What is the critical period for development of the CNS?
When during gestation is the nervous system sensitive to teratogens?
Almost all of gestation
Neurulation is the process of…
Forming the neural tube
Gastrulation occurs during which week of gestation?
Gastrulation begins with the appearance of the ______________________
During gastrulation, cells of the epiblast migrate towards the ____________________. What happens once it gets there?
Cells of the epiblast
All three germ layers are derived from ____________________
Where is the notochord found?
Between ectoderm and endoderm
The notochord gives rise to the __________________
The ___________________ gives rise to the nucleus propulsus
How is the neural plate derived?
The ectoderm overlying the notochord thickens into the neural plate
The dorsal view of the trilaminar embryo shows the ____________________ superiorly
_________________ is the name of the process of folding that results in a closed tube of neuroectoderm
What is neurulation?
Process of folding that results in a closed tube of neuroectoderm
What happens 16-18 days post-fertilization?
Formation of neural plate
When in gestation does formation of neural plate occur?
What happens 19-20 days post-fertilization?
Neural folds elevate
When in gestation does neural folds elevate?
What happens 21-24 days post-fertilization?
Fusion of neural folds
When in gestation does fusion of neural folds?
What happens 25 days post-fertilization?
Cranial neuropore closes
When in gestation does cranial neuropore close?
What happens 27 days post-fertilization?
Caudal neuropore closes
When in gestation does caudal neuropore close?
The closure of the neural tube begins at the level of the __________________
First five somites
Neurulation commences as the neural plate begins to crease and the…
Lateral lips of the neural tube (neural folds) begin to approximate each other
What causes anencephaly?
Failure of the cranial neuropore to close
What is the most common neural tube defect?
What is spina bifida?
A cleft in the vertebral column with a corresponding skin defect and possible exposure of the spinal cord
Spina bifida is most commonly seen in which region of the back?
What causes spina bifida?
Failure of the caudal neuropore to close
What is the most common form of spina bifida?
Spina bifida occulta
What is the difference between spina bifida vs spina bifida occulta?
Spina bifida occulta has a cleft in vertebral column but without skin and neural structure defects
What is meningocele?
Severe form of spina bifida
Sac containing the meninges pushes through the vertebral column defect
What is meningomyelocele?
Severe form of spina bifida
Sac contains meninges and neural tissue
Which form of spina bifida has tissues and nerves exposed and is more prone to infection?
Which form of spina bifida is known as complete spina bifida?
In this variation of spina bifida, the cleft may extend through the entire spine from the cervical region to the sacrum
How do you prevent neural tube defects?
The forebrain is aka ___________________
The midbrain is aka ___________________
The hindbrain is aka __________________
Where is the cephalic flexure located?
Where is the cervical flexure located?
Inferior border of the rhombencephalon
What encephalons make up the prosencephalon?
What encephalons make up the mesencephalon?
What encephalons make up the rhombencephalon?
What structures make up the diencephalon?
Thalamus and hypothalamus
Thalamus and hypothalamus make up the _______________________
What structures make up the telencephalon?
Cerebral hemispheres make up the ______________________
What structures make up the mesencephalon?
Midbrain makes up the _______________________
What structures make up the metencephalon?
Pons and cerebellum
Pons and cerebellum make up the ______________________
What structures make up the myelencephalon?
Medulla makes up the ___________________
All the encephalons appear during which week of gestation?
Neural tube is aka _______________________
Neural tube will become the ________________________
At what month of gestation does the brain develop sulci and gyri?
30 weeks/6 months
When during gestation do ventricles start to form?
What is hydrocephalus?
Accumulation of CSF
Why does accumulation of CSF cause hydrocephalus?
Skull bones are not fused so it expands
What is the first evidence of eye formation in the embryo?
Appearance of the optic nerve
The future lens will develop from the ____________________
The optic cup is connected to the brain by the _____________________
The inferior part of the optic vesicle invaginates creating the ______________________
What are the layers of the eye?
__________________ is the part of the retina that contains the photoreceptors
Most congenital eye defects involve what part of the eye?
Inferior aspect of the eye
Choroid fissure fuses during which week?
What is coloboma? What is it caused by?
Gap on inferior portion of the iris
Portions of the choroid fissure remain open
What are the three layers of the neural tube from innermost to outermost?
When the neural tube closes, it produces primitive nerve cells called ____________________
Neuroblasts develop from the ____________________ layer of the neural tube then they migrate into the __________________ layer
The ___________________ of the neural tube contains nerve fibers emerging from the neuroblasts in the mantle layer
The white matter of the spinal cord is made up of which neural tube layer?
The gray matter of the spinal cord is made up of which neural tube layer?
What is the sulcus limitans?
Separates grey matter (mantle layer) into ventral and dorsal
What separates grey matter (mantle layer) into ventral dorsal?
Dorsal root of spinal cord comes from the ________________
Ventral root of spinal cord comes from the _________________
What happens in week 8 in the spinal cord?
Vertebral column grows faster than spinal cord resulting in conus medullaris
Where do you insert needle for lumbar puncture?
After conus medullaris
The conus medullaris ends at ___________ in newborns and at ____________ in adults
The PNS largely develops from _________________ cells
During _________________, folds of neuroectoderm approximate each other in the midline
Neural crest cells are derived from _________________ that are initially at a zone between the neural plate and surface ectoderm
How does the PNS develop from the neural crest?
Folds of neuroectoderm approximate each other
Neural crest cells detach from the neural tube and migrates to regions around the body
What are neurocristopathies?
Pathologies that arise from defects in the tissues that contain cells of the neural crest
What is the genetics behind DiGeorge’s syndrome?
Deletion on chromosome 22
DiGeorge’s syndrome is a type of ____________________
What PNS structures are developed from the neural crest? (6)
Dorsal root ganglia
Cranial nerve sensory ganglia
_________________ is formed from clusters of neural crest cells located along future spinal cord and they grow processes that extend into the alar plate. These processes will become fibers that will convey __________________ information into the CNS
Dorsal root ganglia
Nerve fibers in the dorsal root are formed from the ____________________
Since some visceral afferent neurons and somatic afferent neurons use the same DRG, some information can be confused, such as pain in the arm during an MI. What can this cause?
Sympathetic fibers travel to the heart from which spinal level?
Nerve fibers in the ventral root are formed from the ____________________
Preganglionic sympathetics are found at which spinal level?
Postganglionic parasympathetics are found at which spinal level?
Which cranial nerves have sensory ganglia derived from the neural crest?
True or false. Preganglionic neurons are neural crest cell derived.
False! They are derived from neural tube
True or false. Postganglionic neurons are neural crest cell derived.
Which ganglia make up the paravertebral ganglia?
Sympathetic trunk ganglia
Which ganglia make up the prevertebral ganglia?
Superior mesenteric ganglion
Are the paravertebral and prevertebral ganglia sympathetic or parasympathetic?
Which ganglia make up the intrinsic ganglia?
Ganglia in target organ
Which ganglia make up the head/neck ganglia?
Neural crest cells migrate in what direction? Because of this, what is the last region they colonize?
What causes Hirschprung’s disease?
Failure of neural crest cell migration to the distal gut tube
What would a biopsy show in a patient with Hirschsprung’s disease?
Absence of ganglia in the lower colon
How is Hirschprung’s disease usually treated?
Surgical resection of part of the bowel lacking ganglia