Lecture 3

Question 1

Explain the process of neural embryonic development (neural tube development).

Answer 1

The mammalian central nervous system is derived from the ectoderm of the embryo. In the third week of human development the neuroectoderm appears and forms the neural plate along the dorsal side of the embryo. The neural plate is the source of the majority of neurones and glial cells of the CNS. A groove forms along the long axis of the neural plate and, by week four of development, the neural plate wraps in on itself to give rise to the neural tube, which is filled with CSF.

Question 2

Which structures does the neural tube form?

Answer 2

As the embryo develops, the anterior part of the neural tube forms a series of bulges called vesicles, which become the primary anatomical regions of the brain (forebrain- prosencephalon, midbrain- mesencephalon and hindbrain- rhombencephalon)

Question 3

What is neuronal migration and what may disruption of this process cause?

Answer 3

Method by which neurons travel from their origin or birthplace to their final position in the brain. Several methods of doing this (radial, tangential etc). Disruption can cause malformations in humans including severe mental retardation, epilepsy and various intellectual disabilities.

Question 4

What are the 2 main neuronal subtypes that populate the cerebral cortex?

Answer 4

Excitatory pyramidal neurons and inhibitory interneurons.

Question 5

What are neurocutaneous syndromes (phakomatoses)?

Answer 5

Neurological disorders characterised by visible cutaneous manifestations.

Question 6

What is the most well known neurocutaneous syndrome? And what is its common symptoms?

Answer 6

Neurofibromatosis type 1 –> complex multi-system human disorder caused by a mutation of a gene on chromosome 17 that is responsible for the production of neurofibromin. Causes tumours along the nervous system which can grow anywhere in the body. Common symptoms include brownish red spots in the coloured part of the eyes, benign skin tumours, larger benign tumours of nerves, scoliosis, learning difficulties, multiple café au lait etc.

Question 7

What is the cause of a neural tube defect?

Answer 7

The rostral and/or caudal end of the neural tube may fail to close in any of its layers.

Question 8

What is spina bifida and what are the 3 types?

Answer 8

Birth defect where there is incomplete closing of the backbone and the spinal cord. 3 types of spina bifida; occulta, meningocele and myelomeningocele and they all have different severities. Reduced folate acid during pregnancy is linked to the condition.

Question 9

What causes cortical heterotopia, and what are the associated symptoms?

Answer 9

Abnormal neuronal migration leading to clumps of grey matter located in the wront area of the brain. This causes excess electival discharge in grey cells leading to epileptic seizures. Can also cause severe mental retardation.

Question 10

Which disease manifestation is shown in the image?

Answer 10

Holoprosencephaly –> cephalic disorder in which the prosencephalon (the forebrain of the embryo) fails to develop into two hemispheres. Causes defects in the development of the face and in brain structure and function. Usually the malformations are so severe that babies die before birth.

Question 11

What is cerebral palsy and what are the associated symptoms?

Answer 11

A group of permanent disorders of the development of movement, caused by non-progressive disturbance that occurred in the developing fetal or infant brain in the parts that control movement, balance and posture. Often symptoms include poor coordination, stiff muscles, weak muscles and tremors.

Question 12

Name 3 non poly-Q triplet repeat diseases

Answer 12

1. Fragile-X syndrome
2. Myotonic dystrophy
3. Friedriech’s ataxia

Question 13

Name 3 X-linked diseases

Answer 13

1. Duchenne MD
2. Adrenoleukodystrophy (affected adrenal gland in the white matter)
3. Peripheral nerve degeneration (Charcot Marie Tooth or concave foot).