Neuroembryology

Question 1

In the 3rd week of human development, what are the 3 major parts of the brain?

Answer 1

The forebrain, midbrain, and hindbrain.

Question 2

What kind of embryonic precursor is most of the nervous system coming from?

Answer 2

All from the ectoderm, specifically the neuroectoderm.

Question 3

What is the embryogenic derivation of the notocord?

Answer 3

It’s from the mesoderm.

Question 4

What does the neuroectoderm turn into?

Answer 4

It turns into the neural tube, which later turns into the spinal cord or the brain.

Question 5

What is the function of the notocord in the developing embryo?

Answer 5

It extends all the way through the fetus from the anterior to posterior pole giving the fetus symmetry. It contains cells that makes transcription factors.

Question 6

Which transcription factor is responsible for initiation of the folding of the neuroectoderm? What releases it?

Answer 6

Sonic Hedge Hog (Shh), released by the notocord.

Question 7

What are the “Neural crest cells?”

Answer 7

These are the very tips of the neuroectoderm as it begins to envaginate, and it is the precursor to the PNS.

Question 8

What is the fate of the neural crest cells after it has been formed?

Answer 8

It splits into two bilaterally across the neural tube, and turns into things in the PNS like the spinal ganglia, etc.

Question 9

What is the “primitive streak?”

Answer 9

From 16 days old, there is an envagination that begins from the back of the fetus all the way up to the middle of the fetus, and that envagination is the precursor of the neuroectoderm envaginating.

Question 10

What is the “Hensen’s node?”

Answer 10

It’s basically a coordination complex composed of beating cilia (probably clockwise direction) that also contains liquid and signaling molecules. The idea is that it gives the developing organs a “sense of direction of where to go.”

Question 11

What are the two “neuropores” and what do they form?

Answer 11

The invaginating neural tube starts invaginating in the center and closes caudal and rostral from there, leaving the very ends last to close. The Rostral neuropore turns into the brain and basically everything else turns into the spinal cord.

Question 12

What are “somites?”

Answer 12

These develops on either side of the CNS (specifically the part that turns into the spinal cord), they are of mesodermal origin and as such they become structures like the vertebrae, ribs, and musculature.

Question 13

List all the cells that develop from the neural crest cells: (7 things).

Answer 13

1. Sensory ganglia of the cranial and spinal nerves.
2. Autonomic and enteric ganglia.
3. Schwann cells.
4. Melanocytes.
5. Adrenal Chromaffin cells.
6. Pia/arachnoid membranes (however, dura is mostly of mesoderm origin).
7. Connective tissues of the head (skull bones, jaw).

Question 14

Which neuropore closes earlier?

Answer 14

The rostral (anterior) neuropore closes 2 days earlier than the posterior.

Question 15

What is the “neural canal?” When does this happen?

Answer 15

It is the lumen inside the neural tube. Rostral neuropore closes around 25th day, caudal closes 27th.

Question 16

What is the only derivitive of the notocord that remains in humans after they develop?

Answer 16

The nucleus pulposis of the intervertebral discs.

Question 17

What are 3 layers of the neural tube, starting from the inside and then going outwards?

Answer 17

The inner most is the germinal layer, adjacent to that is the mantle layer and in the outermost is the marginal layer.

Question 18

What is the initial composition of the walls of the neural tube?

Answer 18

Pseudostratified neuroepithelium.

Question 19

What is the birthplace of the neurons and macroglia?

Answer 19

The germinal layer of the neural tube.

Question 20

What is derived from the germinal layer of the neural tube?

Answer 20

Epithelial lining of the ventricles, central canal, choroid plexus (that makes the CSF), and it is the birthplace of all neurons and macroglia.

Question 21

What is the purpose of the mantle layer?

Answer 21

It is where the neurons and macroglia go to differentiate into the neuroblasts and the glioblasts, and then differentiate into neurons and macroglia.

Question 22

What is the marginal layer of the neural tube responsible for?

Answer 22

It’s the derivative of the white matter (axons).

Question 23

Another name for the germinal layer is the…?

Answer 23

Ependymal layer.

Question 24

What is the groove that seperates the dorsal plate and the ventral plate? What are the dorsal and ventral plates called?

Answer 24

The groove is called the “Sulcus Limitans” and it seperates the alar plate (dorsal) from the Basal plate (ventral).

Question 25

What is the function of the dorsal and ventral plates?

Answer 25

The dorsal plate differentiates into the sensory neurons whereas the ventral plate develops into the motor and interneurons.

Question 26

What are the three types of neurons that make up the “Macroglia”?

Answer 26

Ependymal cells that make up the choroid plexus, Astrocytes, and oligodendrocytes.

Question 27

Mesenchymal cells turn into microglial cells, what is their derivation and function?

Answer 27

They are not derived from neuroectoderm, their function is basically support cells. They function as a kind of macrophage, in that they clean up the debris.

Question 28

What are “Prosencephalon” “Mesencephalon” and “Rhombencephalon?”

Answer 28

Forebrain, midbrain and hindbrain, respectively.

Question 29

What is “Leptomeningis”?

Answer 29

Combination of the pia and the arachnoid.

Question 30

During the 4th week the brain has 3 divisions, but by the beginning of the 5th week the brain has 5 divisions. What are they?

Answer 30

The forebrain (prosencephalon) and hindbrain (rhombencephalon) divides. The prosencephalon divides into the Telencephalon and diencephalon, and the rhombencephalon turns into the Metencephalon and the Myelencephalon.

Question 31

What are “pyrimids”?

Answer 31

Motor fiber tracts that run from the cortex all the way down to the spinal cord. Found in the ventral brain.

Question 32

Where is the 4th ventricle found?

Answer 32

At the height of the myelencephalon.

Question 33

What are the structures that we should expect to find in the myelencephalon? (7 things)

Answer 33

Medulla oblongata, part of the 4th ventricle, CN 8,9,10,11,12.

Question 34

What are the two main “bulges” on opposite sides found in the metencephalon?

Answer 34

Ventral bulge is the pons, Dorsal bulge is Cerebellum.

Question 35

What is the general relationship between the pons and the cerebellum? Generally describe the function of the pons and the cerebellum.

Answer 35

The cerebellum is shooting off fiber tracts that all basically congregate in the pons and then branch off into the rest of the brain. The Pons is the relay station, whereas the cerebellum is largely focused on balance, sensory perception, fine motor control etc.

Question 36

What would we find in the metencephalon?

Answer 36

The larger part of the 4th ventricle, the pons and the cerebellum, and CN 5 6 7 8 (8 overlaps into the myelencephalon, as does the last bit of the 4th ventricle).

Question 37

What are the two major components of the midbrain? What do they do generally?

Answer 37

The crus cerebri (cerebral peduncle) and the substantia nigrans. Crus cerebri are motor fiber tracts that travel from the CNS to the motor spinal cord. The substantia nigrans makes dopamine. It is also involved with the basal ganglia and therefore involved with emotion, cognition, learning, and motor.

Question 38

What is the “tectum?” What is it derived from and what does it contain?

Answer 38

The roof of the mesencephalon, it is an alar plate derivitive. It contains inferior colliculi (auditory) and superior colliculi (vision).

Question 39

What does the cerebral peduncle (crus cerebri) surround?

Answer 39

It is the “floor” of surrounding the cerebral aqueduct.

Question 40

Where is the “epithalamus” located and what does it do?

Answer 40

It is located in the forebrain, specifically in the diencephalon. It’s located dorsal and posterior, connects the limbic system, and includes the pineal glands, produces melatonin.

Question 41

Where is the thalamus located? What does it do?

Answer 41

It’s located below the epithalamus in the diencephalon part of the forebrain. It relays sensory input to the cerebral cortex.

Question 42

Where is the hypothalamus located?

Answer 42

Below the thalamus in the forebrain, it has nervous and endocrine functions through the pituitary gland.

Question 43

What does the hypothalamus basically control?

Answer 43

Body temp, hunger, thirst, circadian rhythm.

Question 44

List all the things found in the diencephalon.

Answer 44

Epithalamus, Thalamus, Hypothalamus, Optic vesicles (which contains the optic tract and the retina). Also the 3rd ventricle.

Question 45

What does melatonin allow you to do?

Answer 45

Helps control day/night rythm, “diurnal rythm.”

Question 46

From what structures do the eyes develop from?

Answer 46

The “Optic Cups.”

Question 47

What is the most rostral part of the brain and where is it found?

Answer 47

Lamina terminalis, and it is found in the telencephalon.

Question 48

What ventricles are found in the telencephalon?

Answer 48

The lateral ventricles, where a lot of CSF production is occurring.

Question 49

Where is the cerebral cortex located, and what is the function of the cerebral cortex?

Answer 49

It is located in the telencephalon, its functions include communication and speech (Broca’s and Wernicke’s area), movement (primary motor cortex), Sense of smell (olfactory bulbs), and memory.