Nerve Structure Flashcards
What is the perikaryon?
The cell body of the nerve
Give two other terms synonymous with terminal bouton.
Presynaptic neurone and axon terminal
Describe some distinguishing features of synaptic junctions under an electron microscope.
. Electron dense layer on postsynaptic side
. Neurotransmitter vesicles on presynaptic side
Describe the surface area: cytoplasm ratio of neurones.
Very large surface area: cytoplasm ratio
Why do neurones need lots of rough endoplasmic reticulum?
Neurones have a very large surface area of membrane, so need lots of RER to produce lots of proteins to maintain the membrane.
What are Nissl bodies? How do these appear on electron micrographs?
Nissl bodies are clumps of RER. They appear as dark dots.
What is a pseudounipolar neurone? Why is this structure sometimes beneficial?
. Neurone with perikaryon pushed to one side
. Means that the path along dendrites and axon is as uninterrupted as possible for maximal transduction speed
Very long axons utilise an efficient transport system to aid transduction. Describe this system.
. Microtubuli and neurofilaments used as rails, kinesin and dynein used as vehicles to move ions
Why are the majority of brain tumours of glial origin?
Glial cells are capable of mitosis, so have the potential to divide uncontrollably, but neurones are post-mitotic therefore can’t divide uncontrollably.
Name the three main glial cells.
Astrocytes, oligodendrocytes, microglia
What are astrocytes?
. Glial cells whose ‘feet’ touch neurones, other glial cells, and capillaries
. Take nutrients from capillaries and transfer them to neurones
. Form blood brain barrier and seal on CNS surface
What are oligodendrocytes?
Glial cells that make myelin
What forms the myelin sheaths in the central nervous system and peripheral nervous system?
. CNS- oligodendrocytes from myelin sheath
. PNS- Schwann cells form myelin sheath
What are microglia cells?
. Immune cells in CNS
. Can release cytokines to attract other immune cells, can phagocytose pathogens and act as local APCs
. Also involved in maintenance and remodelling of CNS, e.g. removing underused synapses
How do you identify astrocytes, oligodendrocytes, and microglia under the microscope?
. Astrocytes- larger lighter oval nuclei
. Oligodendrocytes- compact round dark nucleus, sometimes with granulation
. Microglia- bean-shaped, more elongated
What is epineurium?
Connective tissue surrounding fascicles of axons
What is perineurium?
Connective tissue that bundles axons into fascicles
What is endoneurium?
Connective tissue between axons within a fascicle
How many myelin sheaths does one Schwann cell produce?
One Schwann cell produces one myelin sheath (in PNS)
Why do axons have slack?
So that if they are stretched they don’t snap
Name the type of cell which covers perikarya in peripheral nervous system ganglia
Satellite cells
What does the central nervous system consist of?
The brain and spinal cord, surrounded by cerebrospinal fluid
What does the peripheral nervous system consist of?
Peripheral nerves and ganglia, surrounded by interstitial tissue and interstitial fluid
Where is the location of the perikarya and axons of afferent and efferent neurones?
. Afferent neurones have their perikarya in the PNS and their axons in the CNS
. Efferent neurones have their perikarya in the CNS and their axons in their CNS
