Flashcards in Neurones, Nerve Fibres and Peripheral Nerves Deck (83):
What does the nervous system comprise of at the gross level?
What are the main functional components of the nervous system?
Brain and spinal cord
How are the brain, spinal cord and nerves related?
They are all interconnected
What 2 units can the brain, spinal and nerve be reconstituted into?
How many pairs of cranial nerves are there?
How many pairs of segmental nerves are there?
What is the nervous system made up of?
Trillions of nervous system cells
What does analysis show of nerve cells?
They can be broadly divided into 2 types
What are the 2 cell types of the nervous system?
How much of the nervous system cells are glia?
Which type of nervous system cells are responsible for sophisticated brain function?
What is the purpose of neuroglia?
Brings form to nervous system
How can neuroglia be divided?
Into microglia and macroglia
Where does microglia come from?
Where does macroglia come from?
How can glia be stained in micrographs?
By the Golgi-Silver Impregnation technique
What do the sub-types of macroglia vary depending on?
Which division of nervous system in question
How do the microglia sub-types vary throughout the body?
They probably don't
What are the characteristic neuroglia in the CNS?
Which neuroglia in the CNS have the largest cell count?
What do the astrocytes constitute?
The blood-brain barrier
What is the purpose of astrocytes?
What is the purpose of oligodendrocytes?
How many cells can oligodendrocytes myelinate at a time?
Up to 250
What happens if an oligodendrocyte become damaged?
Lots of subsequent cells affected
What do ependyma do?
Line the ventricles and central canal of the spinal cord for circulation of cerebrospinal fluid
What is the purpose of microglia?
Immunity and inflammation
How do microglia assist in immunity and infection?
They remove infected material
What happens if the microglia are faulty?
It can affect the BBB, which can lead to infections in the brain
What are the characteristic neuroglia of the PNS?
- The Schwann cell
- Sattelite cells
What are the main functions of Schwann cells?
Insulation of the peripheral nerve axons
What is the purpose of insulation of peripheral nerve axons?
Speed up impulse conduction
How many Schwann cells myelinate 1 axon?
What do Satellite cells do?
Physical support of neurones in the PNS
What is a neurone?
The specialised functional unit of the nervous system
What are the main features of the neurone?
What do some neurones have?
Specialisations of cell bodies called dendrites
What does the neurone require when staining?
Different staining for different parts
What is the purpose of the cell body?
The ‘engine’ of the neuroen
How do cell bodies vary?
In size and shape
What does the neurone cell body contain?
- Nissl substance
- Golgi apparatus
What is the purpose of the Nissl substance?
What is the purpose of the Golgi apparatus in the cell body of a neurone?
Packaging of transmitters into vesicles
How do collections of cell bodies appear in fresh/unstained tissue?
What do collections of cell bodies in the nervous system make up?
The grey matter
What makes up the white matter of the nervous system?
What is a typical example of grey matter in CNS?
What are collections of nerve cell bodies in the PNS known as?
What else is the term ganglion used to describe?
Cysts and raised inguinal lymph nodes
What happens in the initial segment?
Where the action potential is initiated
What is different about the initial segment?
It has a high volume of voltage-gated sodium channels
How do axons of neurones differ from each other?
Which axons are not myelinated?
What do non-myelianted axons have?
Intermingling sodium and potassium channels
What axons are myelinated?
What is conduction of electrical impulses corrected to?
The level of axonal myelination
How many times does a Schwann cell wrap itself around an axon on average?
Give 4 diseases that demyelinate axons
- Multiple Sclerosis
- Guillain Barre
Where does demyelination result in faster conduction?
Axons of x-sectional diameter less the 1µm
What happens in an unmyelinated axon?
There is depolarisation along entire length of axon
What happens in a myelinated axon?
There is depolarisation only at Nodes of Ranvier
How much does the myelin sheath of a single Schwann cell?
Average of 100µm
How are any two successive Schwann cells separated?
By an unmyelinated axonal segment known as node of Ranvier
How big is a node of Ranvier?
~1µm in length
What is the appearance of nerves?
Reflective, shiny, whiteish
What causes the appearance of nerves?
Their myelin sheathing
What is a peripheral nerve a typical example of?
White matter of the PNS
What is a nerve covered in?
What does the nerve contain?
How are groups of nerves arranged?
In groups called fascicles
What covers fascicles?
What is found in fascicles?
What covers axons?
How do metastases travel?
In the plane of the epineurium
What are the membranous envelopes of cranial and spinal nerves?
What attaches epineurium to the adjacent nerve fascicle?
What are the membranous envelopes of fibres tracts continuous with ?
Coverings of the brain and spinal cord, called meninges
What are the membranous envelopes of the fibre tracts?
What happens to the proximal segment of a severed neurone?
- The proximal segment soon seals up the damage to prevent leakage, forming a nerve stump
- Its cell body suddenly swells with increased contents
- The nucleus is displaced from its central position to peripheral margins
- The axon usually regrows
What is the displacement of the nucleus to peripheral margins known as?
What is the regrowing of the axon being severed known as?
What happens to the distal segment of a severed neurone?
It undergoes Wallerian degeneration