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Flashcards in Cytology Deck (106):
1

cell classification

polarity

functional

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polarity classifications

number of poles:
1: multipolar
2: bipolar
3: pseudo-unipolar

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bi-polar

specialized- seen in sensory systems
(smell, sight, vestibular)

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multi-polar

most common
predominant kind of neuron in CNS and PNS

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pseudo-unipolar

evolves for speed/faster conduction- bypasses cell body so it doesn't have to travel through

seen for pain/pressure
self propagating

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golgi I

LONG axon which projects from one subsystem to another (brain-->SC, SC-->foot)

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Golgi II

(interneurons)
SHORT axons
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)

1: segmental
2: propriospinal

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segmental golgi II

project only to the same segment

associative: same side (ipsilateral fiber)

commissural: opposite side (contralateral fiber)

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Propriospinal golgi II

project to other SC segments

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tract cells

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)

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Functional classifications

1: directional
2: action on other neurons
3: discharge patterns
4: neurotransmitter release

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directional classifications

afferent

efferent

interneurons

point of reference is usually the CNS; when it is, then you can refer to them as sensory or motor neurons

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afferent=

coming to the point of reference (CNS)
usually "sensory"

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efferent=

leaves the point of reference (CNS)
usually "motor" in the sense that it innervates muscles

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actions on other neurons

excitatory:

inhibitory:

modulatory:

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modulatory=

changes how the system reacts to the next time the stimulus is introduced

endorphins- modulate system to feel less pain to same painful stimulus

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discharge patterns

tonic or regular spiking

phasic or bursting

fast spiking

thin spike

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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

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phasic (or bursting) discharge pattern

"dynamic"
only on when they are stimulated and go off quickly; quick adapting

stimulate a neuron, fires, stops when stimulus is removed

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fast spiking discharge pattern

fast firing rates

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neurotransmitter release

cholinergic neurons

GABAergic neurons

glutamatergic neurons

dopaminergic neurons

serotonin

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cholinergic neurons

excitatory to muscle
inhibitory to PNS

acetylcholine- usually always excitatory, used to contract muscle and inhibit the heart

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GABAergic neurons

primary inhibitors

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glutamatergic neurons

excitatory

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dopaminergic neurons

excitatory and inhibitory

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serotonin

excitatory

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nucleus

contains genetic material (chromosomes) including information for cell development and synthesis of proteins necessary for cell maintenance and survival.
covered by a membrane

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nucleolus

produces ribosomes necessary for translation of genetic information into proteins

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nissl bodies

groups of ribosomes used for protein synthesis

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endoplasmic reticulum (ER)

system of tubes for transport of materials within cytoplasm

Rough ER: have ribosomes- important for protein synthesis

Smooth ER: no ribosomes

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golgi apparatus

membrane-bound struction important in packaging peptides and proteins (including neurotransmitters) into vesicles

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microfilaments/neurotubules

system of transport for materials within a neuron and may be used for structural support

passes nutrients/proteins up and down axon

anterograde

retrograde

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mitochondria

produce energy to fuel cellular activities

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anterograde

produced in cell, going down to synapse away from home

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retrograde

coming back towards nucleus or cell body of neuron

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cell hillock

where AP is generated because it has the lowest threshold

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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

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elements of the intracellular matrix

structural- keep axon together

1: actin filaments

2: neurofilament

3: microtubules

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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

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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

most numerous

aligned in orderly parallel arrays

10nm in diameter

forms the neurofibrillary tangles of Alzheimer's

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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

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axons

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!

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neuroglia cells

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

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main functions of neuroglia cells

1: developmental- radial astrocyytes (scaffold, release GFs)

2: support

3: nurture

4: maintenance of a relative constant environment
-nutritive
-impulse conduction
(can control the environment - absorb K or Na to modulate impulse conduction )

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spongioblast

precursers to glia cells
they continue to grow and divide after birth

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neuroglia classification (CNS)

ASTROCYTES
-fibrous
-protoplasmic
-perivascular glia

OLIGODRODENDROGLIA

MICROGLIA

EPENDYMAL

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astrocytes

neuroglia
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

PERIVASCULAR GLIA:

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oligodrodendroglia

neuroglia

myelin producing cells in the CNS (in PNS myelin producing cells= Scwann cells)

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microglia

neuroglia

mesodermic
come in when the blood comes in, cleans up debris

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myelin

fatty substance that insulates the nerve fiber

doesn't heal well; chemical doesn't allow neuron regeneration to occur

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Ependymal

glia cells

remnants of neuroepithelial cell lining that becomes more CT like

lines the ventricle system; single layer

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choroid plexus

multiple layers of ependymal that produce CSF

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zomula occlusions=

tight junctions between glial cells in BBB

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Glia cells in the periphery

SCHWANN- myelin

SATELLITE GLIA- astroglia like functions

PERINEURAL GLIA- structure

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Scwann cells

produce myelin in the periphery and support axon in environment

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satellite glia cells

astrocyte in ganglia in PNS

similar function in CNS; ganglion is a collection of neurons in periphery

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perineural glia cells

protective covering of nerve fiber for structure

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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

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what are the 7 types of synapses?

1- axospinous
2- axodendritic
3-axosomatic
4-axoaxonic
5-chain
6-en passant
7- electrical

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axospinous synapse

axon synapses with spine of dendritic tree (spine is a bulbous extension of the dendrite to increase surface area)

spines are extensions on dendrite

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axodendritic synapse

axon synapses with dendrite without use of spine

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axosomatic synapse

axon synapses with cell body (soma)

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axoaxonic synapse

axon synapses with axon

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chain synapse

goes to 2 different things

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en passant synapse

goes to >2 places

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electrical synapse

doesn't use chemicals
usually gap junctions

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neuromuscular junction

l

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iontotropic

most common

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metabotropic

k

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axon branches can divide into...

collateral branches

axon is not 1 string/fiber, gives off collaterals or branches (can give off as many as it wants)

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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

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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

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what is the subdural space?

potential space between dura and arachnoid mater
no adhesions

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what are the 3 sheaths around a peripheral nerve?

Endoneurium

Perineurium

Epineurium

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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

76

what is the perineurium?

the layer around a bundle of axons (fascicle)

acts as the BBB of the peripheral nerve
tight junctions
provides mechanical strength
primary load bearing portion

small arterioles and venules located longitudinally in this area

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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

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what are the 2 subtypes of epineurium?

1: Epifasicular

2: Interfasicular

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what does the epifasicular epineurium do?

surrounds and infiltrates the entire nerve bundle externally

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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

81

the perineurium is composed of:

type I and II collagen

oriented in oblique, longitudinal and circumferential directions

up to 15 cell layers thick

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what is the primary load bearing portion of the peripheral nerve?

the perineurium

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basal lamina is type ? collagen

type IV collage

84

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

85

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

86

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)

87

what does myelin do?

acts as an insulater
speeds up AP
AP jumps from node to node (node of Ranvier)

"saltatory conduction"

88

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

89

what are the 3 nerve fiber classifications?

general (G) or special (S)

visceral (V) or Somatic (S)

Afferent (A) or Efferent (E)

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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

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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

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afferent or efferent nerve fiber classification

afferent: sensory

efferent: motor

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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)

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what do GSA nerve fibers control?

conscious sensation (pain, temperature, touch, proprioception)

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what do GVA nerve fibers control?

visceral sensation (mainly pain from ischemia, blood pressure, etc)

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what do GSE nerve fibers control?

voluntary motor to skeletal muscle (derived from myotomes)

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what do GVE nerve fibers control?

autonomic motor to smooth and cardiac muscle and glands (parasympathetic, sympathetic- preganglionic and postganglionic fibers)

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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)

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what do SVA nerve fibers control?

visceral sensations of taste and smell

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what do SVE nerve fibers control?

?

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what do SSA nerve fibers control?

somatic sensations of vision, heading and equilibrium

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what do SSE nerve fibers control?

? voluntary motor to skeletal muscle (derived from branchiomeres)??

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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

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ventral root classification:

ventral root: motor
greek letters (alpha, beta, gamma, delta)
efferents don't conduct as fast as afferents

dorsal root: sensory
roman numerals

105

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)

106

erlanger size classification of fibers are further subdivided into:

fibers are further subdivided by mean conduction velocity:

alpha: large diameter fibers, innervate extrafusal muscle (straited skeletal muscle outside the muscle spindles)

gamma: small diameter fibers; innervate intrafusal muscle fibers (within muscle spindles)

beta: intermediate fibers: innervate both intrafusal and extrafusal fibers

delta: