Flashcards in Cytology Deck (106):
number of poles:
specialized- seen in sensory systems
(smell, sight, vestibular)
predominant kind of neuron in CNS and PNS
evolves for speed/faster conduction- bypasses cell body so it doesn't have to travel through
seen for pain/pressure
LONG axon which projects from one subsystem to another (brain-->SC, SC-->foot)
make connections with other neurons in the same subsystem
most numerous; short or no axon;
neurons that integrate things (connect dorsal horn to ventral horn of C5 on the same side)
segmental golgi II
project only to the same segment
associative: same side (ipsilateral fiber)
commissural: opposite side (contralateral fiber)
Propriospinal golgi II
project to other SC segments
similar to golgi I but reside only in the CNS
forms tracts- collections of axons carrying the same kind of information (project to higher or lower levels of communication; fasiculus)
2: action on other neurons
3: discharge patterns
4: neurotransmitter release
point of reference is usually the CNS; when it is, then you can refer to them as sensory or motor neurons
coming to the point of reference (CNS)
leaves the point of reference (CNS)
usually "motor" in the sense that it innervates muscles
actions on other neurons
changes how the system reacts to the next time the stimulus is introduced
endorphins- modulate system to feel less pain to same painful stimulus
tonic or regular spiking
phasic or bursting
tonic (or regular spiking) discharge pattern
firing- always firing at a rhythmic rate and changed by increasing or decreasing firing rate; slow adapting
stimulate a neuron, continue to fire for a long time
phasic (or bursting) discharge pattern
only on when they are stimulated and go off quickly; quick adapting
stimulate a neuron, fires, stops when stimulus is removed
fast spiking discharge pattern
fast firing rates
excitatory to muscle
inhibitory to PNS
acetylcholine- usually always excitatory, used to contract muscle and inhibit the heart
excitatory and inhibitory
contains genetic material (chromosomes) including information for cell development and synthesis of proteins necessary for cell maintenance and survival.
covered by a membrane
produces ribosomes necessary for translation of genetic information into proteins
groups of ribosomes used for protein synthesis
endoplasmic reticulum (ER)
system of tubes for transport of materials within cytoplasm
Rough ER: have ribosomes- important for protein synthesis
Smooth ER: no ribosomes
membrane-bound struction important in packaging peptides and proteins (including neurotransmitters) into vesicles
system of transport for materials within a neuron and may be used for structural support
passes nutrients/proteins up and down axon
produce energy to fuel cellular activities
produced in cell, going down to synapse away from home
coming back towards nucleus or cell body of neuron
where AP is generated because it has the lowest threshold
function of the intracellular matrix
1: gives the cell its shape and stiffness
2: provides the mechanisms for cell growth and motility
3: provides the internal network over which molecules and organelles are transported
elements of the intracellular matrix
structural- keep axon together
1: actin filaments
actin filaments (don't memorize)
STRUCTURAL INTEGRITY- gives membranes structure
-closely associated with the cell membrane- forms a dense network
- responsible for developing and maintaining surface irregularities of cells (i.e. dendritic spines) and growing axons
-3-5 nM in diameter
-key role in the dynamic function of the cell's periphery (ie motility or growth cones during developmental, formation or pre- and post morphologic specializations
intermediate filaments (neurofilaments (neurons)) (don't memorize)
(railroad track for structures to move and and down the axon)
gives cells mechanical integrity- bones of the cytoskeleton
give high tensile strength
aligned in orderly parallel arrays
10nm in diameter
forms the neurofibrillary tangles of Alzheimer's
microtubules (don't memorize)
largest intracellular protein
abundant in all cells
in neurons, provide rigidity by x-linking with neurofilaments
essential in the transport of macromolecules and membrane bound structures
long scaffolds- extend the full length of the neuron
responsible for maintaining the neuron's processes
not only transports AP but moves fluids
if you take an axon off a muscle the muscle will atrophy
can be up to a meter long!
non-neural cells of CNS & PNS
outnumber neurons 5-50x & comprise 40% of the total CNS (most numerous cell in the NS)
determine what goes in/out of BBB
main functions of neuroglia cells
1: developmental- radial astrocyytes (scaffold, release GFs)
4: maintenance of a relative constant environment
(can control the environment - absorb K or Na to modulate impulse conduction )
precursers to glia cells
they continue to grow and divide after birth
neuroglia classification (CNS)
located everywhere. look like neurons
help make blood brain barrier (BBB); controls diffusion; most predominant
FIBROUS: maintain the integrity of the axons in the white matter
PROTOPLASMIC: touching the cells-gray matter
myelin producing cells in the CNS (in PNS myelin producing cells= Scwann cells)
come in when the blood comes in, cleans up debris
fatty substance that insulates the nerve fiber
doesn't heal well; chemical doesn't allow neuron regeneration to occur
remnants of neuroepithelial cell lining that becomes more CT like
lines the ventricle system; single layer
multiple layers of ependymal that produce CSF
tight junctions between glial cells in BBB
Glia cells in the periphery
SATELLITE GLIA- astroglia like functions
PERINEURAL GLIA- structure
produce myelin in the periphery and support axon in environment
satellite glia cells
astrocyte in ganglia in PNS
similar function in CNS; ganglion is a collection of neurons in periphery
perineural glia cells
protective covering of nerve fiber for structure
what is glia reaction to injury?
GLIOSIS= proliferates of astrocytes to form plaques or scars
primarily astrocytes start to multiply, take form of a plaque, grow processes, take place of injury. Not a good thing bc it forms a barrier and new growth can't get by. major problem with regeneration in CNS
what are the 7 types of synapses?
axon synapses with spine of dendritic tree (spine is a bulbous extension of the dendrite to increase surface area)
spines are extensions on dendrite
axon synapses with dendrite without use of spine
axon synapses with cell body (soma)
axon synapses with axon
goes to 2 different things
en passant synapse
goes to >2 places
doesn't use chemicals
usually gap junctions
axon branches can divide into...
axon is not 1 string/fiber, gives off collaterals or branches (can give off as many as it wants)
what are the meningeal layers surrounding the CNS?
pia mater: like skin
arachnoid: like spandex; goes over bumps and dents
dura mater: like overcoat; extends into the peripheral nerve and is renamed Epineurium
dura mater attaches to periosteum of bone
what is the subarachnoid space?
space between the pia and arachnoid matter that is filled with CSF
there is where a spinal tap is done
what is the subdural space?
potential space between dura and arachnoid mater
what are the 3 sheaths around a peripheral nerve?
what is the endoneurium?
the layer around an axon of a peripheral nerve
between axons is a loose CT of type I & II collagen longitudinally oriented
what is the perineurium?
the layer around a bundle of axons (fascicle)
acts as the BBB of the peripheral nerve
provides mechanical strength
primary load bearing portion
small arterioles and venules located longitudinally in this area
what is the epineurium?
the layer around a whole nerve bundle
originally known in the CNS as the dura mater
then attaches to the periosteum of bone
* only meninge to continue
what are the 2 subtypes of epineurium?
what does the epifasicular epineurium do?
surrounds and infiltrates the entire nerve bundle externally
what does the interfasicular epineurium do?
it is loosely attached to the epifasicular allowing for sliding of 1 fasicle independently on another
large amount of interfasicular epineurium
helps facilitate the dispersion of compressive forces
the perineurium is composed of:
type I and II collagen
oriented in oblique, longitudinal and circumferential directions
up to 15 cell layers thick
what is the primary load bearing portion of the peripheral nerve?
basal lamina is type ? collagen
type IV collage
blood supply of the peripheral nerves
blood vessels enter the epineurium periodically along the length of the nerve
divides into arterioles that form anatomatic network in epineurium and perineurium
vessels in endoneurium turn into capillaries and travel longitudinally
3 parallel arteries: regional nutrient, epinutrient and perinutrient
what are the characteristics of an unmyelinated nerve?
unmyelinated cells usually travel together
multiple neurons for 1 schwann cell
usually very thin and slow conducting
all have a schwann cell membrane surrounding
what are the characteristics of a myelinated nerve?
1:1 relationship with schwann cell
1 schwann to 1 axon
schwann cell wraps its plasma membrane around the axon and forms the myelin sheath
(pushes into cell and wraps around and around)
what does myelin do?
acts as an insulater
speeds up AP
AP jumps from node to node (node of Ranvier)
myelin in the CNS
in CNS, no plasma membrane around anything
unmyelinated- nothing around it
myelinated- just myelin, no membrane
this is bc oligodendrogliocytes are not in 1:1 ratio
oligo shoots of processes to wrap around neighboring cells. one can produce myelin for many axons at segment. still have slatatory conduction bc you still have nodes of Ranvier.
This is why there is no functional regenerationg bc there is no plasma membrane around nerve forming a tube to show the nerve to to go/grow. Tube also provides nutrition in PNS. since nerve can't figure out where to grow in CNS, it becomes a neuroma
tube is neurolemma sheath
PNS schwann cells create a tube around all the axons so regeneration is possible. tube tells nerve where to go
what are the 3 nerve fiber classifications?
general (G) or special (S)
visceral (V) or Somatic (S)
Afferent (A) or Efferent (E)
general vs. special nerve fiber classification:
general: distributed throughout the body
spinal nerves and CNs
special: restricted area of the body
only in some CNs
hearing, taste, smell; special motor in CNs
visceral or somatic nerve fiber classification:
visceral: autonomic/brachial arches
ANS, origin is from gill region of developing embryo, organs
somatic: somites, body, skin, muscle joints
afferent or efferent nerve fiber classification
what are the anatomic functional components of general nerve fibers?
General somatic afferent (GSA)
General somatic efferent (GVA)
General visceral afferent (GVA)
General visceral efferent (GVE)
what do GSA nerve fibers control?
conscious sensation (pain, temperature, touch, proprioception)
what do GVA nerve fibers control?
visceral sensation (mainly pain from ischemia, blood pressure, etc)
what do GSE nerve fibers control?
voluntary motor to skeletal muscle (derived from myotomes)
what do GVE nerve fibers control?
autonomic motor to smooth and cardiac muscle and glands (parasympathetic, sympathetic- preganglionic and postganglionic fibers)
what are the anatomic functional components of special nerve fibers?
special visceral afferent (SVA)
special visceral efferent (SVE)
special somatic afferent (SSA)
special somatic efferent (SSE)
what do SVA nerve fibers control?
visceral sensations of taste and smell
what do SVE nerve fibers control?
what do SSA nerve fibers control?
somatic sensations of vision, heading and equilibrium
what do SSE nerve fibers control?
? voluntary motor to skeletal muscle (derived from branchiomeres)??
Erlanger size classification of fibers
A fibers: largest with lots of myelin, very fast conduction
B fibers: small with a little myelin; ANS
C fibers: unmyelinated (small in diameter, slow conducting); ANS
ventral root classification:
ventral root: motor
greek letters (alpha, beta, gamma, delta)
efferents don't conduct as fast as afferents
dorsal root: sensory
sensory root nerve classification by Lloyd:
sensory neurons classified based on diameter --> speed of conduction
Ia: from muscle spindle, proprioceptors
Ib: from GTO (touch and pressure receptors)
II: secondary from ms spindles, touch and pressure receptors and pacinian corpuscles (vibration)
III: small lightly myelinated fibers; touch & pressure, pain & temp
IV: pain & temp (different from III only in speed (fast pain vs slow pain)