nervous system development Flashcards
gastrulation
17 days of gestation
gastrulation forms the gastrula with the neural plate at the centre of the 3 layers:
ectoderm = skin and nervous system
endoderm = lining of viscera
mesoderm = bones and muscles
neurulation
22 days of gestation
neural plate changes shape to form the neural tube (from neural groove - centre) and neural crest (from neural fold - just outside groove)
neural tube - what does it form?
forms the CNS and ventricular system
neurons of the CNS examples =
pyramidal neurons of cerebral cortex
purkinje neurons of cerebellum (hind brain)
ventral horn motor neurons → cell bodies in the spinal cord
neural crest - what does it form?
forms the PNS
neurons of PNS examples =
dorsal root ganglion neurons (pseudo-unipolar neurons → one dendrite and one axon)
sensory neurons with cell bodies in dorsal root ganglion
autonomic neurons e.g. post-ganglionic parasympathetic neurons, enteric neurons
other cells formed in neural crest =
Chromaffin cells (adrenal medulla cells that release adrenaline)
Schwann cells (myelinating the PNS)
differentiation - 3 functionally distinct areas formed
prosencephalon (forebrain)
mesencephalon (midbrain)
rhombencephalon (hindbrain)
differentiation occurs rostrally (forebrain) then caudally
differentiation - secondary brain vesicles in forebrain (2)
telencephalic vesicles = project laterally and become cerebral hemispheres of brain
optic vesicles = optic stalk (becomes optic nerve - composed of retinal ganglion neurons) and optic cup (becomes retina)
all part of the CNS - including the retina!
forebrain (prosencephalon) differentiation - grey matter divisions (2)
telencephalon = two lateral ventricles (hemispheres) = cerebral cortex and basal telencephalon
diencephalon = third ventricle = thalamus and hypothalamus
forebrain (prosencephalon) differentiation - white matter (2)
corpus callosum - between hemispheres
internal capsule - carries info from cerebral cortex into and out of thalamus and beyond
midbrain (mesencephalon) differentiation - 3 areas
tectum (dorsal - back)
cerebral aqueduct = connects 3rd ventricle (thalamus and hypothalamus) with 4th ventricle (pons etc.)
tegmentum (ventral - front) - has a large white matter tract which rungs along the front
midbrain (mesencephalon) differentiation - rostral areas (3)
front
in tectum =
superior colliculus = input/output to/from eyes (sensory input and motor output to control muscles for focusing)
periaqueductal grey = control and processing of pain
in tegmentum =
red nucleus and substantia nigra = muscle control (fingers and toes particularly - core muscles from elsewhere in midbrain) - evolutionary part of motor system
midbrain (mesencephalon) differentiation - caudal areas (1)
inferior colliculus = info from auditory system
hindbrain (rhombencephalon) differentiation - formation and 3 main areas
fourth ventricle
rhombic lips move dorsally to become cerebellum
3 areas:
rostral = pons
dorsal = cerebellum
caudal = medulla - medullary pyramids = white matter tract to carry info to/from spinal cord and cortex
hindbrain (rhombencephalon) differentiation - cerebellum structure and function and result of damage
aka the “little brain”
structure =
2 hemispheres with central part (vermis)
many folia (like gyri and sulci) to increase SA
function =
receives input from different areas through the pons via pontine nuclei:
vestibular system (inner ear for balance and posture)
spinal cord (locate where limbs are in space)
cerebral cortex
damage = lack of coordination, balance, and control of movement
prosencephalon divisions overview
lateral ventricles =
telencephalon = cerebral cortex and cerebral nuclei (basal ganglia, amygdala, basal forebrain)
third ventricle =
diencephalon = thalamus, hypothalamus, retina
mesencephalon divisions overview (cerebral aqueduct)
cerebral aqueduct =
superior and inferior colliculi, red nucleus, substantia nigra
