Nerve tissue Flashcards
What are the two types of cells in the Nervous system?
-neurons or nerve cells -supporting cells
What is the difference between the nerve cells of the PNS and CNS?
PNS - Schwann cells surround nerve processes - Satellite cells - surround nerve cell bodies in ganglia -CNS - glial cells
Describe some basic information of the neuron.
-structural functional unit of the NS -10 billion in humans -consist of central process- axon -peripheral process - dendrite
Do neurons replicate?
no
What is the name of the neuron cell body
Perikaryon
Describe some of the structural components for the perikaryon.
-Nissl bodies -Mitochondria -large peripheral GA
What are Nissl bodies?
-stacks of RER -extend into dendrites -depend on the cell body for maintenance
Where can you find Nissl bodies?
In the dendrites but not the axons
Describe the parts of the neuron.
What carries information to the cell body
dendrites
What has a greater diameter dendrite or axon?
dendrites
Are dendrites myelinated?
no
What are the purpose of arbonizations called dendritic trees on dendrites?
-allows for a greatly increase in the receptor surface of the neuron
Where are axons origins on the nerve cell?
Axon Hillock
What are the components of the Axon Hillock? What organelles are not present here?
In- microtubules, neurofilaments, mitochondria, vesicles, terminal arborizations Not present - Nissyl (RER) and Golgi
What is the purpose of the axons?
carry information from the cell body.
How many axons and dendrites per neuron?
1 axon and may have numerous dendrites
Axolemma
axon plasma membrane
Axoplasm
axon cytoplasm lacks a golgi complex but contains SER, RER and elongated mitochondria - lacks a golgi apparatus
Golgi Type I neurons
- motor nuclei of CNS - axons more that 1 meter long ex. muscle
Golgi Type II neurons
- golgi cells in the cerebellum - have short axon - axon branched near target organ
Where do sensory neuron travel?
receptor to CNS
Where do motor neuron travel?
CNS or ganglia to effector cells
What are interneurons?
connections between neurons and include internuncial, central and intercalated neurons, (99% of neurons). They regulate signal transmission between neurons.
How are neurons classified?
by the number of processes
Multi-polar neuron
one axon and 2 or more dendrites
Bipolar neuron
one axon and one dendrite
Unipolar (pseudo-unipolar in higher animals)
one process (axon) that divides close to cell body into two processes
Distinguish between anterograde and retrograde transport.
Axon transport is bidirectional - ANTEROGRADE - cell body to periphery via kinesin - RETROGRADE - axon terminal & dendrites to cell body via dynein
What are synapses?
-specialized junctions between neurons that facilitate transmission of impulses between neurons, axons and effector cells.
How many synapses can occur on one neuron?
few to a thousand
What is the name of the end of the axon.
Swollen bulb or BOUTON
Two types of synapses
Electrical and Chemical
What is an important structural component of the electrical synapse?
gap junctions which facilitate movement of ions between cells - action potential is directly from presynaptic cell to post synaptic cell.
Cells that contain electrical synapse.
Nexus in smooth muscle Gap junctions in cardiac muscles
What are the three components of chemical synapse?
- -PRESYNAPTIC BOUTON -
- SYNAPTIC CLEFT
- -POSTSYNAPTIC MEMBRANE
What facilitates information transfer at the presynaptic bouton?
synaptic vesicles which release transmitters into the synaptic cleft
How big is the synaptic cleft?
20-30nm
Patient comes in with gradually progressing stiffness, difficulty walking, and uncontrolled involuntary movement of legs and arms. What is a possible diagnosis and its mechanism of action?
Parkinson’s disease Physiology: loss of dopamine secreting cells in substantia nigra and basal ganglia Increase in the number of glia cells.
What is a treatment for Parkinson’s disease?
synthetic dopamine
What component of the nervous system is affected in someone with Myasthenia Gravis?
Neuromuscular junction where their is an autoimmune attack on acetylecholine receptors.
What are some cells found in the PNS?
-Schwann cells -Satelite cells
Cells of the CNS
- Ependymal cells - Neuroglial cells : astrocytes, Oligodendrocytes, microglia
Describe the nucleus of a neuronal cell body.
The nucelus is large, sperical and pale-staining and is centrally located in most neurons.
What cell is responsible for myelination in the PNS?
- Schwann cells
What is another name for a sheath of Schwann?
Neurilemma
What is in the Schwann cell cytoplasm?
nucleus few mitochondia and a small golgi region
What area on a neuron are free of myelin?
axon hillock and terminal axon arborizations
Nodes of Ranvier
gaps in the myelin sheath that allow for saltatory conduction of impulses. “jumping” from node to node.
Describe the stages of myelination
Insert picture : a) A Schwann cell nestles itself around an axon. b) While continuously producing myelin, the Schwann cell winds a sheath-like protrusion around the axon yielding multiple layers. c) Finally, these layers are compacted into a tightly packed insulation coat.
What is this image
Myelinated nerve fiber
What are the components of the myelin cytoplasm?
-Inner collar of Schwann cytoplasm between axon and myelin - Schmidt-Lantermann clefts - small islands of cytoplasm within lamellae of myelin Perinodal cytoplasm - at node of ranvier Outer collar of perinuclear cytoplasm- around myelin Insert picture.
Unmyelinated cells
enveloped by a single invagination of schwann cells. - axon is in a cleft of the cytoplasm of a schwan cell with a single mesoaxon
Saltatory Conduction
myelinated axons conduct faster than unmyelinated ones. - called “jumping” from node to node - Speed is related to the thickness of myelin and axon.
Guillian Barre Syndrome
results in loss of muscle co-ordination and cutaneous sensation when there is a large amount of lymphocytes, plasma cells and macrophage surround nerve fibers
Multiple Sclerosis
Gradual degeneration of the myelin and destruction of oligodendrocytes
What are Satellite cells? what do they look like? What do they surround?
-surround ganglionic neuronal cell bodies -Cuboidal shape - only able to see nuclei - originate from neural crest cells. - anagolous to schwann cells - insulation and nutrition
What cells are analogous to Schwann Cells?
Satellite cells
Neuroglia (Glial cells of CNS)
more numerous than neurons Three types: Oligodendrocytes, astrocytes, microglia
What are the two types of astrocytes and how can you differentiate between the two of them?
Protoplasmic - prevalent in gray matter Fibrous- more common in white matter - both have elaborate processes extending between vessels and neurons - play a role in scar formation in the CNS
What allows astrocytes to be viewed by immunohistochemistry?
they contain fibrillary acidic protein marker
What cell may play a role in regulating the tight junction in the Blood Brain Barrier?
astrocytes
What forms the Blood Brain Barrier?
capillary endothelium with occluding junctions with an envelop of astrocytes on the basal lamina capilaries
Which area of the brain does not have astrocytes wrapping the basal lamina capillaries?
Choroid plexus and posterior pituitary
Oligodendrocytes
cells that create myelin on CNS neurons. - align in rows between axons -each oligodrocyte gives off several tongue-like process that wraps around the axon.
How many nerve fibers can one oligodendrocyte for myelin sheaths for?
3-50 nerves
Microglia
mononuclear phagocytes -small numbers that proliferate during disease -secrete immunoregulatory cytokines
Ependyma cells serve what roll in the CNS
line fluid filled cavities of the CNS - cuboidal to columnar shaped to allow for fluid transporting characteristics
Choroid plexus
modified ependyma cells and capilary loops that produce cerebrospinal fluid.
dendrites
cell body
neuroglia
axon
Distinguish between neuron in the CNS and PNS
What kind of nerves are labeled U and M?
Unmylenated and Mylenated
What is the arrow pointing at?
Satellite Cells
Describe some of the components of a Neuron cell body in a ganglion?
A neuron in the ganglion is surrounded by satellite cells and covered with Schwann cells on the axons.
What kind of cell is this?
Astrocytes
What is this arrow pointing at?
Ependyma - which is a cuboidal to colummnar cell that plays a role in production of CSF
What are the choroid plexus?
Choroid plexus is invaginated folds of pia mater rich in dilated fenestrated capillaries covered by simple cuboidal cells
Where is the choroid plexus found?
two lateral, 3rd and 4th ventricles and all the regions where epnymal cells liein contact with pia mater
What is the function of the choroid plexus?
produces CSF
What are each of the villus of CP covered with what layer of the CNS (pia, aracnoid or dura)
vascularized pia mater covered by cuboidal ependymal cells.
What is the function of the CSF?
acts as a mechanical shock absorber and important for CNS metabolism
What areas of the brain does the CSF fill?
- ventricles
- central canal of spinal cord
- subarachnoid space
- perivascular spaces
What is this tissue and what are some important components of it?
Choroid Plexus with simple cuboidal cells.
What is this tissue?
Choroid Plexus
What is this tissue?
longitudinal section of myelinated peripheral nerve fibers
What are the three components of connective tissue sheaths?
- Endoneurium
- Perineurium
- Epineurium
What is the Endoneurium?
Thin layer of reticular fibers produced by Schwann cells.
(Electron micrograph of a cross section through a nerve, showing the epineurium, the perineurium, and the endoneurium. The epineurium is a dense connective tissue rich in collagen fibers (Col) and fibroblasts (arrow). The perineurium is made up of several layers of flat cells tightly joined together to form a barrier to the penetration of the nerve by macromolecules. The endoneurium is composed mainly of reticular fibers (RF) synthesized by Schwann)
Describe the perineurium?
- surrounds bundles of nerve fibers
- sheath of unique connectivie tissues
- cells are joined by tight junctions
- forms barrier to passage of most macromolecules
- protects nerves from aggression
- contractile cells
- numerous actin filaments
What part of sheath serves as a blood-neuron barrier. Separates the vascular tissue from the interstitial space between individual neurons
Perineurium
Which component of the sheath protects nerves from aggression and are contractile?
perineurium
What are the epineurium?
- outmost tissue of the peripheral nerve
- typical dense connective tissue that binds fascibles together
- oftan contains adipose tissues and is vascular
Does the perineurium have a vascular supply?
Vascular supply from the epineurium penetrates the perineurium
What is this longitudinal section?
Peripheral nerve
What are the two type of ganglia
Sensory and Autonomic
Which ganglia is pseudounipolar with thick fascicles?
Sensory ganglia
Which ganglia are multipolar, smaller and far apart?
Autonomic ganglia of the parasympathetic and sympathetic system
Describe sensory ganglia?
- craniospinal (dorsal root ganglion)
- pseudounipolar neurons
- larger
- close together
- thick fascicles
Describe Autonomic ganglia
- Sympathetic and parasympathetic
- multipolar neurons
- smaller
- far apart
- diffuse nerve fibers
What kind of ganglia is this?
Sympathetic ganglia
What kind of ganglion is this?
Sensory ganglion
C- capsule
So- soma (cell body)
Cc - capsule cells
F- nerve fiber
What is the outflow of the sympathetic pathway?
Thoraco Lumbar outflow via norepinephrine
What is the outflow of the parasympathetic pathway?
cranio-sacral outflow acetylcholine
What are the two plexus of the Enteric Nervous system?
- myenteric (Auerbach)
- submucous (Meissner)
What is the tissue?
Enteric nervous system- consits of ganglia and postganglionic networks
- composed of unmyelinated nerve fibers intermingled with neuronal cell bodies.
What is Hirschsprung Disease?
- Congential mega colon.
- arrest of one of the neural crest cells to one segment of the distal colon
- no innervation of the colon
- sign and symptoms: unable to pass stool at birth, with no vomiting, no abdominal distention.
*
What is the composition of grey matter?
neuron cell bodies and their dendrites along with axons and glia.
Describe what white matter looks like?
- mostly myelinated fibers
- arranged in three pairs of funiculus - anterior, lateral and posterior
- functionally related bundles called tracts
Label each component of the picture.
Cc - central canal
Gc- grey commissure
VH-ventral horn
DH-dorsal horn
WM- white matter
What is in the cortex of the brain?
Grey matter- contains cell bodies, axons, dendrites, glial cells and synapses
What are the nuclei?
Islands of grey matter found in deep portions of cerebrum and cerebellum
What does white matter mostly consist of in the brain?
Myleniated axons of nerve cells, glial cells, vessels.
Describe the 6 layers of the cerebrum?
Cerebral cortex which contains pyramidal cells in layers three and five.
What kind of tissue is dura mater?
dense irregular connective tissue
What are the three layers of the brain?
- pia - most intimate layer attached to the brain
- arachanoid - delicate web like connective tissue
- dura - composed of dense irregular connective tissue
What are nuclie?
conglomeration of grey matter deep with in the cerebrum and cerebellum
Where is the CSF found?
in arachnoid space
What is the outer grey matter of the brain called?
cortex
What kind of cells are interneurons?
multipolar
What kind of neuron are sensory neurons?
unipolar
What is the primary component of myelin?
lipids
What is a basket cell?
type of neuron in the CNS
What is an internuncial neuron?
interneuron
What is another name for neuron cell body?
soma
What is tightly attached to the periosteum of skull and spinal column?
Dura matter
What is labeled as n?
multipolar neuron
Where are synaptic vessicles found?
Terminal bouton
What happens to the potassium in a resting neuron membrane?
The potassium is greater inside the cell than outside the cell.
What happens to nissyl bodies after they are injured?
undergo chromatolysis
Which structure forms trabeculae around which CSF flows?
arachnoid matter
What features typify the theorny spine (gemmules) that project from dendrites?
Sites of symaptic contact with bouton terminal
What cells are primarily found in white matter?
fibrous astrocytes
Where is unmyelinated axons found in the CNS?
They can be found in grey and white matter.
What is shown here?
spinal ganglion
What is the most common cell in the CNS?
Oligodendrocyte
What cell type surrounds neuronal perikaryn located in the ganglion?
satallite cells
After transecting an axon, what changes occur distally?
retrograde degeneration aka complete axon degeneration
