Transcript Temporal Aspects of Visual Extinction

Chapter 4 Embryological Development of CNS
 Chris Rorden
University of South Carolina
Norman J. Arnold School of Public Health
Department of Communication Sciences and Disorders
University of South Carolina
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MCQ
 The parasympathetic
system:
a) Conserves and restores
energy
b) Facilitates digestion and
absorption of nutrients
c) Facilitates excretion of
waste products
d) All of the above
The sympathetic division typically functions
in actions requiring quick responses.
The parasympathetic division functions with
actions that do not require immediate
reaction.
The main actions of the parasympathetic
nervous system are summarized by the
phrase “rest and digest"
(in contrast to the "fight-or-flight" of the
sympathetic nervous system). A useful
acronym used to summarize the functions
of the parasympathetic nervous system is
SLUDD (salivation, lacrimation [production
of tears], urination, digestion and
defecation).
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MCQ
 The hypothalamus is involved
in regulation of:
a)
b)
c)
d)
Food consumption
Body heat
Water intake
All of above
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MCQ
 The cingulate gyrus
a) Is a medial structure of
the cortex.
b) Is located in the brainstem
c) Is located in the
cerebellum
d) Is a lateral structure of
the cortex
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Cingulate Gyrus
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MCQ
 Functions of the brainstem include
a) Swallowing, respiration, and blood pressure
regulation
b) Vision, language, and muscle coordination
c) Emotional memory, executive function, and visual
processing
d) Calculation, reading, and writing
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MCQ
 The Colliculi
a) Are located on the
anterior brainstem
b) Are located on the
posterior brainstem
c) Are located on the
ventral frontal lobe
d) Are located in the insula
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Colliculi = Corpora Quadrigemina
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MCQ
 Which is part of the
cortical spinal tract?
a) Internal Capsule
b) Lateral Geniculate
Nucleus
c) Dura mater
d) Cerebellum
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Internal Capsule
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Chromosomes and genes
 Humans have 46 Chromosomes
–
–
–
–
Roundworm 2
Chimps 48
Amoeba 50
Butterflies 380
 22 pairs are alike in both sexes
 1 pair determines sex
 X (female) or Y (male)
 Genome is all DNA in all chromosomes
 A Gene is the sequence of DNA
required for a product to be expressed
(proteins, enzymes)
Chromosome
during division
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Types of Division
Mitosis
– For general body growth and function
– Regularly occurring for much of our body during
our entire life
Meiosis
– Special division during reproduction
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Gametogenesis (involves meiosis)
 Meiosis – cell division where
number of pairs is cut in half
 Process of forming reproductive
units:
– Gametes
 Male – Spermatozoa
– From puberty through adult life
 Female – Ovum
– Completed prior to birth ~2 million
– Oocyte = germ cell
Chris Rorden:
Oocyte – like oah in noah
Meiosis – like my
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Zygote (fertilized egg)
Produced from combination of male and female
parent chromosomes
Mitotic Division Begins
New Cells called Blastomeres which form a Morula
Two-cell
Stage
Four-cell
Stage
Morula
~3 days
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Morula
Morula develops central cavity called
Blastocyst
Blastocyst attaches to uterine wall
One week from fertilization to implantation in
uterine wall
– Allows blastocyst to get nutrients and excrete
waste products
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Blastocyst
Embryoblast
Blastocyst
Trophoblast
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Blastocyst
Uterine stroma
Trophoblast cells
Embryoblast
Blastocyst cavity
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The first week
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The second week: Bilaminar Embryo
Embryo has two primary layers: Epiblast & Hypoblast
Cytotrophoblast
Amniotic Cavity
Epiblast
Hypoblast
Primary Yolk Sac
Exocoelomic Membrane
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When does life begin?
 British Warnock Committee (1984) suggested
experimentation on the human embryo within the first
14 days of its development.
1. Because before this time implantation in the uterus is
not complete;
2. Because only after this time do the embryo cells lose
their so-called ‘totipotency’: Because after the 14th
day there no longer exists the possibility that
monozygotic twins could be formed from a single
embryo.
3. Appearance of ‘primitive streak’ considered as ‘the
sign’ of a ‘new’ human subject
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Third week: Trilaminar Embryo Develops
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Week 3
Embryo Trilaminar: three
layers between amniotic
cavity and yolk sac
– Ectoderm – future
covering (skin, nails, hair,
but also CNS)
– Mesoderm – future
muscles, bones, heart
– Endoderm – future
digestive tract
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Week 3
Primitive Streak Forms dorsally
Forms neural tube, notochord (cartilaginous
rod, future spine) and neural crest cells
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Presomite Embryo – 18 days
Cut edge
of amnion
Neural plate
Primitive pit
Primitive streak
(mesoderm)
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Early Highlights
Day 18 - Neural plate invaginates (encloses) to
form neural groove
Day 22 - Neural Tube Forms
– Becomes brain and spinal cord
About the same time, Neural Crest Forms
– Becomes cranial and spinal nerve ganglia
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Presomite Embryo – 20 days
Cut edge
of amnion
Neural groove
Somite
Primitive streak
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Neural Tube
 Anterior 2/3 will form brain
 Caudal 1/3 will form spinal cord
 Day 25 - Cranial opening closes
 Brain has 3 sections
– Prosencephalon
– Mesencephalon
– Rhombencephalon
 Day 27 - Caudal end closes
 Problems cause neural tube defects
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Human Embryo – 22 days
Neural fold
somites are
masses of
mesoderm that
will eventually
become skin,
skeletal muscle ,
and vertebrae.
Optic placode
Somite
Cut edge of amnion
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Human Embryo – 23 days
Cranial neuropore
Pericardial bulge
Caudal neuropore
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Week 5
Prosencephalon Develops
– Telencephalon (cortex)
– Diencephalon (thalamus, hypothalamus)
Mesencephalon Develops (mid brain)
Rhombencephalon
– Metencephalon (pons, cerebellum)
– Myelencephalon (medulla)
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Telencephalon
Optic Vessels - retinae, optic nerve
Cerebral Hemispheres - Lateral Ventricle
Medial Connection – Corpus Callosum
Olfactory Lobe
Corpus Striatum
– (Caudate N. & Lenticular N.)
Cerebral Cortex
– Very primitive though 20 weeks
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Third Trimester
All structures present at birth
All structures become more distinct in Third
Trimester
Commissures develop
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MCQ
 What is abnormal in
this image?
A. No gray matter
B. No Cerebral Spinal
Fluid
C. Subcortical band of
gray matter
D. Looks like a normal
brain
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Seven Steps of CNS Development
1.
2.
3.
4.
Production of initial neurons and glial cells
Migration of cells to definitive location
Selective gathering of cells to functional group
Cytodifferentiation (axon, dendrite, synaptic
patterns)
5. Selective death of some cells in groups (Apoptosis)
6. Outgrowth of axons to specific target cells and
establishment of connections
7. Elimination of certain connections and functional
stabilization of others
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Maturation of CNS
 At birth, all neurons you will ever have present.
– Only a few exceptions (neurons involved w smell)
 Process of myelination signals onset of mature
function
– Slow process
 Partially completed completed by age 7
 Axons and dendrites not until teens
 Some areas continue to age 70
 Some cells have programmed cell death (Apoptosis)
– tadpoles lose their tails and pigeons' feet become
unwebbed. Crucial in brain
 Note: not all developmental language disorders
present at birth.
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Myelin Sheaths
Short Gaps (Nodes of Ranvier) on Axons
– Speed up neural activity
In CNS, formed by Oligodendrocytes
Type of Glial Cell
In PNS, formed by Neurilemmal or Schwann
cells
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Rate of Myelination Varies
Spinal tract completed by 9th month
Major motor tracts by 2 years
Cerebrum and Cerebellum into the teens
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Abnormal Development
Anencephaly
Anencephalic
– Cerebral Hemispheres reduced
or missing
– More common in Females
Cranial Bifidum
– Bone fusion presented by brain
or spinal cord protruding through
skull
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Anencephalic Newborn
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Spinal Bifida
 Spinal Bifida Cystica
– Portions of the meninges or neural tissues not
enclosed by posterior vertebral arches
 Spina Bifida Occulta
– Dimple on spinal column on top of an opening
in between vertebrae
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Other Developmental Conditions
Hydrocephaly
– Enlarged head, brain atrophy mental deficiency
– Excessive production of CSF or obstruction of
drainage pathways
–
http://neurosurgery.seattlechildrens.org/conditions_treated/hydrocephalus.asp
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Causes of hydrocephalus
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Hydrocephalus Treatment
Many adults had
developmental
hydrocephalus with
no problems
Others need urgent
surgery
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Microcephaly
Brain and Skull cap
are small
Face is normal
Mental Retardation
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