Brain and Behavior Flashcards - Day 1
Sudden inability to produce language - above or below FM?
Above
Inability to move or feel both legs - above or below FM?
Below (arm, head, face, OK)
Sensory loss of entire right side of face, arm, and leg - above or below FM?
Above
Inability to walk - above or below FM?
Could be above or below
Weakness that worsens in the late afternoon - above or below FM?
Below
Weakness of the left face, arm, and leg - lesion is on what side of the brain?
Right
Color: bone on CT
white
Color: CSF on CT
black
Color: grey matter on T1 MRI
grey
Color: white matter on T1 MRI
white
Color: CSF on T1 MRI
black
Color: grey matter on T2 MRI
grey
Color: white matter on T2 MRI
black
Color: CSF on T2 MRI
white
Lissencephaly
Defect of cerebral cortex; all gyral folds and sulci are missing: smooth brain
Pachygyria
Broad, thick folds – gyral clefts do not extend all the way to ventricles
Polymicrogyria
Too many small gyri
Double cortex
gray matter lining ventricles; due to failure of neurons to migrate properly during development
Focal MCD
lack of grey/white differentiation in one location
Diencephalon
Olfactory lobes, hippocampus, cerebrum
Telencephalon
Retina, epithalamus, thalamus, hypothalamus
Metencephalon
Cerebellum, pons
Myelencephalon
Medulla
Mesencephalon
midbrain
otx2
transcription factor essential for the formation of all anterior structures; absence of otx2 can result in anencephaly
FGF
signals from anterior telencephalon, promote expression of Pax6 and repress Emx2
Pax6 : Emx2 gradient
helps determine identities of neurons in the telencephalon along the AP axis; formed by mutual repression of each other’s expression
Hox genes
Specifies rhombomere segmental identity along the AP axis
Anterior - posterior patterning: rhombomere identity
Hox genes
Dorso-ventral patterning
Localized inductive cues, including sonic hedgehog (Shh) and bone morphogenic proteins (BMPs)
Shh is expressed where?
Ventral midline, nearly entire length of neural tube
holoprosencephaly
loss of bifurcation of forebrain, results in single holosphere; one of key defects associated with its development is loss of key Shh signaling components
How does Shh pattern the dorsal-ventral axis?
Different concentrations of Shh repress expression of certain transcription factors; some pairs of TxFx are mutually repressive → leads to combinatorial output of TxFx sequence that determines cell fate along the dorsal-ventral axis
Potency of neural crest cells
multipotent
Fates of neural crest cells
Sensory ganglia
Non-neuronal melanocytes
Adrenal neuro-secretory cells
Autonomic ganglia
Inside-out maturation
newer neurons migrate past older neurons to assume more superficial positions; newest neurons are at the surface, applies to EXCITATORY neurons
Inhibitory neurons: migration
generated in ventral telencephalon & migrate to cortex
Failure of GABAnergic specification or migration can lead to…
inhibitory interneurons in cortex & epilepsy
Guidance cues
Secreted and transmembrane molecules that influence axon trajectories.
Robo-3 receptor
guidance cue receptor; defects in humans can lead to horizontal gaze palsy
EphrinA
repellent, expressed at HIGH levels in POSTERIOR tectum; axons expressing high levels of EphA terminate in anterior positions
EphrinB
attractant, expressed at HIGH levels in VENTRAL tectum; axons expressing high levels of EphB are drawn to ventral positions
Neurotrophins
family of extracellular signaling molecules; promote the survival of specific neurons
Trophic factors
secreted by post-synaptic cells, required for cell survival
Nerve Growth Factor (NGF)
trophic factor, secreted by sympathetic targets, taken up by sympathetic nerve endings & transported back to the cell body, prevents neurons from self-destructing
