Brain Development

Question 1

Neural Tube Development

(Diagram)

Answer 1

Question 2

Alar Lamina

Answer 2

Dorsal thickening from neuroepithelium which contain nerve cell bodies that will form processes that exit thickening into marginal layer of neural tube

Question 3

Basal Lamina

Answer 3

Ventral thickening from neuroepithelium which contain nerve cell bodies that will form processes that exit thickening into marginal layer of neural tube

Question 4

3 Main functional types of Neurons

Answer 4

1. Motor (efferent): from basal lamina of neural tube
2. Association (interneurones): from alar lamina of neural tube
3. Sensory (afferent): from neural crest

** All 3 having different functions (functional types), they all have a different developmental origin within the developing NS

-basal lamina is the source of all efferent neurons

Question 5

Motor Neurons

Answer 5

• Convey messages from the CNS to the periphery of the body. (i.e. to supply muscles with motor neurons taking impulses from CNS to different limbs of body).
• Efferent.
• Carrying impulses out of the CNS to the periphery of the body

Question 6

Association or Interneurons

Answer 6

• Neurons like this connect or associate one point in the CNS with another point in the CNS, but they never leave the CNS unlike the motor neurons. Could be anything, one bit of spinal cord to another bit of spinal cord. Associated one point of CNS with another.
• By far the most numerous in the Nervous system!

Question 7

Sensory (afferent) Neurons

Answer 7

• bring information in from the periphery of the body.
• From the skin to the CNS.
• Doing the opposite thing to efferent neurons in terms of signal transfer.

Question 8

3 Vesicles of “3 vesicle stage of Brain”

Answer 8

• Forebrain
• Midbrain
• Hindbrain
• Development of Brain I
• Ventricles contain cerebrospinal fluid
• shows 3 obvious expansions of this cranial end of neural tube
• hindbrain becomes the part continuous with the rest of the neural tube and this leads to the formation of the spinal cord

Question 9

“5 Vesicle Stage of Brain”

Answer 9

• Soon after 3 vesicle stage:
• Forebrain region forms a growth pouch-like on either side
• two expansions of forebrain vesicles
• becomes 5-vesicle stage due to added expansions

Question 10

Brain Regions

Answer 10

Question 11

Pontine Flexure

Answer 11

• Hindbrain elongates somewhat and tends to grow in length so much that to accommodate it has to be folded. Becomes V-shaped or U-shaped –> Pontine Flexure

Question 12

Pons and Medulla Oblongata

Answer 12

• the Pontine Flexure:

allows for 2 different parts of the brain to develop from the hindbrain vesicle. More rostral part is the pons. And the most caudal part becomes continuous with the spinal cord and is called the medulla oblongata.

Formation is due to elongation of the hindbrain vesicle

Question 13

Secondary Neural Structures to Adult Neural Structures

Answer 13

Question 14

Parts of the Brain

(including all that composes forebrain, midbrain, and hindbrain)

Answer 14

Question 15

Parts of the Telecephalon

Answer 15

• cerebral hemispheres (2)
• Largest parts of telencephalon. Form connections that join the left hemisphere with the right
• limbic system
• olfactory bulb
• interconnecting structures (commisures)

Question 16

Parts of Diencephalon

Answer 16

Question 17

Gross Description of parts of the brain

Answer 17

• Cerebrum
• Cerebellum
• Brainstem

-medulla oblongata, pons, midbrain

Question 18

View of Brain Stem with Cerebellum Removed

Answer 18

Question 19

Interventricular Foramen

Answer 19

• The lateral ventricles connected to the third ventricle by theinterventricular foramina
• In the brain, the interventricular foramina (or foramina of Monro) are channels that connect the paired lateral ventricles with the third ventricle at the midline of the brain

Question 20

Corpus Callosum

Answer 20

• The corpus callosum is a thick band of nerve fibers that divides the cerebral cortex lobes into left and right hemispheres
• It connects the left and right sides of the brain allowing for communication between both hemispheres

Question 21

Neural Tube

Answer 21

Formation: Notochord induces its overlying ectoderm –>neuroectoderm–> neural plate= Elongated thickening of ectoderm –>lateral parts rise–> neural folds process continues & ends meet & fuse–> Neural tube

• Marginal Layer: formed primarily of nerve Cell processes (white matter
• Mantle Layer: Cells
• Alar Lamina- cells here–> Interneurons (reside soley in CNS)
• Basal Lamina- cells here–> Motor (efferent) neurones
• Neuroepithelial (ventricular) Layer- major proliferative layer & 1st to develop

Question 22

Neural Crest

Answer 22

Formation: During NT formation, some cells of the neural folds breakaway to form two continuous cords- the neural crests, which run almost the whole length of the NT at its dorsolateral aspects

• NC cells can differentiate into: Spinal ganglia (dorsal root), ANS ganglia & ganglia of some cranial nerves, sensory afferent neurones, chromaffin cells & Schwann cells

Question 23

Development of Brain

Answer 23

1. The neural tube forms 3 primary brain vesicles: forebrain, midbrain & hindbrain
2. Outgrowths from the prosencephalon grow either side of the forebrain vesicle & form the telencephalon & diencephalon–> 5 vesicles
3. From the hindbrain form the

• metencephalon (pons)&
• myelencephalon (medulla)

Question 24

Parts of the Brain

Answer 24

Developmental- parts of the brain can be subdivided based on their embryonic origin. Divisions:

• Hindbrain- medulla oblongata, pons & cerebellum
• Midbrain
• Forebrain:
• Diencephalon (midline component): epithalamus, thalamus, hypothalamus
• Telencephalon (paired outgrowths): cerebral hemispheres (2), limbic system, olfactory bulb, Interconnecting structures (commissures)

Gross- parts of the brain can also be subdivided based on their appearance. Divisions:

• Cerebrum, Cerebellum & Brainstem (medulla oblongata, pons, midbrain)
• But diencephalon doesn’t fit into any of these groups

Question 25

Pontine Flexure Formation & re-location of alar lamina (dev. of Hindbrain)

Answer 25

The brain grows rapidly in size & it becomes difficult to accommodate it in the space--\> available various changes particularly in hindbrain vesicle which elongates rapidly & is forced to fold upwards--\> **pontine flexure**, * this affects the dorsal part of the tube mainly, the lumen becomes a horizontal cavity- horizontal (rather than a vertical slit) and the alar lamina now lies lateral to the basal lamina

Question 26

Develpment of the Cerebellum | (Dev. of the hindbrain)

Answer 26

* **Cerebellum**= main derivative of hindbrain. It develops from **paired dorsal upgrowth** either side of the hindbrain--\> these **enlargen** & eventually meet together at midline & **fuse--\>** cerebellum in adult being a single part of the brain. * Cerebellum is attached to pons & medulla oblongata by peduncles (stalks). * When cerebellum starts to develop its more or less like the rest of the CNS consisting of a deeply placed mantle zone--\> grey matter and an outer region (marginal zone) --\>white matter, some of the grey matter migrates out of the deeply placed mantle zone & ends up on the surface of the cerebellum forming a layer on the outside- the cortex, * some grey matter remains in the deeply placed mantle zone & is known as the deep nuclei

Question 27

Brain Development of the Forebrain

Answer 27

* **As the telencephalon/ cerebral hemispheres** develop, pattern development is like in cerebellum i.e. **grey matter** from deeply placed mantle zone migrates out to lie on the surface of the cerebral hemisphere--\> **cerebral cortex** some of the grey matter **remains** in the depths of the cerebral hemisphere= **basal nuclei** * The 2 sides of the cerebral hemisphere are linked by many groups of fibres known as the **commissures** of the brain, the largest of which is the **corpus callosum**

Question 28

Neural Crest Cells | (what will they become?)

Answer 28

* **_Neural Crest Cells that remain adjacent to the neural tube_** eventually develop into neurons, which populate the peripheral ganglia ***(peripheral sensory neurons and neurons of the visceral motorsystem)*** * **_neural crest cells that migrate away from the neural tube_** produce neurons of the ***enteric nervous system, the medullary parts of the adrenal glands, glia, skin melanocytes, and a variety of craniofacial tissues***

Question 29

Anencephaly

Answer 29

* Failure of the rostral and caudal neuropore to close at the end of development (embryology) * abnormal persistence of these openings leads to a common malformation of brain and spinal cord where the nerve tissue may be exposed on the surface of the body