Lecture 11 Flashcards
How many neurons are there in the human brain? What do they do?
10 (to the power of 12)
Excitable cells that do the “signalling”
How many non-neuronal cells are there in the human brain? what do they do?
More than 10 to the power of 11
Glia = glial cell - neuroglia
Non-excitable which support the function of the excitable cells
What are the four basic neuron types?
Multipolar neuron
Bipolar neuron
Pseudo-unipolar neuron
Unipolar neuron
What is an example of unipolar neurons?
Dorsal root ganglia
What is an example of a bipolar neuron?
Retina
How does the structure of multipolar neurons relate to its function?
Possesses a single axon and many dendrites and branches - allows connections and transmission of “information” with many neurons
Where can multipolar neurons be found in?
Hippocampus
- Involved in memories
- In order to sort through these data to produce a “narrative” or story of an episodic memory
What are the three major glial cell types?
Macroglia
Microglia
Ependyma
What are the three major macroglial cells?
Astrocytes
Oligodendrocytes
Schwann cells
What is the structure of astrocytes?
Fibrous Protoplasmic - varies in shape - heterogeneous - different physiological features depending on where they are in the brain
What are the functions of astrocytes?
Create the brain environment, build up the micro-architecture of the brain parenchyma
Maintain brain homeostasis, store and distribute energy substrates
Control the development of neural cells
Synaptogenesis and synaptic maintenance
Brain defence
What is the difference between fibrous and protoplasmic astrocytes?
Fibrous - white matter (myelinated axons) - Many fibrils in cytoplasm Protoplasmic - Found in gray matter only - Shorter, stouter processes - Few cytoplasmic fibrils and organelles
How do astrocytes multiply?
Divide after injury
Occupy the spaces left by injured neurons
e.g. Prion diseases - causes holes in brain
What is a prion disease that results from cannibalism?
Kuru
- from eating human brains
What is the scientific name for mad cow disease?
Spongiform encephalopathy
How else do astrocytes function as?
High affinity uptake systems for neurotransmitters
e.g. glutamate, GABA
May act as storage systems for neurotransmitters when they are needed
How do astrocytes deal with excess neurotransmitters in the cleft that has to be removed?
- Some neurotransmitters called “neuropeptides” simply diffuse out of the cleft and cannot exert their influence. They are destroyed by surrounding tissues in minutes or hours.
- Some neurotransmitters are transported back into the presynaptic terminal for reuse (reuptake) or into the postsynaptic terminal uptake
e. g. serotonin and noradrenaline
What is an enzyme that break down neurotransmitters in the cleft?
AChE
What inhibits the activity of AChE?
Anti-AChE
Breaks down AChE so ACh keeps firing at neuromuscular junction - results in twitching
Basal lamina of blood vessels is almost entirely covered by what glial cell?
Astrocytes
What forms the “neurovascular bridge”?
One dendrite at the blood vessel, with its other at the neuronal membrane, synapse or axon
What happens when neuron firing rate increases?
Astrocyte Ca influx increases
Release of vasoactive subtances from astrocyte
Blood vessel diameter changes
What has fMRI measurements shown when looking for metabolic support?
Astrocytes control blood flow to certain parts of the CNS
What are microglia?
Short spiky processes
Wide distribution
Major inflammatory cell type in the brain
What are microglia derived from?
Circulating monocytes
What is the phagocytosis of microglia similar to?
Macrophages
What do microglia respond to?
Pathogens and injury by becoming activated
What happens when microglia is activated?
Changes morphology
Proliferate and migrate to the site of infection/injury
They phagocytose and destroy pathogens as well as remove damaged cells
What are ependyma?
Epithelia lining ventricles and spinal canal (aqueduct)
What is the structure of ependyma?
Ciliated, cuboidal/columnar cover capillaries - choroid plexus
What is the majority of ependyma cells?
Ependymocytes
What are Tanycytes and what do they supposedly do?
Send chemical signals from CSF to CNS?
3rd and floor of 4th ventricle
What do choroid epithelial cells do?
CSF formation and flow
waft CSF keeping it flowing
