Nervous System II

Question 1

What are nerves?

Answer 1

Bundles of peripheral neurons
Can be efferent (motor) or afferent (sensory) but most are mixed

Question 2

Where are proteins produced for axonal transport?

Answer 2

In the soma

Question 3

What does axon lack for protein production?

Answer 3

Lacks ribosomes and ER necessary, therefore produced in cell body and transported down axon and brought back to be broken down

Question 4

Anterograde?

Answer 4

Axonal transport from soma down axon

Question 5

Retrograde?

Answer 5

Axonal transport from terminal to soma

Question 6

How is protein transported down the axon?

Answer 6

ATP hydrolysis drives motor proteins to walk along tracks and carry vesicles containing transmembrane proteins, organelles, cytoskeleton proteins, etc

Question 7

What is fast axonal transport?

Answer 7

• smaller proteins (membrane bound proteins and organelles)
• anterograde: up to 400 mm/day
• retrograde: 200 mm/day

Question 8

What is slow axonal transport?

Answer 8

• cytoplasmic proteins (enzymes) and cytoskeleton proteins
• anterograde: up to 8 mm/day
• may be slower due to pausing, some retrograde

Question 9

What are the 2 motor proteins?

Answer 9

Kinesins - anterograde (positive end)
dyneins - retrograde (negative end)
Both fast transport and kinesins slow

Question 10

What are synapses?

Answer 10

Meeting point between two neurons
Point of communication between neuron and adjacent cell
- cell sending signal is pre-synaptic
- cell accepting signal is post-synaptic
- majority are chemical synapses

Question 11

Is the synaptic cleft open space?

Answer 11

No, space contains Extracellular matrix (proteins and carbs) that hold pre and post synaptic cells in close proximity

Question 12

How do billions of neurons in brain find correct targets?

Answer 12

• depends on chemical signals (neurons will search out)
• axons of embryonic neurons contain growth cones that sense and move toward particular chemical signals

Question 13

What do growth cones depend on?

Answer 13

Growth factors, molecules in Extracellular matrix and membrane proteins

Question 14

What happens once a neuron reaches a target cell?

Answer 14

A synapse forms and communication exists
- synapse must be maintains through repeated use
- synapses continually changing and forming

Question 15

What does glia do for neurons?

Answer 15

Communicated with neurons and provide important biochemical support

Question 16

What are the glial cells in the CNS?

Answer 16

Ependymal cells, Astrocytes, microglia, oligodendrocytes

Question 17

What are the glial cells in the PNS?

Answer 17

Schwann cells and satellite cells

Question 18

What is myelin?

Answer 18

A substance composed of multiple concentric layers of phospholipid membrane wrapped around an axon
- provides structural stability, acts as insulation around axon to speed up electrical signals (saltatory conduction), supply trophic factors

Question 19

What are the myelin forming glia?

Answer 19

• oligodendrocytes CNS
• Schwann cell PNS

Question 20

How does myelin wrap oligodendrocytes?

Answer 20

• wrap the axons of up to 50 neurons
• each arm wraps one segment of an axon and can wrap around up to 150 times

Question 21

How does myelin wrap around Schwann cells?

Answer 21

Each segment of myelin is one single Schwann cell
-most afferent and efferent have Schwann

Question 22

What is multiple sclerosis?

Answer 22

• disorder resulting from demyelination in brain and spinal cord
• disrupts electrical signals