1.3 Development of CNS and PNS

Question 1

Define gyrus…

Answer 1

Raised bit of the fold of the cerebrum

Question 2

Define sulcus…

Answer 2

Dip of the fold of part of the cerebrum

Question 3

Which part of the cortex is in the post central sulcus?

Answer 3

Sensory

Question 4

Which part of the cortex is in the pre central sulcus?

Answer 4

Motor

Question 5

What is the cortex?

Answer 5

Thin layer of grey mater in the cerebrum

Question 6

At which week does CNS development occur?

Answer 6

Week 3

Question 7

Which part of the embryo forms the NEURAL PLATE?

Answer 7

It is formed by the ectoderm in the mid dorsal region.

Question 8

What other cells do the neural crest cells form?

Answer 8

Parafollicular cells of thyroid 
Dorsal root ganglion 
Melanocytes
Odontoblasts - teeth
Adrenal medulla 
Autonomic ganglia 
Trocheal cartilage 
Schwann cells

Question 9

What forms the ventricles?

Answer 9

Neural tube lumen

Question 10

Where does fusion of the neural tube begin?

Answer 10

Cervical region

Question 11

How does the cavity of the tube remain in communication with the amniotic cavity?

Answer 11

Cephalic and caudal neuropores

Question 12

Which neuropore closes first and at which day?

Answer 12

Cephalic - day 25

Caudal - day 27

Question 13

Which conditions can occur if the neuropores don’t close correctly?

Answer 13

Cephalic - anencephaly

Caudal - spina bifida

Question 14

What can prevent the incorrect closing of these neuropores?

Answer 14

Folic acid - 400micrograms

Question 15

How can a fusion deficit be detected?

Answer 15

Ultrasound scan and mother’s raised levels of alpha-fetoprotein

Question 16

Explain; meningocele, myelomeningocele and spina bifida occulta

Answer 16

Meningocele - Protrusion of meninges through a gap in the spine
Myelomeningocele - Spinal cord and meninges protrude; spinal cord not formed properly
Spina bifida occulta - causes a cleft which is covered by the skin

Question 17

What are the three primary brain vesicles that form by the fourth week

Answer 17

Prosencephalon, Mesencephalon and Rhombocephalon

Question 18

By what week do the 5 secondary brain vesicles form?

Answer 18

5th week

Question 19

Name the 5 secondary brain vesicles and what they form

Answer 19

Prosencephalon - Telencephalon (cortex), Diencephalon(thalamus and hypothalamus)
Mesencephalon - Midbrain
Rhombocephalon - Metencephalon(pons and cerebellum), Myelencephalon(medulla)

Question 20

Which ventricles supply each of the 5 brain vesicles?

Answer 20

Telencephalon - lateral centricles
Diencephalon - third ventricle
Metencephalon - fourth ventricle

Question 21

When does the surface of the brain fold?

Answer 21

15 weeks, major sulci formed by 28 weeks

Question 22

By which week do all the neurons form?

Answer 22

12 weeks

Question 23

What makes the brain grow after that time?

Answer 23

Synaptic connections - glial growth

Question 24

How can you form new connections?

Answer 24

New ones can only be made by reorganisation

Question 25

Why do rapidly growing cells require lots of nourishment?

Answer 25

Cells need to reach a certain size before dividing - G1

Question 26

By which age would re-nourishment not restore the brain?

Answer 26

Age of 2

Question 27

Define the somites; dermatome, myotome, sclerotome

Answer 27

Dermatome - skin
Myotome - muscles
Sclerotome - connective tissue

Question 28

What is the grey matter organized into?

Answer 28

Basal lamina - ventral - motor

Alar lamina - dorsal - sensory

Question 29

What do the lamina form in the spine?

Answer 29

They form the dorsal and ventral horn

Question 30

How many pairs of cranial and spinal nerves are found in spinal nerves?

Answer 30

Cranial - 12

Spinal - 31

Question 31

Which neurons in the CNS are formed from the neural tube?

Answer 31

Preganglionic autonomic neurons and motor

Question 32

Which PNS neurons form the neural crest?

Answer 32

sensory and post ganglionic