Development of the Nervous System Flashcards
What is the nervous system developed from? What is the notochord formed from?
ECTODERM
- notochord = MESODERM
Induction of the neural plate is done by what structure? Which week of development?
NOTOCHORD (mesodermal origin)
- induces invagination of neural plate
What cells form the cranial nerve sensory cells and dorsal root ganglia cells? Where do they form?
NEURAL CREST CELLS
- form post-ganglionic Autonomic cells (parasympathetic & sympathetic)
- form at the top of the neural tube, will push away & migrate laterally
What 6 distinct neurons do the NEURAL CREST cells differentiate into?
- Cranial Nerve Sensory & Ganglion cells
- Dorsal Root Ganglion Cells
- Post-ganglionic Autonomic
- CHROMAFFIN cells of adrenal medulla
- SCHWANN CELLS
- Melanocytes
NOT VENTRAL ROOT**
What do the mesodermal cells alongside the neural tube begin to form?
SOMITES
- Skeletal muscle
- Vertebrae
- Dermis
What 3 distinct vesicles does the anterior aspect of the NEURAL TUBE develop into?
- Prosenchephalon (forebrain)
- Mesencephelon (midbrain)
- Rhombencephelon (hindbrain)
What 5 vesicles form from the 3 vesicles of the Neural Tube?
- Telencephelon
(cerbral cortex, basal ganglia, hippo campus, amygdala) - Diencephelon
(thalamus, hypothalamus, choroid plexus, pineal body) - Mesencephelon
(tegmentum, tectal, peducular regions) - Metencephelon
(pons, cerebellum) - Myelencephalon
( medulla/brainstem)
Which areas have the greatest growth?
Cerebral hemisphere (telencephelon)
&
Brainstem
(myelencephelon)
What are the 3 main flexures?
- Cephalic
- Pontine
- Cervical
(in order)
What are the 2 secondary vesicles of the forebrain/prosencephelon? What regions does each secondary vesicle cover? What ventricles?
- Telencephelon & Diencephelon
2) T= cerebral cortex & basal ganglia, amygdala D = 1 - thalamus 2- hypothalamus 3 - pituitary 4 - pineal gland
3) T= Lateral Ventricle( of Monroe)
D= 3rd Ventricle
What are the 3 layers of the Neural Tube? Which layer is 1st to form & fastest growing?
- Ventricular (inner layer)
- Mantle (intermediate layer) –> GRAY MATTER (cell bodies)
- Marginal Layer (outer)
- White matter –> AXONS
MMV
VENTRICULAR!!! first & fast proliferating
Which cells of the 3 layers become gray matter? Which become white matter?
GREY = MANTLE (2nd layer –> cell bodies)
White = MARGINAL (outer layer–> Axons)
What do Alar Plate neurons contribute to? Basal Plate?
Where are they found in regards to the Sulcus Limitans?
Alar = SENSORY pathways
- DORSAL to Sulcus
Basal Plate = MOTOR
- Ventral to the Sulcus Limitans
Which cells will invade the adjacent somites?
those more VENTRALLY within the mantle
Basal Plate = MOTOR–> to the ventral root of spinal chord
Which axons form the TRACTS??
Axons in the MARGINAL zone
white matter –> axons
- grow to brain or spinal chord
What are the fibers within the Dorsal Sensory Horn?
In the Ventral Motor Horn?
Following options:
GSA, GVA, GVE, GSE
Dorsal:
- GSA - sensory input (touch, pain, temp)
- GVA - sensory to smooth muscle(internal organs)
- GVE - parasympathetic
Ventral:
1. GSE - motor to skeletal muscle (alpha motor neurons**)
A 7 day old infant was evaluated because of intermittent vomiting that began a day after birth. A barium enema demonstrated contraction of the colon near the rectum and a length of colon proximal to the contraction was severely distended. Biopsy revealed an absence of autonomic ganglia cells in the colon. The most likely cause of this disorder was:
a. defective formation or migration of neural crest cells
b. failure of closure of the rostral neuropore
c. failure of closure of the caudal neuropore
d. lack of separation of the telencephalic vesicles
e. increased proliferation or migration of CNS neurocytes
A) Defective formation or migration of neural crest cells
What forms from the lateral ends of the BRAINSTEM? Because the roof plate expands, where is the ALAR plate relative to the basal plate?
FOURTH VENTRICLE
*****LATERAL to the basal plate
alar = sensory Basal = Motor (a= 1st, B = 2nd)
Which foramen develop laterally in the Medulla(myelencephelon)? Medially? Which contains sensory components & which motor?
Laterally = Foramen of LUSCHKE (sensory)
Medially = FORAMEN OF MAGENDIE (motor)
What are the 2 principle components of the Metencephelon?
- PONS
- Cerebellum!!!
t. PC
What are the 2 basic divisions of the pons?
- Dorsal Tegmentum
- Ventral Region
Dorsal = Tegmentum Ventral = BASILAR PONS
What is derived from the DORSAL aspect of the Alar Plate? Central Part?Lateral?
CEREBELLUM***
central = VERMIS
lateral = Cerebellar Hemispheres
What is the function of the cerebellar cortex?
integrating information –> motor memory or muscle memory
Why is cell migration in the cerebellum different from brainstem & spinal chord?
- cells near surface migrate INWARD to form granule cell layer
- push cells from proximal to distal layers
What are the 3 regions of the Midbrain? Which section of the brain is it?
MESENCEPHALON
- Tectal Region - dorsal –> Sensory info (colliculi)
- Tegmentum - middle
- Peduncular - ventral
What important structure is formed in the cavity of the midbrain vesicle?
Aqueduct of Sylvius OR
Cerebral Aqueduct
- CSF from forebrain ventricle to the fourth ventricle
What types of fibers are found in the Midbrain?
- GSE - (oculomotor)
- GVE (edinger westphal nuc.)
- GSE (Trochlear Nuc.)
- GSA ( mesencephalic nuc. of 5)
1,2,3, 4
What types of fibers are in the PONS?
5 , 6 , 7,
- GSE (CN 6)
- GVE (sup. Salivatory Nuc.) (CN 6)
- SVE (CN 9 - motor facial nuc.)
- GSA (CN 5 - principle sensory nuc.)
- GSA (CN. 5)
What types of fibers are in the medulla oblongata?
1, GSE - CN 12
- GVE - CN 10
- SVE
- SVA
- GVA
- SSA
- GSA -
8,9,10,12
What types of fibers are in the spinal chord?
GSE
GVE
GVA
GSA
From what are the optic vesicles formed? What will the rostral part form? The medial portion?
FOREBRAIN (diencephelon)
- Rostral –> forms TELENCEPHALON
- Medial –> DIENCEPHELON
Where is growth most rapid in the diencephalon? Because it is so rapid, what is the “bridge” that forms between?
THALAMUS
- MASSA INTERMEDIA!
(3rd ventricle will form here)
From what does the hypothalamus form? What does it control?
3rd ventricle –> ventral region slower –> forms HYPOTHALAMUS
- control sleep, digestion, body temp, emotion (via limbic)
other ventral structures: optic chiasm maxillary bodies tuber cinerum infundibulum
From what is the Cerebral cortex derived?
TELENCEPHELON
- most rostral-
- 2 outpocketings (Cerebral Hempisheres)
- median–> LAMINA TERMINALIS
How do the lateral ventricles communicate with the lumen of the diencephalon?
Via interventricular FORAMEN OF MONRO
What is formed from the continued growth of the cerebral hemispheres?
CEREBELAR CORTEX
What is formed once the roof plate of the Cerebral Hemispheres fuse with the pia mater containing the vascular mesodermal tissue?
CHOROID PLEXUS of the LATERAL VENTRICLE
What forms the medial surface of the telencephalic vesicle?
Hippocampal formation (archipallium)
What connects the hippocampus with the hypothalamus?
FORNIX
What are the 3 commissures of the TELENCEPHALON and what do they connect?
- Corpus Callosum - Left & right hemispheres
- Anterior COmmisure - limbic system & temporal lobe
- Posterior Commissure - visual & integrative components
What is the disorder when the posterior neuropore fails to close?
Spina Bifida
What are the 3 types of spina bifida and their symptoms?
- Spina Bifida Oculta
- no neural tissue, defect is covered by skin/patch of hair - Spina Bifida Cystica
- neural tissue protrudes through arch –> cyst sac
A) meningocele - only fluid
B) Meningomyelocele - neural tissue in sac
- Rachischisis
- neural tissue become necrotic, or fails to form
*** fix w/ folic acid
- What is it called when the meninges protrude through the defect in the ossification of the skull?
. If only the meninges protrude through the defect (hole),
= meningocele.
If brain tissue protrudes through the defect in the skull it is called what?
If brain tissue protrudes it is a
meningoencephalocele!!
If the ventricles are involved, it is called what?
if the ventricles are involved
= meningohydroencephalocele
What is the last thing to form?
SKULL
- nervous system before skull formation
What is exencephaly? What happens if brain tissue becomes necrotic? What is it called if the defect continues into the spinal chord?
Cephalic Neural Tube does not close
- skull does not form
- MALFORMED brain exposed
- necrotic –> called ANENCEPHALY
- CRANIORACHISCHISIS
What is the name for the defect when CSF accumulates in the ventricular system? How does this occur? Where does fluid build up?
HYDROCEPHALY
- narrowing, stenosis of AQUEDUCT OF SYLVIUS
- builds up in LATERAL VENTRICLES
–> skull expands since cranial sutures have not fused
What is the term for the caudal displacement of the posterior canal fossa though the foramen magnum? What usually gets displaced?
- herniation of CEREBELLUM
called:
Arnold - Chiari Malformation
What is microcephaly?
Cranial vault that is smaller than normal
- due to lack of Brain Development
- small forehead
A two day old female infant presents with a small pigmented area at the midline on her lower back. Close examination reveals a small tuft of delicate hairs associated with a small cutaneous dimple. Which of the following most closely signifies with this defect?
a. Rachischisis
b. Encephalocele
c. Spina bifida aperta
d. Spina bifida cystica (sac like defect exposed)
e. Spina bifida occulta
E. SPina Bifida Occulta
A stillborn infant was noted to have a grossly abnormal skull and cerebrum. The parietal bones, most of the occipital bones, and most of the frontal bones above the orbits were absent. A malformed remnant of the cerebrum, with few recognizable structures, was exposed at the site of the skull defect. The most likely explanation for this malformation was:
a. defective formation or migration of neural crest cells
b. failure of closure of the rostral neuropore (anencephaly)
c. failure of closure of the caudal neuropore
d. blockage of the cerebral aqueduct
e. increased proliferation or migration of CNS neurocytes
b. failure of closure of the rostral neuroprore (anencephaly)
A 7 year old boy is brought to the pediatrician by his mother, who complains that the boy has had progressive difficulty seeing/reading the assignments posted on the board by the teacher. Examination reveals a boy who is noticeably small for his age, has partial vision loss in both eyes peripherally, but otherwise appears healthy. MRI of the brain reveals a craniopharyngioma – Rathke’s pouch tumor – which is an aberrant outpocketing of the stomodeum. Which one of the following is most directly involved in the developmental defect seen in this boy?
a. Adenohypophysis
b. Neurohypophysis
c. Optic chiasm
d. Hypothalamus
e. Thalamus
A.) Adenohypophysis
A child is born with a large mass on the forehead, a partially cleft nose, and ocular hypertelorism (widely spaced orbits). CT and MRI reveal a defect in the frontal bone and a mass containing fluid, portions of the frontal lobe, and a cavity that is continuous with the anterior horn of the right lateral ventricle. Which of the following best describes this type of mass?
a. Meningocele
b. Meningoencephalocele
c. Meningohydroencephalocele
d. Meningomyelocele
e. Microencephaly
c. Meningohydroencephalocele
