Neurohistology/ The Basics Flashcards
What are the two classes of Nerve Cells?
Neurons- Nerve cells
Glia- Supporting cells
Dendrites/ Dendrite Arborization
Dendrites
-Receive the impulse
-Usually there are many.
Arborization
- Where there are A LOT of dendrites (Think of a bid tree).
- Purkinje Cell in Cerebellum
- Helpful to have so may dendrites because it has to take in a lot of info in order to help with balance and coordination.
Axon Hillock
- Where the cell body meets the axon
- The closer another (second) cell’s axons is the axon hillock of the first axon the more likely the first axon will get the second to fire.
Node of Ranvier
- Gap between myelin
- Helps to propagate the signal down the axon by letting in Na+ and K+ out which causes more depolarization. (salutatory Conduction)
Unipolar Neuron
- has two axons
- Cell body is usually in the DRG
- Sensory neuron
Multipolar Neuron
- Has many axons coming out of the body
- Motor neuron
Bipolar Neuron
- One axon and one dendrite
- Specialized one’s are found in the ear and eye.
- They are inter-neurons
Four Main Functions of Glial Cells
- Provided Structure for the neurons
- Surrounds neurons and holds them in place - Forms the Myelin Sheath
- Insulates one neuron from another
- Speeds the Nerve Conduction Velocity (NCV), with help from nodes of Ranvier - Supplies Nutrients & O2 to neurons
- Destroys pathogens and removes dead neurons.
Degenerative Myelin Diseases
- Damage to the myelin sheaths in the brain and spinal cord.
- When myelin degenerates there are problems with neuron responses getting “crossed” where they shouldn’t be, so neurons are firing that shouldn’t be.
- Example: MS, an autoimmune disease in which the oligodendrocytes are attacked by the person’s own antibodies.
Schwann Cells
General Info:
-PNS
-Myelinates one neuron by wrapping around axon
-Nodes of Ranvier are btw each schwann cell.
NCV:
Myelinated: Aprx, 100m/s, Larger diameter
Nonmyelinated: Aprx, 1 m/s, Smaller Diameter
Oligodendroglia / Oligodendrocytes
General:
- CNS
- Myelinates many neurons.
- Insulates and protects
- Increase NCV
- Involved in pathologies such as Alzheimer’s disease and MS
Astrocytes
General:
- CNS
- Most common Glial cell
- Provide structural support
- Insulates Neurons
- Maintains the Blood Brain Barrier
- When injured they divide and wall off the damaged areas
- Act as scavengers by removing neurotransmitters from synaptic cleft
- Clean up other debris during early development and recovery of injury
Microglia
General/Protective:
-CNS
- Function as phagocyte by destroying bacteria, cells and other material.
- Important during injury, infection, or disease.
- Important during brain development.
Destructive:
- In Alzheimer’s disease and Aging they release toxic compounds into the neural environment.
- HIV/AIDS virus can stimulate a cascade of cellular breakdown.
Got to be a balance between protective and destructive roles
