Day 1 Flashcards
In neurulation - which part forms the epidermis?
Epidermal ectoderm
Describe the process of neurulation
- Neural groove forms in neural ectoderm, neural fold forms @ same time
- Epidermis forms, neural crest cells start to migrate
- Neural tube fully forms, neural crest cells migrate
At what point does neurulation begin?
3-4 weeks
How does neural development begin (prior to neurulation?)
3 layer embryo = endoderm, mesoderm, and ectoderm
What will endoderm eventually form?
Digestive system, lining the lungs, urethra, glands, bladder
What will mesoderm eventually form?
muscles, bones, heart, lungs, reproductive system, excretory system
What will ectoderm eventually form?
skin, nails, hair, and all parts of NS
What embrionic layer encloses the neural tube?
Ectoderm (neural)
What remains after closure of neural tube?
Cervical and rostral closures (they remain open until the 26th day of development
How does the organization of the neural tube reflect that of the mature SC?
Posterior cells = sensory, anterior cells = motor
What happens to the neural tube at the end of the 4th week?
Vesiculation! Rostral end bulges and forms: 1) Forebrain (prosencephalon) 2) Midbrain (mesencephalon) 3) Hindbrain (rhombencephalon)
What happens to the neural tube at 5-6 weeks development?
Devides into 5 secondary vesicles
1) telencephalon (cortex and other deeper features)
2) diencephalon (thalamus and hypothalamus)
3) mesencephalon (mibrain)
4) metencephalon (pons and cerebellum)
5) Myelencephalon (medulla)
What is the process of forming different bulges/parts of the neural tube CALLED?
Vesiculation
What happens after vesiculation?
Continued development…
Neural tube widens to form ventricles
Neural proliferation
How does neural proliferation occur/what does it entail?
Neurons are formed from neural progenitor cells
1) Progenitor cells do mitosis and form one progenitor cells (which continues to divide) and one neuron (does not divide) or glial cell
What are somites?
Balls of tissue under conscious control
What type (structural) of neurons are most sensory neurons?
Pseudounipolar
What type (structural) of neuron are most of our neurons (aside from sensory)?
Multipolar
Do humans have unipolar neurons?
No - none in vertebrates
What type of cells in our bodies are bipolar neurons?
Retinal ganglion cells
List all of the CNS glia
Astrocytes
Ependymal cells
Oligodendrocytes
Microglia
List the PNS glia
Schwann cells
Satellite cells
Fxn of astrocytes?
Janitors of the CNS (mop up extra neurotransmitter)
Provide structural support
Fxn of microglia?
Macrophages of the CNS
Fxn of ependymal cells?
Produce CSF (they line ventricles)
Fxn of oligodendrocytes?
Wraps axons with myelin (1 olig. can wrap many axons)
Fxn of Schwann cells?
Myelination in the PNS
Fxn of satellite cells?
Wrap around peripheral ganglia
What is the difference between ganglia and nuclei?
Ganglia are outside CNS, nuclei are inside CNS
What is occuring neurophysiologically in MS?
The immune system sees myelin as foreign and attacks it
What are some sx of MS?
Fatigue, diplopia (double vision), cognitive sx.
List the steps in the timeline of neural development
- Cleavage
- patterning starts in cleavage and blastulation - division of cells and polarity developing
- Blastulation
- Implantation
- Gastrulation
- primitive streak
- notocord
- somites
- Neurulation
- tube formation
- neural crest cells
- Embryonic folding
- Vesiculation
What does Gastrulation form?
3 primordial layers
- Endoderm
- Mesoderm
- Ectoderm
When do the rostral and caudal neuropores close?
Rostral: day 24
Caudal: day 26
How do the cells organize themselves in the neural tube during neurulation?
- Alar column is dorsal/posterior/sensory
2. Basal column is ventral/anterior/motor
When are the ventricles formed?
During neural proliferation (growth) after vesiculation completes
What do the ventricles develop from?
from the canal of the neural tube
What happens during/after cell proliferation?
Cerebral folding (weeks 12-onward) Cell migration (weeks 12-onward) Axonal pathfinding (weeks 12-onward)
What is occuring in neural development from 6mo-18+years?
Synaptogenesis
Cell differentiation into neurons and glia
Development of what areas continues beyond the late teen years?
Frontal lobe
Hippocampal area
At what stage does myelination occur?
4 months gestation to 2 years post-partum
Which fibers are myelinated first?
Spinal cord: Sensory, then motor (corticospinal fibers myelinated by 2 years)
Brain: very little myelination of brain by birth, fibers of basal ganglia first, very little cerebral fxn, mostly reflexes, respiration, sucking, swallowing
Why does Spina Bifida occur?
Failure to close caudal neuropore
What are the types of Spina Bifida and their clinical implications?
1) Occulta - gap in arches of vertebral columns, may be marked by tuft of hair, not clinically significant
2) Meningocele - Bulge of meninges creating meningeal cavity (SC not bulging out)
3) Myelomeningocele - bulge of meninges and cauda equina and maybe even small portion of SC
- Can result in nerve impingement
- Can cause Arnold Chiari phenomenon where SC and brain are pulled caudally causing hydrocephalus
What can occur due to failure to close the rostral neuropore?
Anencaphaly - deadly
What is cerebral palsy?
A group of motor disorders
- Caused by damage to brain in utero or shortly after birth
List some of the types of cerebral palsy and the associated brain areas
1) Spastic CP (M1 - lack inhibition)
2) Dyskinetic CP (basal ganglia - uncontrollable mvmt)
3) Ataxic CP (cerebellum - poor balance/coordination)
Within the meninges of the brain, which are real and false spaces?
Describe how the false spaces can become real?
1) Epidural - false space, swells with bleeding of meningeal artery
2) Subdural space - false space, shearing of bridging vein can cause subdural bleed
3) Subarachnoid space - real space, if there is a bleed here it free bleeds due to the amount of space which is very dangerous
Describe the 2 important parts of the periosteal dura (in the brain)
Falx cerebelli: separates hemispheres of cerebrum
Tentorium cerebri: supports weight of cerebrum above cerebellum
What do the falx cerebrum and tentorium cerebelli create space for?
They create caverns which provide space for venous sinuses to run through
What is the fxn of arachnoid granulations?
Reabsorb CSF
What space does the Pia Mater in the brain form?
Perivascular space: surround blood vessels as they exit the brain
