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Neurosciences > Exam3Lec7TheCerebralCirculation&NeuronalEnvironment > Flashcards

Exam3Lec7TheCerebralCirculation&NeuronalEnvironment Flashcards

1
Q

Blood supply of the brain and spinal cord arises from what structure?

A

two sets of branches from the dorsal aorta (subclavian arteries and common carotid arteries)

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2
Q

Subclavian arteries gives rise to what?

A

Vertebral arteries

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3
Q

What artery branches off the common carotid arteries?

A

Internal carotid arteries.

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4
Q

What are the 2 major branches of the internal carotid artery (ICA)?

A
  • anterior cerebral a (ACA)
  • middle cerebral a(MCA)
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5
Q

Vertebral arteries that supply the spinal cord give rise to what arteries?

A
  1. branches that merge into anterior spinal artery (single artery in ventral surface)
  2. posterior spinal artery (paired arteries in dorsal surface)
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6
Q

What are the supplementary arteries of the spinal cord?

A

Medually arteries ( short 10-12 segmental arteries that joins the anterior/posterir spinal artery)
they arise from the segmented branches of the aorta

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7
Q

An obstruction/ damage (surgery) of medullary artery could lead to loss of blood supply to the spinal cord. What function would be lost?

A
  • posterior spinal blood supply -loss of sensory fxn
  • anterior spinal blood supply- loss of motor fxn
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8
Q

Basilar artery is formed by what?

A

basilar a. (midline) is formed by right and left vertebral a

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9
Q

____ joins the blood supply from the internal carotids in an arterial ring structure called _____

A

basilar a, Circle of Willis

Internal carotid and vertebral circulations are joined at the Circle of Willis.

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10
Q

What does the circle of willis interconnect?

A

Interconnects the internal carotid and vertebral circulation

An anastomosis with the communicating arteries helps assure cortical circulation if one system slowly becomes occluded.

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11
Q

How does the Circle of Willis interconnects the internal carotid and vertebral circulation

A

Posterior cerebral a. < - > posterior communicating a. < - >middle cerebral/internal carotid a. < - > anterior cerebral a < - > anterior communicating a.

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12
Q

What branches are part of the Circle of willis?

A

ACA and MCA (branches off the ICA)
PCA
Ant/Post communicating a

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13
Q

If one of the major arteries becomes occluded, the Circle of Willis secures that all regions of the brain are still able to receive the blood by which structures?

A

Two small bridging arteries:
1. anterior (Ant) communicating a
2. posterior (Post) communicating a

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14
Q

What is the blood supply to the cerebellum, and what portion of the cerebellum does it supply (3)?

A

Vertebral circulation
SCA – supplies the superior portion of the cerebellum
AICA – supplies the lateral portion of the cerebellum
PICA – supplies the inferior portion of the cerebellum

superior cerebellar artery
ant inf cerbellar artery-
pist inf cerebellar artery

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15
Q

What is the blood supply to the midbrain?

part of brainstem

A
  1. Posterior cerebral artery (terminal branches off vertebral artery)
  2. Superior cerebellar artery
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16
Q

What is the blood supply to the pons?

part of brainstem

A
  1. Superior cerebellar artery
  2. Basilar artery
    * Anterior inferior cerebellar artery (AICA)

AICA and PICA and branches of the basilar artery to the brainstem

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17
Q

What is the blood supply to the medulla?

part of brainstem

A
  1. Anterior inferior cerebellar artery (AICA)
  2. Posterior inferior cerebellar artery (PICA)
  3. Vertebral arteries
    * Anterior and posterior spinal aa

AICA and PICA and branches of the basilar artery to the brainste

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18
Q

Why is it important to discuss the blood supply to various regions of the brain?

A

A compromised blood supply to the brain results in the “Structure Damage/Deficit” in the brain (affects the Somatosensory System)

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19
Q

Anterior circulation to the forebrain is formed by what two arteries?

A

anterior cerebral (ACA)
middle cerebral (MCA)

braches off ICA

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20
Q

Posterior circulation to the posterior cerebral cortex, thalamus, and the brainstem is formed by what arteries?

A
  1. posterior cerebral (PCA )
  2. basilar
  3. vertebral
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21
Q

What are the deep penetration cerebral arteries?

A

lenticulostriate arteries (end arteries)

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22
Q

Branches of ____ and ____ supply blood to the cortex and to the deep structures.

A

ACA, MCA

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23
Q

Where do the lenticulostriate arteries branches off of and what does it supply?

A

The lenticulostriate arteries branches off MCA supply blood to the deep structures such as basal ganglia, internal capsule, and hippocampus.

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24
Q

A high incidence of damage of deep penetrating cerebral arteries in patients with what?

A

chronic hypertension and in the elderly: rupture (intracerebral hemorrhage) or occlusion (lacunar infarct).

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25
Q

Deep Penetrating Cerebral arteries can also be called what? If an occlusion occurs here, what occurs?

A

end arteries which supply regions without significant collateral blood supply. Therefore, their occlusion results in stroke syndromes (aka lacunar stroke)

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26
Q

True or False: The size of the infarct ranges from small, (lacunes) to large areas in brain

A

True

note that lacuna strokes can go unoticed but can cause death

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27
Q

Lacunae strokes are occlusions of what?

A

Lenticulostrate arteries

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28
Q

What happens to the brain cells after a lacunar stroke?

A

Within a few months of the infarction, the necrotic brain cells are reabsorbed by macrophages, leaving a small cavity a “lake” or “lacune.” The cells distal to the occlusion die.

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29
Q

The brain uses ____ of normal cardiac output and ____ of body’s O2 consumption

A

15%, 25%

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30
Q

The overall cereberal blood flow rate is ____ but due to neural activity, blood flow ____ in active areas of the brain during various mental activities.

A

constant, increases

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31
Q

The ratio of ____ in particular regions of the brain increases due to increased regional demand for oxygen.

A

hemoglobin to deoxyhemoglobin

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32
Q

What is an aneurysm?

A

balloon-like swelling of arterial wall near bifurcation

can break can cause bleeding and cause obstruction in blood flow

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33
Q

The venous drainage exits skull through what vessel(s)?

A

Venous blood drains from the brain through superficial and deep veins into the dural sinuses (Superior Sagital Sinus), which then drain into the internal jugular (IJ) vein.

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34
Q

What makes up the cerebral microvasculature? (Microvasculature: Deep Penetrating Cerebral Arteries and Capillaries )

A
  1. basal lamina of blood vessels: borderlines b/w bv and what’s outside
  2. blood-brain barrier (BBB) of capillaries: connection b/w cells w/in BBB
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35
Q

What is the Virchow-Robin Space (perivascular space)?

A

Its a Perivascular subpial space around large blood vessels in the brain

NOT CAPILLARIES

36
Q

Where does the Virchow-Robin Space (perivascular space) end?

A

Space stops at the capillary level (stops where capillary starts)

They surround and follow the path of penetrating cortical arterioles e.g. Lenticulostriate aa. (not around capillaries).

37
Q

What is the clinical significance of VRS?

A

VRS has a tendency to dilate so you can identify enlarged VRS which have been associated with age, dementia and incidental inflammatory white matter lesions e.g., in multiple sclerosis.

38
Q

What are VRS “Vascular cuffs?

A

the location of leukocyte aggregation during viral encephalitis.

39
Q

What is the glymphatic system?

A

a macroscopic waste clearance system that utilizes a unique system of perivascular tunnels, formed by astroglial cells, to promote efficient elimination of soluble proteins and metabolites from the central nervous system.

40
Q

The glymphatic system facilitates brain-wide distribution of whichcompounds?

A

glucose, lipids, amino acids, growth factors,and neuromodulators

41
Q

When does the glymphatic system function?

A

mainly during sleep and is largely disengaged during wakefulness.

42
Q

What are the 3 types of barriers of the CNS barrier system?

A
  1. Choroid plexus CSF-Blood barrier: tight junctions in the choroid epithelium
  2. Blood- Brain Barrier(BBB): tight junctions in the endothelial cells
  3. Arachnoid-CSF-Blood Barrier: (separates CSF from EC fluids and blood of the dura) tight junctions in the arachnoid cells
43
Q

Once you reach the ____ you are at the blood brain barrier

A

intracerebral capillary

44
Q

What is the BBB composed of?

A

Small capillary surrounded by glial feet processes of astrocytes, containing tight junctions between the endothelial cells coming together to form the BBB

Formed by endothelial cells with tight junctions (brain non-fenestrated) and glial feet processes of astrocytes.

45
Q

True or False: Astrocytes participate in the formation of the BBB

A

True

46
Q

____ is formed by endothelial cells with tight junctions and glial feet processes of astrocytes

A

BBB

47
Q

Fxn of BBB

A

BBB limits and restricts diffusion of solutes in blood such as bacteria, and large or hydrophilic molecules. It separates and protects the brain from blood-borne pathogens

48
Q

What is a region within the brain with no BBB?

A

Circumventricular organs (CVOs)

49
Q

Circumventricular organs (CVOs) are known as what?

A

functional “gates” in the BBB

50
Q

Name 4 characterizations of the Circumventricular organs (CVOs)

A
  1. have higher capillary density compared to other areas in the brain
  2. No BBB
  3. There are fenestrations and pericapillary space in the endothelial cells of the brain capillaries in CVOs.
  4. Examples are the Neurohypohysis and Pineal gland and Median eminance of the hypothal

have neuro endocrine fxn: have no tight jxns b/w endothelial cells and can send products quickly to bood stream,

51
Q

What is the Arachnoid-CSF Blood Barrier

A

Separates CSF from EC fluids and blood of the dura and has meningothelial cells with tight jxns in the arachnoid cells

52
Q

What are meninges?

A

3 CT layers that protect brain, brainstem, and the spinal cord

53
Q

Review: 3 layers of Meninges

A
  1. Dura mater (outermost, thick layer
  2. Arachnoid mater (spiderlike projections that bridge overfolds and tissues of cortex)
  3. Pia mater (inner, delicate layer closely adhering to cerebral cortex)

pia mater travels with perivascular space and “hugs: the brain tisse

54
Q

What is the subarachnoid space filled with?

A

CSF

55
Q

What does the Arachnoid-CSF-
Blood barrier contain?

A

Arteries and veins that supply and drain the CNS. Has meningoepithelial(modified CT)

prevents things from skull and dura from getting in SAS

56
Q

What is the subdural space, and what can occur here?

has a star

A

Subdural space is b/w the dura matter and arachnoid and it is an artifact. An subdural hematoma can occur here

57
Q

What are the cerebral ventricles?

A

Interconected spaces filled with cerebral spinal fluid (CSF) and lined by ependymal cells

58
Q

Where do the Lateral (or First and Second) ventricles (the largest) , Third and Fourth ventricles lie?

A

Lie in the core of the forebrain and brainstem

59
Q

Where is CSF produced?

A

A modified vascular structure-choroid plexus (CP)

60
Q

Modified ependymal cells where there is active secretion of CSF

A

Choroid plexus

61
Q

What lines the CSF filled ventricles?

A

epithelial-like cells of ependyma (cuboidal to columnar)

62
Q

What is the epithelial –like cells of ependyma involved in

A
  1. Involved in absorbing CSF
  2. May be modified w/in the ventricles to produce CSF: part of the choroid plexus (CP) present in each of the ventricles

No external lamina (unlike epithelium), cilia and microvili on the apical surface of the cell.

63
Q

Review: Ependymal cells

A
  • Lines inner surface of brain surface
  • ciliated
  • may be modifies w/in ventricles to produce CFS: part of choroid plexus
64
Q

Review: What are 2 fxns of the ependymal cells?

A
  1. Movement of CSF
  2. bidirectional transport of materials b/w CSF and neuropil
65
Q

What ventricle is the Choroid plexus (CP) located at?

A

in each of the ventricles

66
Q

For the CP CSF-blood barrier, do the CP epithelial cells have tight jxns?

A

YES

CP endothelial cells of the capillaries are fenestrated

67
Q

Explain the circulation of the CSF

review

A

CSF from ventricles flows from ependymal cells of the lateral ventricle, 3rd, and perforarations of the 4th ventricles into the subarachnoid space, then through arachnoid villi, and finally drains into the venous sinuses in arachnoid villi.

68
Q

What is the choroid plexus villi?

A

Protruding structure w/ folded regions covered by ependymal cells with tight jxn

69
Q

Choroid epithelium almost completely surrounds what?

A

Choroidal capillaries

70
Q

Formed by the ependymal epithelial cells of the choroid plexus connected by tight junctions.

A

Choroid plexus and Blood CSF barrier

71
Q

What do ependymal cells receive?

A

Some plasma components from leaky blood capillaries, so there is no jxn there so those components can penetrate within the ependynmal cells. Then the ependymal cells makes the components into CSF

72
Q

What are the 3 layers choroid plexus?

A
  1. Fenestrated capillary
  2. Scatter pial cells and collagen
  3. Choroid epithelial-like ependymal cells with tight jxns

Pia faces subarachnoid space with blood supply,
ependyma faces ventricles

73
Q

CSF is produced by what type of secrection?

A

Active secretion by CP into ventricles and not passive diffision from blood

74
Q

What is the composition of CSF and what controls the composition?

A

Clear and colorless, low in protein and similar (but not identical) to seum in ionic composition.
Choroid plexus controls the composition

low in K+ high in Na+

75
Q

Blood- CSF Barriers: Summary

  • The ____ is a vascular tissue found in all cerebral ventricles.
A
  • The choroid plexus is a vascular tissue found in all cerebral ventricles
76
Q

Blood- CSF Barriers: Summary

What is the functional unit of the CP?

A

a capillary enveloped by a layer of differentiated ependymal epithelium.

77
Q

Blood- CSF Barriers: Summary

Unlike the capillaries that form the blood-brain barrier, what do the choroid plexus capillaries contain?

A

Choroid plexus capillaries are fenestrated and have no tight junctions (the endothelium, does not form a barrier to the movement of small molecules).

78
Q

Blood- CSF Barriers: Summary

What is the The Blood-CSF barrier at the CP formed by?

A

Epithelial-like ependymal cells with the tight junctions

79
Q

Blood- CSF Barriers: Summary

Envelops the brain is the other barrier with connective tissue (CT) meningiothelial cells of this membrane also linked by tight junctions.

A

Blood-CSF barrier in the arachnoid membrane

80
Q

Serves as a “sink” for some subtances from the brain

A

CSF system

81
Q

What is a route for neurohormones?

A

CSF

82
Q

How does the CSF drain?

A

Into venous sinuses from arachnoid villi

83
Q

What is hydrocephalus?

A

when there is no proper CSF flow with an excess of CSF in the intracranial cavity leading to enlargement of the ventricles and compression of the brain.

problem with CSF transport

84
Q

What are 3 causes of hydrocephalus?

A
  1. excess production of CSF (from a tumor)
  2. a deficiency in CSF reabsorption.
  3. blockage of CSF circulation (the most common- reason-obstructive hydrocephalus)
85
Q

What is obstructuve hydrocephalus?

A
  • Circulation of CSF can be obstructed at any point in the pathway of CSF, e.g., tumor can occlude path of CSF.
  • The severity of the occlusion would depend on the stage of tumor progression/tumor growth.

non obstructicve hydrocephalus: Normal production of CSF, but the re-absorption of CSF is defective.

86
Q

Give an example of Obstructive Hydrocephalus

A
  • Obstruction can occur at the cerebral aqueduct resulting in the decreased passage of CSF from 3rd ventricle to 4th ventricle.
  • For example, presence of colloid cyst of the third ventricle could obstruct foramina of Monro and result in obstructive hydrocephalus.
87
Q

Explain how CSF can act as a diagnositc tool (reflection of a disease)

A
  • in fungal infections, lymphocyte count is elevated
  • in bacterial inf (meningitis), the neutrophils are 90% of the CSF cell count

the normal leukocyte count in the CSF is 5-10 cells/ml,

Neurosciences (28 decks)

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