon with synapses possible at every expansion
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what happens to the presynaptic membrane at the sitre of synaptic contact
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thickening of axolemma
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the presynaptic membrane containts ____ which regulate the entry or release (from ____) of _____ at axon terminal, an even necessary for neurotransmitter release
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voltage-gate Ca++ channels, mitochondria, Ca++ ions
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that happens to axolemma of postsynaptic membrane
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thickens
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what is the subsynaptic web of the postsynaptic membrane
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electron dense area that looks like a desmosome
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how big is synaptic cleft
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fix distance (20-30nm in width)
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what is the synaptic cleft
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narrow space through which neurotransmitters pass
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size and appearance of synaptic vesicles
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40-60nm, small, polymorphic, membrane-bound
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what do synaptic vesicle contain and where are they found
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neurotransmitters, found in axoplams of presynaptic neuron
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how do synaptic vesicle discharge the naurotransmitters
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exocytosis
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neurotransmitters are ___,_______ and _____ by presynaptic neurons
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produced, stored and released
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how does ntm get across synaptic cleft
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diffusion
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how do ntm activate postsynaptic neuron
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bind to receptors located on postsynaptic membrane
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4 common types of ntm in mammalian CNS
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acetylcholine, norepinephrine, amino acids, endorphins/enkphalins
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Ach is at ______ jxns, all _____ synapses, and ______ synapses
|
myoneural, parasympathetic, preganglionic sympathetic
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|
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where is norepinephrine
|
postganglion sympaethetic synapses
|
|
|
examples of amino acid ntm
|
glutamic acid (excitatory), gamma-aminobutyric acid (GABA,inhibitory), dopamine, serotonin, glycine
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|
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what are endorphins/enkaphalins involved in
|
pain transmission systgems
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|
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_______ are also used in neurotransmission and act to modulate the effect of classical ntm
|
peptides- (i.e. gelanin, substance P)
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|
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1 step of synapse- ______ reaches axon terminal
|
action potential
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|
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after ntm bind to the postsynaptic membram the receptors initiate ______ impulses via change in ______
|
bioelectric, intracellular ions
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what are nerve fibers
|
indiviual axons of neurons
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|
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Nerve fibers may be enveloped by _______ or ____
|
myelin sheath or Schwann cells
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|
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can you see nerve fibers w/ nake eye
|
no
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what is the myeline sheath and what produces it
|
insulating lipid made by oligodendrocytes (CNS) and Schwann Cells (PNS)
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|
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what part of the myelinating cell froms the myelin sheath
|
several layers of the plasma membrane
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where is the sheath not continuous along the axon
|
node of ranvier
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does the myelin sheath have uniform thickness along axon
|
yes
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myelin sheath is most commonly visualized using what
|
osmium
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what is the major dense line
|
3 nm thick, sites of fusion of inner leaflets of plasma membranes of the myelinating cell, EM
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what are intraperiod lines
|
1-2 nm thick, sitres of close contact, but no fusion, of the extracellular surfaces of adjacent myelinating cells
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what are the clefts of Schmidt-Lantermann
|
cone shaped discontinuities in the myeline sheath in peripheral myelinated nerves, can see w/ light microscope
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what is the inner mesaxon
|
inner fusion point of myelinated cell processes immediately adjacent to axon
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what is the outer mesaxon
|
outer intercellular point of apposition of membrane of the myelinating cell
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are the nodes of ranvier only in PNS
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no- CNS and PNS
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in the PNS the _______ covers the nodes of ranvier
|
Schwann Cell cytoplasm- not always the case w/ oligodendrocytes in CNS
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|
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what are internodes
|
nerve segments between adjacent node of Ranvier, from .08-1mm
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|
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How are nerve fibers classified (A,B, & C)
|
on rates of impulse and various morphologic characteristics
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Type A Fibers are _______ w/ _____- exhibit _____ internodal regions and _____ conduction velocity
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thick, myelinated, long internodes, high conduction velocity (15-100 m/sec)
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Type B Fibers have a _____ diameter than type A, _______ myelin than type A and conduct impulses at ____ velocity
|
small diameter than A, thinner myelin than A, moderate velocity (3-14 m/sec)
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|
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Type C fibers- are _____, lacks _______, ensheathed by ________ conducts at ___ velocity
|
thin fibers, lacks myelin, schwann cells or oligodendrocytes, slow velocity (.5-2 m/sec)
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|
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nerves are bundles of nerve fibers w/in ______
|
CT sheath
|
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why are nerves white to naked eye
|
b/c of myelin
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how are nerves separated anatomically
|
definitive CT layers
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what are CT layers or nerves formed by
|
fibroblasts
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3 layers of CT around nerves
|
epineurium, perineurium, endoneurium
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the epineurium is the outermost layer of ______ CT, referred to as ______, can be ___ in reconstructive microsurgery
|
fibrous dense, fascia, sutured
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Perineurium surround each _____ and divides nerves into __
|
bundles of fibers, fasicles
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|
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at the inner surface of perineurium ________ cells are connected by _______ preventing the _____- movement of ________ and forming the _______
|
squamous epithelial cells, tight junctions, passive, macromolecules, blood-nerve barrier
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|
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the endoneurium is the ___ layer of _____ fibers prodcued by __ that surrounds individual nerve ______
|
thin, reticular fibers, Schwann cells, nerve fibers
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|
|
3 functional classifications of nerves
|
sensory, motor, mixed
|
|
|
sensory nerves contain only _____ fibers from the _______ to the _________
|
sensory (afferent), periphery to CNS
|
|
|
Motor nerves contain only _____ fibers from the ______ to the ________
|
motor (efferent) from CNS to effector organ
|
|
|
Mixed nerve is the most ____, carrying both ______ and _____ fibers
|
common, afferent and efferent
|
|
|
what do the basic principles of histophysiology refer to
|
the microanatomical specializations required for generation of bioelectricity
|
|
|
what is histophysiciology fundamentall based on
|
inter- and extracellular ion balance across neuronal membrane
|
|
|
resting membrane potential exists across the ______ of all _______ cells
|
plasma membrane, electrically competent
|
|
|
in healthy cells, Resitng membrane potential does not vary with time when cell is _______
|
electrically inactive
|
|
|
resting membrane potential undergoes ____ changes upon activation
|
controlled
|
|
|
In resting membrane potential K+ is __x higher ______ the cell and Na+ is ____x higher ___the cell
|
K+is 20x higher inside, Na+ is 10x higher outside
|
|
|
the PM of neurons is highly permeable to ____ ions (they diffuse _____)exstablishing ____ charge on outersurface of membrane
|
K+, outward, positive charge on outer surface
|
|
|
K+ diffusion established + membrane charge is offset by ___________gradient
|
intracellular anionic molecules (i.e. Cl-) gradient )the interior of the cell is 40-100 mV neg. charge compared to outside)
|
|
|
the resting membrane potential exists by action of ________ which exchanged ___ for ___
|
Na+-K+ pump, which exchanges Na+ for K+
|
|
|
what is the electrical activity that occurs in a neuron as an impulse ir propagated along the axon
|
action potential
|
|
|
action potential is characterized as the movement of _____ charge along the _____ of the axon
|
negative, outside
|
|
|
is action potential all or nothing
|
yes
|
|
|
how fast can action potential go
|
up to 1000 per second
|
|
|
to generate an action potential an excitatory stimulus partially _____ a portion of the postsynaptic membrane
|
depolarizes- makes it less negative via primarily local increases in Ca++
|
|
|
Once the membrane reaches its critical threshold, ______ opens and ______ enters the cell
|
voltage-gated Na+ channels open and Na+ enters cell
|
|
|
Na+ entering cell causes _____ or resting membrane potential
|
local reversal- external surface becomes neg.
|
|
|
The ____ channels then close for 1-2 millseconds called the _____
|
Na+, refractory period
|
|
|
_____ remain open during the refractory period returining the membrane to its resting potental ( although their is a bried period of _____)
|
Voltage-gated K+ channels, hyperpolarization
|
|
|
when is the cell ready to respond to another stimulus
|
once cell returns to resting state
|
|
|
propagation of action potential results from the diffusion of ____ ions into the cell laterally beginning at the site of synaptic activation
|
Na+
|
|
|
during propagation of action portential Na+ spreads toward the axon terminal in the target neuron this is call ______
|
orthodromic spread
|
|
|
why is the action potential unidirectional
|
as Na+ channel inactivation occurs at/near the soma preventing movement of impulse to cell body (antidromic spread)
|
|
|
where is propogation most rapid
|
in myelinated fibers
|
|
|
what is saltatory conduction
|
action potential jumping from one internodal segment to the next
|
|
|
what does death of neurons result from
|
injury and/or disease that affects the soma
|
|
|
neuronal death gives rise to ____ loss of nervous tissue
|
permanent
|
|
|
in the CNS neuron death is follow by proliferation of _______, a response to fill in areas of neuronal loss
|
neuroglia (e.g. astroglia)
|
|
|
transection of axons induces changes at the _____ including _____
|
cell body including chromatolysis (dissolution of Nissl substance)
|
|
|
does transection of axons result in neuron death
|
typically no but initiates choreographed axonal response
|
|
|
what happens first when axon is transected
|
degeneration of distal axonal segment
|
|
|
how does the distal axonal segment degrade
|
the axon and assoc myelin degrades and is cleared by macrophages, Schwann cells proliferate forming a cellular column which remain attached to the effector organ
|
|
|
the regeneration of the proximal axonal segment only happens where
|
in PNS
|
|
|
first step of proximal axonal segment regeneration
|
segment immediately adjacent to the lesion degenrates and is cleared
|
|
|
what happens next in proximal axonal segment regeneration
|
growth at distal end begins and progresses toward Schwann cell columns (.5-3 mm/day)
|
|
|
when is the regeneration of the proximal axonal segment successful
|
if/when it enters the column and interacts w/ effector organ
|
|
|
does function regeneration of axons occur in CNS
|
no
|
|
|
how many Americans are spinal cord injured
|
250,000
|
|
|
___% of spinal cord injuries are paraplegic and ___% are quadraplegic
|
52% paraplegic, 47% quadraplegic
|
|
|
how many new injuries each year
|
11,000
|
|
|
____% spinal cord injuries are male
|
82% male
|
|
|
56% of injuries occur between ages of ___ and ___
|
16 &30
|
|
|
Average age of spinal cord injured person
|
31
|
|
|
average lifetime costs for paraplegics, age of injury 25
|
$428,000
|
|
|
average lifetime costs for quadriplegics, age of injury 25
|
$1.35 million
|
|
|
SCI are most commonly caused by- from most common to least
|
car accidents, violence, falls, sports-related
|
|
|
What is the 3rd leading cause of death in US
|
Stroke (#1 cardiovascular, #2 cancer)
|
|
|
Stroke is the leading cause of ______ disability in US
|
serious, long-term
|
|
|
how many stroke survivors alive today
|
4.7 million
|
|
|
between ages of 45 and 64, 8-12% of _____ strokes and 37-38% of _______ strokes result in death w/in 30 days
|
8-12% ischemic, 37-38% hemorrhagic
|
|
|
someong in US suffers stroke every _____ sec, every ____ mintues someone dies of stroke
|
suffers stroke every 45 sec., dies of stroke every 3 to 4 min
|
|
|
where do 50% of stroke deaths occur
|
out of hospital
|
|
|
what is multiple sclerosis and how is it caused
|
autoimmune disorider where CNS myelin is attacked via inflammatory reactions causing plaques of inflammation and demyelination
|
|
|
MS AKA
|
disseminated sclerosis, encphalomyelitis disseminata
|
|
|
how common is MS in young adult females
|
2-150/100,000
|
|
|
what is the etiology and cure for MS
|
unknown and none
|
|
|
MS attacks ____ and causes death of _____
|
myelin, oligodendrocytes
|
|
|
several MS forms occur discretely (_______ form) or intensifying over time (________ form)
|
relapsing, progressive
|
|
|
Lou Gehrig's disease AKA
|
Amyotrophic lateral sclerosis (ALS)
|
|
|
symptoms of ALS
|
extreme skeletal muscle wasting
|
|
|
why is there skeletal muscle wasting in ALS
|
loss of motorneurons in spinal cord
|
|
|
why is ALS fatal
|
loss of respiratory muscles and subsequent respiratory failure
|
|
|
rate of incidence is double in men between what ages
|
50-70
|
|
|
ALS may involve both ____ & ___
|
LMNs and UMNs
|
|
|
neuroglial tumors represent more than 50% of all _______ tumors
|
intracranial
|
|
|
what are neuroglial tumors derived from
|
astrocytes, oligodendrocytes, ependymocytes
|
|
|
do neuroglial tumors differ in severity
|
yes
|
|
|
2 types of neuroglial tumors
|
benign oligodendrogliomas (slow-growing),
malignant astrocytomas (fast-growing) |
