What is the funciton of ependymal cells?
They are epithelium-like cells tht line fluid-filled ventricles to produce and control the release of cerebrospinal fluid (CSF). The brain floats in CSF.
What fraction of the nervous system do neurons and glial cells make up?
Neurons make up 10% of the nervous system. Glial cells make up 90%.
What are astrocytes and what is their function?
- Astrocytes are glial cells and are most abundant in the brain as they fill spaces between neurons and vessels.
- They influence neurite growth
- Control the chemical content of extracellular space. E.g. potassium buffering as accumulation of potassium in one region of the brain may be dangerous. E.g. regulate neurotransmitter in synapse.
- Help maintain blood-brain barrier.
- Wrap arround synapses with less than one micrometer separation between astrocytes and axons and dendrites.
What are the rates of slow and fast axoplasmic transports?
Slow: 1-10 mm/day
Describe the difference between anterograde and retrograde axoplasmic transport. Include:
- protein involved
Anterograde transport is towards the synapse from the soma, while retrograde axoplasmic transport is from the synapse to the soma. In anterorgade axoplasmic transport, materials packaged into vessicles are carried by kenosin down the microtubules, while in retrograde, the vesicles are carried by dynein.
Retrograde e.g.: rabies virus
What is the difference between pyramidal cells and stellate cells?
Pyramidal cells cells send information to other regions of the nervous system. Stellate cells collect information locally and are involved in informaiton processing.
What is the difference between spiny and aspinous neurons?
Spiny neurons have neurites with spines, while aspinous neuron neurites do not have spines.
Describe the relative concentrations of sodium, potassium, chloride and calcium ions inside and outside a neuron.
Explain the difference between Schwann cells and oligodendroglia.
Oligodendroglia are found in the CNS and are able to wrap around as many as 30 axons. Schwann cells are found in the PNS and are able to wrap around only one segment of one axon.
What are the main functions of glial cells?
- Support neural funciton
- Possibly information transmission
What is the difference between Golgi Type I and Golgi Type II neurons?
Golgi Type I neurons project axons from one region of the brain to another, e.g. pyramidal cells. Golgi Type II neurons form local neuron circuits and are involved in computation, e.g. stellate cells.
Do dendrites contain ribosomes?
Yes. This means that inputs received by dendrite may control protein synthesis. This may be the underlying principle of memory formation.
What are microglia?
Microglia are specialised immune cells within the brain. They may be macrophages that remove debree associated with dead/degenerating neurons. They fight inflammation within the brain.
What are the four main types of glial cells?
- Meylinating glia; Oligodendrocytes in the CNS and Schwann cells in the PNS
- Ependymal cells
Describe the microtubules in neurons and their role.
- 20nm in diameter
- Run longitudinally
- Mediate intracellular transport
- Control extension and retraction of neurons.
- Polymerisation and depolymerisation allow change in neuron structure. This is regulated by microtubule associated proteins (MAPs). They anchor michrotubules to each other and to other part of the neuron.
- Do not extend into the axon terminals.
Describe microfilaments in neurons and their role.
- 5nm in diameter
- Linked to microtubules and the membrane
- Maintain the cell's shape
Describe neurofilaments and their role.