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anat 312 > lecture 10 > Flashcards

lecture 10 Flashcards

1
Q

early in vertebrate evolution, what dominated, the brainstem or the cerebellum?

A

brainstem - didn’t have much else in the brain

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2
Q

early in vertebrate evolution, what was the main visual and auditory region?

A

the tectum

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3
Q

as the brain evolved, what became more dominant?

A

cerebrum plugged into the sensory and motor systems, eventually taking on an executive role

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4
Q

what are the three main functions of the brainstem?

A
  • its a conduit
  • CNs III-XII enter and leave
  • it has integrative functions
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5
Q

explain how the brainstem acts as a conduit

A

informations relayed between the periphery and the cerebrum/cerebellum

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6
Q

are the ascending pathways through the brainstem sensory or motor?

A

sensory pathways

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7
Q

what do the ascending pathways through the brainstem include?

A
  • dorsal columns medial lemniscus

- spinothalamic tract

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8
Q

what are the functions of the dorsal columns medial lemniscus?

A

proprioception, touch and pressure sensation

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9
Q

what are the functions of the spinothalamic tract?

A

pain and temperature sensation

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10
Q

where do the ascending pathways relay?

A

in thalamus to cortex

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11
Q

do the ascending pathways crossover?

A

yes - near the level of input

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12
Q

describe the descending pathways through the brainstem

A

these are upper motor neuron axons destined to synapse on lower motor neurons in the ventral horn and intermediate horn of the spinal cord

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13
Q

what do upper motor neurons form?

A

the corticospinal tracts

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14
Q

are there upper motor neurons in the brainstem’s vestibular, red, tectal and reticular nuclei?

A

yes - also descend and synpase on lower motor neurons in the brainstem/sc

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15
Q

what are the oldest motor control areas?

where do they now work?

A
  • upper motor neurons in the brainstem’s vestibular, red, tectal and reticular nuclei
  • work with the newer motor and premotor cortex
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16
Q

why is upper motor neuron an imprecise term?

A

not necessarily above, just descending pathway

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17
Q

do the descending pathways cross over?

A

yes - 90% at the medulla, rest at the SC

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18
Q

where do the descending pathways origionate?

A

in the primary motor area of the cerebral cortex

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19
Q

what would be the result of a lesion to the cortiocospinal tract?

A

locked-in syndrome

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20
Q

what is locked-in syndrome?

A

paralysis, but full conciousness because most upper motor neuron axons are cut but cortical cognitive function is ok

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21
Q

when is locked-in syndrome common?

A

after stroke

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22
Q

diseases or lesions to the brain stem can lead to:

  • visual disturbances
  • pupil abnormalities
  • muscle weakness
  • hearing problems
  • vertigo
  • swallowing problems
  • speech difficulty
  • voice changes
  • coordination problems

which cranial nerves are involved with each dysfunction?

A
  • CN II
  • CN III
  • CN V
  • CN VII
  • CN VII
  • CNs IX-XII
  • CN IX, XII
  • CN X
  • CN VII

(guesses)

23
Q

what are the integrative functions of the brainstem?

A
  • cardiovascular control
  • respiratory control
  • pain sensitivity control
  • influencing conciousness (awareness, alterness and the sleep cycle)
24
Q

is brainstem damage lifethreatening? why or why not?

A

yes - bc of integrative functions

25
Q

describe cardiovascular control with respect to the brainstem

A
  • skeletal muscle ergoreceptors in the heart send afferents to cardiovascular areas of the brain via group III and IV muscle afferents
  • parasympathetic (vagal) efferents slow down HR (Ach)
  • sympathetic efferents speed up HR (adrenaline)
26
Q

describe respiratory control with respect to the brainstem

A
  • respiratory areas in the pons and medulla receive higher (cortical) and CN IX/X input from aorta and lungs
  • output affects autonomic traffic to lungs and respiratory muscles
27
Q

describe Brown-Sequard’s concept of rostral-caudal deterioration of brain function in response to global ischemia

A

cerebral cortical function is lost before brainstem (& hypothalamus) function (in respone to global ischemia)

28
Q

what Is the persistent vegetative state (PVS)?

A

chronic neurological disorder of conciousness characterized by wakefullness without awareness

29
Q

where is the damage with PVS?

A
  • cerebral cortical neurons
  • thalamic neurons
  • their white matter connections

sparing of hypothalamus and brainstem

30
Q

what does PVS result from?

A

extensive bilateral lesion to higher brain gray matter or white matter

31
Q

in a PVS patient, how do we know the brainstem is working but the higher brain is not?

A

missing:

  • awarness of self/environment
  • language comprehension/expression
  • sustained, purposeful, reproducible or voluntary behavioural responses

retained:

  • intermitten wakefullness (have sleep/wake cycles)
  • hypothalamic and brainstem autonomic functions
  • cranial nerve reflexes (pupillary, corneal, vesibulo-ocular, gag)
32
Q

what is coma?

A

deep state of unconciousness usually caused by severe head trauma

33
Q

why does coma arise?

A

from bilareral lesions to the reticular network in the brainstem

34
Q

what must function during coma to prevent the higher brain from shutting down?

A

reticular activating system (RAS)

35
Q

how are coma and PVS different?

A

the higher brain is not neccessarily damaged

36
Q

what is brain death?

A

if a patient does not wake up to at least a level of PVS then the RAS is damaged - need RAS for upper brain function

37
Q

what does conciousness require? describe.

A
  • upper brainstem function

- RAS must be intact for the content of conciousness to be expressed

38
Q

conciousness is a function of:

A

the cerebral hemispheres

39
Q

what is the most common cause of death for patients with brainstem injury?

A

apnea (patient can’t breathe without ventilator)

40
Q

why does breathing stop before the heart in patients with brainstem injuries?

A

pressure on the brainstem from the free edge of the tentorial notch

41
Q

describe “brain dead”

A

RAS is not functioning and the patient cannot breathe (patient fails apnea test)

42
Q

is recovery possible with PVS?

A

no

43
Q

is recovery possoble with coma?

A

yes

44
Q

is recovery possible with brain death?

A

no

45
Q

what may cause brain death?

A

severe head injuries or massive intracranial hemorrhages

46
Q

how does head injury threaten brainstem function?

A

pooling blood and/or swelling causes a space-occupying lesion that forces the brain down due to the rigid cranium

47
Q

what is a cingulate herniation?

A

brain swells from one hemisphere into other

48
Q

what is an uncal herniation? what is the result?

A
  • cortex pushes medially and down into cerebellum/brainstem

- result - midbrain/pons damage

49
Q

what is a downward (transtentorial) herniation?

A

cortex pushes down into cerebellum/brainstem

50
Q

what is the result of cingulate herniation, uncal herniation, or downward (transtentorial) herniation?

A

brainstem tissue is under pressure, which causes damage to brainstem function and often death

51
Q

what is external herniation?

A

cortex swells out of the head if a fracture opens the cranium

52
Q

what is cerebellar herniation through the formamen magnum? what is the result?

A
  • cerebellum swells down in through foramen magnum

- medulla damage

53
Q

the brainstem is also the origin of 6 ________ systems that send inputs to ______

what is the result?

A
  • neurotransmitter
  • entire higher brain
  • cause different kinds of global brain activation

anat 312 (18 decks)

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