CNS Development Flashcards
When is the ICM observed?
The Inner Cell Mass is observed when the cells reach the blastocyte stage
What are the initial first two layers of the ICM?
The epiblast and hypoblast (once implanted)
At the stage where the Inner Cell Mass is differentiated into two layers, what is it called?
The bilaminar embryonic disc.
What is the layer of the bilaminar embryonic disc closest to the trophoblast (outer layer cells)?
The epiblast
What does the epiblast contribute to?
It will become the embryo, and contribute as well to some extraembryonic tissue
What is the layer of the ICM that borders the blastocoel cavity?
The hypoblast
What does the hypoblast become?
It is a temporary layer that plays a role in the yolk sac and laying out the body plan.
When is the single layered blastula reorganized? What is it organized into?
It goes through gastrulation to become a gastrula ( a 2 or 3 layered cell).
What is the end of gastrulation marked by?
The establishment of distinct cell lineages and the axes of the body
What are the three body axes (with examples?)
Frontal/Coronal plane - cut through the top of the head to remove the face
Transverse plane - separates the torso, divides the upper and lower halves of the body
Median Sagittal plane - Separates the left and right sides of the body
What are the 4 anatomical directions we use to define the embryo?
Doral/Ventral and Caudal/cranial
What are the three layers of the gastrula?
Endoderm, mesoderm, ectoderm
How are gastrula layers classified regarding the primitive groove?
Cells that invaginate through the primitive groove are called the endoderm, cells that are left behind make up the ectoderm, and cells in the middle are the mesoderm.
What gastrula cell layer is closest to the blastocoel cavity?
The endoderm
What layer of gastrula cells make up the brain and nervous tissue? What else does this layer differentiate into?
The ectoderm developed the brain and nervous system but also all the outer layers such as skin and sweat glands.
What type of organs arise from the mesoderm?
The ones that support movement and support ie. muscles, cartilage, bone, connective tissue
What organs arise from the endoderm layer?
Internal organs ie. GI system, endocrine systems, liver
What happens to the inside of the neural tube?
It becomes the ventricular system
What happens to the neural plate to form the neural tube?
The neural fold develops
What 3 types of structures do the fusion of the neural fold lead to?
The Neural tube, the neural crest, and somites
What arises from the neural tube?
The CNS
What is neurulation?
It is the process where the ectoderm folds inwards to form the neural tube
What does the neural crest form in development?
The PNS
What do somites form in development?
Vertebrae of spinal column and related muscle.
Draw The parts of the neural tube from a transverse cross section as well as well as a dorsal point of view.
What are the two neural tube failure to close birth defects and which ends of the tube do they come from?
Anencephaly is the failure of the cranial end to close, and spina bifida is failure of the caudal end to close
What is the thickest layer of the gastrula and what does it become?
The ectoderm is the thickest and folds to become the neural tube.
What is the prevalence of spinal bifida and what is the form of it that presents with a fluid filled cyst?
It occurs in 1/1000 births and the form with a cyst is myelomeningocele
What is hydrocephalus?
It is the fluid buildup of CSF around the brain
What is the cause of hydrocephalus?
The incomplete closure of the cranial end of the neural tube (anencephaly)
What are the three major types of neural crest (PNS) developmental cells? What type of cell is rare and excluded from this list?
Multipotent, bipotent, unipotent
Depending on how many cells they can differentiate into
There are also a small population of pluripotent stem cells
What is the process of differentiation of a pluripotent stem cell?
They differentiate into different progenitor/precursor cells, which are differentiated again by different transcription factors/mitogens into a certain type of cell
How many cells are present in the baby at the time of the closure of the neural tube?
around 125,000
What is the rate of neuron development in birth and how many are expected to be there by birth?
The rate of development is roughly 250K / minute to end with around 100 million cells by birth
What stage is development seen to be in around 4 weeks?
The Three vesicle/vessel stage
What are the three vesicles of the three vessel stage?
Prosencephalon/forebrain
Mesencephalon/midbrain
Rhombencephalon/hindbrain
What is the first vesicle that starts to differentiate?
The forebrain
What are the three subdivisions of the forebrain once it starts to develop? How do they move spatially as they develop?
The telencephalic vesicles move laterally, the remaining section in the middle is the diencephalon, and optic vesicles form on the sides of the diencephalon
What do telencephalon neurons proliferate into?
- Cerebral Cortex
- Basal Telencephalon (motor control/learning)
- Olfactory Bulb
What does the diencephalon differentiate into?
- The thalamus
- The hypothalamus
What ventricle is closest to the diencephalon?
The 3rd ventricle
What ventricles differentiate laterally?
The lateral ventricles
What grey matter structure links the two hemispheres of the brain together?
the corpus callosum
What is the internal capsule?
It is a grey matter structure that links the cortex and thalamus to the brain stem
What does the basal telencephalon primarily differentiate into?
Basal Ganglia and associated structures:
1. Striatum
2. Globus Pallidus
3. Subthalamic Nucleus
4. VL thalamus
What are the two subsections of the Striatum?
The caudate nucleus and putamen
What is the role of the basal ganglia?
It is involved with purposeful motor activity, slow and sustained contractions, and inhibiting muscle tone
Where are electrodes attached to in novel Parkinson’s research to relieve symptoms of extreme tremors?
The subthalamic nucleus
What are the two largest subdivisions of the differentiated basal telencephalon?
The basal ganglia and associated structures, and the limbic system
What is the role of the limbic system?
Motivation, emotion, learning, memory
What stage of neural development happens between weeks 3-4 to 5-6?
The 5 vesicle stage
What are the 5 vesicles of the 5 vesicle stage?
- The Telencephalon(cerebral hemispheres)
- The Diencephalon
- The mesencephalon
- The metencephalon
- The myelencephalon
What does the rhombencephalon differentiate into in the 5 vesicle stage?
The Metencephalon and the Myelencephalon
What does the mesencephalon differentiate into?
The pons and cerebellum
What does the myelencephalon grow into?
The medulla oblongata
What three structures do the midbrain develop into and what is their combined function?
It differentiates into the tectum, Cerebral aqueduct, and tegmentum (dorsal to ventral), which become the pathway for cortex to spinal cord fibers
What is the cerebral aqueduct?
It is a small thin ventricle that combines the 3rd and 4th ventricles.
What are the two subdivisions of the tectum? What are their functions?
Superior colliculus: Eye sensory info input
Inferior colliculus: Hearing sensory info input
What is the role of the tegmentum?
Motor function, regulates awareness/attention/some autonomic functions
What are the two structures that arise form the tegmentum?
The substantia nigra and the red nucleus.
What is the role of the red nucleus?
It is involved in motor coordination
What disease is correlated with a diminishing of the substantia nigra?
Parkinsons
What is the role of the substantia nigra?
Dopamine regulation
What structures does the rostral portion of the hindbrain contain in the 5 vessel stage?
The cerebellum, pons, and 4th ventricle
What structures does the caudal portion of the hindbrain contain in the 5 vesicle stage?
The 4th ventricle, the medulla, and medullary pyramids
What is the unique feature of the cerebellum primary movement centre?
It does not have contralateral control, the left side controls the left of the body and the same with the right
What is the role of the cerebellum?
Primary motor control and mostly balance
What is the role of the pons?
It connects the cortex and the medulla, and also is a communication point between the two hemispheres
What is the role of the medulla?
ANS control, also midbrain motor and sensory neurons travel through the medulla
What happens in the medulla during development in terms of the lateral organization of neurons?
Decussation, the axons cross over to the other side of the body
What neuronal tract does not cross over at the medulla? What is their role?
The ventral corticospinal tract does not cross over and innervate the trunk muscles.
What are the subdivisions of the limbic system? (6)
Amygdala, hippocampus, fornix, Cingulate cortex, septum, and mamillary bodies
What is the limbic system processing cycle?
The neocortex encodes emotional coloring by communicating with the cingulate cortex, which is tied to the hippocampus, which communicates with the hypothalamus through the fornix, which links to the anterior thalamic nuclei, which links back to the cingulate cortex
