Cells of the Nervous System Flashcards
What are the protrusions coming out of dendrites called?
Dendritic spines
- These receive the majority of synapses
- Dendritic spines can have multiple synapses e.g. over 80,000 spines per cell
Describe the arrangement of primary, secondary and tertiary dendritic spines.
Primary dendritic spines come off the vertices of the pyramid
Secondary dendritic spines come off the primary
Tertiary dendritic spines come off the secondary
what type of cells do you have lots of in the cerebellum
Purkinje cells
Where do axons originate?
Axon hillock
How does the diameter of the axon change as it moves further from the cell body?
It doesn’t - the axon diameter stays the same the whole distance and so the conduction velocity remains the same the whole way
Describe the cytoskeleton of axons.
They have abundant intermediate filaments (needed for tensile strength )and microtubules and neurofilaments.
What are the three domains of an axon? Describe them.
Paranode - next to the Node - where there are tight junctions between the ends of the myelin sheath and the axon
Juxtaparanode - next to the paranode, underneath the myelin sheath - potassium and calcium channels are found here
What are the two forms of axon terminal?
Butons and Varicosities
Where are varicosities found?
Along smooth muscle where one axon will stimulate the contraction of several smooth muscle cells
- Sometimes axons will synapse with many smooth muscle cells as it passes so you have multiple swellings containing neurotransmitter called varicosities
What are the three arrangements of axons?
Axo-axonic: often modulatory
Axo-somatic: often inhibitory
Axo-dendritic: often excitatory
Describe fast axonal transport. What is a key feature of axonal transport?
Vesicles of neurotransmitter are carried along microtubules
These microtubules are unidirectional because the microtubules are polarised. There is retrograde transport(moving vesicles containing various molecules back to the cell body) but that occurs along other unidirectional microtubules.
What happens when the axon is damaged during multiple sclerosis?
If there is a restriction in the axon then you begin to see swellings caused by the accumulation of neurotransmitter.
What is the difference between Golgi Type I cells and Golgi Type II cells?
Type 1 has long axons whereas Type II have short axons
What are some features of the synapses?
Abundant mitchondria: lots of energy needed for ion pumping and synaptic transmission, therefore synpase is sensitive to oxygen deprivation.
- can be either inhibitory or excitatory
- competing inputs are integrated in the postsynaptic neurone-NEURONAL INTEGRATION
what is pseudounipolar neurone
Pseudounipolar:
- tend to be sensory
- have 2 fused processes which are axonal in structure
- signal recieved goes straight axon terminal without going through soma
where is bipolar neurones found
involved in the white matter of the cerebral cortex
What is the most abundant cell type in the CNS and what roles do these cells have?
Astrocytes -
- star shape
- they are the support cells of the central nervous system
- numerous Intermediate filaments bundles in the cytoplasm of fibrous astroglia
- They are facultative macrophages, they are part of the blood brain barrier, they are involved in homeostasis - soaking up neurotransmitter, scaffold of neuronal migration and axon growth
What are the two types of oligodendrocyte?
Interfascicular and Perineuronal
Myelin forming cells of the CNS
Give two myelin disease states.
- Multiple Sclerosis (loss of myelin due to autoimmune reaction)
- Adrenoleukodystrophy (leads to progressive loss of myelin)
What is the role of microglia?
How do microglial cells change as they respond to a change?
They are the immune cells of the CNS.
- Cell shape changes and if the stimulus is strong enough it becomes phagocytic
- MS - microglial cells could be the ones destroying the myelin sheath
State some structural features of the cell body, dendrites and axons.
Cell body - large nucleus with prominent nucleolus, abundant rough ER, well developed Golgi, large number of mitochondria
Dendrites - spread from cell body and branch frequently, dendritic spines receive majority of synapses
Axon - emerges at axon hillock, one axon per cell but they branch extensively, microtubules and neurofilaments are prominent
Where are Golgi Type I and Golgi Type II cells found?
Golgi Type I - pyramidal cells of the cerebral cortex, purkinje cells of the cerebellum, anterior horn cells of the spinal cord, long axons
Golgi Type II - short axons, stellate cells of the cerebral cortex and cerebellum
What is the normal morphology of sensory neurones?
Pseudounipolar - two branches, one running to the CNS and another to the sensory receptor
State some differences between the axo-dendritic, axo-somatic and axo-axonic synapses.
Dendritic - excitatory
Somatic - inhibitory
Axonic - modulatory
