Development of the nervous system

Question 1

Which of the three germ layers does the nervous system arise from?

Answer 1

Ectoderm

Question 2

Which structure that arises in the ectoderm forms the basis of the nervous system?

Answer 2

Neural plate

Question 3

What happens to the neural plate once it starts to develop?

Answer 3

Starts to invaginate/fold > forms tube beneath ectoderm

Question 4

What is the tube that forms beneath the ectoderm when the neural plate invaginates known as?

Answer 4

Neural groove

Question 5

Where does the neural groove lie in relation to the notochord?

Answer 5

Neural groove is above notochord

Question 6

What happens to the neural groove after it begins to form?

Answer 6

Deepens > edges come together and join in midline > creates a tubular structure that can break free from overlying ectoderm

Question 7

What is the tubular structure formed from the folding of the neural groove called?

Answer 7

Neural tube

Question 8

How is the neural tube formed?

Answer 8

Neural groove deepens > edges come together and join in midline > creates a tubular structure that can break free from overlying ectoderm

Question 9

What is the first physical structure of the nervous system to form?

Answer 9

Neural tube

Question 10

Describe the neural tube?

Answer 10

Simple tube Single cell thick

Question 11

What does the neural tube go on to form?

Answer 11

Brain and spinal cord

Question 12

What does the hole in the neural tube go on to form?

Answer 12

Ventricular system

Question 13

What does the ventricular system arise from?

Answer 13

Hole in the neural tube

Question 14

Describe the gradient that exists in the neural tube?

Answer 14

Rostral to caudal gradient

Question 15

What is the consequence of the rostral to caudal gradient in the neural tube?

Answer 15

Development occurs faster at the head end and slower at the tail end Rostral end is older

Question 16

Describe the order of neural tube closure?

Answer 16

Closure tends to start towards middle, and leave ends of neural tube open

Zippers shut up and down from that midpoint

Question 17

Gove examples of birth defects that arise as a result of failure of closure of the neural tube?

Answer 17

Spina bifida

Anencephaly

Question 18

Are the five ‘zipping’ processes in the closure of the neural tube dependent on each other?

Answer 18

No, largely indepedent

Question 19

Briefly describe the segmentation process of the neural tube?

Answer 19

Rostral end of tube starts to well

3 distinct vesicles form

Further segmentation of these vesicles occurs

Question 20

Name the three vesicles initially formed by the segmetation of the neural tube? Which brain structure does each vesicle correspond to?

Answer 20

Prosencephalon (forebrain)

Mesencephalon (midbrain)

Rhombencephalon (hindbrain)

Question 21

What does the prosencephalon further divide into?

Answer 21

Telencephalon and diencephalon

Question 22

What does the rombencephalon further didvide into?

Answer 22

Seven segments (r1-r7)

Question 23

Whathappens to the part of the neural tube that does not become segmented?

Answer 23

Intact neural tube goes on to form spinal cord

Question 24

What do the pons and cerebellum arise from?

Answer 24

Metencephalon division of rhombencephalon

Question 25

What does the medulla arise from?

Answer 25

Myelencephalon division of rhombencephalon

Question 26

What are the major derivatives of the telencephalon?

Answer 26

Cortex, basal ganglia, hippocampus

Question 27

What are the major derivatives of the diencephalon?

Answer 27

Thalamus and hypothalamus

Question 28

What does the caudal part of the neural tube go on to form?

Answer 28

Spinal cord

Question 29

Describe the structure of the developing brain after neural tube segmentation has occured?

Answer 29

series of thin-walled bubbles

Question 30

What is the neural crest?

Answer 30

cells tha lie between the neural groove and neural tube after the neural tube forms

Question 31

What is the fate of the neural crest?

Answer 31

Cells migrate away to form a variety of structures: - melanocytes - PNS - muscle, cartilage and bone of skul, jaw, face and pharynx - dentine

Question 32

Why are neural crest cells able to migrate so far throughout the developing embryo?

Answer 32

Cells are incredibly mobile

Question 33

What is the longest migration that the neural crest cells undergo?

Answer 33

Enteric migration Enter gut at oesophagus and migrate down to anal end

Question 34

What feature of neural crest cells to cancer cells regain when they metastasise?

Answer 34

Ability to migrate through body tissues

Question 35

What is the epithelium of the neural tube called? Describe it?

Answer 35

Neuroepithelium Sinle cell thick, pseudostratified columnar

Question 36

How is the cortex developed?

Answer 36

Neuroepithelium adds layers (6) Dividing cells at the base move to new position at the outer

Question 37

Which defects can lead to cortex malformation?

Answer 37

Defects in genes that affect migration

Question 38

What is induction?

Answer 38

Developmental process in neurons that gives us the variety of neuronal types that we need for a functioning brain Process for differentiating neurons

Question 39

Describe the process of induction that occurs in the spinal cord?

Answer 39

Neural tube sits on top of notochord, which acts as prime organiser Notochord sends out signals which affects closest part of neural tube Floor plate formed \> ANTERIOR/VENTRAL identified Roof plate formed \> POSTERIOR/DORSAL

Question 40

Why is the floor plate so important in spinal cord development?

Answer 40

Cells start releasing signals \> forms diffusion gradient up and across rest of spinal cord \> cells immediately next to them know that they are in ventral part of spinal cord \> form ventral horn motor neurons

Question 41

What is the consequence of the absence of the floor plate?

Answer 41

No motor neurons develop

Question 42

How are interneurons induced in the spinal cord?

Answer 42

Appear just dorsal to motor neurons due to inductive events

Question 43

How do axons grow?

Answer 43

Grow out to meet target cell Towed into position by growth cone

Question 44

What are pioneer axons?

Answer 44

First axons to appear Form a scaffold which later axons can build upon/follow

Question 45

What are growth cones?

Answer 45

Structures which guide axon growth and tow them into position

Question 46

Describe the structure of growth cones?

Answer 46

Dynamic structure of cytoskleleton

Question 47

What guides axon navigation?

Answer 47

Growth steers towards target due to diffusible and membrane bound signals

Question 48

Is the development of the nervous system complete at birth?

Answer 48

No; only a crude nervous system

Question 49

What is the critical period in the development of the nervous system?

Answer 49

Time after birth in which refinement of the crude NS occurs

Question 50

What is the effect of temporary eye closure during the critical period on the visual cortex?

Answer 50

Cortex changes Open eye has greatly increased representation , deprived eye has greatly reduced representation