Lecture2 Flashcards
What rotation occurs during fetal development?
the lower extremity rotates
During fertilization, how is egg brought to Fallopian?
picked up by fimbria, directed to opening of Fallopian tube
Enables Sperm to Enter Egg
lytic enzymes in the acrosome
DNA joining from egg and sperm timing
24 hours post-fertilization
First Week of Development
Day 1-fertilization, Day 2-first mitotic cycle, Day 3-morula development, Day 5-cell differentiation within morula to form inner cell mass, Day 6-7-late-stage blastocyst
Day 2 - First Mitotic Cycle
sperm and egg haploid DNA to the diploid, second mitotic cycle by the end of Day 2
Day 3 - Morula Development
16 cell cluster has genetic makeup to create every cell of body (stem cells)
Day 5 - Differentiation of Morula
inner cell mass will develop into embryo, entering uterus, thickened uterine walls have developed rich blood supply and glands for nutrition (must occur PRIOR to implantation)
Blastocyst
embryoblast (inner cell mass) and blastocyst cavity within the trophoblast membrane
Week 2 Inner Cell Mass Differentiation
2 cell layers: epiblast and hypoblast (also there is an amniotic cavity and the primary yolk sac–anyone else craving an omelet?
Gastrula Phase
end of 2nd week, 3 cell layers (epiblast/ectodermal, mesoderm, hypoblast/endodermal)
Gastrula Phase Key Terms
neural groove, notocord, neural crest, somites
Neural Groove
day 19 Gastrula Phase, develops in the neuroectoderm, cells start to grow together creating a tube with neural cells on outside and space on inside (spina bifida or encaphaly if skin doesn’t grow over)
Notocord
appears for short time in Gastrula Phase, sends out signals to cell layers in development
Neural Crest
Gastrula Phase, junction of neuroectoderm and ectoderm proper, sensory cells for the spinal cord
Somites
Gastrula Phase, these develop into peripheral nerves
Day 22.5 - so basically like 3 weeks and you are blissfully unaware
neural ectoderm has closed creating neural tube, mesoderm has separations for axial and appendicular skeleton, closure of neural tube starts in middle and moves towards ends (anterior/posterior neuropore), somites at top–>cranial nerves and spinal cord–>peripheral nerves
First Month of Fetal Development/Late Gastrula Phase 17-41 Days
(primary vesiscle stage) optic placode developing, ear placode, heart beat, aortic arches, limb buds from mesoderm
Neuronal Growth and Differentiation
- proliferation 2. migration 3. outgrowth of axons and dendrites 4. synapse formation and elimination 5. transneuronal influence 6. myelination
Proliferation Phase of Neuronal G&D
lots of mitotic action, more neurons made than those that live
Migration Phase of Neuronal G&D
cells born close to inner surface of neural tube and migrate out, throughout 9 months waves are created and sent out, when born all brain cells have been created (you are getting dumber as you read this)
Outgrowth of Axons and Dendrites Phase of Neuronal G&D
once cells are migrated the axons and dendrites grow out caused by chemical signals
Synapse Formation and Elimination Phase of Neuronal G&D
axon’s filopodia searching for chemical signals and synapses, only stay with affirmative response, synapses form and break and can strengthen or weaken
Transneuronal Phase of Neuronal G&D
synapse is made, neurotransmitters are transferred for growth factors, symbiotic relationships
Myelination Phase of Neuronal G&D
goes on until 14 yrs old, increases coordination, faster response, peak physical performance in late 20s, early 30s
Ventricular Zone of Neurogenesis
neurons arise from the proliferative epithelium that covers the ventricular space throughout the neural tube, during early mitosis the contents of body are close to this zone
Marginal Zone of Neurogenesis
nuclear material will transmigrate from ventricular zone out to marginal zone
S Phase
chromosomes being split in mitosis
Embryonic Day 30
primary vesiscles forming (enlargments of the neural tube that form different parts of brain), rest of neural tube is spinal cord, cerebrum (longer proliferation phase)
Three Primary Vesicale form:
forebrain, midbrain, hindbrain
Forebrain
adult derivatives are lateral ventricles and midbrain
Midbrain
vertebral aqueduct and midbrain
Hindbrain
fourth ventricle and pons, medulla, and cerebellum
Secondary Vesicle Stage
forebrain (telencephalon and diencephalon), midbrain (mesencephalon), hindbrain (metencephalon, myelencephalon aka fourth ventricle)
Telencephalon
from forebrain, lateral ventricles, , grows over top of diencephalon, will be cerebral cortex
Diencephalon
from forebrain, third ventricle, will be basal ganglia, thalamus, retina of eye and optic nerves
Mesencephalon
new name for midbrain, develops into cerebral aqueduct
Metencephalon
from hindbrain, develops into pons
Myelencephalon
from hindbrain, develops into medulla
Late Secondary Vesicle Stage
nose, mouth, eye, limb buds, lungs, heart, liver, gut all seen…by day 40 this little nugget is all ready for some proliferation
Environmentalist’s View on Neuronal Guidance (Nurture)
can’t get appropriate synapses in deprived environment, need enriched environment (interaction with others)
Hard Wired View on Neuronal Guidance (Nature)
chemical signals that stimulate development, cell adhesion molecules are example of this, environment does not affect
Pioneer Axons
grow out looking for signals and other axons can scaffold along them and follow them, intial connection for other axons to follow (don’t be a follower…be trendsetter)
Neuronal Guidance
environmentalist’s view, hard-wired view, pioneer axons, neuronal cell adhesion molecules, synapse formation
Coricobulbar Control
controls the head, motor control over eyes and tongue for example, neuron sends out pioneer axon and axon goes down spinal cord and synapses on a neuron out to a muscle
Corticospinal Control
controls the body, tectum forms off a branch of the axon (mesencephalon, pons, DCN, SC also form collateral branches), anterior and lateral tract that originate in the cerebral cortex and run through spinal cord carry motor fibers
Spinal Nerve Grey Matter
neurons located on the inside, shaped like a butterfly
Anterior Horns of the Spinal Nerve
motor portions
Posterior Horns of the Spinal Nerve
sensory portions
Roots of Spinal Nerves
dorsal and ventral roots coming off the anterior and posterior horns
Dorsal Root Ganglion
off dorsal roots, contain cell bodies of first order sensory neurons, derivatives of neural crest, bifurcated axon (peripheral/dendrite and central/axon process)
Sympathetic Nervous System Neuron Origination
from the lateral horn of the spinal nerve, exit spinal cord via the ventral horn and leave spinal nerve through white ramus communicans entering sympathetic chain of ganglia
Options in Sympathetic Chain Ganglia
- synapse on a postganglionic cell at the level it enters 2. higher levels and synapse a postganglionic cell 3. lower levels 4. exit sympathetic chain through a splanchnic nerve going to a visceral nerve
Ganglia
collection of neurons
Ventral Primary Ramus
named nerve portion of a typical spinal nerve
Dorsal Primary Ramus
small branch that comes off spinal cord and moves posteriorly, bascially innervates the skin and the muscles of the back
