Biomed from JKHALLER Flashcards
What part of the embryo does the nervous system arise from?
Ectoderm
What region of the neural tube gives rise to the cerebrum?
Telecephalon
What region of the neural tube gives rise to the thalamus, hypothalamus, and epithalamus?
Diencephalon
What region of the neural tube gives rise to the midbrain?
Mesencephalon
What region of the neural tube gives rise to the pons and cerebellum?
Metencephalon
What region of the neural tube gives rise to the pons and myelencephalon?
Medulla oblongata
What are the 5 key steps in neural development?
- Patterning
- Neural Migration
- Axonal Migration
- Synaptogenesis
- Myelination
What drives neural patterning?
Signaling molecules like BMP4 (Bone morphogenic protein) and their concentration gradients
What are the structures that surround the closed neural tube and secrete signaling molecules to aid in patterning?
Notocord, Ventral, SHH
Neural Crest, Dorsal, BMP4
How do neurons migrate?
From inner surfaces to outer surfaces along glia “highways”
Does neuronal migration occur before or after patterning?
TRICKED YA. These occur in parallel with each other.
What are some potential consequences of improper neural migration?
Childhood epilepsy, mental retardation, and lack of sense of smell.
What are the 3 main processes in the migration of axons?
Pathway selection, target selection, address selection.
What are the 2 mechanisms by which guide cells can work to execute axonal migration?
Short and long range (both attraction and repulsion)
What is synaptic stabilization?
At birth, you have about 2500 synapses / neuron. By age 2 this triples. In adulthood these inactive synapses are eliminated.
One study utilized young animal models to mimic stroke. They created 5 groups: control, inactive, restraint, early training, and delayed training. What did they find?
- training of any type leads to physiological reorganization of CST
- early training but NOT delayed leads to behavioral change
We know that weeks 4-8 post-natal development the CST forms cholinergic interneurons. One study examined this finding. What did they find?
Lots more AcH secreted at the level of the SC with early training.
Early intervention/training has been shown to drive 3 main mechanisms of neural development. What are they?
Cortical reorganization, cortical spinal plasticity, increased cholinergic interneurons
Describe the process of myelination through development.
- Starts @ 28 weeks gestation
- Posterior limb or Internal Capsule @ 36 weeks
- Most of CST is completed at 2 years of age
- Continues through adolescence
Briefly describe patterns of myelination through development.
- inferior > superior
- posterior > anterior
- proximal > distal
- sensory before motor
- projection before association
What are projection fibers?
Connect the brain to SC
What do association fibers connect?
Connect different parts of the same hemisphere
What is an ocular dominance column?
Columns in the lateral geniculate nucleus consisting of neurons that receive signals from the left eye only or the right eye only
What is cerebral palsy?
A group of permanent disorders of development of movement and posture caused by non-progressive (so, more acute episodes or lack of development) disturbances in the developing brain.
What is dystonia?
Uncontrollable muscle contraction (either from twisting and repetitive movements or abnormal fixed postures).
What is choreoathetosis?
Irregular movements in the combo of chorea (irregular contractions and athetosis (twisting/writhing)
Define the gross motor classification scheme (GMCS) for functional ability of individuals with CP?
- walks without limitations
- walks with limitations
- walks using device
- self-mobility with limitations, may use powered mobility
- transported
What is the incidence of CP?
2-3/1000 children
What is the most common type of CP seen?
Spastic (specifically diplegia)
What are some prenatal, perinatal, and postnatal etiologic risk factors of CP dev’pt?
Prenatal - infex, maternal diabetes/illness, abnormal placental attachment, clotting abnormalities, intrauterine growth restriction
Perinatal - prematurity, umbilical cord abnormalities, low birth weight, maternal illness
Postnatal - neonatal infex, trauma, CVA, acidosis
Pre-term babies are 30% more likely to develop CP. What is the main reason for this?
Structural and functional immaturity of blood vessels so that these kids are susceptible to ischemic and hemorrhagic injury.
Why is the germinal matrix so susceptible to CVA?
Poor blood flow (ischemia) and fragile walls of arterial vessels (hemorrhage)
In addition to structural and functional immaturity of cerebral vasculature, what are some additional risk factors of CP development for preterm infants?
- less autoregulation of cerebral blood flow
- ineffective myocardial fx
- delayed ductus arteriosis and foramen ovale closure
- oligodendrocytes still in pre-myelination phase
What is periventricular leukomalacia (PVL)?
Primary arterial ischemic injury to arterial end-zones affecting immature white matter
In what areas does periventricular leukomalacia (PVL) primarily occur?
bilaterally in frontal and/or parietal lobes
What is the grading system for intraventricular hemorrhage (IVH)?
- Bleed in geminal matrix
- Bleed into lat ventricles w/ no hydrocephalus
- Bleed into lat ventricles w hydrocephalus
- parenchymal hemorrhage / periventricular hemorrhagic infarction (PVHI)
Is PVHI typically unilateral or bilateral? What about PVL (Periventricular Leukomalacia)?
PVHI (unilateral)
PVL (bilateral)
What are the complications of intraventricular hemorrhage?
Obstructed drainage in terminal vein > ischemia / obstruction of CSF pathways > compression/ischemia of white matter
Describe the presentation of PVL.
bilateral, if frontal LE > UE spastic diplegia with spared cognition, parietal cognition and vision are affected and motor can be affected.
What is the presentation of a cerebellar injury?
Hypotonia/ataxia
Cognition/language affected
Behavioral challenges
What is the presentation of periventricular infarction?
severe unilateral impairment
Does posthemorrhagic hydrocephalus tend to affect LE or UE more?
LE
For infants who suffer full term brain injuries, what areas of the brain are most susceptible to ischemia? Why is this the case?
Developing neurons in deep grey matter of cortex and brainstem, due to high metabolic activity / demand of glu and O2
What are cerebrovascular injuries commonly experienced by full term infants?
global hypoxia/ischemia, ischemic infarct, hemorrhage
How can infants who experience global hypoxia/ischemia have no deficits?
“brain-sparing” blood flow diverts blood from major organs to supply areas of the brain in need of it.
Global hypoxia/ischemia can be brief/incomplete, prolonged/incomplete, or brief/complete. Describe what areas are damaged in each condition.
Brief/incomplete - no deficits
Prolonged/incomplete - white matter injury and end-organ damage
Brief/complete - deep gray matter