10/21: CNS Part 1 Flashcards
What layer does the CNS develop from?
Ectodermal layer
- subspecialized layer called the neuroectoderm
When is the neural formation complete?
4 weeks gestation
What does an anterior neuropore closure defect lead to?
Anencephaly
What does a posterior neuropore closure defect lead to?
Spina bifida
When does hemispheric division of the cerebrum occur?
Between 4 and 6 weeks gestation
How does division occur?
Caudal to rostral
(posteiror -> anterior)
What does lack of division lead to?
Various degrees of haloprosencephaly
When does formation of the corpus callosum begin at?
10 weeks gestation
When does gyral formation begin?
After division of the two cerebral hemispheres is complete
What are cells of the CNS?
Neurons
Glial cells
- astrocytes
- oligodendrocytes
- microglia
- ependymal cells
What is intracranial hypertension?
Mean CSF pressure of more than 200mm of water
_____________ and __________ commonly occur together but do not necessarily coexist
Intracranial hypertension; brain edema
What is brain edema?
Increase in brain volume that is due to an increase in its water content
What is well localized brain edema characterized as?
Little or no clinical evidence of brain dysfunction
What is severe brain edema characterized as
Major focal or generalized signs of brain dysfunction and or medullary failure or respiration and circulation failure
What is cytotoxic edema?
Cellular swelling of glial, neuronal, and endothelial cells
What matter does cytotoxic edema involve?
White and grey matter
What is interstitial edema?
Increased brain fluid due to block of CSF absorption
What matter is involved in interstitial edema?
White matter
What is the most common form of brain edema?
Vasogenic edema
What is vasogenic edema characterized as?
Increased permeability of brain capillary endothelial cells
Which matter is involved in vasogenic edema?
White matter is more vulnerable than grey matter
What is hydrocephalus?
Increased volume of CSF within the cranial cavity
What population does hydrocephalus occur more in?
Infants associated with enlarged head
What is hydrocephalus caused by?
Obstruction to the CSF circulation
What is trauma?
Blunt force head injury - lesions may be parenchymal and/or traumatic vascular injuries
What is concussion?
Clinical syndrome of altered consciousness secondary to head injury - sudden disruption of neurologic function
What is contusion?
Direct parenchymal injury of the brain (similar to bruising)
What is an epidural hematoma?
Skull fracture and middle meningeal artery injury
What is an epidural hematoma followed by?
Rapidly developing signs of cerebral compression
What is a subdural hematoma?
Venous bleeding from bridging veins
What is subdural hematoma follow by?
Gradual signs of cerebral compression-hours-days-weeks
What is diffuse axonal injury (DAI)?
Widespread but often asymmetric axonal swellings that appear within hours of the injury
What is the third major cause of death in the US after heart disease and cancer?
Cerebrovascular disease
What is the most common clinical designation that applies to relatively acute cerebrovascular damage of the CNS due to different disorders?
Stroke
What vascular disease are Impairment of blood supply and oxygenation?
Hypoxia, ischemia, and infarct of the brain
What vascular diseases are rupture of CNS vessels?
Hemorrhage
What are infarcts?
Tissue necrosis more frequent than hemorrhage (75-80%)
What are hemorrhages?
associated with arterial hypertension,
atherosclerosis, vascular malformations, berry aneurysms,
trauma, coagulopathy
What is transient ischemic attack?
reversible
episodes of impaired neurological function
What are transient ischemic attacks considered to be precursors of?
More serious occlusive events
What is global cerebral ischemia?
generalized reduction of cerebral perfusion (cardiac arrest, shock, sever hypotension)
What is focal cerebral ischemia?
localized reduction or cessation of
blood flow to a defined portion of the brain
What is hypoxia?
Low partial pressure of oxygen
Impairment of bloods oxygen carrying capacity
Inhibition of oxygen use in the tissue
