Lecture 3

Question 1

What is the Myelin Sheath formed by a Schwann cell?

Answer 1

Fat Layer (electrical insulation) that increases the speed of action potentials

Question 2

What is the axon?

Answer 2

Transmits information away from the soma (similar to a wire)

Question 3

What is the Node of Ranvier?

Answer 3

Exposed region of axons

Question 4

What is the collateral axon?

Answer 4

Branch and plug into another cell (branching increases innervation to other cell)

Question 5

What is the pre-synaptic terminal?

Answer 5

Enlargement of the end of the axons branches

Question 6

What is a multipolar neuron?

Answer 6

Motor neurons

• Many dendrites and an axon.
• Dendrites receive approximately 10,000 inputs

Question 7

What is a bipolar neuron?

Answer 7

• Has a dendrite and an axon.
• Retina, olfactory, epithelium.

Question 8

What is a pseudo-unipolar neuron?

Answer 8

Appears to have an axon and no dendrites.

• Somatosensory neuron

Question 9

What is a Cortical pyramidal cell?

Answer 9

A motor neuron

Question 10

What is the cerebellar purkinje cell?

Answer 10

Located in the cerebellum

a unique type of neuron-specific to the cerebellar cortex

Question 11

What are sensory neurons?

Answer 11

• Carries information from body periphery into the nervous system (gives rise to perception)

Question 12

What is Afferent?

Answer 12

Information coming into the CNS

Question 13

What are interneurons?

Answer 13

Most numerous, relay and local

Question 14

What are relay (projection) interneurons?

Answer 14

Long axons, conveys signals over large distance (one part of brain to another)

Question 15

What are local interneurons?

Answer 15

Short axons, connections with neurons

Question 16

What are Glial cells?

Answer 16

• Not neurons…neurons supporting cells.
• 2-10x more numerous than neurons.
• Do not have neuritis
• Not electrically excitable

Question 16

What are motor neurons - efferent?

Answer 16

Information leaving the CNS.

Question 17

What are the types of Glial cells?

Answer 17

• Astrocytes
• Microglia
• Oligodendrocytes
• Schwann Cells

Question 18

What are Astrocytes?

Answer 18

• Star-shaped cell bodies

Question 19

What are the Microglia?

Answer 19

• Protective Function

Question 20

What are the Oligodendrocytes?

Answer 20

• Forms myelin sheath in the CNS

Question 21

What are Schwann cells?

Answer 21

• Forms myelin in the PNS

Question 22

What are the functions of Astrocytes?

Answer 22

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

Question 23

What are the functions of microglia?

Answer 23

• 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)

Question 24

What are free radicals?

Answer 24

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

Question 25

What do free radicals disrupt?

Answer 25

- Cell Membrane - Proteins - DNA

Question 26

What are the effects of myelination?

Answer 26

- Insulates the axon. - Prevents the length dependent decay of the action potential. - Increases efficiency/speed of action potential propagation.

Question 27

How does myelination speed up action potentials?

Answer 27

- Induces Na+ channel (protein) clustering at nodes. - Improves axonal transport.. increase in neural filament. - Leads to larger diameter/Cross Sectional Area

Question 28

What is the speed of myelinated axon?

Answer 28

100m/s

Question 29

What is the speed of unmyelinated axon?

Answer 29

1m/s

Question 30

What type of axon would detect a fly?

Answer 30

The myelinated axon.

Question 31

What type of axon would it be if you did something that caused pain?

Answer 31

The unmyelinated axon. - Pain neurons are not active all the time (why they are unmyelinated)

Question 32

What are Oligodendrocytes?

Answer 32

Inside the central nervous system and behave similarly to Schwaan Cells by producing myelin

Question 33

How do they signal for myelination?

Answer 33

- Release of ATP and adenosine from neuron - Stimulates Glial Cells to produce myelin.