Central Nervous System

Year 1 - Semester 2

Which 2 structures make up the CNS?

brain and spinal cord

What protects the CNS?

bony structures and meninges

What are the 3 main regions of the brain?

forebrain, midbrain, hindbrain

A

sulci

B

gyri

C

fissure

D

cerebrum

E

diencephalon (thalamus and hypothalamus)

F

midbrain

G

Pons

H

medulla oblongata

I

spinal cord

J

cerebellum

How are the 3 regions of the brain defined?

embryological origin

Where does the CNS receive afferent information from?

peripheral nervous system

processes involved in brain development

neurulation, neuronal proliferation, neural migration, apoptosis, synaptogenesis, myelination

neurulation

process where the flat neural plate folds and fuses to form the neural tube

neural migration

process during which neurones move around the CNS and out to their specific locations in the PNS

synaptogenesis

the formation of synapses between neurones

myelination

the formation of myelin sheaths around the axons of neurones

What is the cerebrum divided into?

left and right cerebral hemispheres

Where do the cerebral hemispheres arise from?

the embryonic prosencephalon

Which structures make up the diencephalon?

thalamus and hypothalamus

Which structure in the brain do most of the cranial nerves arise from?

brain stem

Function of cerebellum

to organise and refine motor activity, to coordinate gait, to maintain posture, to control muscle tone and voluntary muscle activity, to compare intended movements with the outcome

notochord

a cylinder of mesodermal cells which are responsible for inducing formation of the neural plate via secretion of chemical signals (including sonic hedgehog protein)

neurulation process

1. notocord secretes sonic hedgehog protein which causes the neural plate to bend medially to form the neural groove

2. neural groove deepens and its ectodermal walls thicken at the dorsal lips to form the neural folds

3. superficial ectoderm either side of the dorsal surface of the neural tube proliferate to form the neural crest

4. neural folds fuse to close the neural tube, beginning in the cervical region and proceeding rostrally and caudally

Which embryonic germ layer does the neural plate form from?

(dorsal) ectoderm

What causes spina bifida

incomplete caudal fusion of the neural folds in the neural tube

What structures does the neural crest give rise to?

cells in PNS, meninges, some structures of the head

Where does the sonic hedgehog protein work predominantly?

ventral region

neuropores

the holes at the rostral and caudal ends of the neural tube which close last

In which breeds is it common for the neural tube to not fully fuse?

tailless breeds

Which section of the neural tube do brain vesicles develop from?

rostral pole

What are the 3 primary brain vesicles which develop first?

prosencephalon, mesencephalon, rhombencephalon

Which region of the brain develops from the prosencephalon?

forebrain

Which region of the brain develops from the mesencephalon?

midbrain

Which region of the brain develops from the rhombencephalon?

hindbrain

What are the 5 secondary brain vesicles?

telencephalon, diencephalon, mesencephalon, metencephalon, myelencephalon

At what stage does the embryo develop the primary brain vesicles?

3-4 weeks

At what stage does the embryo develop the secondary brain vesicles?

5 weeks

Which structure in the brain develops from the telencephalon?

cerebrum

Which structures in the brain develop from the diencephalon?

eye cup, thalamus, hypothalamus, epithalamus

Which structure in the brain develops from the mesencephalon?

midbrain

Which structure in the brain develops from the metencephalon?

pons and cerebellum

Which structure in the brain develops from the myelencephalon?

medulla oblongata

A

diencephalon

B

cephalic flexure

C

rhombic lip

D

developing cerebellum

E

pontine flexure

F

cervical flexure

G

pons

H

medulla

I

infundibular stalk

J

optic vesicle

functions of cerebrospinal fluid

to provide nutrition to CNS tissues, to act as a cushion and physically support the CNS, to act as a volume buffer to accomodate small amounts of CNS swelling, to maintain a stable environment for neurones, to help the movement of neurotransmitters around the CNS

Which structures form brain hemispheres?

telencephalic vesicles

holoprosencephaly

a single-lobed brain and a single central eye caused by failure of the prosencephalon to divide

How does CSF access inner CNS cells in the brain?

an interconnected series of ventricles in the brain which leads into a central canal in the spinal cord

Which number corresponds to the lateral ventricle of the brain?

2

Which number corresponds to the third ventricle of the brain?

3

Which number corresponds to the fourth ventricle in the brain?

7

Which structures make up grey matter?

nerve cell bodies, dendrites and synapses

Which structures make up white matter?

axons of neurones

nuclei

clusters of nerve cell bodies within the CNS

ganglia

clusters of nerve cell bodies within the PNS

What gives white matter its white appearance?

the presence of fat in the myelin around the neurone axons

glial cells

non-neuronal supporting cells in the CNS and PNS

tracts

bundles of axons in the CNS

nerves

bundles of axons in the PNS

corpus callosum

a major tract of white matter which connects the 2 cerebral hemispheres in the brain together

corpus striatum

basal nuclei in deep parts of the brain hemispheres which are interwoven with white matter tracts

function of corpus callosum

to allow exchange of information between the 2 brain hemispheres

What type of epithelium initially lines the neural tube?

pseudostratified columnar epithelium

Which 3 layers does epithelium in the neural tube differentiate into?

germinal, mantle, marginal

What is found in the germinal layer of the neural tube?

neuronal and glial progenitors

What is found in the mantle layer of the neural tube?

mitotic cells in interphase or differentiating into neurones or glia

What is found in the marginal layer of the neural tube?

axons of neurones/ white matter

What structure separates the 2 cerebral hemispheres of the brain?

longitudinal fissure

Which structure separates the cerebrum from the cerebellum?

transverse fissure

A

longitudinal fissure

B

cruciate sulcus

C

transverse fissure

What is the main sulcus in the brain?

cruciate sulcus

What is the main gyrus in the brain?

sylvan gyrus

X

cruciate sulcus

Y

sylvan gyrus

What are the bulges in the cerebrum known as?

gyri

What are the furrows in the cerebrum known as?

sulci

What are the folds in the cerebellum known as?

folia

What are the lobes of the cerebrum?

frontal, parietal, temporal, occipital

A

frontal lobe

B

cruciate sulcus

C

parietal lobe

D

occipital lobe

E

temporal lobe

F

lateral sulcus

A

motor cortex

B

somato-sensory cortex