Topography of the Brain

Question 1

neurulation

Answer 1

neuroectoderm cells receive inductive signals from notochord
cells thicken to form neural plate (day 20)
lateral neural plate margins fold inwards to form neural tube (day 24)

Question 2

neural tube layers

Answer 2

ectoderm 
neural crest cells 
mantle layer (becomes brain parenchyma)
ependymal layer (lines ventricles)
lumen (becomes ventricles and central canal)

Question 3

what do neural crest cells differentiate into?

Answer 3

neurons and glia of sensory and autonomic nervous systems
cells of adrenal gland
epidermis
skeletal/connective tissue of the head

Question 4

neural tube defects

Answer 4

anencephly

spina bifida

Question 5

what is anencephaly?

Answer 5

neural tube defect - failure of anterior neuropore to close
forebrain is exposed
1 in ~1000 pregnancies
fatal

Question 6

what is spina bifida?

Answer 6

neural tube defect
failure of posterior neuropore to close
leads to open vertebral canal
1-2 in ~1000 pregnancies
morbidity: 25%
occulta: hidden, vertebral arch defect only
cystica: meningeocele = meninges project out

Question 7

what happens at embryonic day 36?

Answer 7

neural tube expands to form main brain regions
prosencephalon (forebrain)
mesencephalon (midbrain)
rhomencephalon (hindbrain)

Question 8

prosencephalon

Answer 8

forebrain
telencephalon = cerebral hemispheres
optic vesicles = eyes
diencephalon = thalamus/hypothalamus

Question 9

rhombencephalon

Answer 9

hindbrain
metencephalon = pons/cerebellum
myelencephalon = medulla

Question 10

telencephalon

Answer 10

comprises cerebral hemispheres/cerebral cortex
components of limbic system
basal ganglia

Question 11

cerebral cortex

Answer 11

outer layer of cerebral hemispheres
folded to form gyri and sulci
different areas have different functions

Question 12

important gyri/sulci

Answer 12

precentral gyrus - motor
postcentral gyrus - sensory
central sulcus: divides frontal from parietal lobe
lateral sulcus: divides temporal from parietal lobe

Question 13

cortex areas

Answer 13

primary motor cortex
somatosensory cortex 
visual cortex 
prefrontal cortex 
auditory cortex 
olfactory cortex 
gustatory cortex

Question 14

corpus callosum

Answer 14

white matter tract linking cerebral hemispheres
- genu (anterior)
- body (middle)
splenium (posterior)
many sensory neurons pass through splenium

Question 15

deep brain structures

Answer 15

many brain nuclei and white matter tracts deep to cerebral hemispheres
interconnected to form important neural pathways
limbic system, basal ganglia

Question 16

limbic system

Answer 16

deep brain structure - spans telencephalpon and diencephalon 
main components:
cingulate cortex 
fornix
hypothalamus
mamillary bodies
amygdala
hippocampus

Question 17

fornix

Answer 17

semi-circular white matter tract connecting hippocampus with mamillary bodies

Question 18

hippocampus

Answer 18

looks like a seahorse
sits in floor of lateral ventricle
connected to mamillary bodies via the fornix

Question 19

basal ganglia

Answer 19

series of interconnected nuclei at base of forebrain

Question 20

corpus striatum

Answer 20

lentiform + caudate nucleus

Question 21

lentiform nucleus

Answer 21

lens shaped

sits lateral to caudate nucleus

Question 22

caudate nucleus

Answer 22

c-shaped

sits in wall of lateral ventricle

Question 23

capsules

Answer 23

internal, external and extreme
internal forms major white tract
connects cortex to brainstem

Question 24

diencephalon

Answer 24

comprises the thalamus and hypothalamus

Question 25

thalamus

Answer 25

paired structure
relays sensory information to the cortex
involved with voluntary movement, personality and consciousness

Question 26

hypothalamus

Answer 26

inferior to thalamus
important for homeostatic control
coordinates ANS and endocrine responses
involved in thermoregulation feeding, drinking and circadian rhythms
receives inputs from the limbic system
sits between optic chiasm and mamillary bodies

Question 27

mesencephalon and rhombencephalon

Answer 27

form brainstem and cerebellum

Question 28

brainstem

Answer 28

midbrain, pons and medulla
contains:
- cranial nerve nuclei
- vital respiratory and cardiovascular centres
- vomiting centre
- nuclei involved with motor control, sleep
- white matter tracts

Question 29

midbrain

Answer 29

cerebral peduncles (feet of the brain) = white matter tracts connecting pons with diencephalon 
superior colliculus = vision, eye movements 
inferior colliculus = auditory, relay nuclei 
red nucleus = motor coordination, relay between cortex and cerebellum 
substantia nigra = dopaminergic neurons, art of basal ganglia

Question 30

pons

Answer 30

relays information to cerebellum
90% axons descending through midbrain synapse here
contains reticular formation = nuclei concerend with sleep, motor control

Question 31

medulla oblongata

Answer 31

contains nuclei important for controlling respiration and cardiovascular system
pyramid: corticospinal tract - main voluntary motor pathway
olive: formed by olivary nuclei - motor relay to cerebellum
cuneate tubercle, gracile tubercle

Question 32

cerebellum

Answer 32

posterior to brainstem
connected to brainstem by cerebella peduncles 
outer gray matter, inner white matter 
2 hemispheres (connected by vermis), 3 lobes (anterior, posterior, flocculonodular)
main functions:
- control of posture
coordinating and planning limb movements
control of eye movements 
arbor vitae