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From Flashcardlet > Neuro 68: Blood supply > Flashcards

Neuro 68: Blood supply Flashcards

1
Q

Transient iscehmic attack (TIA)

A
  • transient episode of neurological dysfunction
  • caused by focal CNS ischemia –> w/out acute infarction!
  • 1/3 of pt with a TIA go on to have a stroke w/in 5 yrs
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2
Q

Ischemia

A
  • loss of oxygen and glucose due to an interruption of the blood supply
  • can be reversible or irreversible
  • is the cause of a stroke the majority of the time
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3
Q

Infarction: what is it + 3 common causes

A
  • IRREVERSIBLE ischemic injury
  • has lasting neurologic deficits
  • sx are restricted to the territories supplied by the blood-vessel
  • 3 causes:
    1. thrombosis
    2. embolus
    3. other: atherosclerosis, increased or decreased bp, aneurysm, etc.
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4
Q

Thrombosis

A
  • development of a blood clot that occludes a vessel

- sx will develop over minutes to hours

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5
Q

Embolus

A
  • a circulating mass from a distant location
  • occludes a vessel
  • sx are SUDDEN and maximal
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6
Q

Hemorrhage

A
  • bleeding from an artery or a vein
  • causes destruction or compression of brain tissue
  • less common cause of stroke
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7
Q

Aneurysm

A
  • weakening of the wall of arteries
  • usually at branch points
  • causes vessel wall to progressively balloon
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8
Q

What happens where there is a decreased blood supply to an area of the brain

A
  • ischemic cascade: release of excitatory NTs (esp glutamate) from impaired neurons –> depolarization –> activation of NMDA receptors –> influx of Ca –> enzymatic activation –> cytotoxic edema –> irreversible cell death
  • changes can occur w/in minutes to hours
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9
Q

Ischemic penumbra

A
  • the tissue surrounding the core region of infarction will also be iscehmic
  • reversible
  • this portion of tissue may be viable b/c of collateral circulation
  • will eventually infarct if blood supply is not restored in hours to days
  • strategies to limit the damage of a stroke focus on saving the penumbra
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10
Q

Which 2 things will significantly worsen the effects of ischemia?

A
  1. fever

2. hyperglycemia

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11
Q

Regulation of cerebral blood flow and astrocytes

A
  • increase in neuronal activity –> increase in cerebral blood flow to the active are
  • release of glutamate at synapses –> taken up by astrocytes –> release of molecules from the astrocyte endfeet –> vasodilation in nearby vessels –> provides more glucose for uptake by the astrocytes & neurons for energy
  • this concept is also used for fMRI and PET imaging
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12
Q

Regulation of cerebral blood flow and CO2

A
  • hyperventilation causes vasoconstriction –> decreases cerebral blood flow to the brain
  • can reduce the increase in ICP that results from intracranial hemorrhages
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13
Q

Main sources of blood for the hemispheres, brainstem, and spinal cord

A
  1. internal carotid arteries

2. vertebral arteries

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14
Q

Internal carotid a.

A
  • arises from the common carotid
  • gives rise to the anterior, middle, and opthalmic arteries in the skill
  • supplies cerebral hemispheres (including the dura) and the eye
  • forms the circle of willis with the vertebral a.s
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15
Q

Vertebral a.

A
  • arrises from the subclavian a.
  • gives rise to numerous vessels that supply the brainstem, cerebral hemipsheres, cerebellum, and the spinal cord
  • forms the circle of willis with the internal carotid a.s
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16
Q

Circle of willis

A
  • formed by the anastamoses of the internal carotids and vertebral a.s
  • blood does not normally flow from one side of the circle of willis to another, but if an occlusion occurs on one side the opposite side can provide collateral supply
  • provides deep penetrating branches to supply the diencephalon too
17
Q

Blood supply to the cerebral hemisphere

A
  • arrises from 2 primary sources: internal carotid and vertebral arteries
  • supperficial branches of the vertebral supply the surface and penetrating branches supply the deep structures
18
Q

Anterior cerebral a.

A
  • supplies the medial surface of the hemispheres

- also gives branches to the corpus callosum, caudate, and internal capsule

19
Q

Posterior cerebral a.

A
  • supplies the inferior surface of the temporal and the medial surface of the occipital lobes
  • also supplies ht ethalmus and the choroid plexus of the lateral ventral
20
Q

Middle cerebral a.

A
  • supplies the majority of the lateral surface of the hemispheres
  • also supplies the putamen/globus pallidus (via the lenticulostriate arteries) and the internal capsule
  • *many of the major sensory and motor areas are here!
21
Q

Lenticulostriate a.

A
  • small, penetrating branches of the MCA
  • supply deep structures including the putamen and globus pallidus
  • infarcts in these can cause focal deficits
22
Q

Anterior choroidal a.

A
  • branch of the internal carotid a.
  • supplies the choroid plexus of the temporal horn of the lateral ventricle, huppocampus, amygdala, optic tract, lateral geniculate nucles, meyer’s loop, globus pallidus, and internal capsule
  • runs deep into the temporal lobe
23
Q

Posterior communicating a.

A
  • branch of the internal carotid

- supplies the optic chiasm/tract, diencephalon, and internal capsule

24
Q

Blood supply to the internal capsule

A
  • its complicated!
  • includes: internal carotid, anterior cerebral, middle cerebral, anterior choroidal, and the posterior commisure
  • infarcts in any of these can produce sx!
25
Q

Blood supply to the thamlus/diencephalon

A

-posterior cerebral artery, posterior comissure

26
Q

Blood supply to the brainstem

A
  • 2 vertebral a. –> 1 basilar a. –> 2 posterior cerebral a.
  • supplies the medulla, pons, midbrain, cerebellum, and spinal cord
27
Q

Posterior inferior cerebral a.

A

-supplies the inferior surface of the cerebellum in addition to the brainstem with the anterior inferior cerebellar a.

28
Q

Anterior inferior cerebral a.

A

-supplies the inferior surface of the cerebellum in addition to the brainstem with the posterior inferior cerebellar a.

29
Q

Superior cerbellar a.

A

-supplies the superior surface of the cerebellum and its deep nuclei

30
Q

Basilar a.

A

-has many branches that supply the left or the right sides

31
Q

Blood supply to the caudal medulla (P–>A)

A
  1. posterior = posterior spinal a.
  2. vertebral a.
  3. anterior = anterior spinal a.
32
Q

Blood supply to the rostral medulla (P–>A)

A
  1. posterior = PICA
  2. vertebral
  3. anterior = anterior spinal
33
Q

Blood supply to the pons (P–>A)

A
  1. posterior = long circumferentials
  2. short circumferentials
  3. anterior = paramedian a.
    * *overlapping supply: caudal pons = AICA and long circumferentials
    * *overlapping supply: rostral pons = SCA and long circumferentials
34
Q

Blood supply to the midbrain (P–>A)

A
  1. posterior= long circumferentials
  2. short sircumferentials
  3. anterior = paramedian a.
    * *overlapping supply: paramedian branches of the PCA/basilar & longcircumferentials/SCA
35
Q

Alternating hemiplegia

A
  • sx of paralysis on one side of body and cranial nerve deficits on the other side
  • caused by a localizing lesion in the brain stem
  • due to the involvemnt of the corticospinal tract and the CN nucleus or its fibers in a lesion –> each level of the brain stem has branches of vessels that supply territories that contain both CST and CNs
36
Q

Blood supply to the spinal cord

A
  • vertebral a –> 1 anterior & 2 posterior spinal a.

- anastamose with branches of the segmental radicular arteries

37
Q

Radicular arteries

A
  • arrise from intercostal, lumbar, and sacral arteries
  • have branches that anastamose with the anterior and posterior spinal aa.
  • there are more posterior than anterior, so infarct is more likely anteriorly & thats where a lot of important tracts are, etc.
  • travel along wiht the dorsal and ventral spinal roots toward the spinal cord
38
Q

Anterior spinal artery

A
  • gives off alternating branches to the left and right
  • so infarcts will only cause one sided sx
  • anterior has less feeders than posterior, so infarcts are more common
39
Q

Venous drainage of the brain

A

superficial deep cerebral veins –> venous sinuses –> internal jugular vein

From Flashcardlet (79 decks)

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