Topography of the Brain Flashcards
neurulation
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)
neural tube layers
ectoderm neural crest cells mantle layer (becomes brain parenchyma) ependymal layer (lines ventricles) lumen (becomes ventricles and central canal)
what do neural crest cells differentiate into?
neurons and glia of sensory and autonomic nervous systems
cells of adrenal gland
epidermis
skeletal/connective tissue of the head
neural tube defects
anencephly
spina bifida
what is anencephaly?
neural tube defect - failure of anterior neuropore to close
forebrain is exposed
1 in ~1000 pregnancies
fatal
what is spina bifida?
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
what happens at embryonic day 36?
neural tube expands to form main brain regions
prosencephalon (forebrain)
mesencephalon (midbrain)
rhomencephalon (hindbrain)
prosencephalon
forebrain
telencephalon = cerebral hemispheres
optic vesicles = eyes
diencephalon = thalamus/hypothalamus
rhombencephalon
hindbrain
metencephalon = pons/cerebellum
myelencephalon = medulla
telencephalon
comprises cerebral hemispheres/cerebral cortex
components of limbic system
basal ganglia
cerebral cortex
outer layer of cerebral hemispheres
folded to form gyri and sulci
different areas have different functions
important gyri/sulci
precentral gyrus - motor
postcentral gyrus - sensory
central sulcus: divides frontal from parietal lobe
lateral sulcus: divides temporal from parietal lobe
cortex areas
primary motor cortex somatosensory cortex visual cortex prefrontal cortex auditory cortex olfactory cortex gustatory cortex
corpus callosum
white matter tract linking cerebral hemispheres
- genu (anterior)
- body (middle)
splenium (posterior)
many sensory neurons pass through splenium
deep brain structures
many brain nuclei and white matter tracts deep to cerebral hemispheres
interconnected to form important neural pathways
limbic system, basal ganglia
limbic system
deep brain structure - spans telencephalpon and diencephalon main components: cingulate cortex fornix hypothalamus mamillary bodies amygdala hippocampus
fornix
semi-circular white matter tract connecting hippocampus with mamillary bodies
hippocampus
looks like a seahorse
sits in floor of lateral ventricle
connected to mamillary bodies via the fornix
basal ganglia
series of interconnected nuclei at base of forebrain
corpus striatum
lentiform + caudate nucleus
lentiform nucleus
lens shaped
sits lateral to caudate nucleus
caudate nucleus
c-shaped
sits in wall of lateral ventricle
capsules
internal, external and extreme
internal forms major white tract
connects cortex to brainstem
diencephalon
comprises the thalamus and hypothalamus
thalamus
paired structure
relays sensory information to the cortex
involved with voluntary movement, personality and consciousness
hypothalamus
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
mesencephalon and rhombencephalon
form brainstem and cerebellum
brainstem
midbrain, pons and medulla
contains:
- cranial nerve nuclei
- vital respiratory and cardiovascular centres
- vomiting centre
- nuclei involved with motor control, sleep
- white matter tracts
midbrain
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
pons
relays information to cerebellum
90% axons descending through midbrain synapse here
contains reticular formation = nuclei concerend with sleep, motor control
medulla oblongata
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
cerebellum
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
