cortical deficits, cerebral blood flow, and CSF Flashcards
What is motor apraxia?
uncoordinated and on-purposeful movements after lesions to specific regions fo premotor cortex
dyslexia
visual receptive aphasia (word blindness)- unable to appreciate meaning of written word; angular gyrus
auditory receptive aphasia
unable to appreciate meaning of sounds; medial temporal lobe
somatosensory agnosia
unable to perceive stimuli related to touch; parietal cortex
anomia
unable to name object; lateral occipital/temporal lobe
prosopagnosia
unable to recognize faces; ventral temporal lobe
How much of the resting cardiac output goes to the cerebral blood flow?
15%
nutrients require transporters into pervascular space; what is is?
astrocytes end feet supply neurons
Glucose uptake in the brian independent of insulin via….
GLUT 1 or GLUT 2
What occurs when there is no glucose to the brain?
glycogen in neurons is sufficient for about 2 minutes
-after 2 minutes may result in coma or death
What controls CBF directly?
chemoreceptors in periphery and brainstem
What regulates CBF?
glutamates
astrocytes calcium wave dilates vessels
What are the 4 large arteries invovled in cerebral blood supply?
2 internal carotid arteries (anteriror circulation), 2 vertebral arteries (posterior circulation)
Merging of arteries forms the Circle of Willis. What is the anterior supply made of?
Middle cerebral (2) Anterior cerebral (2) Anterior Communication
Merging of arteries forms the Circle of Willis. What is the posterior supply composed of?
Posterior Communicating (2) Posterior Cerebral (2) Superior Cerebellar (2) Basilar Anterior Inferior Cerebellar Vertebral (2) Posterior Inferior Cerebellar(2)
What is the watershed area of the anteriror cerebral artery supply?
adjacent arterial branches supply the same cortical region
What does the anterior cerebral artery supply blood to?
medial cortex
What does the posterior cerebral artery supply blood to?
occiptal and medial temporal cortex
lesions in the posteriror cerebral artery supply would cause what?
deficits in vision and apsects fo memory
What does the middle cerebral artery (MCA) supply?
almost entire lateral surface fo the brain
What are the components of the superior division of the middle cerebral artery supply?
Frontal, parietal
Deep vessels supply key internal structures
Broca’s area
What are the components fo theinferior division of the middle cerebral artery supply?
Temporal lobe and small portion of occipital lobe
Wernicke’s area
What do the lenticulostriate arteries do?
supply basal ganglia and interal capsule
What does a rupture of lenticulostriate arteries do?
cerebrovascular accident (CVA) and extreme functional deficits
in local autoregulation of the CBF; what does increase in H+ do?
causes vasodilation to increase CBF, depresses neuronal activity
in local autoregulation of CBF; what does an oxygen deficiency do?
angiogenesis increases vascularity and oxygen supply
Increased [H+] in the brain causes….
increase CBF, decreased neuronal activity
What effect do alkaline conditions have on CBF?
increase neuronal activity, increase CO2, and increase H+
What is the CNS ischemic respone?
activates by severe cerebral ischemia ‘emergency response’
- CO2 activates chemorecptors directly in vasomotor center (medulla)
- extreme increase in BP increase CBF dfor ten minutes
- increased flow at expense of other orgams (kidney, heart)
What is vasovagal syncope in ANS regulation of vasomotor center?
intense empotion (limbic circuits) activate anterior hypothalamus to increase vasodilation and cause fainting
What is the mechanism of the astrocytes in CBF?
high neuronal activity cause increas in glutamate release
astrocytes take up glutamate which tirggers calcium waves
calcium waves cause release of vasoactive metabolites whcih cause artery dilation and increase in CBF
Functions of CSF
cushions th ebrina
nmaintians nutrients
detoxification by microglia
signaling-circumventricular organs, pineal and area postrema monitor and regulate CSF
What is the CSF flow sequence?
lateral ventricles–> third ventricle–> aqueduct of sylvius–> fourth ventricle–> foramen of magendie–> cisterna magna–> subarachnoid space–> arachnoidal villi
What produces CSF?
choroid plexus- mostly from lateral ventricle
How much CSF is produced a day?
500 mL
What is the mechanism of CSF production?
sodium actively transported by epithelial cells into ventricle, chloride follows, water then follows (osmosis)
CSF composition is similar to blood; what are the components?
[Na+ ] ~ equal to blood
[Cl – ] ~ 15% > than blood
[K + ] ~ 40% < than blood
[Glucose ] ~ 30% < than blood
What is the BBB composed of?
tight junctions on capillary endothelial cells, tight junction on arachnoid cells and by specialized ‘leaky’ junctions on cells in choroid plexus
What are circumventricular organs?
blood brain barrier 'leaky' in certain areas Median eminence Endocrine releasing factors Pineal- melatonin and serotonin release modulates circadian rhythm Subfornical organ- Osmoreceptors and thermoceptors Organum vasculosum- Osmoreceptors
CSF drainage perivascular space
continuous with subarachnoid space- route for discharge of toxins, debris, and waste
Two types of CVA (stroke)
ischemic and hemorrhagic
causes of ischemic stroke
thrombosis (local blood clot) embolism (fragment of blood clot), systemic hypotension (severe shock), venous thrombosis (dural venous sinuses)
4 types of hemorrhage which causes blood accumulation
- extradural- between skull and dura mater
- subdural- between dura and arachnoid
- subarachnoid- between arachnoiid and pia
- intracerebral- within brain parenchyma (intraparenchymal)
characteristics of extradural hemorrhage
lens shape
rupture of feeder arteries
onset 3-4 hrs
characteristics of subdural hemorrhage
crescent shape
rupture of bridging veins (dural drianage)
characteristics of subarachnoid hemorrhage
along gyri/sulci
sudden rupture of cerebral vessel or aneurysm
“thunderclap” headache
characteristics of intracerebral hemorrhage
deep penetrating vessels
~10% of cerebral hemorrhage
Lesions increase intracranial pressure (ICP); what can this cause?
compression of vasculature causing ischemia (coma/death)
increases capillary pressure causing additional edema
vicious cycle causes herniation of vital neurological sturctures and cranial nerves resulting in coma/death
