BIO 467 Neuro Exam 1 (Latest 2021) Correct Study Guide Latest Updated

NEUROBIOLOGY – EXAM 1 NOTES

NERVOUS SYSTEM DEVELOPMENT .
Early Development
 Embryogenesis – development of the embryo (the earliest form of the organism)
o Includes Fertilizations, cleavage, morula, and blastocyst stages
o Represents the period of time up to the implantation of the early embryo into the uterine wall by
the syntrophoblast
 Takes ~8 days until the embryo is implanted into the uterus (posterior uterine wall)
o Being to see different areas of development
 Inner cell mass – superior pole of the blastocyst; site of development of embryonic cell
layers (polarity)
o Problems with early stage/implantation
 Oocyte can be fertilized too high and become ectopic pregnancy
 Fertilization/cleavage
o Zygote undergoes division
o Inner cell mass forms superiorly and a cystic chamber forms below that’s supportive of embryo
 Syncytiotrophoblast – offshoot of the cytotrophoblast and stimulates lacunae formation
(vascular supportive tissues)
 What contains the inner cell mass and trophoblast
 Basically placenta formation
 Inner cell mass becomes more defined
o Embryonic disk – distinct early division of embryonic cell layers in the inner cell mass; consists
of 2 things
 Primary ectoderm – forms the roof of the primary yolk-sac
 Embryonic endoderm – closely applied to its outer surface facing the amniotic cavity
 Happens ~16 days
o Extraembryonic Coelom – body cavity that develops around day 12 (space that’s not inner cell
mass)
 Shrinks down ~ day 13 to help anchor the embryo (connecting stalk)
 Becomes a well-developed vascular bed
 Formation of the Primitive Streak – extensive polarization of cells around day 16
o Primitive Streak – (16 days) stream/indentation of cellular activity moving from the narrower
posterior portion of the embryonic disk to the wider anterior portion (back to front)
 Causes blastocyst to become bilaminar
 Epiblast – ectodermal
 Hypoblast – endodermal
 Primitive (Henson’s) Node – small cellular bump at anterior end of primitive streak
 Primitive Pit – opening of the neuroenteric canal at the center of Henson’s node
 Cells of hypoblast and epiblast mix – creates mesoderm
o Neural ectoderm – surface ectoderm
o Notochord – anterior midline (dorsal-tubular) structure; forms from
primitive pit mixing (day 18)
 Nucleus pulposis in intervertebral disks
 Notochord triggers rapid proliferation of surface ectoderm to
invaginate and begin to make nervous system
 Notochordal Accessory Structures
o Somites – (21-24 days) layed down alongside notochordal axis; give rise to PNS structures
 Cause 2 membranous regions form
 Prochordal Plate – at front of primitive node; becomes anterior aspect
(stomadeum/mouth)

,  Cloacal Membrane – at back of primitive node; becomes posterior aspect
(hindgut/urogenital)
o Neurotubular epithelium – gives rise to CNS stuctures
o Pericardial bulge – where the thorax and cardiac region develop (22 days)
Neurulation – at 28 days formation of the nervous system (dorsal tubular nervous system)
 Rapid proliferation of neuroectoderm leads to invagination of nervous sytem
o Neural tube – open tubular structure formed by proliferation from front to back
 Openings: anterior and posterior neuropores
 Neural crest cells – lateral borders of evolving neural tube; develop into neuron
populations that are associated with the PNS (ex: dorsal root ganglia)
 α-fetoprotein – released into spaces because CSF is forming which causes tubes to close; prevents too
much pressure on the developing brain
 can be seen in a mom’s blood test
o High levels – increase risk of Spina Bifida or hydrocephalis/anacephalis
 Inhibits fusion of posterior vertebral column
o Low levels – increased risk of Down’s Syndrome
 Neural tube closes (lots of problems form because of this) from middle to outside; so anterior and
posterior aspects need to close
o Primary Vesicle – closing of both ends of neural tube; basically the CNS
 Most anterior aspect – prosencephalon (forebrain)
 Behind that – mesencephalon (midbrain)
 Behind the mesencephalon – rhombencephalon (hindbrain)
 Last – spinal cord
o Secondary Vesicle – further growth/differentiation of primary vesicle by transverse
segmentation (4 regions versus six regions)

 Forebrain
 Telencephalon – very important because it leads
to cerebral hemispheres and lateral ventricles
 Diencephalon – thalami (third ventricle)
 Mesencephalon – grows at constant rate and leads to
midbrain and aqueduct of sylvius
 Rhombencephalon
 Metencephalon – into pons and cerebellum
 Myelencephalon – into medulla
 Spinal cord
 Evagination – folding/flexion of neural tissue is small developing skull
o Telencephalon evaginates off very quickly
 Orbits grow and optic capsule grows and need to beat the orbital walls
 Pituitary is growing down and up (rathke’s and infundibulum)
 Auditory vesibular apparatus is growing as well
o So it has to fold on itself to fit in the skull
 Flexion of developing brain
 Cervical flexure – at the junction of the rhombencephalon and the spinal cord
 Cephalic flexure – at the region of the mesencephalon
 Pontine flexure – between the metencephalon and myelencephalon
 Derivations of the Embryonic Brain *****
o Telencephalon (part of prosencephalon)
 Cerebral cortex
 Basal nuclei
 Olfactory bulbs/tracts

,  Lateral ventricles
o Diencephalon (part of prosencephalon)
 Optic chiam/tracts/nerves
 Thalamus
 Hypothalamus
 Third Ventricle
o Mesencephalon
 Mid-brain nuclei
 Cerebral aqueduct
o Metencephalon (part of Rhombencephalon)
 Pons
 Cerebellum
 Fourth ventricle
o Myelencephalon (part of Rhombencephalon)
 Medulla oblongata
 Fourth ventricle



NERVOUS SYSTEM OVERVIEW
Anatomical Definitions
 CNS – brain, brainstem, spinal cord
o Dorsal tubular nervous system – from neurotubular epithelium
o Site of perception and integration of sensory info
o Initation and coordination of motor activity
 PNS – cranial nn., spinal nn. (ANS)
o From neural crest cells
o Conveys neural impulses to CNS form sensory receptors and from CNS as output to muscles and
glands
o 2 parts
 Somatic Nervous System
 Afferent neurons – cell bodies in posterior dorsal root ganglia
 Efferent neurons – located in anterior brainstem or spinal cord grey matter
 Visceral Nervous System
 Afferent neurons – from viscera
 ANS – efferent to SM, cardiac muscle, and glands (2nd order cells)
Cranial nerves
 12 pairs
 Can have CNS components with nuclei in the brain or brainstem
 Have PNS component with sensory or motor cell bodies in peripheral ganglia
Spinal Cord and nerves
 In general
o Extends from base of skull to coccygeal area of the vertebral canal
o 32-33 spinal nn. designated by region – come out below vertebra #
 8 cervical (first one comes out above 1st vertebra), 12 thoracic, 5 lumbar, 5 sacral, 2-4
coccygeal
o Ends at L2 to form conus medullaris
o Lumbosacral Cistern – meningeal encased cerebrospinal fluid filled space that lumbar/sacral
spinal nerves travel through
 Core of spinal cord
o White matter – outer shell of cord, consists of myelinated fibers