Histology of neural tissue Flashcards
what are neuroglia (glial cells)?
non nervous support cells, each with their own specific functions
what are the functions of glial cells?
- mechanical support
- metabolic
- provide protection
how do glial cells provide mechanical support?
surround neurones and hold them in place
how do glial cells provide protection?
destroy pathogens and remove dead neurones
how are glial cells useful for metabolic uses?
supply nutrients and oxygen to neurones
what are the CNS glial cells?
astrocytes
oligodendrocytes
microglia
ependymal cells
astrocytes structure
largest and most numerous of glial cells
- star shaped
- many radiating processes
- processes are in contact with neurones’ cell bodies, axon and walls of the capillaries
functions of astrocyte
- control access of blood vessels to extracellular fluid surrounding CNS nerve cells -forms blood brain barrier
- contain glycogen microfilaments which give structural strength and protection to CNS
- stabilise structure after injury - produce scar tissue
direct neural growth during development
control interstitial environment incl recycling neurotransmitters
functions of oligodendrocytes
- wrap themselves around axons or form myelin to improve conducting velocities of the axon
- can myelinate up to 16 axons - unlike Schwan cells
structure of microglia
small, slender cells with numerous cytoplasmic process - which have fine n=branches
function of microglia
form from the same stem cells as macrophages and monocytes - undertake similar function in the brain
- make up 5% of glial cells - numbers inc rapidly if infection is present
what are ependymal cells?
cells that line the central canal of the spinal cord and ventricles of the brain
structure of ependymal cells and possible function
have branching processes that make contact with other glial cells
- possible function is monitoring composition of cerebrospinal fluid
what are the different types of neurones?
multipolar
pseudounipolar
bipolar
what is the structure of and function of multipolar neurons
- A type of neurone that possesses a single axon but may dendritic extensions to allow for the integration of lots of information from other neurons
- Includes motor neurons and interneurons
- Found in the CNS and autonomic ganglia
what is the structure of and function of pseudounipolar neurons
- Sensory neuron in the PNS
- The axon is split into 2 branches
- The central axon extends from the cell body to the spinal cord
- The peripheral axon extends from the cell body to the periphery (skin, joint or muscle)
- It should not be confused with a bipolar neuron as its’ a sensory neuron with the cell body located in the centre but as an extension
- Found in the dorsal root ganglia and sensory ganglia of cranial nerves
what is the structure of and function of bipolar neurons
- Has two extensions from the cell body
* These types of neurons are specialised for a special function such as taste, hearing, sight and other senses
what are types of matter
- White Matter = Collection of myelinated axons
* Grey Matter = Collection of neural cell bodies and neuroglia
what is a motor unit
- A motor unit consists of skeletal muscle fibres and axon terminals of that motor neuron that innervate that muscle fibres
- Lots of motor units make up a motor pool
- Motor End Plate = Synaptic connection between a motor nerve and a muscle cell
what is the anatomy of a neuron?
dendrites
cell body
axon
synapse
what are dendrites?
- numerous short processes which inc surface area available for connecting with axons from other neurones
what does the cell body contain?
nucleus and most other cell organelles
what is an axon and its function?
a long process often stretching for long distances, which is responsible for transmitting information from the neuron to other cells
what is a synapse
?
specialised junctions between axons and other cells to allow communication
neuronal transmission- what is needed
pre synaptic neuron
post synaptic neuron
synapses
neuronal transmission - what does pre synaptic neuron do
generates an AP which arrives at the pre synaptic terminal, causing neurotransmitter release
neuronal transmission - what does post synaptic neuron do
neurotransmitter activates the post synaptic terminal on dendrites which transmit a signal to the cell body
neuronal transmission - what do synapses do
they are the integrative unit of the neuron
- contain high conc of ion channels and cell membrane receptors
how does neuronal transmission occur
vesicles containing neurotransmitters which are released from the pre synaptic site and diffuse across the synaptic cleft and interact with receptors on the post synaptic site
how can speed of conduction be increased
insulation of an axon - to release leakage of currents from the membrane
what is used as insulation for axons and where is it made
myelin
-schwaan cells (PNS) and oligodendrocytes (CNS)
what is the structure of myelin
many layers of modified membranes which have high proportion of lipids which are goof electrical conductors
what does the myelin sheath do
prevents the nerve action potential being continuously propagated along the axon and therefore it jumps from node to node in saltatory conduction velocity
what is the distance between the two nodes of ranvier
internode
what are Schmidt lanterman clefts
regions of un compacted myelin
Small pockets of cytoplasm left behind during Schwann cell myelination
structure of Peripheral nerve - what is the endoneurium
delicate connective tissue surrounding the individual nerve fibres (Axon and schwaan cell)
structure of Peripheral nerve - what is the perineurium
layers of fibroblasts surrounding small bundles of fibres - fascicles
structure of Peripheral nerve - what is the epineurium
connective tissue sheath surrounding all if the fibres forming the nerve
how many NMJs does one muscle fibre have?
only one
