Development Of Nervous System

Question 1

What is the notochord?

Answer 1

Refers to a rod of cells

Question 2

Where is the notochord located?

Answer 2

Runs in the midline of the embryo

In the mesoderm layer

Question 3

During what process is the notochord formed?

Answer 3

Gastrulation

Question 4

What is the function of the notochord?

Answer 4

Releases signalling molecules
Which diffuse upwards to the overlying ectoderm
Stimulate it to differentiate into neuroectoderm

Question 5

What is the neural plate?

Answer 5

Refers to a thickening of neuroectoderm

Question 6

What are neural folds?

Answer 6

Refers to the edges of the neural plate moving upwards

Question 7

What is the neural groove?

Answer 7

Refers to the depression in the neural plate between the neural folds

Question 8

What is neurulation?

Answer 8

Refers to the formation of the neural tube

Question 9

How does neurulation occur?

Answer 9

Elevated edges of neural plate curl towards each other
Meet each other in the midline
Fuse together to form neural tube

Question 10

What are neuropores?

Answer 10

Refers to openings at the ends of the neural tube

Question 11

Where are the anterior and posterior neuropores located?

Answer 11

Anterior neuropore - cranial end of neural tube

Posterior neuropore - caudal end of neural tube

Question 12

What happens to the neuropores during development?

Answer 12

Close up completely

Question 13

What developmental abnormality causes neural tube defects?

Answer 13

Neuropores do not close up completely

Question 14

What are two types of neural tube defects?

Answer 14

Spina bifida/cleft spine

Anencephaly

Question 15

What developmental abnormality causes spina bifida?

Answer 15

Posterior neuropore doesn’t close up completely

Question 16

Where does spina bifida occur in the spine?

Answer 16

Lumbo-sacral region

Question 17

What is the structure of a low-severity spina bifida?

Answer 17

Spinal cord is deep

Cyst made up of meninges and CSF is near the surface

Question 18

What is the structure of a high-severity spina bifida?

Answer 18

Cyst made up of meninges and CSF is deep

Spinal cord is near the surface

Question 19

What are the signs of spina bifida? Why do they occur?

Answer 19

Neurological deficits, due to problems with spinal cord
But no cognitive delay because no problem with brain

Hydrocephalus, due to meninges being abnormally tethered to spinal cord

Question 20

What developmental abnormality causes anencephaly?

Answer 20

Anterior neuropore doesn’t close up completely

Question 21

What is meant by anencephaly?

Answer 21

Cranial structures do not develop, including the brain

Question 22

How are neural tube defects diagnosed?

Answer 22

Raised maternal serum alpha-fetoprotein

Ultrasound scan

Question 23

Why is maternal serum alpha-fetoprotein raised with neural tube defects?

Answer 23

This is an embryonic protein that leaks out of the neural tube defect into amniotic fluid and then maternal circulation

Question 24

How are neural tube defects prevented?

Answer 24

Folic acid pre-conceptually for 3 months and during the first trimester

Question 25

What does the spinal cord develop from?

Answer 25

Most of caudal end of neural tube

Question 26

How does the cauda equina develop?

Answer 26

Initially vertebral column and spinal cord are same length But then vertebral column grows faster Spinal nerve roots elongate downwards to exit at their corresponding intervertebral foramina

Question 27

How many primary brain regions are there? What are they called?

Answer 27

Three | Forebrain, midbrain and hindbrain

Question 28

When do the primary brain regions develop?

Answer 28

As the neural folds form

Question 29

When do the primary brain vesicles develop?

Answer 29

As the neural tube forms

Question 30

How many secondary brain vesicles are there?

Answer 30

Five

Question 31

What are flexures?

Answer 31

Folds in the cranial neural tube

Question 32

Why do flexures form?

Answer 32

Cranial neural tube grows and runs out of space | So it folds to maximise its use of space

Question 33

How many flexures are there? What are they called?

Answer 33

Two | Cervical and cephalic

Question 34

Where along the cranial neural tube is the cervical flexure?

Answer 34

Between the spinal cord and hindbrain

Question 35

Where along the cranial neural tube is the cephalic flexure?

Answer 35

In the midbrain

Question 36

What does the ventricular system develop from?

Answer 36

The lumen of the neural tube

Question 38

What is hydrocephalus?

Answer 38

Accumulation of CSF in the ventricular system

Question 39

How is the neural tube organised?

Answer 39

Deep layer Intermediate layer Marginal layer Dorsal end Ventral end

Question 40

What is the deep layer of the neural tube made up of?

Answer 40

Neuroepithelial cells

Question 41

What is the function of the neuroepithelial cells of the deep layer of the neural tube?

Answer 41

Line the ventricular system | Produce CSF

Question 42

What is the intermediate layer of the neural tube made up of?

Answer 42

Neuroblast cell bodies

Question 43

What is the marginal layer of the neural tube made up of?

Answer 43

Processes of neuroblasts

Question 44

What are the dorsal and ventral ends of the neural tube made up of?

Answer 44

Dorsal end is made up of roof plate Ventral end is made up of floor plate

Question 45

What is the function of the roof and floor plates of the neural tube?

Answer 45

Regulate dorsal and ventral patterning of the neural tube | Divide intermediate layer into alar plate and basal plate

Question 46

Where are neural crest cells located in the embryo?

Answer 46

Lateral border of neuroectoderm

Question 47

What happens to neural crest cells during development?

Answer 47

Become displaced and enter the mesoderm Undergo epithelial to mesenchymal transition Migrate to other regions of embryo

Question 48

What do neural crest cells develop into?

Answer 48

Wide range of structures E.g. cranial nerve ganglia, dorsal root ganglia, autonomic ganglia, Schwann cells, connective tissue of face and skull, septum of heart, melanocytes

Question 49

What developmental abnormalities can occur with neural crest cells?

Answer 49

Problems with migration Problems with morphogenesis

Question 50

What is an example of a condition with abnormal development of neural crest cells?

Answer 50

DiGeorge syndrome

Question 51

What abnormalities are present in people with DiGeorge syndrome due to abnormalities in neural crest cell development?

Answer 51

Congenital aphasia of thymus gland Aplastic parathyroid glands Cardiac defects

Question 52

What body system is the first to begin development?

Answer 52

Nervous system

Question 53

Which body system is the last to complete development?

Answer 53

Nervous system

Question 54

When does the nervous system complete development?

Answer 54

End of first year after birth

Question 55

Which body system is the most susceptible to damage during pregnancy? Why?

Answer 55

Nervous system | Because it is developing throughout the entire pregnancy

Question 56

What is the relative position of the alar plate?

Answer 56

Dorsal

Question 57

What is the function of the alar plate?

Answer 57

Sensory functions

Question 58

What is the relative position of the basal plate?

Answer 58

Ventral

Question 59

What are the functions of the basal plate?

Answer 59

Motor functions

Question 60

What causes hydrocephalus?

Answer 60

Blockage of ventricular system | E.g. stenosis, infection, tumour

Question 61

How is hydrocephalus treated?

Answer 61

Use of shunt

Question 62

How does the brain develop?

Answer 62

Primary brain regions develop Then primary brain vesicles Then secondary brain vesicles

Question 63

How does the ventricular system develop?

Answer 63

When the five secondary brain vesicles form, there is an empty space in each one These empty spaces develop into the ventricles