Histology Flashcards
What is the key cell of the nervous system?
The neuron
What are neurons supported by?
Glial cells
What are the 5 different glial cells of the nervous system?
Astrocytes
Oligodendrocytes
Schwann cells
Ependymal cells
Satellite cells of ganglia
What are the immune cells of the nervous system?
Microglia
True or false: Microglia are a type of glial cell?
False!
How many layers of neurons are there in the neocortex?
6
What are the 2 specialised regions of the CNS?
Ventricular system and choroid plexus
What is the role of the ventricular system?
Formation and passage of CSF
What is the choroid plexus?
Vascular structure arising from the wall of each ventricle.
Forms the CSF
What are ependymal cells?
Low columnar or cuboidal cells that line the central canal of the spinal cord and the ventricles within the brain.
What do ependymal cells have in some places?
Cilia on apical surface to aid CSF flow.
How are ependymal cells different to epithelial cells?
They are non basal laminar
How are neurons specialised for signalling?
- Morphologically distinct
- Electrically active
- Rapid communication
- Long distance projections (axons)
- Specialised (e.g. transduction mechanisms for the various senses)
How do neurons differ from other cells?
Specialised for signalling
High level of protein synthesis
Metabolically active
Terminally differentiated
What will neurons that are morphologically distinct from one another have?
Different functions
What are the 3 components of the neuron responsible for its morphology?
Actin
Intermediate filaments
Microtubules
What role does actin play in regulating neuromorphology?
Dynamic assembly/disassembly, allowing for shape changes and movement (e.g. spines and growth cones).
Which component of the neuron underpins the changes in spines and growth cones seen in plasticity?
Actin
What are the properties of intermediate filaments found in neurons?
In all neuronal processes
Permanent
What are the properties of microtubules found in neurons?
Dynamic
Composed of tubulin
Axon transport
Which component of the neuronal cytoskeleton plays a role in axonal transport?
Microtubules
What are the 3 different functional divisions to the neuron?
Dendrites - Inputs
Soma - Maintenance (also inputs, too)
Axon & axon terminal - Output
Where is a high proportion of the total cell volume of the neuron found?
In the axons and dendrites.
What is axonal transport critical in the supply of?
Cell-body derived elements
The axon terminal requires so many components but can’t synthesise them
Which part of the neuron is often involved in damage?
The axon - because it is so long and often traverses long distances.
What type of potentials does the membrane carry?
Graded potentials
What must be present within and on either side of the neuronal membrane for graded potentials to be conducted?
Unequal distribution of positively charged ions on either side of the membrane.
Membrane must contain Na+/K+-ATPase pumps and ion channels
Which part of the neuron is specialised for inputs?
Dendrites
What type of signal is that which travels along the dendrites?
Graded potential - passive electrotonic current
What type of signal is that which travels along the axon?
Action potential
What is the difference between graded potentials and action potentials in terms of signal conductance?
Action potentials propagate much further than graded potentials.
What is the output signal of the axon?
Exocytosis of chemical neurotransmitter at the synapse.
Which components of the neuron are visualised with a Nissl stain?
Organelles, e.g. free ribosomes and organelles
Where are all proteins of the neuron synthesised? Why is this a problem?
In the soma.
A problem because the axon terminal is a great distance from the soma.
What are the passive support functions of astrocytes?
Neurotransmitter uptake and regulation
K+ homeostasis
Neuronal energy supply
Maintenance of the blood brain barrier
Aid in myelination
Injury response and recovery
What are the active support functions of astrocytes?
Modulation of neuronal function and blood flow
How do glial cells regulate neurotransmitter uptake and degradation?
They express glutamate and GABA transporters used to shunt neurotransmitter out of the synapse.
What happens to neuronal excitability when glutamate transporters in glial cells are inhibited?
Neurons become more depolarised, increasing excitability.
Glia show modulations in which intracellular ion?
Calcium
What is the calcium wave?
A propagating wave of calcium influx throughout the astrocyte, used as the signal both in and between glia when an external stimulus is applied.
What can calcium waves in astrocytes be initiated by?
Neurotransmitters (e.g. ATP, Glutamate)
Trauma
Spontaneous
Inflammatory mediators
How can astrocytes modulate neuronal function?
Via vesicular excretion of glutamate or ATP onto neuronal membrane.
What effect does the calcium wave have on the neuron? How?
Neurons are inhibited by calcium wave.
ATP is released from the astrocyte onto the neuron
How do astrocytes regulate the vasculature?
Calcium waves initiated within an astrocyte cause vasoconstriction or vasodilation via the release of ATP.
What do oligodendrocytes and Schwann cells do?
Myelinate axons
Where in the nervous system are oligodendrocytes found?
In the CNS
Where in the nervous system are Schwann cells found?
In the peripheral nervous system
What effect does myelination have on the neuron?
Provides electrical insulation for neurons.
Increases conduction velocity.
Other than their location, what is a major difference between oligodendrocytes and Schwann cells?
Oligodendrocytes extend processes that wrap around parts of several neurons, whereas Schwann cells wrap around one axon only.
What are the small gaps between the myelin sheathings of an axon?
Nodes of Ranvier
Of what origin are the microglia?
Haematopoietic origin
Mesodermal derivative
What percentage of cells in the mouse brain are microglia?
5-20%
Which immune cell do microglia resemble?
Macrophages - they are phagocytic
What do microglia do?
Constantly survey they CNS and change rapidly in response to inflammation or injury
Upregulate cytokines/growth factors.
What are peripheral nerves composed of?
One or more bundles (fascicles) of nerve fibres.
What is each fascicle of a peripheral nerve fibre surrounded by?
Perineurium - collagenous tissue
What is generally present in a peripheral nerve fibre if there is more than one fascicle present?
A further layer of collagenous tissue - the epineurium
What is the endoneurium?
The loose vascular supporting tissue surrounded each nerve fibre and Schwann cell within each individual fascicle.
What are ganglia?
Aggregations of cell bodies of neurons outside the CNS
What are the 2 types of ganglia?
Sensory and autonomic ganglia
What do the sensory ganglia house?
The somata of sensory neurons
Where are the sensory ganglia found?
In the dorsal root of the spinal cord (dorsal root ganglia)
What do the autonomic ganglia house?
The somata of post-ganglionic neurons
What do ganglia contain?
Cell bodies, nerve fibres and satellite cells (supporting cells in ganglia)
