Session 1 - Lecture 2: Development of the CNS Flashcards
Outline the embryological development of the nervous system and some associated problems, these include: Neurulation, spinal cord, brain, ventricles, alar and basal plates and neural crest development.
Outline the main steps of the formation of the neural tube.
Gastrulation –> produces the notochord –> induces neurulation –> neural plate forms –> lateral edges elevate –> mid-region depresses (neural groove) –> neural fold gradually approach each other in midline and fuse –> produces neural tube (by day 28-32).
What is the main function of the notochord?
Important signalling role - directs conversion of overlying ectoderm to neuroectoderm.
Name some neural tube defects and how they can occur.
Result from failure of the neural tube to close, if this occurs cranially = anencephaly (absence of brain), incompatible with life.
If this occurs caudally = spina bifida (spine split), commonly occurs lumbosacrally, neurological deficits, hydrocephalus (accumulation of CSF within the brain –> increased pressure inside the skull) nearly always occurs which can lead to cognitive delay.
Rachischisis = failure of neural fold elevation –> neural tube does not form.
How are neural tube defects diagnosed and how can they be prevented?
Diagnosis = raised maternal serum alpha-fetoprotein and ultrasound sonography. Prevention = folic acid pre-conceptually (3 months) and for the first semester reduces incidence by 70%.
What does most of the length of the neural tube give rise to?
Spinal cord
Up to what month is the spinal cord the same length as the vertebral column and what happens after this time?
3rd month after which the vertebral column begins to grow faster and the spinal roots must elongate as they still exit at their intervertebral foramen. This eventually leads to the formation of the cauda equina.
Generally, at what level does the cauda equina begin and how is the administration of local anaesthetic delivered via lumbar puncture?
L1, lumbar puncture is given at L3/L4 level to avoid spinal cord injury.
Which three primary brain regions can be distinguished during neural folding?
Forebrain/prosencephalon, midbrain/mesencephalon and hindbrain/rhombencephalon present as three primary brain vessels at the cranial end after neural tube closure (4th week).
When are the secondary brain vesicles formed and what are they called?
5th week of development. Telencephalon, diencephalon, mesencephalon, metencephalon and myelencephalon (cranial to more caudal).
What do primary brain vesicles give rise to in terms of secondary brain vesicles and mature derivatives?
Prosencephalon –> telencephalon –> cerebral hemispheres
Prosencephalon –> diencephalon –> thalamus
Mesencephalon –> midbrain
Rhombencephalon –> metencephalon –> pons, cerebellum
Rhombencephalon –> myelencephalon –> medulla oblongata
Why are flexures formed within the brain during development?
Growth and development at the cranial neural tube end exceeds available space linearly so it must fold up thus the neuraxis does not remain straight.
Name the different flexures that arise during brain development and where they are found.
Cervical flexure = spinal cord - hindbrain junction
Cephalic flexure = midbrain region
How does the ventricular system develop develop within the brain?
Tubular structure of developing CNS persists during development –> interconnected reservoirs are filled with CSF produced by choroid plexus cells that line the ventricles.
What is the role of the ventricular system?
To cushion the brain and spinal cord within their bony cases.
Name a ventricular system abnormality and briefly describe it.
Hydrocephalus –> most common in newborns suffering from spina bifida, treat using shunt, can occur if blockage of ventricular system e.g. tumour or infection.
