lecture 1 : cells of the nervous system Flashcards
what is a neurone?
this is a highly organised metabolically active cell involved in cells signalling
what are the features of the cell body?
- large nucleus with a prominent nucleolus
- there is abundant Rough endoplasmic reticulum
- there is a well developed golgi
- abundant mitochondria
highly organised cytoskeleton - numerous lysosomes
what are the features of dendrites?
- they receive incoming information
- dendrites have protrusion called dendritic spines that receive the majority of synapses
- they increase the surface area of the neurone
what cells does the cerebellum have a large number of?
the cerebellum has a large number of purkinje cells
what are
primary dendrites ?
secondary dendrites ?
tertiary dendrites?
from vertices of pyramid
form primaries
form secondaries
what is the axon hillock?
this is where the action potential is generated
what are axons organised into?
- node - sodium channels are found here
- paranode - ends of the myelin are bound to the axon to form tight junctions
- juxta paranode - area adjacent to paranode where potassium and calcium channels are found
what are unmyelinated sections called?
the nodes of ranvier
where are the terminals located?
they are close to the target
what are the two forms of axon terminals?
boutons - this is a standard synapse
varicosities - this is when axons may synapse with many smooth muscle cells so there are many swellings containing neurotransmitters
what are prominant features in axons?
microtubules and neurofilaments
what feature is present in the post synaptic neurone?
- there are lots of mitochondria present
- this is due to large amounts of ion pumping and synaptic transmission
what are the two types of synaptic inputs ?
- they can be excitatory
- they can be inhibitory
how do neurones interact together?
the competing inputs are integrated in the postsynaptic neurone - this is neuronal integration
what are the types of synapse?
- axon dendritic (excitatory)
- axon somatic (inhibitory)
- axon anoxic (modulatory)
what is anterograde transport?
this is the transport of materials needed for neurotransmission away from the soma
what are the two types of anterograde transport and what do they consist of ?
- fast anterograde:
consists of synaptic vesicles, transmitters and mitochondria - slow anterograde:
this is the bulk cytoplasmic flow of soluble constituents
what is retrograde transport?
- this is the transport of materials towards the soma
what is fast retrograde?
- transport of substances happens from the EC space
- trophic growth factors
- uses different molecular motors
what happens in multiple sclerosis?
this is a restriction on the axon which causes swellings to occur due to accumulation of vesicles of neurotransmitter at the restricted point
what is a pseudo unipolar ?
- these neurones have two fused processes that are axonal in structure
- they are normally sensory neurones
- the signal received passes directly to the axon terminal without going through the soma
what is a bi polar neurone?
- this is involved in the white matter of the cerebral cortex
- the soma is in the same line of action as the axon
what is a golgi type 1 multipolar?
what are examples
- these have highly branched dendritic trees
- the axons extend for large distances
- pyramidal cells (cerebral cortex)
- purkinje cells
(cerebellum) - anterior horn cells
(spinal cord)
what are golgi type 2 multipolar cells?
what are examples
- they are highly branched dendritic trees
- they have short axons
- glutamate transmitters
- stellate cells (found in the cerebellum and cerebral cortex)
what are the three main types of neurone?
- sensory
- motor
- interneurone
what are sensory neurones?
they are normally pseudo uni polar with one process that divides into two branches
- one branch to the CNA
- one branch to the sensory receptor
what are motor neurones?
- they conduct signals form the CNA to the effectors
- they are generally multipolar with large somas
what are interneurones?
- these are neurones whose somas and processes remain inside the CNS
- they can be large multipolar neurones or small bio polar circuit neurones
what is a nucleus?
- this is a group of un-encapsulated neuronal cell bodies within the CNS
what is a lamiae?
these are layers of neurones of similar type and function
what is a ganglion?
these are groups of neuronal soma in the peripheral nervous system that are encapsulated to form a ganglion
what are fibre tracts?
these are groups or bundles of axons in the CNS
what are nerves?
nerves are discrete bundles of axons outside of the CNS
what are neuroglia?
what are the different neuroglia?
these are the support cells of the CNS
- astrocytes
- oligodendrocytes
- microglia
- ependymal cells
- immature progenitors
- Schwann cells
- Satellite cells
what is the structure of astrocytes?
- multi processed star like shape
- most numerous cell in the CNS
- there are gap junctions present
what are the functions of astrocytes?
- they are a scaffold for other cell types and aid the growth of axons
- the formation of the blood brain barrier
- transport of substances from the blood to the neurones
- the removal and the degradation of neurotransmitters
- the synthesis of neurotrophic factors
- potassium buffering
- scar tissue formation
- glioma formation
what are oligodendrocytes?
they are the myelin forming cells of the CNS
what are the types of oligodendrocytes
what is the structure of oligodendrocytes?
- the main types are interfascicular and perineuronal
- they have small and spherical nuclei
- they have thin process
- there are prominent golgi
- they are highly metabolically active
what are the functions of oligodendrocytes?
- the maintenance of the myelin sheaths
(much smaller than schwann cells) - they produce many myelin internodes
what are the diseases concerning myelin?
- multiple sclerosis
(this is the loss of myelin due to an autoimmune disease) - adrenolebukodystrophy
(this is a progressive loss of myelin)
what are microglia and whats the structure?
- they are the immune cells of the CNS
- they are derived from the early development of the blood monocytes that invade the brain
- they have dense lysosomes, lipid droplets and residual bodies
what are the functions of the microglia?
- macrophage population for the brain
- they are antigen presenting
- they are needed for tissue presenting
- they are synapse stripping
whats the structure of ependymal cells?
and what are ependymal cells?
- they are epithelial cells that line the ventricles of the brain and the central canals of the brain
- they have apical microvilli and cilia
- there are gap junctions
- there are no tight junctions
what are schwann cells?
- any axons outside the CNS are myelinated by the schwann cells
- one schwann cell myelinated one axon
- they can also perform the functions of astrocytes and promote repair
what are satellite cells?
- each soma in a spinal ganglion (PNS) is surrounded by metabolically active supportive satellite cells
