Lecture 4

Question 1

A neuron receives 547 EPSP and 526 IPSP. This neuron will be:
A. Depolarized
B. Inhibited
C. Neither depolarized nor inhibited

Answer 1

B. 548-526=21, in order for a neuron to be depolarized, it requires 50-100 EPSPs.

Question 2

What is myelin formed by?

Answer 2

Cell membrane of glial cells (Schwann cells in PNS, oligodendrocytes in CNS)
*Made of fat

Question 3

Where do ion channels cluster on neurons?

Answer 3

Nodes of Ranvier (gaps in myelin sheath)

Question 4

At what speed are AP’s transmitted in myelinated axons?

Answer 4

Avg 100m/sec

Question 5

At what speed are AP’s transmitted in un-myelinated axons?

Answer 5

Avg 1m/sec (way too slow)

Question 6

Which axon will conduct action potentials faster?
A. Large diameter
B. Small diameter

Answer 6

A

Question 7

Which axon will conduct action potentials faster?
A. Thick myelin sheath
B. Thin myelin sheath

Answer 7

A

Question 8

Explain the role of myelin in Multiple Sclerosis

Answer 8

• The immune system attacks oligodendrocytes in the brain and spinal cord (CNS)
• Damages axons in later states of the disease
• Forms “sclerotic plaques” visible on MRI
• Overall decreased transmission of action potential

Question 9

Explain the role of myelin in Guillain-Barre Syndrome

Answer 9

• The immune system attacks schwann cells in the PNS (cranial nerves and spinal nerves)
• Some variants damage axons
• Autoimmune disease, usually preceded by an infection

Question 10

What type of glial cell creates the Blood Brain Barrier? How do they do this?

Answer 10

Astrocytes
-Have processes called “endfeet” that surround capillaries in the brain and spinal cord –> these direct the capillary endothelial cells to create the BBB

Question 11

What type of glial cells remove dead cells?

Answer 11

Microglia

-CNS phagocytes

Question 12

What type of glial cells produce and secrete cerebrospinal fluid (CSF)?

Answer 12

Ependymal cells

Question 13

What are the three stages of development of the nervous system in the first 28 days gestation?

Answer 13

1. Neural plate
2. Neural fold
3. Neural tube (neural crest)

Question 14

What does the neural crest form?

Answer 14

• Sympathetic trunk
• Dorsal root ganglia
• Adrenal medulla
• Enteric nervous system (GI tract neurons)

Question 15

What does the neural tube form?

Answer 15

• Brain

- Spinal cord

Question 16

What are the two types of neural tube defects?

Answer 16

• Anencephaly

- Spina bifida

Question 17

Which neural tube defect is incompatible with life? Why?

Answer 17

Anencephaly. The neural fold does not fully close into the neural tube in the cranial direction (brain/spinal cord don’t form)

Question 18

What happens to the neural tube in spina bifida?

Answer 18

The neural fold doesn’t close into the neural tube in the caudal direction

Question 19

What can reduce the risks of neural tube defects?

Answer 19

Folic acid

Question 20

What parts of the brain form from the cranial direction?

Answer 20

Forebrain, midbrain, hindbrain

Question 21

What parts of the brain form from the caudal direction?

Answer 21

Spinal cord

Question 22

What structures does the forebrain form?

Answer 22

• Right and left cerebral hemispheres

- Diencephalon = thalamus and hypothalamus

Question 23

What structures form from the hindbrain?

Answer 23

• Cerebellum
• Pons
• Medulla

Question 24

Where is cerebrospinal fluid produced?

Answer 24

Ventricles

Question 25

Where does CSF move around?

Answer 25

Subarachnoid space

Question 26

What is the order of meninges from deep to superficial?

Answer 26

-Pia mater, arachnoid (subarachnoid space in between these two), dura mater

Question 27

What is the flow of ventricles from cranial to caudal?

Answer 27

Right and Left lateral ventricles –> 3rd –> cerebral aqueduct –> 4th –> subarachnoid space* or central canal

*After subarachnoid space –> dural sinuses –> heart