nervous system Flashcards
what is nervous tissue composed of
100 billion neurons and trillions of glial support cells
what does classification of nervous tissue depend on
differ in types of cells
describe nervous tissue classification anatomically
cns = brain, cerebellum, spinal cord = gray and white matter, can distinguish between
pns = nerve ganglia, nerve fibers
describe nervous tissue classification histologically
nerons - nerve cells
neuroglia - glial cells equivalent to the ct = involved in support, neuron protection, defense and nutrition
what is difference between CNS gray matter and white matter
gray = cell bodies of neurons, neuroglia
white = neuronal cell processes (axons), neuroglia
what is neuron
functional unit of nervous system
what does neuron consist of
dendrites
cell body
axons
describe dendrites
Receives signals
neurons synapse with each other and other things
describe cell body
integrates incoming signals from dendrites and outgoing signals to axons
soma, perikaryon
organelles and nucleus
describe axons
transmits signals to another neuron or effector cell
what is present in grey matter cns and ganglia pns
dendrites and cell bodies
what is present in white matter cns and nerve fiber pns
axon
what are the dots
nissl bodies
how to tell axon from dendrite
dendrites still have nissl bodies
axon hillock has no nissl bodies at begining of axon
do all nerons look the same
neurons have complex moprhology
perikaryons can be spherical, ovoid or angular
can have more than 2 processes = multipolar
not all neurons are typical and many have multiple polarities
name and describe types of neurons
pyramidal - brain cortex
purkinje - cerebellum
motor neurons - spinal cord
pseudounipolar - spinal ganglia, bifurcates- opens in 2, arborizes, branches
bipolar = retinal, olfactory, mucosa, originates from same cell body then goes in 2 opposite directions
name parts of cns
cerebrum
cerebellum
spinal cord
what does cns show when sectionned
regions of white or grey matter when sectioned
what does gray matter have
neuronal cell bodies and neuroglial cells
what does white matter have
axons and neuroglial cells
appears white due to presence of myeline around myelinated axons
where is cerebrum
upper portion of brain
what is function of cerebrum
integration of sensory information (from peripheral nervous system= sensory modalities = olfactory,touch, language,learning,nearing
initiation of voluntary motor Responses - motor cortex
describe histology of cerebrum
white matter appears lighter
gray matter appears darker, more homogenous
describe white matter of cerebrum
both longitudinal and cross section
broken up appearance
where myelin used to be - white spaces, does not preserve well
describe gray matter of cerebrum generally
can trace where axons are
entirely different
no myeline since no axons
cell bodies and nucleus
smaller = neuroglial cells in white and gray mater = support cells, maintains, supports and protects tissue
describe gray matter of cerebrum specifically
6 layers in cerebral cortex
pyramidal neurons are most prominent - pyramidal shaped, arranged in paralel with another, larger than glial cells, see bulky cell bodies
where is cerebellum found
part of hindbrain
describe function of cerebellum
integration of sensory information (from PNS) Fine tunes voluntary motor Responses = integrate and refine info for complex movement
describe damage or lesions to cerebellum
can still do voluntary movement but harder and worse
less fine tined, poor balance, posture, harder to learn fine movements
describe histology of cerebellum
cerebellar cortex - gray matter has 3 layers =
molecular
purkinje
granular
describe molecular layer of cerebellum
sparse neurons
describe purkinje layer of cerebellum
very large neruons
dendrites project into molecular layer
axons project into granular layer
describe granular layer of cerebellum
very small densely packed neurons
axons are unmyelinated = project into molecular layer where they synapse with dendrites of purkinje cells
what is function of spinal cord
relay messages from brain to body
pass sensory info from sensory receptors to brain
coordinate reflexes that are managed by spinal cord alone - like patellar/knee jerk reflex
describe white and gray matter of spinal cord
white = white spaces, cord bundles, relatively all circular - can say its cross section
gray matter = have cell bodies
name parts of pns
somatic
autonomic
describe somatic system
sensory nerve fibers that send sensory info to CNS afferents - Receives
processes & integrates ·motor fibers that project from CNS to skeletal muscle (efferent)- away through spinal cord through motor nerve fibers
describe autonomic system
controls smooth muscle of internal organs and glands
involuntary
what is pns - which cells
ganglia - grouping of cell bodies
nerve fibers - bundles axons, H&E staining
where are cell bodies located of pns and cns
sensory and autonomic neurons have cell bodies in ganglia
neuron cell bodies of motor neurons are located in spinal cord
what forms myelin
oligodendrocytes in cns
schwann cells in pns
what is myelin like
lipoprotein
are all axons myelinated
NOOO
what is function of myelin
electrical insulation
faster conduction of nerve impulse
what are nodes of ranvier
gaps between myeline sheath that promote transmission of ap
when is axonal conduction faster
axonal conduction of nerve impulse is faster in myelinated axons and even faster in axons with thicker myelin sheath
describe myelination in cns
oligodendrocytes in cns white matter produce myelin sheath
several axons myelinated by one individual oligodendrocytes
= wraps around and around - concentric layers of myelin = myelin sheath
what is myeline sheath
several layers of modified cell membrane containing lipoprotein called myelin
what is myelin composed of
phospholipids
sphingolipids
proteins = myeline basic protein, MP2 etc
what does autoimmune response against myeline result in
demyelination
MS
landry guillain barre etc
describe myelination in PNS
schwann cells produce myelin sheath
one axon is myelinated by one shcwann cell
where does axon begin and end
beings at axon hillock
ends in terminal arborizations and end bulbs called terimal boutons which are apart of synapses
what does terminal bouton depend on
depends on goal of info
what can synapses form between
axon and dendrite
axon and cell body
axon and axon
synapses can be….
excitatory or inhibitory
what are neuroglia
Multiple different cell types with different roles, supports neurons in different ways
neuroglial cells provide support, protection and nutrition to neurons
name 3 kinds of neuroglia
astrocytes
oligodendrocytes
microglia
describe astrocytes - what
largest neuroglial cells
found in white matter of cns
has pedicles or vascular feet
describe oligodendrocytes - what
found in gray and white matter of cns
describe microglia - what
scattered throughout cns
smallest neuroglial cells
darkly stained
derive monocytes
describe astrocytes - function
form and maintain blood brain barrier
removes ions and neurotransmitter remnants like GABA and glutamate
describe oligodendrocytes - function
satellite cells around neurons in CNS are oligodendrocytes
in white matter = produce myelin
Specialized function = support neuron , make synapse quicker and faster and insulate conduction of nerve
describe microglia - function
function as phagocytes clearing debris of damaged structured in cns
what are processes
axons and dendrites
