Cell Types of the Nervous System Flashcards
How many neurones are there in the human brain?
10^10 - 10^12
How many more non-neuronal cells are there than neurones?
Ten times as many
What are unipolar neurones? Give an example
Neurones with one process
Dorsal root ganglia
What are bipolar neurones? Give an example
Neurones with two processes
Retinal bipolar cells
In a motor neuron, what kind of space do the dendrites occupy?
A spherical space known as a symmetrical dendritic field
What kind of space do the dendrites of Purkinje cells occupy?
Planar dendritic field
What kind of cells have apical dendrites?
Pyramidal cells
Which cells have a planar dendritic field?
Purkinje cells
Which cells have a symmetrical dendritic field?
Motor neurons
What are the most common type of neurones in the brain?
Cerebellar granule cells
Are olfactory granule cells unipolar, bipolar or multipolar?
Bipolar with cilia
What kind of synapses do olfactory granule cells form, why?
Dendrodendritic synapses as they are anaxonic
What are the 3 main types of glial cells?
- Macroglia
- Microglia
- Ependyma
Give an example of one of the major subclasses of macroglia
Astrocytes
Also, oligodendrocytes and Schwann cells
What type of glial cell are astrocytes?
Macroglia
Astrocytes can be ______ or ________
Fibrous, protplasmic
What shape are astrocytes?
Star-shaped
Are astrocytes unipolar, bipolar, or multipolar?
Multipolar, has lots of long processes
How are astrocytes associated with blood vessels?
Enwrap blood vessels to form an extra layer
What do astrocytes form?
Glia limitans - lies between cerebral cortex and pia mater
What does the glia limitans lie in-between and what is it formed by?
In-between the cerebral cortex and pia mater. It is formed by astrocytes
Do astrocytes make connections with synapses?
Yes
Where are fibrous astrocytes found?
In white matter
Where are protoplasmic astrocytes found?
In grey matter
Difference between the intermediate filaments in fibrous and protoplasmic astrocytes
Fibrous astrocytes have many intermediate filaments whereas protoplasmic astrocytes have shorter, fewer intermediate filaments
Which type of astrocytes have shorter, fewer intermediate filaments?
Protoplasmic astrocytes
Give 2 examples of specialised astrocytes
- Retinal Müller cells
- Radial glia e.g. Bergmann glia
Retinal Müller cells
Columnar cells that spand width of the retina
Bergmann Glia
These are multipolar and span from pia mater to Purkinje cell layer. Stem cells in adult brain
Roles of astrocytes
- Spatial buffering
- Neurotransmitter uptake
- Glucose metabolism
Roles of astrocytes: Explain the process of spatial buffering
- Active neurones release K+
- Astrocytes are very permeable to K+
so astrocytes act like functional syncitium - Astrocytes span from synapse to blood vessel
Spatial buffering regulate [K+]
Why is the homeostatic balance of K+ important in the brain?
Could alter firing of action potentials
Astrocytes are permeable to which ion?
K+
What do astrocytes span from?
Synapse to blood vessel
What does spatial buffering regulate?
The concentration of potassium ions
Spatial buffering in the retina
- Photoreceptors release K+ when stimulated
- Müller cells take up K+
- [K+] reduced near the photoreceptors
Which glial cell aids in the homeostatic balance of K+ in the retina?
Retinal Müller cells
Roles of astrocytes: Neurotransmitter uptake
- important inactivation mechanism
Glutamate and GABA is taken into astrocytes rather than being broken down
Which neurotransmitters are taken up by astrocytes?
Glutamate and GABA
Roles of astrocytes: Glucose metabolism
Glucose = main energy substrate
Astrocytes store most glycogen in the CNS
Glycogen metabolised and some lactic acid (3 carbon) passed to neurones
Neurons prefer 3-carbon energy source
Which cells store the most glycogen in the CNS?
Astrocytes
What do astrocytes metabolise? What is produced as a result?
Glycogen and glucose maybe. Lactic acid is produced
What kind of carbon energy source do neurones prefer?
3-carbon energy source
What are microglia processes like?
Short and spiky
What kind of cells are microglia derived from?
Circulating monocytes
Are microglia phagocytic?
Yes
Are microglia enucleate?
No
Microglia
- Short, spiky processes
- Wide distribution
- Derived from circulating monocytes
- Phagocytic
What is ependyma?
Epithelia lining brain ventricles and central canal of the spinal cord
What lines the brain ventricles and central canal of the spinal cord?
Ependyma
What is ependyma composed of?
Ependymocytes
Can also get tanycytes in the hypothalamic region
What are tanycytes?
Special ependymal cells found in the third ventricle of the brain, and on the floor of the fourth ventricle and have processes extending deep into the hypothalamus
Choroid plexus
- Modified ependymal cells
- Chloride epithelial cells
- CSF formation and flow
How is ependyma associated with the choroid plexus?
Consists of modified ependymal cells
Do glial cells make specialised junctions with each other, if so, what kind?
Yes, gap junctions
How many non-neuronal cells are there?
10 times as many neuronal cells
