Histology of the Nervous system Flashcards
nucleus of the neurone?
it is centrally located
spherical-ovoid shape
relatively euchromatic
prominent nucleolus
cytoplasm of neurone cells?
chromatophilic substance (Nissl substance)
rER
ribosomes
polyribosomes
neurone processes?
dendrites
axons
neurone functions?
sensory neurones
interneurons
motor neurons
sensory neurons?
afferent neurons that transmit changes in body to brain (senses)
interneurons?
lie between sensory and motor neurons
90% of neurons and interneurons
process, store and retrieve information
motor neurons?
efferent neurons that send signals out to muscles and glands
types of neurons?
unipolar and pseudounipolar
bipolar
multipolar
unipolar and pseudounipolar neurones?
mammals - initially bipolar and become unipolar as they develop
sensory ganglia located in roots of cranial and spinal nerves
body with single axon that bifurcates into central and peripheral branches
peripheral branches of unipolar and pseudounipolar neurones?
receptors sensitive to environment stimuli
central branches of unipolar and pseudounipolar neurones?
conveys environmentally induced excitation into CNS
bipolar neurone?
two processes: dendrites, axon
typically afferent neurones that convey sensory information to CNS
some interneurones are bipolar
multipolar neurons?
many dendrites
single axon
typically, efferent motor neurones that convey signals from CNS to effectors
some interneurones are multipolar
types of synapses?
axo-dendritic
axo-somatic
axo-axonic
dendro-dendritic
neuroglia/glial cells?
they make up >90% of nervous system
Important role in neuronal development, activity, plasticity and recovery from injury
small cells (compared with neurons)
ectodermal origin (except microglial cells - mesoderm)
what interactions with glial cells are essential?
glia-neuron interactions and glia-glia interactions are essential
what are astrocytes?
pale, ovoid nuclei, largest among glial nuclei
what do astrocytes do?
they provide support to neurons through glia fibrils
store glycogen and release glucose
ion pumps - regulate Na+
insulate synapses and release substances that modulate synapse sensitivity
how do astrocytes help with immune function?
act as antigen-presenting cells to T-lymphocytes
secrete chemokines and cytokines
influence Th cells’ response and monocyte/microglia effector functions
shape of oligodendrocytes?
small, spherical and densely staining nuclei
few branches
grey matter - perineuronal satellite cells, growth factor providers
White matter - myelin sheaths around axons - speed AP propagation through CNS
Biogenesis and maintenance of myelin
microglia?
mesodermal origin
small, elongated chromophilic nuclei
synthesise and release trophic factors
cytotoxic defence properties
transform into macrophages - antigen presenting and phagocytic properties
secrete cytokines - TNFα, IL-1β
important role - viral infection, autoimmunity and neurodegenerative disorders
pericytes?
associated with CNS capillaries (part of BBB)
believed to have contractile abilities
phagocytic
ependymal cells?
epithelial cells that line the ventricular cavities within the brain and central canal of the spinal cord
what type of cells are ependymal cells?
they are cuboidal - (appear columnar) cells
they have motile cilia
what do the ependymal cells make up and what does it allow?
choroid plexus epithelium - modified ependymal cells WHICH allows nutrients from blood to be transported to ventricles of brain
what do the modified ependymal cells do?
they cover surfaces of choroid plexus villi and produce cerebrospinal fluid (CSF) by active secretion of Na+
where are modified ependymal cells found?
in brain ventricles
cuboidal cells w/ microvilli vs. cilia
tanycytes found where?
hypothalamus
what are tanycytes?
they are modified ependymal cells - hypothalamis walls of third ventricle
basal process of tanycytes allows them to do what?
to make contact with capillaries and neurons
what are tanycytes thought to play a role in?
in hypothalamic hormone release into hypothalamic pituitary portal system
how do tanycytes play a role in hypothalamic hormone release?
act as sensors in feedback mechanisms
play a role in transfer of hypothalamic hormones from CSF to portal blood
what cells are part of PNS?
Ganglionic gliocytes
satellite cells
histologically central nervous tissue includes?
brain
spinal cord
optic nerve
retina
origin of central nervous tissue?
common embryological origin
white matter of CNS?
dense accumulation of myelinated axons
collections of tracts - fasciculi or lemnisci - same origin and destination
grey matter of CNS?
rich in neuronal bodies, glial cells and neuropil
neuropil - axons, terminal branches, dendrites, and glial processes that collectively form a background matrix for the cell bodies and seen with light microscopy
layers of central nervous tissue?
molecular layer
external granular layer
external pyramidal layer
internal granular layer
internal pyramidal layer
fusiform (multiform) layer
molecular layer of cerebral cortex of central nervous tissue?
(lamina molecularis) - neuropil - apical dendrites from pyramidal neurons and terminal branches of superficial cortical afferent fibres
external granular layer of cerebral cortex of central nervous tissue?
(lamina granularis externa) - small interneurons
external pyramidal layer of cerebral cortex of central nervous tissue?
(lamina pyramidalis externa) - small medium pyramidal neurons - send axons to adjacent cerebral cortex
internal granular layer of cerebral cortex of central nervous tissue?
(lamina granularis interna) smaller satellite neurons that receive specific sensory input
internal pyramidal layer of cerebral cortex of central nervous tissue?
(lamina pyramidalis interna) medium-large neurons that send axons into white matter
fusiform layer of cerebral cortex of central nervous tissue?
(lamina multiformis) spindle-shaped neurons that send axons into white matter
central nervous tissue of cerebellum?
white matter - deep to cortex - 3/4 pairs of cerebellar nuclei
Dentate
Emboliform – interposed
Globose – interposed
Fastigial – interposed
cerebellum fibres?
input fibres - climbing fibres
and mossy fibres
climbing fibres of cerebellum?
each fibre makes numerous synapses-in-passing on one dendritic tree
thought to carry ‘error signals’ that help in learning new motor controls
originate from inferior olive of medulla oblongata
mossy fibres of cerebellum?
multiple origins
feed sensory information to cerebellum w.g. senses, proprioception etc.
thalamus - central nervous tissue?
integrator/relay of sensory information
no white or grey matter distinction
over 50 neuronal nuclei, each with a specific function
hippocampus - central nervous tissue?
part of the limbic system
two - left and right
head, body and tail
hippocampus - structure?
two interlocking parts of grey matter
hippocampus proper
dentate gyrus
S-shape in transverse section - seahorse
what is the hippocampus functionally divided into?
into four subfields - each has special arrangement of pyramidal neurons
CA1, CA2, CA3, CA4
brainstem - central nervous tissue?
uniform grey matter (no grey/white matter distinction)
fundamental to basal body activity such as cardiovascular tone, respiratory activity and consciousness
where do most cranial nerves exit from?
from the brain stem - various nuclei tracts
white matter of spinal cord?
outside (opposite to cortex)
divided into funiculi (dorsal, lateral, ventral)
myelinated and unmyelinated axons travelling up and down
grey matter of spinal cord?
inside (opposite to cortex)
dorsal sensory horns - small neurons
ventral motor horns - motor neurons
middle canal of spinal cord lined by?
ependymal cells
meninges? - what do they do?
they cover brain, spinal cord and optic nerve
contain cerebrospinal fluid
constitute protective barrier
Dura Mater? central nervous tissue?
dura mater (pachymenix) - superficial
thick and strong
thick collagen bundles and elastic fibres orientated longitudinally in spinal dura but more irregular in cranial
fibrocytes, nerves, lymph and blood vessels
inner surface - lined by multiple layers of flattened fibrocytes to which outer cells of arachnoid membrane adhere
arachnoid mater of the meninges?
outer layer of flattened fibrocytes
inner layer of loosely arranged flattened fibrocytes with small bundles of collagen fibres
arachnoid trabeculae
subarachnoid space - CSF
arachnoid villi - penetrate walls of dural venous sinuses - one way valves for drainage of CSF
meninges - pia mater?
highly vascular layer
collagen fibres, elastic network, fibrocytes, lymphocytes, mast cells
basal lamina vs. glial limiting membrane (astrocyte processes)
outer layer - flat fibrocytes
nerves?
hundreds of axons, each sheathed or myelinated by neurolemmocytes and all organised into fascicles enveloped by connective tissue
endoneurium?
fibrocytes and collagen fibres surrounding individual neurolemmocytes
perineurium?
fibrous tissue surrounding nerve fascicle
epineurium?
fibrous tissue surrounding multiple fascicles
blood vessels of peripheral nervous tissue?
vasa nervorum
blood-nerve barrier?
epithelioid cells and endothelium of endoneurial microvessels
perineural epithelioid cells - sqamous concentric sheets
Ganglia - peripheral nervous tissue:
neuron cell bodies
spinal ganglia located in dorsal spinal roots and ganglia in cranial nerve roots are referred to as sensory ganglia - bodies from primary afferent neurons
afferent neurons of peripheral nervous tissue are…
they are unipolar except in sense organs (bipolar)
autonomic ganglia?
multipolar cell bodies
postganglionic neurons?
cholinergic - synthesise and release ACTh
adrenergic - noradrenaline
