Embryology

Question 1

Neurulation

Answer 1

Neural plate–> Neural folds–> Neural groove–> Neural tube or neural crest

Question 2

What does the neural tube form?

Answer 2

Brain (rostral to 4th pair of somites) and spinal cord (caudal to 4th pair)

Question 3

What does the neural crest form?

Answer 3

PNS and variety of non-neural structures (melanocytes, merkel cells, chromaffin cells)

Question 4

What does the neural canal form?

Answer 4

Ventricles of the brain and central canal of the spinal cord

Question 5

3 layers that form spinal cord

Answer 5

Ventricular, intermediate, marginal

Question 6

Ventricular layer of spinal cord

Answer 6

• Lines neural canal
• Composed of rapidly dividing neuroepithlial cells
• Forms neurons and glial cells and ependyma.

Question 7

Intermediate layer of spinal cord

Answer 7

• Composed of neuroblasts.

- Forms gray matter (containing ALL spinal cord nerve cell bodies)

Question 8

Marginal layer or spinal cord

Answer 8

• Includes axons of neuroblasts

- Becomes white matter

Question 9

Are neurons mitotic?

Answer 9

No. Loose mitotic ability when neuroblasts develop processes. Note: glial cells still mitotic

Question 10

Where are the alar and basal plates formed?

Answer 10

In the intermediate area

Question 11

Where are cell bodies and axons found in relation to the spinal cord?

Answer 11

Cell bodies: inside the spinal cord.

Axons: outside the spinal cord

Question 12

Sulcus limitans

Answer 12

Divides alar and basal plates

Question 13

Alar plates

Answer 13

• Dorsal

- 2nd order SENSORY. Primarily of dorsal horn

Question 14

Basal plates

Answer 14

• Ventral

- MOTOR neurons of ventral (innervate skeletal muscles) and lateral horns (preganglionic)

Question 15

What are primary sensory neurons a part of?

Answer 15

The PNS

Question 16

Where are dorsal root ganglia formed?

Answer 16

Neural crest

Question 17

Where is the roof plate located?

Answer 17

Above the Alar plate (dorsal midline)

Question 18

Where is the floor plate?

Answer 18

Below the Basal plate (ventral midline)

Question 19

What is the function of the roof and floor plates?

Answer 19

Routes for axons to cross the midline of the spinal cord (especially the floor plate)

Question 20

Do roof and floor plates have neuroblasts?

Answer 20

No

Question 21

Neurites

Answer 21

Multiple cytoplasmic processes (One axon + multiple dendrites)

Question 22

What is the path of axons of multipolar motor neurons?

Answer 22

Intermediate layer(basal plate)–> marginal layer–> ventral root (exiting spinal cord)–> final destination

Question 23

Axons of motor neurons in ventral horn synapse where?

Answer 23

Skeletal muscle fibers

Question 24

Axons of motor neurons in the lateral horn synapse where?

Answer 24

Peripheral autonomic ganglia (sympathetic or parasympathetic)

Question 25

What may axons of multipolar sensory neurons (secondary) do?

Answer 25

1. Terminate or synapse within future gray matter (intermediate layer) 2. Enter marginal layer (white matter) where they ascend/descend as tracts or neural pathways

Question 26

What does the dorsal horn receive it's primary synaptic input from?

Answer 26

Sensory neurons in the dorsal root ganglia

Question 27

Are dorsal root ganglia (sensory neurons of the sensory ganglia) pseudounipolar, unipolar, multipolar, bipolar?

Answer 27

Pseudounipolar and unipolar

Question 28

What cell type do dorsal root ganglia begin as embryologically?

Answer 28

Bipolar

Question 29

Are there synapses in the dorsal root ganglion?

Answer 29

No

Question 30

Do axons from the sensory neurons in the dorsal horn stay in the CNS or leave?

Answer 30

Stay in the CNS.

Question 31

If an axon travels in both the CNS and the PNS, will it be myelinated by oligodendrocytes or Schwann cells?

Answer 31

Both

Question 32

Schwann cells

Answer 32

Myelinating glial cells in the PNS

Question 33

Oligodendrocytes

Answer 33

Myelinating glial cells in the CNS. Multiple processes. Can form sheaths around multiple axons

Question 34

When does myelination occur?

Answer 34

4th month prenatally and into 2nd yr of life

Question 35

What are oligodendrocytes and Schwann cells derived from?

Answer 35

Neural crest cells

Question 36

Multiple sclerosis

Answer 36

autoimmune response that destroys myelin sheath and cells. Leads to inflammation, injury, and scarring

Question 37

Positive Babinski sign

Answer 37

Extend toes in infants (normal--incomplete myelination so primitive reflex not inhibited by cerebral cortex). If in adults, indicates pathology of the CNS

Question 38

Spinal cord length at 12 wks

Answer 38

Still about the same length as the vertebral column

Question 39

Spinal cord length at birth?

Answer 39

L2 or L3 level.

Question 40

Spinal cord length in adults?

Answer 40

Inferior border of the L1 (average)

Question 41

will the spinal cord level be at the same level in adults as the original corresponding vertebrae?

Answer 41

No

Question 42

What secondary vesicles does the forebrain (prosencephalon) form?

Answer 42

Telencephalon and diencephalon

Question 43

What does the telencephalon form?

Answer 43

Cerebral cortex. Corpus striatum Olfactory bulbs

Question 44

What does the diencephalon form?

Answer 44

``` Thalamus Hypothalamus Epithalamus Subthalamus Optic nerve and retina Posterior lobe of pituitary ```

Question 45

What secondary vesicle does the midbrain form?

Answer 45

Mesencephalon

Question 46

What does the mesencephalon form?

Answer 46

Tectum Tegmentum Cerebral peduncles

Question 47

What secondary vesicles does the hindbrain (rhombencephalon) form?

Answer 47

Metencephalon and myelecephalon

Question 48

What does the metencephalon form?

Answer 48

Pons | Cerebellum

Question 49

What does the myencephalon form?

Answer 49

Medulla

Question 50

What does the caudal neural tube form?

Answer 50

Spinal cord

Question 51

Brain stem

Answer 51

Midbrain + pons + medulla

Question 52

What structure are the lateral ventricles associated with?

Answer 52

Cerebral hemispheres

Question 53

What structure is the third ventricle associated with?

Answer 53

Diencephalon

Question 54

What structure is the cerebral aqueduct associated with?

Answer 54

Mesencephalon

Question 55

What structure is the fourth ventricle associated with?

Answer 55

Rhombencephalon (hindbrain)

Question 56

Cervical flexure

Answer 56

Junction of hindbrain and spinal cord

Question 57

Cephalic flexure

Answer 57

Midbrain region

Question 58

Pontine flexure

Answer 58

Middle area of rhombencephalon (appears and secondary brain vesicles form)

Question 59

Closed medulla

Answer 59

Continuous with spinal cord. Has a central canal

Question 60

Open medulla

Answer 60

underlies the 4th ventricle

Question 61

Is there rearrangement of the white and gray matter of the myelecephalon?

Answer 61

Yes

Question 62

Where does the sulcus limitans remain in adults?

Answer 62

Pons and medulla

Question 63

How is the cerebellum formed?

Answer 63

Thickening of the alar plate (rhombic lip)

Question 64

What separates the anterior and posterior lobes of the cerebellum?

Answer 64

Primary fissure

Question 65

What separates the flocculonodular lobe from the rest of the cerebellum

Answer 65

Posterolateral fissure

Question 66

Cerebellar cortex

Answer 66

gray matter on outside of cortex with fiber tracts (white matter) and deep nuclei (gray) in center of cerebellum

Question 67

How do the optic nerve and retina form?

Answer 67

Outgrowth of diencephalon (means optic nerve a fiber tract)

Question 68

What is the dual ectodermal origin of the pituitary (hypophysis)

Answer 68

Neuroectoderm and oral ectoderm

Question 69

Infundibulum

Answer 69

Downward extension of diencephalon neuroectomderm (forms posterior lobe of pituitary)

Question 70

Rathke's Pouch

Answer 70

Outgrowth of ectoderm from primitive oral cavity. Makes up anterior lobe of pituitary.

Question 71

Where is the pituitary?

Answer 71

Sella turcica

Question 72

How does telencephalon growth occur?

Answer 72

In a "C" shape. Insula used as "pivot" point

Question 73

Basal ganglia

Answer 73

made up of 7 deep nuclei

Question 74

Fiber bundles (examples)

Answer 74

Include internal capsule, corpus callosum

Question 75

Olfactory tract

Answer 75

Outgrowth of telencephalon. Not associated with brain stem nucleus

Question 76

How do the lateral ventricles communicate with the 3rd ventricle?

Answer 76

Interventricular foramina (of monro)

Question 77

Where does the choroid plexus form?

Answer 77

All ventricles (floor of lateral, and roof of 3rd and 4th)

Question 78

Tela choroidea

Answer 78

Pia + modified ependyma

Question 79

Elements of choroid plexus

Answer 79

Choriodal epithelium (modified ependyma), pia mater, pial blood vessels

Question 80

How is the choroid plexus formed?

Answer 80

Blood vessel proliferation in pia pushes tela choroidea into ventricle in certain locations

Question 81

Which 2 cranial nerves have no cranial nerve nuclei?

Answer 81

Cranial nerves I and II

Question 82

Cranial nerve I

Answer 82

Telencephalon

Question 83

Cranial nerve II

Answer 83

Diencephalon

Question 84

Cranial nerve III, IV

Answer 84

Mesencephalon

Question 85

Cranial nerves V to XII

Answer 85

Metencephalon and myelencephalon

Question 86

Where do cranial nerves III-XII originate or send input to:

Answer 86

Cranial nerve nuclei within brainstem

Question 87

Motor cranial nerve nuclei functional component types

Answer 87

1. general somatic efferent 2. general visceral efferent 3. special visceral efferent

Question 88

Sensory cranial nerve nuclei functional component types

Answer 88

1. general somatic afferent 2. special somatic afferent 3. general visceral afferent 4. special visceral afferent

Question 89

What forms the motor cranial nerve nuclei?

Answer 89

Basal plate neurons develop into 3 columns on both sides of the brain stem

Question 90

What forms the sensory cranial nerve nuclei?

Answer 90

Alar plate neurons forms 4 columns on both sides of the brain stem

Question 91

What are some of the components of the PNS formed by neural crest cells?

Answer 91

``` Dorsal root ganglia Cranial ganglia Autonomic ganglia Enteric ganglia and nerves Schwann cells Satellite cells Connective tissue of aorta Arachnoid and pia Merkel cells Chromaffin cells of adrenal medulla Odontoblasts Melanocytes Cartilage and bones of head and neck ```