1.2.1 Development of the CNS Flashcards
What is gastrulation?
Process where the outer layer of the bilayer germ disc invaginates at the primitive streak to produce a 3 layered disc
What are the 3 layers of the embryonic disc after gastrulation takes place?
Ectoderm
Mesoderm
Endoderm
What tissues does the ectoderm form?
Skin and neural tissue as well as neural crest
What tissues does the mesoderm form?
Heart
Vessels
Muscles
Notochord
What tissues does the endoderm form?
Gut and accessory lining
Inner linings of tubes
How does the notochord induce the formation of the neural tube?
Notochord releases chemicals to the overlying ectoderm to form the neural tube
What is neurulation?
The process of formation of the neural tube
3rd week
Describe the process of neurulation
- Induced by the notochord
- Elevation of the neural folds
- Fusion of the folds at the mid cervical level
- When folds fuse, neural crest cells detach and migrate to their ultimate destinations
- Neural tube zips up rostrally and caudally
Why are the swellings on the rostral neural tube significant?
Swellings will develop and become major parts of the adult brain
What are the 3 major parts of the brain called?
Prosencephalon-forebrain (remember prose means first)
Mesencephalon -midbrain (mes- means middle)
Rhombencephalon- hindbrain (4th ventricle shaped like a rhombus)
How do the eyes start to develop?
Outgrowths of the forebrain forming optic vesicles which then later form optic nerves
What are the two parts of the prosencephalon?
Telencephalon
Diencephalon
What do the telencephalon and diencephalon become?
Telencephalon-becomes most of cerebral hemisphere
Diencephalon-becomes thalamus,hypothalamus and optic nerve/retina (eyes-two-di)
What are the two parts of the rhombencephalon?
Metencephalon- forms the pons and cerebellum
Myelencephalon- forms the medulla
Where do motor structures tend to sit in relation to sensory structures?
Motor tends to sit anteriorly, motor in a car is in the front
Sensory is posterior, think of parking sensors at the back
Why do sensory and motor structures tend to develop in this way?
Due the development of the basal (floor) and alar (roof) plates in the neural tube
Notochord inducts the ventral (anterior) portion of the neural tube to become the basal (floor) plate
What does the basal plate give rise to?
Motor neurones
How does the alar (or roof) plate form?
In the absence of influence from the notochord
What does the alar plate give rise to?
Inter- and sensory neurones
What is the pattern of sensory and motor function in the spinal cord?
Same as the brain, dorsal roots are sensory while ventral roots are motor
Dorsal horn contains sensory neurones and dorsal columns sit posteriorly
Ventral horn contains motor neurons and the corticospinal (motor) tract sits anteriorly
What is the pattern of sensory and motor function in the medulla?
Lemnisci (sensory) posterior
Pyramids (motor) anterior
What is the pattern of sensory and motor function in the midbrain?
Colliculi (sensory) posterior
Cerebral peduncles (motor) anterior
What is the pattern of sensory and motor function in the cerebral cortex?
Primary sensory cortex posterior to pre-central gyrus
How does the cauda equina develop?
Initially there is a one to one relationship between spinal nerves and vertebrae
The spine grows faster than the spinal cord, especially at the lumbar level
Lower portions of the cord are stretched, drawing out the cauda equina
Starts at L2
