Lecture 3 Flashcards
What is the Myelin Sheath formed by a Schwann cell?
Fat Layer (electrical insulation) that increases the speed of action potentials
What is the axon?
Transmits information away from the soma (similar to a wire)
What is the Node of Ranvier?
Exposed region of axons
What is the collateral axon?
Branch and plug into another cell (branching increases innervation to other cell)
What is the pre-synaptic terminal?
Enlargement of the end of the axons branches
What is a multipolar neuron?
Motor neurons
- Many dendrites and an axon.
- Dendrites receive approximately 10,000 inputs
What is a bipolar neuron?
- Has a dendrite and an axon.
- Retina, olfactory, epithelium.
What is a pseudo-unipolar neuron?
Appears to have an axon and no dendrites.
- Somatosensory neuron
What is a Cortical pyramidal cell?
A motor neuron
What is the cerebellar purkinje cell?
Located in the cerebellum
a unique type of neuron-specific to the cerebellar cortex
What are sensory neurons?
- Carries information from body periphery into the nervous system (gives rise to perception)
What is Afferent?
Information coming into the CNS
What are interneurons?
Most numerous, relay and local
What are relay (projection) interneurons?
Long axons, conveys signals over large distance (one part of brain to another)
What are local interneurons?
Short axons, connections with neurons
What are Glial cells?
- Not neurons…neurons supporting cells.
- 2-10x more numerous than neurons.
- Do not have neuritis
- Not electrically excitable
What are motor neurons - efferent?
Information leaving the CNS.
What are the types of Glial cells?
- Astrocytes
- Microglia
- Oligodendrocytes
- Schwann Cells
What are Astrocytes?
- Star-shaped cell bodies
What are the Microglia?
- Protective Function
What are the Oligodendrocytes?
- Forms myelin sheath in the CNS
What are Schwann cells?
- Forms myelin in the PNS
What are the functions of Astrocytes?
1) Separates Neurons: insulates neurons and synapses
2) Regulates extracellular K+: highly permeable to K+ (potassium can move into it)
3) Improves signalling efficiency: absorbs neurotransmitter (chemical) from synaptic spaces.
4) Releases growth factors: refers to proteins that facilitate
What are the functions of microglia?
- Function with astrocytes to protect neurons from toxic substances.
- Protect the CNS from foreign matter through phagocytosis
- Bacteria, dead or injured cells engulfs contaminants
- Protect the CNS from oxidative stress (free radicals)
What are free radicals?
Doesn’t follow natural rules, only disrupts natural pathways.
An occasional oxygen doesn’t pick up a proton to make a protein, instead picks up electrons
What do free radicals disrupt?
- Cell Membrane
- Proteins
- DNA
What are the effects of myelination?
- Insulates the axon.
- Prevents the length dependent decay of the action potential.
- Increases efficiency/speed of action potential propagation.
How does myelination speed up action potentials?
- Induces Na+ channel (protein) clustering at nodes.
- Improves axonal transport.. increase in neural filament.
- Leads to larger diameter/Cross Sectional Area
What is the speed of myelinated axon?
100m/s
What is the speed of unmyelinated axon?
1m/s
What type of axon would detect a fly?
The myelinated axon.
What type of axon would it be if you did something that caused pain?
The unmyelinated axon.
- Pain neurons are not active all the time (why they are unmyelinated)
What are Oligodendrocytes?
Inside the central nervous system and behave similarly to Schwaan Cells by producing myelin
How do they signal for myelination?
- Release of ATP and adenosine from neuron
- Stimulates Glial Cells to produce myelin.
