Nervous system development

Question 1

Steps in neural tube formation

Answer 1

1. Ectoderm overlying notochord thickens = neural plate (neuroectoderm)
2. Folding of neural plate
3. Fusion of neural plate
4. Cr. and cd. neural openings= neuropores
5. Separation of neural tube from the overlying ectoderm

Question 2

Neural crest cells formation

Answer 2

Before fusion, cells at both ends of neural tube separate and form neural crest cells

Question 3

What do neural crest cells differentiate into?

Answer 3

PNS (sympathetic, motor neurons), melanocytes, odontoblasts, adrenal medulla, cr. and facial bones, CT of pharyngeal arches

Question 4

What does the neural tube give rise to?

Answer 4

CNS

Question 5

When does neuropores close for a human?

Answer 5

Cr. : 25 days
Cd. : 28 days

Question 6

What are the 3 flexures of the neural tube?

Answer 6

Midbrain
Cervical
Pontine

Question 7

Midbrain flexure

Answer 7

Level of mesencephalon (disappears in domestic animals)

Question 8

Cervical flexure

Answer 8

Brain and SC (persist slightly in domestic animals)

Question 9

Pontine Flexure

Answer 9

Junction of metencephalon and myelecenphalon but direction is opposite to midbrain and cervical

Question 10

The ______ part of the ______ becomes spinal cord

Answer 10

1. Distal
2. neural tube

Question 11

What are the 5 vesicles of the neural tube?

Answer 11

1& 2: Forebrain (prosencephalon)- telecephalon and diencephalon
3. Mid brain (Mesencephalon)
4 & 5: Hindbrain (rhombencephalon)- metencephalon and myelencephalon

Question 12

Structures derived from the telecephalon (forebrain)

Answer 12

Cerebrum
Lateral ventricles
Olfactory (1) - sensory

Question 13

Structures derived from the diencephalon (forebrain)

Answer 13

Thalamus and hypothalamus
3rd ventricles
Optic nerve (2)

Question 14

Structures derived from the midbrain (mesencephalon)

Answer 14

Midbrain
Mesencephalic aqueduct
Oculomotor (3) and trochlear (4) nerves- motor

Question 15

Structures derived from the metencephalon

Answer 15

Pons and cerebellum
4th ventricle
Trigeminal nerve (5)- sensory (mostly) and motor

Question 16

Structures derived from the myelencephalon

Answer 16

Medulla oblongata
Fourth ventricle
C6-12

Question 17

Terminal end of the SC in relation to the vertebral column

Answer 17

Dog: L 6 & 7
Ruminants: S1
Swine: S 1& 2
Horse: S2
Cat: L7- S3`

Question 18

Myelencephalon cranial nerves

Answer 18

Abducent (motor)
Facial (motor mostly and sensory)
Vestibulocochlear (sensory)
Glossopharyngeal (sensory and motor)
Vagus (Sensory and motor)
Accessory (motor)
hypoglossal (motor)

Question 19

What are the parts of the neural tube?

Answer 19

Ependymal
Mantle
Marginal
Dorsal (alar) plate:
Ventral (basal) plate
Roof
Floor

Question 20

Ependymal

Answer 20

Line brain cavities, central canal of the SC, lines choroid plexus

Question 21

Mantle

Answer 21

Neuroblast: neurons
Gliablast: glia cells
Gray matter of the CNS

Question 22

Marginal

Answer 22

White matter of the CNS
Axons of neurons
Glia cells

Question 23

Dorsal (alar) plate

Answer 23

Sensory neurons
Association neurons (form bulk of nervous system except motor neurons and dorsal root ganglion neurons)

Question 24

Ventral (basal) plate

Answer 24

Extends up to the mesencephalon
Motor neurons innervating skeletal muscles
Sympathetic and parasympathetic neurons located in the lateral horn of the SC

Question 25

Roof

Answer 25

Dorsal Pathway for nerve fibers crossing from one side to the other

Question 26

Floor

Answer 26

Ventral Pathway for nerve fibers crossing from one side to the other

Question 27

Where do nerves originate from?

Answer 27

Axons of neurons in ganglia or nuclei

Question 28

What originates from neural crest cells?

Answer 28

Dorsal root ganglia Autonomic ganglia Schwann cells Satellite cells

Question 29

Where does sensory nuclei and motor nuclei of cr. nerves originate?

Answer 29

Alar plate Basal plate 1

Question 30

Where do sympathetic fibers originate?

Answer 30

Nuclei in the lateral horn of the thoraco-lumbar SC

Question 31

Where do parasympathetic fiber originate?

Answer 31

Nuclei in brainstem (fibers in 3, 7, 9 and 10) Nuclei in the lateral horn of the sacral SC

Question 32

Where is gray matter?

Answer 32

Dorsal horn: association neurons (dorsal plate) Ventral horn: alpha motor neurons (ventral plate) Lateral horn: sympathetic (thoracolumbar) and parasympathetic (sacral)

Question 33

Where is white matter

Answer 33

Axons of neurons Neuroglia cells

Question 34

Meninges

Answer 34

Dura mater: mesoderm Pia-arachnoid: neural crest cells 4 ventricles: 2 later (cerebrum), 3 (thalamus), 4 (pons, medulla oblongata)

Question 35

What connects the lateral ventricles with the 3rd ventricle?

Answer 35

Interventricular foramen

Question 36

What connected the 3rd and 4th ventricles?

Answer 36

Cerebral aqueduct

Question 37

Hydrocephalus

Answer 37

Accumulation of CSF in the ventricular system Caused by excess fluid production, impaired drainage, blockage in the ventricles (cerebral aqueduct)

Question 38

Hydranencephaly

Answer 38

Cerebral hemispheres are replaced by 2 fluid sacs Caused by malformation of mantel layer of telencephalon

Question 39

Cerebellar dyplasia and atrophy

Answer 39

Purkinje cells and granular neurons are affected Common in kittens and calves Caused by prenatal viral infection

Question 40

Dysraphias

Answer 40

Results from defects in the normal closure of neural tube

Question 41

Cr. Bifida

Answer 41

Cleft in neurocranium Meningocele: meninges herniate Meningoencephalocele: meninges in cerebal hemissphere herniate Common in sheep and pigs

Question 42

What causes cr. bifida?

Answer 42

Failure to close frontal/ parietal suture Defect in the closure of cr. part of neural tube

Question 43

Spinal bifida

Answer 43

Affects the SC Meningocele: meninges herniate Meningomyelocele: Meninges and SC herniate

Question 44

What is spinal bifida caused by?

Answer 44

Defect in the formation and fusion of verteral arch which is related to the abnormal closure of nerual tube

Question 45

Anencephaly

Answer 45

Absence of telencephalon and much of diencephalon Cranium fails to develop which is caused by dysraphias of cr. neural tube