PBL 1

Question 1

From which layer of gastrulation, does the Nervous System form?

Answer 1

Ectoderm

Question 2

What is the function of the notochord?

Answer 2

To induce neuralation

Question 3

What structure does the notochord eventually become?

Answer 3

Nucleus pulposis of the intervertebral disc

Question 4

How many days after fertilisation does neurulation occur?

Answer 4

21 days

Question 5

At what days do the anterior and posterior neuropore close?

Answer 5

Anterior - day 25

Posterior - day 27

Question 6

What are neural crest cells?

Answer 6

Cells that escape from the each of each neural fold. They later become spinal and automatic ganglion cells, and Schwann cells of peripheral nerves

Question 7

What do the alar and basal plates become?

Answer 7

Alar plates - sensory grey matter (dorsal horns)

Basal plates - motor grey matter (ventral horns)

Question 8

What are the morphogens involved in dorsoventral axis patterning, and where are they secreted from?

Answer 8

BMP - secreted from the dorsal neural tube

SHH (sonic hedgehog) - secreted from the ventral neural tube

Question 9

What are the morphogens involved in anterior-posterior axis patterning and where are they secreted from?

Answer 9

FGF - secreted from the posterior (caudal) end
Retinoic acid - secreted from the anterior (cephalic) end

Hox B also plays a role in AP axis patterning

Question 10

What are the 3 primary brain vesicles?

Answer 10

Prosencephalon - forebrain
Mescencephalon - midbrain
Rhombencephalon - hindbrain

Question 11

What are the 5 secondary brain vesicles and what do they give rise to?

Answer 11

Telencephalon - cerebrum 
Diencephalon - thalamus, hypothalamus, epithalamus, subthalamus
Mescencephalon - midbrain 
Metencephalon - cerebellum + pons 
Mylencephalon - medulla oblongata

Question 12

How do neuronal progenitor cells stop differentiating?

Answer 12

• due to acute loss of apical polarity
• shedding of apical complex so they are no longer progenitor cells
• apical abscission results in dis-assembly of the centrosome-primary cilium complex, this results in the shutting down of SHH signals, allowing the cell to stop dividing and become a neuron
• apical abcission is mediated by down regulation of N-Catherine and actin-myosin contraction

Question 13

What is perventricular heterotopia?

Answer 13

Where neuronal progenitor cells fail to move away from the apical surface, forming clumps of tissue

Question 14

What is Joubert Syndrome?

Answer 14

Where progenitor neuronal cells have dysfunctional primary cilium, so axonal projections are facing the wrong way (lots of neurons going the wrong way)

Question 15

What neural tube defects can arise when different parts of the neural tube fail to close?

Answer 15

Anterior neuropore failed closure - anencephaly
Posterior neuropore failed closure - spina bifida
Complete neural tube fail closure - craniorachischisis

Question 16

What is an Arnold Chairi malformation?

Answer 16

Where the brain tissue extends into the spinal canal, parts of the lower brainstem and cerebellum protrude through the foramen magnum

Question 17

What are the diagnostic signs of neural tube defects while the baby is still in the womb?

Answer 17

• elevated AFP
• lack of spontaneous leg movements
• lemon/banana sign
• ventriculomegaly (enlargement of ventricles)

Question 18

What is the lemon/banana sign seen on an ultrasound?

Answer 18

Banana - refers to the shape of the cerebellum (due to Arnold chairi?)

Lemon - reflects to the lemon shaped head due to scalloping of frontal bones (Due to decreased intraspinal pressure)

Question 19

Which Arnold Chiari malformation is most commonly seen in spina bifida?

Answer 19

Type II

Question 20

What are the 3 types of spina bifida? Describe them.

Answer 20

Myelonmeningocyle - protrusion of meninges and spinal cord
Meningocele - protrusion of the meninges
Spina bifida oculta - small gap in spinal cord (hair, dimple or birthmark around the site of the lesion)

Question 21

In what region of the spinal cord is spina bifida most likely to be missed?

Answer 21

L5-S2 region

Question 22

What are the main symptoms of spina bifida myelomeningocele?

Answer 22

• Weakness or paralysis of the legs
• Bowel and urinary incontienence
• loss of sensation in the legs
• hydrocephalus (build up of CSF on the brain)
• learning difficulties

Question 23

What are the risk factors for spina bifida?

Answer 23

• Low folic acid during pregnancy
• Family history
• Poorly controlled diabetes
• Taking anti-seizure medications

Question 24

Why is the breach position more common in babies with spina bifida?

Answer 24

Babies undergo spontaneous spasms, resulting in the leg not developing strongly enough to kick the baby round into the normal birthing position

Question 25

What is ventriculomegaly and what can it cause?

Answer 25

Enlargement of the ventricles due to an obstruction in CSF flow from the forth ventricle into the subarachnoid space Can cause hydrocephalus (accumulation of CSF in the brain)

Question 26

What are the eye movement abnormalities associated with hydrocephalus?

Answer 26

Incomplete or slow abduction of the eye - due to a cranial nerve VI palsy

Question 27

Where is a lumbar puncture inserted into to avoid hitting the spinal cord?

Answer 27

Inserted into the lumbar cistern L4/L5 region - landmarked by the posterior iliac crest At this region it is the cauda equina only

Question 28

What is the difference between bipolar type I and II?

Answer 28

Bipolar I: - At least one episode of mania lasting longer than a week - May also experience depressive episodes Bipolar II: - At least one episode of severe depression - Symptoms of hypomania (mild mania without psychotic symptoms)

Question 29

What are the pharmacological treatments used to treat bipolar disorder?

Answer 29

- Lithium carbonate - Anticonvulsants e.g. Semisodium valproate (depakote) - Antipsychotics e.g. Neuroleptic