L21) Nervous tissue structure and function Flashcards
Define the CNS and PNS
* Describe the structure of grey and white matter (in CNS and PNS)
* Describe the structure of the neuron (and its variations)
* Describe the structure and function of the synapse (and its variations)
* Describe the structure and function of neuroglial cells (glial cells) * PNS-Schwanncells
* CNS - astrocytes, oligodendrocytes, microglia, ependymal cells * Astrocytesandtheblood-brainbarrier
* Summarise the function(s) of nerves
* Electrical conduction, neurotransmitter production, and release, etc.
* Describe the signs, symptoms and cause of multiple sclerosis
Name the two nervous system divisions?
- CNS - central nervous system
- PNS -peripheral nervous system
What does the CNS consist of?
Composed of:
* Brain
* Spinal cord
Contains:
* Relay neurons
What does the PNS consist of?
Composed of:
* Cranial nerves
* Spinal nerves
* Peripheral nerves
Contains:
* Sensory neurons
* Motor neurons
Where is the grey matter in (a) the brain? (b) the spinal cord?
(a) peripheral in brain - ‘nuclei’
(b) central in spinal cord - H or butterfly shaped
what does the grey matter consist of?
- nerve cell bodies
- dendrites
- axon terminals
- non-myelinated axons
- neuroglia (support cells)
where is the white matter in (a) the brain? (b) the spinal cord?
(a) central in brain
(b) peripheral in spinal cord
what does the white matter consist of?
- myelinated material
what are the anterior and posterior prongs of the grey matter referred to as in the spinal cord? and what are they connected by?
- ventral horns (VH) and dorsal horns (DH) respectively
- connected by the grey commisure (GC)
what does the white matter of the spinal cord contain? what is visible in this section?
- contains nerve fibres that form ascending and descending tracts
- blood vessels of the pia matter, ventral fissure and some dorsal roots of spinal nerves are visible
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what is the difference between the axon myelination in the CNS vs the PNS?
- in CNS, myelin produced by and part of an oligodendrocyte
- in PNS, myelin produced by and part of schwann cell
What are the four different types of neurones?
- motor
- sensory
- integrative
- anaxonic
what is the location and function of a motor neuron?
- location: CNS to periphery
- function: to seend signals to effector tissues
what is the location and function of a sensory neuron?
- location: periphery towards CNS
- function:to send environmental signals to integrative centre
what is the location and function of a integrative neuron?
- location: CNS
- function: collate all information
what is the location and function of a anaxonic neuron?
- location: retina (some parts of the CNS)
- function: act as relays
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how is a neurotransmitter synthesised?
- immature vesicle contains only enzyme in its membrane
- as it travels the length of the axon, it starts to synthesise the neurotransmitter
- after neurotransmitter release, the vesicles has two fates: (1) recycled through clanthrin-coated endocytosis. (2) lost to neurolemma
transport in done through microtubules
what are the five different types of synapses?
- (a) axosomatic - direct to the plasma membrane of nerve or cell
- (b) axodendritic - axon terminal synapses with dendritic spine
- (c) axoaxonic - synapse at the axonic bouton
- (d) dendro-dentritic
- (e) axo-axonal - impinging dendritic/axonal synapse usually inhibits other inputs
axoaxonic may enhance or inhibit axodendritic/somatic synapse
what nerve fibres are present in the peripheral nerves? what are they seperated by?
- sensory
- integrative
- motor
- seperated by connective tissue layers
state the hierarchy of connective tissue in the peripheral nerves
Endoneurium
* loose connective tissue
* surrounds single nerve cells/axons
Perineurium
* specialised connective tissue - transports proteins
* maintains ionic composition
* surrounds clusturs of axons (fasicle)
Epineurium
* dense irregular connective tissue
* seperates different types of nerves and fills spaces between fasicles
Paraneurium
* fascia that seperates nerves from surrounding structures
clinical correlate - myeline
Damage to myelin:
* in the CNS - cause of MS (multiple sclerosis)
* in the PNS - cause of Guillain-Barre syndrome
how does myelination occur?
- axon sitting in a groove is surrounded by a schwann cell
- the mesaxon membrane initiates myelination by surrounding the embedded axon
- a sheet like extension of the mesaxon membrane then wraps successively around the axon, forming multiple membrane layers
- cytoplasm is extruded from between the two apposing plasma membranes of the schwann cell, which then become compacted to form myelin
