When does CNS sensitive period for major defects begin and how long does it last till?
Sensitive period lasts from week 3 till 16.
When does susceptibility period for minor defect for CNS development last?
Continues through birth
True/False: nervous system is sensitive to teratogens throughout almost all of gestation?
Yes
Is Visceral sensory information in our conscious or not in our conscious awareness?
Not conscious
Is Somatic sensory information in our conscious or not in our conscious awareness?
Conscious
Autonomic nervous system is which part of the peripheral nervous system?
Visceral motor division
What are the subdivisions of autonomic nervous system?
Sympathetic
Parasympathetic
What is the function of somatic motor division?
Conscious movement of the skeletal muscle
Neural tube forms what?
CNS
Which part of the neural tube becomes the brain?
Cranial portion
The brain arose from where?
Cranial portion of the neural tube
Which part of the neural tube becomes the spinal cord?
Caudal portion
The spinal cord arose from where?
Caudal portion of the neural tube
When does gastrulation occur?
Day 15
What happens in gastrulation?
Cells of the epiblast migrate towards the primitive streak, then detach from epiblast and sneak beneath it to form mesoderm
Major source of the nervous system tissue is from which layer?
Ectoderm
True/False: there is a subdivision of ectoderm called neuroectoderm?
Yes
What gives rise to the nucleus propulsus?
Notochord
How is the neural plate formed?
The notochord induces the overlying ectoderm to thicken into the neural plate
What does the neural plate eventually becomes?
Neural tube
Outline the progression of neural tube formation
Notochord -> neural plate -> neural tube
What is neurulation?
Folding f neural plate into a closed tube of ectoderm
When does the neural plate form?
Days 16-18, beginning the process of folding
When does the lips of the neural folds make physical contact?
Around day 22
When does the cranial neuropore close?
Around day 25
When does the caudal neuropore close?
Day 27
What results from a closed neuroectoderm?
Adult CNS structures form
What results in anencephaly?
Failure of cranial neuropore to close
What characterizes anencephaly?
Open defect in the skin with exposure of the cranial neural tube
What is spina bifida?
Most common neural tube defect as a result of neural tube malformation
What characterizes spina bifida?
Cleft in the vertebral column, most typically in the lumbar region
What went wrong during folding that results in spina bifida?
Caudal neuropore incomplete closure
What is spina bifida occulta?
Benign subtype of spina bifida, cleft in the vertebral column but without skin and neural structure defects
What is spina bifida with meningocele?
Sac containing the meninges pushes through the vertebral column
What is a meningomyelocele in spinal bifida
Sac contains meninges and neural tissue
What is rachischisis?
Complete spina bifida, cleft extend through the entire spine from the cervical region to the sacrum
At week 4, which part of the neural tube becomes the forebrain?
Prosencephalon
At week 4, which part of the neural tube becomes the midbrain?
Mesencephalon
At week 4, which part of the neural tube becomes hindbrain?
Rhombencephalon
What are the two named bends called in week 4, and where are they located?
Cephalic flexure- midbrain
Cervical flexure- inferior border of the rhombencephalon
At week 5, which primary vesicles subdivide and form secondary brain vesicles?
Prosencephalon and rhombencephalon
What do prosencephalon become at week 5?
Telencephalon and diencephalon
What do rhombencephalon become at week 5?
Metencephalon and myelencephalon
What does the telecephalon become?
Cerebral hemisphere
What does the diencephalon become?
Thalamus, hypothalamus
What does the mesencephalon become?
Midbrain
What does the metencephalon become?
Pons, cerebellum
What does the myelencephalon become?
Medulla
What is the most caudal portion of the neural tube called?
Myelon
What does the myelon become?
Spinal cord
When does the brain develop its characteristic bumps and grooves?
Later part of gestation, starting around 6 months
Why do gyri and sulci develop?
Later stages in development, as the brain expands it becomes folded in order to fit large piece of nervous tissue into the confines of the cranial cavity
How big is the newborn brain relative to an adult brain?
25% of the adult size
Brain continues to grow as a result of what?
Myelination of axons, begins in the third trimester and continues after birth
What is the function of the ventricles?
Produce CSF
When do ventricles start to form?
Week 5
What happens to the skull when there is hydrocephalus?
Increased intracranial pressure, expansion of the cranial vault, enlarge the head and thin the skull bones
True/False: parts of the eye are CNS extensions
True, optic nerve and neural retina
Which is the innermost layer of the retina?
Neural retina
Which part of the retina contains photoreceptors?
Neural retina
How is the choroid fissure form?
Invagination of the optic vesicle
What is coloboma?
An eye defect as a result of choroid fissure not closing during week 7
What is the mantle layer?
A region of the closed neural tube that produces neuroblasts
What eventually becomes the gray matter of the spinal cord?
Mantle layer
What is the dorsal portion of the spinal cord called?
Alar plate
What is the ventral portion of the spinal cord called?
Basal plate
What is the function of the alar plate?
Sensory
What is the function of the basal plate?
Motor region
What does neural crest develops into?
PNS
Where do neural crest cells derived from?
Ectodermal cells
What is DiGeorge Syndrome?
Genetic deletion on Chromosome 22
What is the clinical presentation of DiGeorge Syndrome?
Facial anomalies, cleft palate, congenital heart defects, problems with the immune system due to an underdeveloped thymus
Issues with guy and kidneys and parathyroid gland issues
Where do neural crest cells arise from?
Neuroectoderm
True/False: preganglionic neurons are derived from neural crest
