Foundation - Microanatomy Flashcards
What are the nervous system’s functional units
Nerve cells (neurons)
Glia cells (neuroglia)
Neurons
basic unit of the nervous system, involved in the
acquisition,
integration,
and transmission of electrical signals
Unique morphology
Neuroglia
homeostasis-maintaining cells that support neurons and allow them to function optimally by performing a variety of functions
Basic structure of neurons
Core region called soma (or cell body)
Branching extensions that collect information named dendrites
One root that transmit messages named axon
have ONLY one axon, but can have many dendrites
How neurons orient themselves in space and time
they are highly polarized
Flow of information on a neuron
is unidirectional
Dendrite → Soma → Axon → Synapse → Dendrite
Types of synapses
- Axon terminal-dendrite
- Axon terminal-spine (1)
- Axon terminal-soma (2)
- Axon – Axon
Synaptic cleft is too large for
ionic changes
→ neurotransmitters
Types of Receiving receptors
Ionotropic - let ions pass in response to neurotransmitter binding. (are ion channels themselves)
metabotropic - require other signaling cascades to connect neurotransmitter binding to ionic activity in neurons. (do not have an ion channel and instead connect to an ion channels through one or more signaling cascade pathways.)
Ways to classify neurons
1) morphology
2) type of info processing
Neuron Morphology
(based on number and placement of
extensions out of the soma)
- Unipolar
- Bipolar
- Multipolar
- Pseudounipolar
Neuron Role
(based on the type of information they process)
1. Sensory - to CNS
2. Interneuron - In CNS
3. Motor - out of CNS
How neuron micro-structure determines macro-anatomy
Types of (CNS) neuroglia
- Astrocytes (1st evolutionary)
- Oligodendrocytes (mylen)
- Microglia (resident immune - OJ from blood)
- Ependymal cells
Others: specialized or ill-defined glia
* NG2 cells
* Radial glia
* Müller glia
* Bergmann glia
astrocytes
+ functions
Issues with - result in severe disease
Star shaped, most abundant glia cell
functions:
1. Regulates neuronal communication
(synaptogenesis)
2. Regulates blood-brain barrier (BBB)
3. Nutrients support to neurons
4. Regulates signal transmission by interacting with
nodes of Ranvier (space between myelin sheets)
5. Repair metabolic damage (ROS; osmotic; pH)
Oligodendrocytes
Cells in charge of myelination in CNS (similar to Schwann cells in PNS)
- They surround axons and produce myelin
- Are the most proliferative cells of the CNS
NG2 cells
act as multipotent precursors to other glia, in particular oligodendrocytes
- can generate olig.
- like stem cells
- important in MS - why MS is like episodes - no more episodes - no more NG2
Mylen
olig produces many proteins - mylen is one
increseas speed of signal - can “jump” with mylen
microglia
+ functions
Originates in the blood - Enter the CNS during embryonic development + never leave
Very long-lived (varies between brain regions)
Main immune cell of the CNS - “Resident macrophages”
Functions:
Travel throughout the brain and spinal cord (1)
* Keep it clean!
* Synaptic pruning (2)
* Removal of death cells (3)
* Remodeling of neuronal networks (4)
ependymal cells
ARE Epithelial cells
- found in the walls of the ventricles
Make and secrete cerebrospinal fluid (CSF)
-Ciliated, create flow of CSF
Evolutionary, as the brain size increases the
ratio of glia : neuron increases as well
- varies greatly from region to region in the brain
