Second run

Question 1

Describe the transformation of the neural groove (and timeline)

Answer 1

• By the end of 3rd wk folds begin to fuse to form neural tube (10th C-stage) - It begins in the from the middle and moves rostrally and caudally - The openings still left at ends - neuropores Rs & Cad close on d-24&27 C.s (11&12) - The neural tube is the forerunner of brain and spinal cord

Question 2

What is the neuroepithelium

Answer 2

The cells lining the neural tube

It will give rise to the neurons and most other cells in CNS

Question 3

What is the neural crest

Answer 3

-Cells from the edges of the neural plate (border with

other ectoderm) that are not incorporated

into the tube and gather dorsal to it

-the migrate dorsally an latterly to from various other

ganglia and nonnerual elements

Question 4

What are placodes

Answer 4

Thickened regions of the ectoderm of the embryonic

head

(remain in the ectoderm after forming of tube)

That are the origin of some neurons and other cells in

the peripheral sense organs

Question 5

What is the first population of cells produced in the neural tube and when does it happned

Answer 5

• Neurons that are formed between the 4^th and 20^th week

Question 6

Describe the initial development of neurons

Answer 6

They migrate , grow cytoplasmic processes and form synaptic connections with other neurons

Question 7

What is apoptosis specifically in neurons

Answer 7

-cell death

• Many neurons die in the normal course of development
• It is genetically programmed process
• The neurons that die are those that failed to make synaptic connections

Question 8

Describe the development of sensory ganglia neurons

Answer 8

• they are derived from the neural crest
• they send neurites to the neural tube and the PNS
• by the 8^th wk the central directed neurites have

extensive synaptic connections with spinal

neurons

• this process continues long after birth

Question 9

What are neuroglial cells (Glia) and where do they

develop

Answer 9

Cells in the nervous system that are not neurons

the CNS the develop in the neural tube

in the PNS the develop from the neural crest

Question 10

what is the first development of neuroglial cells

Answer 10

radial glia - it happens alongside the first neurons

the develop processes from the lumen to the outside

surface of the neural tube

they guide the migration of the young neurons

Question 11

where does neurons originate

Answer 11

in the CNS from the neural tube

in the PNS from the neural crest

Question 12

What is neurulation

Answer 12

Neurulation is a process in which the neural plate bends up and later fuses to form neural tube that will differentiate into the brain and the spinal.

Question 13

What are the first signs of the CNS

Answer 13

before the closure of the neural tube a visibly bigger rostral end of the embryo Precede the brain (with irregularities corresponding its major divisions)

while the remainder of the neural tube becomes the spinal cord.( the closing of the caudal neuropore correspond to its upper lumbar segments)

Question 14

What is secondary neurulation (and when)

Answer 14

The forming of the part of the spinal cord further caudally of the upper lumbar segments

By The joining of vesicles derived from the caudal eminence

continuous with the lumen about 3r weeks after the caudal neuropores closes

Question 15

What is the caudal eminence?

Answer 15

a mass of pluripotent (capable of giving rise to several different cell type ) cells located dorsal to the developing tailbone

Question 16

What are the major divisions of the brain and when do they develop

Answer 16

three major divisions appear at the end of the 4th wk

the prosencephalon (forebrain)

mesencephalon (midbrain)

and rhombencephalon (hindbrain)

During the 5th week, secondary swellings develop in the prosencephalon and rhombencephalon,

So now five: the Telencephalon & diencephalon (both from prosencephalon) mesencephalon,metencephalon & myelencephalon (both from rhombencephalon)

Question 17

What are neuromeres

Answer 17

A longitudinal division of The early embryonic CNS into smaller segments as the brain develops its segments become indistinguishable but the division of the spinal cord persist throughout life

Question 18

What are the 4 division that form in the neural tube

Answer 18

sulcus limitans -A longitudinal groove on in the inner side of each lateral

wall that separates:

the dorsal Alar plate fromventral the basal plate –

they acquire Afferent (sensory) and efferent (motor) connections respectively , running from the

rostral end of the mesencephalon to the caudal end of the spinal cord.

the left and plates become separated by a roof plate and floor plate

Question 19

what connections are formed by the basal and alar plates

Answer 19

Some basal plate cells differentiate into motor neurons, with axons that grow out into the

developing muscles.

The growing axons of neurons of the sensory ganglia enter the alar plate.

Question 20

What the 5 pts of the embryonic brain develop into

Answer 20

Mylencephlon = Medulla oblongata

Metencephalon = Pons and cerebellum

Mesencephalon = Midbrain, consisting of tectum and cerebral peduncles

Diencephalon = Thalamus, epithalamus, hypothalamus, and subthalamus

Telencephalon = Cerebral hemispheres, each containing olfactory system,

corpus striatum, cerebral cortex, and white matter

Question 21

What develops from The lumen of the neural tube

Answer 21

It becomes the ventricular system and the neural canal

A lateral ventricle develops in each cerebral hemisphere.

The third ventricle is in the diencephalon,

the fourth ventricle bounded by the medulla, pons, and cerebellum.

The third and fourth ventricles are connected by a narrow channel, the cerebral aqueduct,

Through the midbrain.

The lumen also remains narrow in the caudal part of the medulla and throughout the

spinal cord, where it becomes the central canal.

Question 22

Describe the Development of the Meninges

Answer 22

The membranous covering of the CNS appear as follows

• On the 4th week A primary (or primitive) meninx that is derived from the mesoderm appeas
• After 1 week fluid filled spaces appear in it
• Subsequent differentiation into 3 layers along the cranial cavity and spinal canal
  
  • The Pia matter – closest to the nervous system
  • The arachnoid matter
  • The dura matter - outer layer closest to the bone

The subarachnoid space ,containng cerebrospinal fluid

(CSF), is between the inner two meningeal layers.

Question 23

What are the 3 flexures in the neural tube where they from and why do they exist

Answer 23

Flexures in the neural tube help to fit the the initially cylindrical brain in what will eventually

be a round head.

The first to form are

cervical flexure at the junction of the rhombencephalon with the spinal cord and the

mesencephalic flexure at the level of the midbrain.

Next The pontine flexure in the metencephalon.

These flexures in the brain ensure that the optical axes of the

eyes (which connect with the prosencephalon) are at right angles to the axis of the vertebral

column. necessary feature of the erect posture of humans.

contrasts with the posture of quadrupedal animals.

Question 24

What is the difference between Ganglia and nuclei

Answer 24

ganglia are clusters of nerve cell bodies in the PNS whereas nuclei are clusters of nerve cell bodies in the CNS

Question 25

what are fiber tracts

Answer 25

Projection fibers of the brain, also known as projection tracts of the brain are a type of white matter tract (axons) that connects the cortex with other areas in the CNS

Question 26

what is anencephaly

Answer 26

failure of the neural folds to fuse In the rostral end – forebrain , cranial vault and much of the

scalp is missing , the diencephalon and brainstem are exposed.

Question 27

what is myeloschisis

Answer 27

failure of the neural folds to fuse In the caudal end

nonfunctional nervous tissue in the lumbosacral region is exposed

Myeloschisis is the severest form of spina bifida

Question 28

What is meningomyelocele,

Answer 28

The dura matter , vertebral arch and skin are missing and there is a visual lump above the surface

Of the caudal part of the spinal cord or associated nerve roots

If the neural parts remain in the vertebral canal is a meningocele – a lump containing CSF

Question 30

What is Spina bifida occulta

Answer 30

the dura and skin remain intact but one

or more bony vertebral arches fail to develop.

Question 31

What is Hydrocephalus

Answer 31

The csf flow is obstructed and it accumaltes at the ventricles , and the increased pressure causes nervous tissue destruction, while the head can be greatly enlarged.