Flashcards in Neuro Histology Deck (31):
List five different types of glial cells
Satellite cells of ganglia
What are microglia and where do they originate?
Immune cells of the CNS, originating from bone marrow
How many layers of neurons are in the cortex?
6 layers differing in cell density and composition
What is the role of the ventricular system?
Production and passage of CSF
What is the choroid plexus and what is its role?
A vascular structure arising from the wall of each ventricle, which produces the CSF
What are ependymal cells? What is their role?
Low columnar or cuboidal cells lining the ventricles within the brain and the central canal of the spinal cord; some have cilia to aid the flow of CSF
How are ependymal cells different to normal epithelial cells?
They have a non-basal laminar (processes that extend deeply)
What is the role of actin in neurons?
Dynamic assembly/disassembly of actin allows shape changes and movement or neurons (e.g. spines, growth cones)
What is the role of intermediate filaments in neurons?
Intermediate filaments are found in all processes and are permanent
What is the role of microtubules in neurons?
Microtubules are dynamic structures composed of tubulin which are responsible for axon transport of important proteins (e.g. neurotransmitters), vesicles and other molecules (e.g. lipids)
What is the soma?
The metabolic centre of the neuron which gives rise to the dendrites and axon
What is the role of dendrites?
To receive information from other neurons
What is the role of the axon?
It acts as the main conducting unit for carrying signals to other neurons
How is the volume of a neuron distributed and what does that mean in terms of pathology?
A high proportion of the total cell volume is in the axons and dendrites; for this reason, random damage often involves the axon, not the soma
What cytological features reflect the neuron's high level of protein production?
Large pale nucleus
Nissl bodies (composed of rough ER or free ribosomes)
List five passive support functions of astrocytes
Neurotransmitter uptake and degradation
Neuronal energy supply
Maintenance of the BBB
Injury response and recovery
Name two active support functions of astrocytes
Modulation of neuronal function
Modulation of blood flow
Why is K+ homeostasis important for maintaining normal neuronal function?
A high extracellular K+ concentration will cause neurons to continually depolarise; astrocytes "suck up" the excess to prevent this from occurring
What is the result of inhibiting GABA and glutamate transporters on glial cells?
Greater magnitude and longer duration of depolarisation; this may lead to cell death
List four factors which may initiate modulations in intracellular calcium inside glial cells
Neurotransmitters (e.g. ATP, glutamate)
How do glial cells communicate?
Via exocytosis of synaptic vesicles, similar to neurons
How do glial cells modulate neuronal function?
ATP released from glia can produce inhibitory calcium waves in neurons
How do glial cells modulate blood flow?
Calcium waves are initiated within an astrocyte and cause vasoconstriction or vasodilation
What are oligodendrocytes and what is their role?
The predominant glial cell of white matter
Responsible for myelinating axons in the CNS
What is the role of Schwann cells?
They are responsible for myelination of axons in the PNS
What is the difference between the action of oligodendrocytes and Schwann cells?
Oligodendrocytes extend processes that wrap around parts of several axons, whilst Schwann cells wrap around only one axon
Does the myelin sheath cover the entire axon?
No, there are small gaps called Nodes of Ranvier which increase speed of conduction
What are the roles of microglia?
To rapidly respond to inflammation or injury by upregulating cytokines and growth factors
Contribute to development (normal function) and disease
Describe the structure of a peripheral nerve
Individual nerve fibre and Schwann cell pairs are surrounded by loose vascular supporting tissue called endoneurium
Bundles of nerve fibres are called fascicles
Each fascicle is surrounded by collagenous tissue called perineurium
If there is more than one fascicle, these are separated by another layer of collagenous tissue called epineurium
What is a ganglion and what does it contain?
An aggregation of neural cell bodies outside the CNS, also containing nerve fibres and satellite cells (support cells of the ganglia)