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Neuroscience > Lab - External Anatomy and Blood Supply of the Brain > Flashcards

Lab - External Anatomy and Blood Supply of the Brain Flashcards

1
Q

how to decide if the lesion is peripheral, or in the spinal cord, or in the brain?

A
  • symptoms in the head (like facial weakness) usually rule out spinal cord (except Horner’s)
  • increased tone usually rules out strictly peripheral pathology
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2
Q

if the lesion is in the brain, how to decide the level?

A

shift your diagnosis rostrally (anteriorly) to accommodate additional reported symptoms
-do NOT shift down/caudally

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3
Q

what level should the lesion be assumed?

A

lesion is at the level of the highest symptom

  • lower symptoms are due to damage to sensory and motor tracts as they passed through midbrain
  • assume a single lesion
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4
Q

what can you guess about the lesion if symptoms occur suddenly?

A

probably caused by a stroke, except if caused by obvious trauma

  • either hemorrhagic or ischemic
  • treatments are different, but symptoms are largely identical
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5
Q

what can you guess about the lesion if symptoms progress gradually over time and are unilateral?

A

likely caused by tumor
-often accompanied by increased intracranial pressure, though large hemorrhagic strokes can also present with increased intracranial pressure

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6
Q

what can you guess about the lesion if symptoms progress gradually over time and are bilateral?

A

usually caused by disease process

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7
Q

what side are symptoms on, and what kind of symptoms are there, if the lesion is in the spinal cord?

A

all sensory and motor symptoms are on the same side as the lesion except loss of pain and temperature

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8
Q

what side are symptoms on, and what kind of symptoms are there, if the lesion is in the brain?

A

lesion is on the same side as the highest symptom (the one which located the level)
-lower symptoms occur on the opposite site

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9
Q

what side are symptoms on, and what kind of symptoms are there, if the lesion is in the forebrain?

A

all sensory and motor symptoms are on the opposite side of the body (olfactory loss is the exception)

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10
Q

what side are symptoms on, and what kind of symptoms are there, if the lesion is in the cerebellum (or its input or output tracts)?

A

all symptoms are on the same side of the lesion

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11
Q

what 3 diagnoses can motor symptoms be reduced to?

A
  1. failure to move (indicates lesion of descending motor pathways)
  2. tremor, incoordination (usually implicate cerebellum)
  3. involuntary, uncontrollable movement (implicates basal ganglia)
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12
Q

what is the telencephalon made of?

A

cerebral hemispheres (cortex, white matter, and basal ganglia)

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13
Q

what is the diencephalon made of?

A

thalamus and hypothalamus

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14
Q

what is the mesencephalon made of?

A

midbrain

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15
Q

what is the metencephalon made of?

A

cerebellum and pons

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16
Q

what is the myelencephalon made of?

A

medulla

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17
Q

what is the forebrain made of?

A

telencephalon and diencephalon

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18
Q

what is the hindbrain made of?

A

metencephalon and myelencephalon

cerebellum, pons, and medulla

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19
Q

what is the brainstem made of?

A

midbrain, pons, and medulla

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20
Q

which cranial nerves originate in the medulla?
what do they collectively control?
what symptoms suggest that the medulla has been compromised?

A

IX (glossopharyngeal), X (vagus), XI (spinal accessory), XII (hypoglossal)

  • collectively control breathing and heart rate
  • ataxic or disrupted breathing (death), or irregular heartbeats suggest medulla has been compromised
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21
Q

which cranial nerves originate in the pons?

what symptoms suggest that the pons have been compromised?

A

V (trigeminal), VI (abducens), VII (facial)

-loss of sensation in face, eye deviated medially, or weakness in facial muscles

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22
Q

where is cranial nerve 8? what are symptoms?

A

vestibulocochlear is in transition between pons and medulla

-ipsilateral deficits in hearing or balance

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23
Q

what is the only cranial nerve that begins on the posterior side?

A

IV (trochlear)

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24
Q

which cranial nerves originate in the midbrain?

what symptoms suggest that the midbrain has been compromised?

A

III (oculomotor), IV (abducens)

  • dilated pupil or eye whose movements are restricted
  • levels of consciousness are controlled by circuits in tegmentum of midbrain, so coma usualloy indicates forebrain or midbrain involvement
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25
Q

which cranial nerves originate in the forebrain?

what symptoms suggest that the forebrain has been compromised?

A

I (olfactory), II (optic)
-loss of smell or more commonly loss of vision indicates forebrain disease, along with changes in “mental” functions, memory, language, and affect

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26
Q

regional functions of cerebral cortex

A

participates in many sensory, motor, and “cognitive” processes

  • is the largest component of our brain (85% by weight)
  • surface is convoluted into gyri and sulci, which define general functional regions
  • interconnected with other side of brain via commissures, including parts of corpus callosum, and anterior commissure
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27
Q

what is the neocortex?

A

what makes up most of the cerebral cortex

  • contains neurons organized in 6 layers/laminae that are numbered from surface of brain to deep white matter
  • -each layer has distinctive morphology
  • -changes in organization between different cortical areas is related to functional specialization
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28
Q

how many divisions of cortex have been defined by histological differences?

A

50 different subdivisions

  • cortical layer IV is made of small stellate neurons with locally ramifying axons, prominent in sensory cortices and receive input from thalamus
  • layer V is made of large pyramidal cells whose axons leave cortex to descend to brainstem and spinal cord; prominent in brainstem and spinal cord
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29
Q

how are connections of group of neurons between different laminae organized?

A

in a vertical/columnar fashion so that cells with similar function span all cortical layers w/in columns

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30
Q

occipital lobe functions

A

associated with visual system; damage causes visual deficits

  • visual info from thalamus to cortex comes first to primary visual cortex (area V1 or area 17)
  • -this area includes part of lingual and cuneate gyri, and within deep folds of calcarine sulcus
  • most of the cortex is on medial hemisphere
  • visual info then spreads to other parts of occipital cortex, then to areas in parietal and temporal lobes (18 and 19)
31
Q

what do lesions in occipital lobe cause?

A

blind spots (scotomas) in half of visual field contralateral to lesion

32
Q

how are sides of the visual cortex interconnected?

A

each side of the visual cortex is interconnected with the ohter side via the splenium of the corpus callosum

33
Q

what is the postcentral gyrus part of what and what does it do?

A

part of parietal lobe associated with somatosensory system

  • analogous to area V1 of occipital cortex (where somatosensory information from thalamus first reaches cerebral cortex)
  • also called area S1 or Brodmann’s areas 3,1,2
34
Q

what does damage to the postcentral gyrus do?

A

somatic sensory deficits (loss of touch, limb position) on opposite side of the body
-due to topographic localization of sensory info within the gyrus, damage to a portion of it will result in sensory loss to only a part of the opposite side of the body and will help to localize damage

35
Q

what is the superior parietal lobule part of what and what does it do?

A

part of parietal lobe associated with guiding movement

36
Q

what does damage to the superior parietal lobule do?

A

lesions sometimes cause “apraxia” (inability to bring limb under sensory or cognitive control)
-patient might not be able to point to an object when asked, even though can see clearly and limbs not paralyzed

37
Q

what is the inferior parietal lobule part of what and what does it do?

A

part of parietal lobe and associated with several cognitive functions

  • in “dominant” left hemisphere, concerned with language
  • in right hemisphere, pathology leads to spatial disabilities
  • -may get lost in own home, “neglect” the left side of his body
38
Q

what gyri are part of the dominant hemisphere of inferior parietal lobule?

A

supramarginal gyrus is part of “Wernicke’s” area to understand language

angular gyrus is gateway through which visual information reaches Wernicke’s area
-damage to this area affects the ability to read

39
Q

how are the parietal lobe and posterior parts of the frontal lobe interconnected?

A

these parts are interconnected through body of corpus callosum

40
Q

what is Heschl’s gyrus/gyri part of? what does it do? what happens if there’s damage in one hemisphere versus both?

A

temporal lobe (AKA transverse temporal gyrii, Brodmann’s areas 41 and 42)

  • primary sensory cortex for audition, but since info from both ears is processed bilaterally in the brain, damage to this area in only one hemisphere produces little deficit
  • damage in both hemispheres causes inability to understand spoken language, since auditory info is cut off from Wernicke’s area
41
Q

what is the superior temporal gyrus part of? what does it do?

A

temporal lobe; associated with audition and posterior portion and superior surface lying within lateral sulcus (planum temporale, posterior to Heschl’s gyrus)
-makes up part of Wernicke’s area in dominant hemisphere (understand language)

42
Q

what are the middle, inferior, and occipito-temporal (fusiform) gyri part of? what do they do? what do bilateral lesions do?

A

temporal lobe; associated with vision, particularly visual memory and perception
-lesions cause prosopagnosia (inability to identify or recognize faces)

43
Q

what are the parahippocampal gyrus and uncus part of? what do they do? what does bilateral damage cause?

A

temporal lobe

  • medial surface has special association with memory
  • bilateral damage can lead to severe amnesia
44
Q

what regions receive terminations of olfactory tract?

A

uncus, anterior part of parahippocampal gyrus, subcallosal gyrus

45
Q

how are the anterior parts of the temporal lobes and olfactory lobes interconnected?

A

they are interconnected via the anterior commissure

46
Q

what is the precentral gyrus part of? what does it do?

A

frontal lobe; AKA primary motor cortex of area 4 (Brodmann), major source of axons that extend to spinal cord and other motor areas for control of voluntary movements

47
Q

what does damage to the precentral gyrus do?

A

weakness (paresis) and movement deficits on opposite side of the body

48
Q

what are the superior and middle frontal gyri (posterior portions) part of? what do they do?

A

frontal lobe; includes “secondary motor” and “premotor” areas that contribute to organization of voluntary movements, including eye movements (frontal eye fields)

49
Q

what does damage to superior and middle frontal gyri do?

A

damage to this part of the brain can result in apraxia

-if damage is in dominant hemisphere, ability to write may be impaired

50
Q

what is the inferior frontal gyrus (posterior portion) a part of? what does it do? what happens if it’s damaged?

A

frontal lobe; in dominant hemisphere, it’s called “Broca’s area” and is needed for programming of speech and writing
-if damaged, patients lose ability to generate fluent speech, although can understand verbal or written statements

51
Q

what is the prefrontal cortex part of? what does it do?

A 
frontal lobe (rostral portions of superior, middle, and inferior frontal gyri)
-far more developed in humans, and functions are hard to delineate but may be for person's personality, planning and sequencing of tasks, etc.
52
Q

what does damage to prefrontal cortex do?

A

personality changes that may be subtle or profound

-patients sometimes develop compulsive, repetitive behaviors (related to impaired ability to plan complex behaviors)

53
Q

how are frontal lobes interconnected?

A

via genu of corpus callosum

54
Q

where does information about speech travel?

A

enters temporal cortex in Heschl’s gyrus, spreads to Wernicke’s area, then relayed to frontal lobe (Broca’s area in inferior frontal gyrus) where commands for speech are organized

55
Q

what is Wernicke’s area made of?

A

posterior parts of superir temporal gyrus and supramarginal gyrus

56
Q

where does visual information directly related to reading travel?

A

from occipital lobe, enters Wernicke’s area via angular gyrus

57
Q

Wernicke’s aphasia

A

receptory or sensory aphasia

  • involves inability to understand language and to speak coherently, but can think words properly
  • in most cases, it’s associated with damage to Wernicke’s area
58
Q

Broca’s aphasia

A

expressive or motor aphasia

-associated with impaired ability to generate speech (or writing) and usually involves damage to Broca’s area

59
Q

what are the 2 major origins of CNS circulation? what provides anastomoses between them?

A

posterior circulation: vertebral arteries (branches of subclavian arteries)
anterior circulation: internal carotid arteries
anastomoses via posterior communicating arteries
-allow one circulation to perfuse the other if the latter occludes gradually from arterial disease
-since these are so small, anastomoses will not protect the brain from a sudden stroke in one of the two circulations

60
Q

what areas of the brain do vertebral arteries supply? what are some branches?

A

posterior circulation; supplies brainstem, cerebellum, and pard of cerebral cortex

  • gives rise to small arteries that travel down spinal cord
  • -2 posterior spinal arteries + 1 anterior spinal artery
  • -travel length of spinal cord and reinforced by segmental branches from aorta
  • as vertebral arteries extend along base of medulla, each gives rise to many medial and lateral branches that penetrate medulla
  • also produce proiminent branches that supply dorsolateral medulla and medial parts of cerebellum (including nuclei) via posterior inferior cerebellar arteries
61
Q

what is the basilar artery? what are its branches

A

where the vertebral arteries join near the junction of the medulla and pons

  • at or just beyond this junction, a pair of branches arise which supply undersurface of cerebellar cortex and central areas of pontine tegmentum (anterior inferior berebellar arteries)
  • then gives off several small pontine arteries that supply medial and lateral parts of pons
  • at rostral end of pons, two more large branches (superior cerebellar arteries) supply superior surface of cerebellar cortex and dorsolateral areas of pontine tegmentum
  • at rostral end of basilar artery, perforating branches contribute to blood supply of crus cerebri, posterior thalamus, and mibrain
62
Q

posterior cerebral arteries

A

bifurcation of basilar artery (distal to perforating branches)

  • travel along medial surface of temporal of occipital lobes
  • send branches to midbrain, posterior parts of thalamus and internal capsule (posterior choroidal arteries)
  • each artery gives rise to a branch that connects the posterior circulation to anterior via posterior communicating artery
  • -gives rise to important perforating branches in thalamus, midbrain, and crus cerebri
63
Q

what is the distribution and major symptoms of a lesion in the anterior spinal artery?

A

ventral 2/3 of spinal cord - branch in spinal cord: paralysis, loss of pain and temperature sense below occlusion

medial medulla - branch in medulla: contralateral sensory loss and paresis, ipsilateral tongue paralysis

64
Q

what is the distribution and major symptoms of a lesion in the posterior inferior cerebellar artery?

A

dorsolateral medulla and pons, medial cerebellum, cerebellar cortex
-Wallenburg’s syndrome: vertigo, loss of balance, ipsilateral “cerebral signs”, loss of facial pain sensation, hoarseness

65
Q

what is the distribution and major symptoms of a lesion in the anterior inferior cerebellar artery?

A

inferior surface of cerebellar cortex, dorsolateral pons
-ipsilateral “cerebellar signs” (tremor, ataxia), facial paralysis, ipsilateral hearing loss, loss of pain and temperature over face ipsilaterally

66
Q

what is the distribution and major symptoms of a lesion in the basilar branches

A

pons, anterior midbrain (crus cerebri)

  • paralysis and loss of sensation in face, body, and limbs
  • can also affect eye movements and cause diplopia
67
Q

what is the distribution and major symptoms of a lesion in the superior cerebellar artery?

A

superior surface of cerebellum, dorsolateral corner of rostral pons
-ipsilateral cerebral signs, contralateral pain and temperature loss, Horner’s

68
Q

what is the distribution and major symptoms of a lesion in the posterior cerebral artery?

A

occipital lobe, medial portions of parietal and temporal lobes, anterior and posterior midbrain, crus cerebri, posterior thalamus

  • if unilateral: blindness in visual field contralateral to affected side, alexia (left)
  • if bilateral (like “top of the basilar”): bilateral blindness, memory loss, somatosensory loss, coma and death
69
Q

what is the distribution and major symptoms of a lesion in the posterior communicating branches?

A

anterior midbrain, crus cerebri, thalamus

-contralateral paresis, coma and death

70
Q

what is the distribution and major symptoms of a lesion in the middle cerebral artery?

A

lateral surface of cortex, insula

-contralateral paralysis, sensory loss, apraxia, aphasia, partial blindness

71
Q

what is the distribution and major symptoms of a lesion in the anterior cerebral artery?

A

medial surface of parietal and frontal lobes

-contralateral parallysis and sensory loss in leg and foot, sometimes apraxia

72
Q

what is the distribution and major symptoms of a lesion in the lenticulostriate artery?

A

basal ganglia, amygdala, internal capsule, anterior thalamus
-possibly involuntary movements (basal ganglia), paralysis, sensory deficits over entire half of body, homonymous visual field deficits (internal capsule)

73
Q

what is the distribution and major symptoms of a hemorrhage in the anterior choroidal artery?

A

hippocampus, anterior choroid plexus, posterior internal capsule
-hemorrhage may cause paralysis, sensory deficits, visual field defect (internal capsule)

Neuroscience (39 decks)

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