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functional neuroanatomy > Week 2 - coverings, ventricles and barriers of the nervous system > Flashcards

Week 2 - coverings, ventricles and barriers of the nervous system Flashcards

1
Q

Why are there barriers between the nervous system and the rest of the the body

A

to enable efficient performance of it’s functions, for protection

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2
Q

name three types of barriers

A
  1. bony structures that physically protect
  2. meanings: three membranes that surround and support
  3. barriers between the internal and external chemical environment
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3
Q

name 2 examples of barriers between the internal and external chemical environments

A
  1. blood - CSF barriers: at its site of production and return to venous blood
  2. blood - brain barrier
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4
Q

Where is the brain situated?

A

in the cranial cavity

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5
Q

what is the cranial cavity divided into?

A

three sections: anterior, middle and posterior cranial fossae

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6
Q

What bones are included in the anterior fossae?

A
  • frontal
  • ethmoid
  • sphenoid
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7
Q

What bones are included in the middle fossa?

A

sphenoid and temporal

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8
Q

What bones are included in the posterior fossa?

A

sphenoid, temporal, parietal, occipital

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9
Q

What other contents are included in the anterior fossa?

A

frontal lobes and olfactory nerves

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10
Q

What other contents are included in the middle fossa?

A

temporal lobes and pituitary glands

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11
Q

What other contents are included in the posterior fossa?

A

brainstem and cerebellum

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12
Q

What are meninges?

A

three membranes, surround and support the brain in the crania cavity and extend down around the brainstem and spinal cord

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13
Q

Name the three meninges

A

dura mater
arachnoid mater
pia mater

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14
Q

describe the dura mater

A

the outermost, tough fibrous membrane loosely surrounding the brain and attached to the skull in places
- has blood and nerve supply

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15
Q

describe the arachnoid mater

A

soft sac-like membrane that also envelops the brain
- fibrous processes extend to the inner Pia
- subarachnoid spaces contains CSF and the CNS arteries and veins

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16
Q

describe the Pia mater

A

follows contours of the brain and adheres to the basement membrane of the brain’s glia surface lining (glia limitans)

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17
Q

Name the layers form skull to CNS

A
  • skull
  • dura mater include. periosteal arteries and veins
  • arachnoid
  • subarachnoid space include. CSF, CNS arteries and veins, arachnoid tabreculae
  • Pia mater
    astrocyte end-feet
  • CNS
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18
Q

What are dural reflections?

A

two large reflections (folds) of the dura which extent into the cranial cavity at the longitudinal and transverse fissures

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19
Q

name the two dural reflections

A

fall cerebri
tentorium cerebelli

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20
Q

What is the fall cerebri?

A

extends from the cranial roof between the cerebral hemispheres

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21
Q

What is the tentorium cerebelli ?

A

horizontal shelf of dura between the cerebrum and cerebellum

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22
Q

Where are the fall cerebri and tentorium cerebella continuous?

A

posteriorly

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23
Q

Where does the brainstem pass through?

A

the gap in the shelf called tensorial incisure

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24
Q

What two layers is the dura mater comprised of?

A

periostea and meningeal

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25
Q

Do the periosteal and meningeal layers ever separate? If so why?

A

yes - to enclose dural sinuses

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26
Q

What dod Ural sinuses contain?

A

venous blood leaving the brain

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27
Q

What is the site of CSF production

A

choroid plexus

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28
Q

What forms the choroid plexus?

A

an invagination fo vascular pa mater into the ventricle forming a highly convoluted tuft of capillaries

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29
Q

Name the three cellular componenets of the chord plexus

A

cellular constituents of the vascular core are the blood vessel endothelium (1) and Pia cells (2), on its ventricular surface, choroidal epithelium (3)

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30
Q

What secretes the CSF into the ventricle?

A

specialised ependymal cells with tight intercellular junctions between them

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31
Q

Describe CSF

A
  • clear and colourless, acellular fluid
  • low in protein, similar but not identical to serum in its ionic composition, contains approx 60% of the glucose of serum
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32
Q

Where is the choroid plexus found?

A

in each ventricle, filled with CSF which flows form one to the next

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33
Q

Into what do the ventricles empty their CSF ?

A

subarachnoid space

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34
Q

What are arachnoid villi?

A

act as one-way valves that allow CSF to leave form the subarachnoid space into venous blood of the dural sinuses

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35
Q

Into what structure does the CSF through the arachnoid villi?

A

form the subarachnoid space into venous blood of the dural sinuses

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36
Q

Where os the CSF in the subarachnoid space collected?

A

into pockets formed where there are irregulatites on the surface of the CNS - cisterns

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37
Q

How many ventricles are there?

A

4

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38
Q

Describe the lateral ventricles (1 and 2)

A
  • c-shaped structures in the deep cerebrum
  • communicate via interventriuclar foramen of Monro w 3rd
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39
Q

How do 1&2 communicate with the 3rd ventricle?

A

through the interventriuclar foramen of monro

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40
Q

Describe the 3rd ventricle

A

a midline slit within the diencephalon, communicates via cerebral aqueduct of the midbrain with the 4th ventricle

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41
Q

name the three openings of the 4th ventricle

A

2 lateral foramina (of Luschka)
1 midline foramen (of Magendle)

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41
Q

describe the 4th ventricle

A
  • tent-like roof pokes up into cerebellum and widens laterally
  • caudal it narrows to form vestal central canal of the casual medulla and spinal cord
  • 3 openings aria CSF to subarachnoid space
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42
Q

What drives the different parts of the ventricular system?

A

the neural canal

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43
Q

What parts of the adult brain derives from the telencephalon (forebrain)

A

cerebral cortex, basal ganglia, hippocampus, olfactory bulb, basal forebrain

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44
Q

What ventricular space is associated to the cerebral cortex, basal ganglia, hippocampus, olfactory bulb, basal forebrain?

A

lateral ventricles

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45
Q

What brain parts of the adult brain are derived from the diencephalon?

A

the dorsal thalamus and hypothalamus

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46
Q

What ventricular space is associated to the dorsal thalamus and hypothalamus?

A

third ventricle

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47
Q

What adult brain parts derive form the mesencephalon ?

A

midbrain (superior and inferior colliculi)

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48
Q

What ventricular space is associated to the midbrain (superior and inferior colliculi)?

A

cerebral aqueduct

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49
Q

What part of the adult brain is derived from the metencephalon?

A

cerebellum, pons

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50
Q

What ventricular space is associated to the cerebellum/ pons?

A

fourth ventricle

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51
Q

What part of the adult Brian is derived from the myelencephalon?

A

medulla

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52
Q

What ventricular space is associated to the medulla?

A

fourth ventricle

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53
Q

What ventricular space is associated to the spinal cord?

A

central canal

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54
Q

Summaries the circulation of CSF

A
  • flows form lateral ventricles to 3rd
  • to 4th
  • to subarachnoid space
  • CSF passes through arachnoid villi (granulations)
  • joins venous blood mainly in sinuses
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55
Q

Is the flow from subarachnoid space to the venous sinus unidirectional or both ways?

A

only in one direction (space ti sinus)

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56
Q

Name the four main functions of CSF

A
  1. physical support and protection
  2. spatial buffer
  3. elimination of waste
  4. chemical communication
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57
Q

Describe CSFs role in physical support and protection

A
  • CNS partially floats in subarachnoid CSF, makes it easier for meninges to stabilise the CNS in the head and spinal cord
  • cushions Brian, eliminates effects of movement and reduces effects of trauma
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58
Q

Describe CSFs role in being a spatial buffer

A
  • some CSF can be displaced as necessary ie. to limit rising intracranial pressure if for example there is damage to a blood vessel
    -> prevents ischaemia due to reduced blood perfusion
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59
Q

Describe CSFs role in elimination of waste

A
  • regulates chemical environment of the CNS by removing water-soluble metabolites
  • these diffuse form Brian into CSF for excretion into venous blood, facilitated by lymphatic system
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60
Q

Describe CSFs role in chemical communication

A

provides a medium for changes in ionic conc., hormones and other neurochemicals to reach neurones

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61
Q

What does the subarachnoid space contain beside CSF ?

A

blood vessels of CNS

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62
Q

Do CNS blood vessels ever penetrate the brain?

A

yes, for a short time tithe with the Pia mater

63
Q

What are the areas around the vessels of the CNS called?

A

perivascular spaces

64
Q

What do perivascular spaces do?

A

they provide a path for CSF to flow from the subarachnoid space into the interstitial spaces of the brain and spinal chord

65
Q

list the different levels from white matter to dura mater

A

white matter
cerebral cortex
perivascular space
artery
pia mater
arachnoid trabeculae
subarachnoid space
arachnoid mater
dura mater

66
Q

CSF flow though the brain is pulsatile in phase with what?

A

the heart rate

67
Q

What are astrocyte processes called?

A

end feet

68
Q

What surfaces possess astrocyte end feet?

A

most neuronal surfaces, of dendrites and cell bodies, some axonal surfaces

69
Q

Where in the brain do astrocyte end feet exist?

A

where the outer surface of the brain meets the inner surface of the Pia

70
Q

What is the lining of astrocyte end feet also called?

A

glia limitans

71
Q

What do end feets do?

A

facilitate CSF - interstitial space interchange of fluid

72
Q

What does every blood vessel in the CNS have?

A

a coat of end feet that separates them from natural tissue

73
Q

What is the glymphatic system?

A
  • analogous tot he body’s lymphatic system that moves excess fluids and wastes into the blood
  • comprises glial cells (astrocytes) and the perivascular space
74
Q

What is CSF’s relation to arteries?

A
  • CSF influx is organised around arteries
  • Arterial pulsation derives CSF movement
75
Q

What Is special about astrocytes expressing aquaporin 4?

A

they are essential for perivascular CSF - interstitial fluid exchange

76
Q

Where do interstitial fluid exists?

A

along veins

77
Q

What happens during slow wave sleep?

A
  • increase of 60% in the interstitial space, which dramatically increases CSF interstitial fluid exchange and metabolite clearance
78
Q

What makes up the blood-brain barrier

A
  1. astrocyte end feet and 2 endothelial cell tight junctions
79
Q

What does the blood brain barrier do ?

A
  • prohibits the free entry of many substances form the blood into the brain
  • lipid soluble molecules can cross this barrier unaided
80
Q

What allows selective transport of material required for brain function?

A

specific transported int he endothelial cell membranes

81
Q

What percentage makes the brain up of the entire body weight?

A

around 2 percent

82
Q

How much percent of oxygen and cardiac output does the brain use?

A

20% of O2 and 15% of cardiac output

83
Q

what can lead to unconsciousness?

A

20 seconds of anoxia (lack fo oxygen)

84
Q

when can anoxia have permanent effects?

A

it it lasts for more than 5 min

85
Q

Describe arteries

A

thin walled, easily blocked and ruptured

86
Q

Describe veins

A

no valves, thin walled, no muscular or elasticity

87
Q

The brain uses autoregulation which occurs in two ways, describe both

A
  • brain blood flow remains constant despite changes in systemic blood pressure, via dilation or constriction of arterioles
  • local responses, mediated largely by astrocytes, provide increased blood flow to activate Brian areas
88
Q

What vessel supplies anterior circulation?

A

carotid artery

89
Q

What vessel supplies posterior circulation?

A

vertebral artery

90
Q

From what artery does the vertebral artery defend from?

A

the subclavian artery

91
Q

How many branches does the aorta have?

A

3 major branches

92
Q

name the three major branches of the aorta

A
  1. brachiocephalic artery
    2 left common carotid artery
  2. left subclavian artery
93
Q

what does the brachiocephalic artery branch into?

A

the right common carotid and right subclavian arteries

94
Q

What does the common carotid artery supply?

A

the external and internal carotid arteries

95
Q

What does the subclavian artery supply?

A

the vertebral artery

96
Q

How high is the percentage for cerebral blood flow of anterior (carotid) circulation?

A
  • 75%
97
Q

What branches are involved in anterior circulation?

A
  • fed by internal carotid arteries
  • main branches include anterior and middle cerebral arteries
98
Q

how much percentage does the posterior circulation make up of the cerebral blood flow?

A

around 25 %

99
Q

what artery feeds the posterior (vertebral) circulation?

A

the subclavian arteries

100
Q

What arises from subclavian arteries?

A

2 vertebral artery

101
Q

how do the two arteries continue after depending from the subclavian arteries?

A

join to form the single basiler artery on the ventral surface of the pons

102
Q

What are the main branches participating in posterior circulation?

A

poster cerebral artery

103
Q

what is the sole blood supply for the brainstem and the cerebellum?

A

the poster circulation

104
Q

What contributes to the blood supply of the spinal cord?

A

the posterior circulation through vertebral artery branches (anterior and posterior spinal arteries)

105
Q

What does the anterior circulation consist of?

A

the internal carotid artery and its branches

106
Q

name the branches of the internal carotid artery

A
  1. ophthalmic
  2. anterior choroidal
  3. middle cerebral
  4. anterior cerebral
  5. posterior communicating
107
Q

What area is supplied by the ophthalmic CA ?

A

orbit and retina

108
Q

What area is supplied by the anterior choroidal CA ?

A
  • diencephalic and subcortical telencephalon structures such as internal capsule, choroid plexus of lateran and third ventricle
109
Q

What area is supplied by the middle cerebral CA ?

A
  • basal ganglia and internal cause - via striate arteries
  • lateral 2/3rds of cortex
110
Q

What area is supplied by the anterior cerebral CA ?

A
  • internal capsule
  • medial side of frontal and parietal lobes
111
Q

What area is supplied by the anterior cerebral CA ?

A
  • internal capsule
  • medial side of frontal and parietal lobes
112
Q

What area is supplied by the posterior communicating CA ?

A

connects carotid and vertebral artery system

113
Q

what is being supplied by superficial vessels?

A

cortical regions

114
Q

What is being supplied by deep or perforating vessels?

A

subcortical grey and white matter

115
Q

What is the main tool used to study blood flow?

A

cerebral angiography

116
Q

name one superficial vessel

A

the anterior cerebral artery (ACA)

117
Q

What does the anterior cerebral artery supply?

A

the medial aspects of the cerebral hemisphere

118
Q

What does the middle cerebral artery (MCA) supply?

A

most of the lateral cortex and insular cortex within the lateral fissure

119
Q

What does the MCA posses?

A

deep perforating arteries - medial/lateral striate arteries

120
Q

What are the main branches of posterior circulation?

A
  • vertebral
  • basilar
  • poster cerebral artery
121
Q

What parts does the vertebral artery supply?

A
  • spinal cord and medulla
  • dorsal medulla and cerebellum via posterior inferior cerebellar artery (PICA)
122
Q

What parts does the basilar artery supply?

A
  • pons
  • cerebellum (AICA and superior cerebellar artery)
123
Q

What parts does the posterior cerebral artery supply?

A
  • midbrain
  • thalamus and optic radiation
  • inferior and medial aspects of temporal and occipital cortex
124
Q

How is the basil artery formed?

A

through fusion of two vertebral arteries

125
Q

Why does the poster circulation system have deep, perforating vessels?

A

arise to provide blood to brainstem

126
Q

What does the poster cerebral artery (PCA) supply?

A

occipital lobe and inferior and medial parts of the temporal lobe

127
Q

What two regions are being supplied by deep vessels?

A

the basal ganglia and the thalamus

128
Q

By what vessels is the basal ganglia being supplied?

A

via ACA and MCA (both striate arteries)

129
Q

By what vessels is the thalamus being supplied?

A

supplied by PCA (anterior and choroidal)

130
Q

What subdivision of the brain stem supplies medial structures?

A

medial vessels - vertebral (and anterior spinal) and basal arteries

131
Q

What subdivision of the brain stem supplies lateral aspects?

A

longer cerebellar and poster cerebral arteries

132
Q

When do the anterior and poster circulations connect?

A
  1. terminal ends of cerebral arteries anastomoses (arteries interconnect)
  2. Circle of Willis - on the ventral brain, proximal parts of carotid and vertebral vasculatures anastomose
133
Q

Name the 6 cortical functional areas

A
  1. primary motor cortex
  2. primary somatosensory cortex
  3. primary auditory cortex
  4. primary visual cortex
  5. Broca’s expressive speech
  6. Wernicke’s receptive speech
134
Q

What could cause functional deficits?

A

a stroke (cell death due to loss of blood supply)

135
Q

What is a homunculus?

A

a topographic representation of the body

136
Q

What does the MCA supply?

A

lateral cortex

137
Q

What does the ACA supply?

A

medial cortex

138
Q

What happens if the ACA is blocked/ ruptured?

A

hemiparesis and hemisensory loss affecting Lowe extremity only

139
Q

What does anastomoses between the ACA and MCA allow for?

A

partial compensation for loss of blood supply if one is occluded

140
Q

Describe the circle of willis

A
  • poster communication arteries of anterior circulation join first part of posterior cerebral arteries
  • together with the anterior cerebral arteries + anterior communicating artery -> arterial circle
141
Q

How many people have the classic circle of wills?

A

only 33 percent, normally channels are closed

142
Q

Describe the blood supply of the spinal cord

A

the single anterior and two poster spinal arteries run the length of the spinal cord

143
Q

where does the anterior spinal artery arise?

A

form the vertebral arteries at the medulla

144
Q

where does the two posterior spinal arteries arise from?

A

vertebral arteira (or PICA)

145
Q

What vessel additionally supplies the spinal cord at lower levels?

A

radicular arteries

146
Q

Where do radicular arteries ascend from?

A

segmental medullary arteries

147
Q

what is venous drainage?

A

blood from the brain and spinal cord drains form capillaries into veins

148
Q

Explain the venous drainage form the brain

A
  • both superficial and deep cerebral veins first drain into dural venous sinuses
  • final sigmoid sinuses return the blood to the internal jugular vein
149
Q

Explain the venous drainage form the spinal cord

A

spinal veins are part of systemic vasculature

150
Q

Describe superficial venous drainage

A
  • superficial cerebral veins cross the subarachnoid space
  • these pierce dura (as bridging veins) as they enter intracranial dural venous sinuses
  • superior and inferior sagittal sinuses drip blood form lateral and medial cortex, joining at the confluence of sinuses
  • blood then travels via transverse sinuses to sigmoid sinuses
151
Q

Where does blood form lower parts of the cortex, basal ganglia and thalamus drain into?

A

the cavernous sinus, which then send the blood the petrosal sing tot he sigmoid sinus

152
Q

What passes through the cavernous sinus?

A

the internal carotid artery

153
Q

what does the great cerebral vein of Galen do?

A

brings blood from deep structures to the straight sinus

154
Q

key concepts

A
  • the anterior carotid and posterior - vertebral - circulations supply blood to the brain
  • the cortical blood supply is derived form the anterior, middle and poster cerebral arteries. Perforating arteries supply deep cerebral structures
  • vessels anastomose (connect) to provide alternative blood flow. At the ventral surface of the brain the circle of willis connects the anterior and posterior circulators
  • spinal cord is supplied by anterior and posterior spinal arteries rostrally arising form the posterior circulation and supplemented by the radicular arteries at lower levels
  • venous return of blood is mediated by deep veins, superficial veins which drain into the dural sinuses. Blood ultimately returns to the systemic circulations via the internal jugular veins

functional neuroanatomy (16 decks)

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