Week 8 - Brain Injury & Damage Flashcards
what 3 mechanisms can cause neuron damage & death
- ischemia
- excitotoxicity
- cerebral edema
how does the brain generate ATP
- largely from aerobic metabolism (requires O2) of glucose
how much hypoxia & hypoglycemia can the brain tolerat?
- can tolerate short term without too much neural death
at what point does the hypoxia result in severe damge
- severe ischemia rapdily results in irreversible neuron destruction within 4-6 min
what is the most abudant excitatory nt in the brain?
- the amino acid glutamine
describe the normal function of glutamate in the brain
- binds predominately to a receptor called NMDA, allowing Na and Ca to enter the cell
how is glutamate neutralized & removed from the synapse after binding to NMDA
- removed from the synapse by a secondary active Na+ co-transporter
how can the neutralization of glutamate become impaired?
- since the removal of glutamate required a secondary active transporter (requires ATP)
- when ATP is unavailable, it cannot be removed
what does the impairement of removal of glutamate cause
- causes intracellular Ca++ to accumulate
- this accumulation accelerates neural cell death
what can cause cerebral edema?
- inhibition of the Na/K+ pump
what does the Na/K pump do
- pumps 2 K+ into the cell
- and 3 Na out of the cell
how does inhibition of the Na/K pump cause cerebral edema? what does this lead to?
- causes Na and water to accumulate in neurons
= increased ICP
how does neuron death & damage effect K+? what does this predispose to
- neural death causes the release of K+ = elevated K+ lvla
- predisposes to seizures
how are lesions to the brain categorized
where they occur
- supratentorial lesions
- infratentorial lesion
what is a supratentorial lesion
- lesions that occurs superior to the tentorium cerebell (remember the tentorium cerebelli separates the cerebrum & cerebellum)
what is an infratentorial lesion
- lesions that occur inferior to the tentorium
what do supratentorial lesions often result ikn?
- location specific dysfunction
- must be quite large to effect consciousness
what do infratentorial lesions often result in?
- easily disrupt the closely bundled motor & sensory tracts
- effect consciousness, resp, and circulatory function
what is the function of the frontal lobe (6)
- intellect
- personality
- abstract thinking & reasoning
- spatial ability
- judging
- planning
what is the premotor cortex? what does it control?
- found in front of the motor cortex
- controls skilled movement
what is the central sulcus
- fissure that separates the motor cortex from the sensory cortex
- also the frontal lobe from the parietal
what is the function of the sensory cortex
- processes incoming sensations
ex. touch, pressure, temp, taste, etc.
how is the sensory & motor cortex organized? list
- specific parts correlate to different body parts
- from top of brain down:
- foot
- leg
- trunk
- arm
- hand
- face
what is the function of the parietal lobe
- contains the sensory cortex
- plays a role in processing sensory info
what is the function of the occipital lobe
- visual area
what is the function of the temporal lobe
- auditory area
what is the function of the cerebellum
- balance
- equilibrium
- coordination
what is broca’s area
speech area
- plays role in speech production
- motor control of speech
- expression of language
what is wernickes area
- important for interpreting & understanding language
what can damage to motor areas cause?
- contralateral weakness
- complete loss of motor ability
- loss of skilled movement
- slow to initiate movements
what does contralateral mean
- occurring on the opposite side
what is the fancy word for weakness
- paresis
what is the fancy word for complete loss of motor ability
- paralysis
what is the fancy word for loss of skilled movement
- apraxia
what is the fancy word for slow to initiate movements
- ataxia
what can damage to the somatosensory areas (sensory cortex, etc.) cause
- numbness = parasthesia
describe the visual field pathway using the L visual field as an example
- L visual field info enters both eyes on the R side of the retinas
- then goes thru the optic nerve
- and crosses over in the optic chiasm = puts all the L field info together from both eyes into the R optic tract which travels to the occipital lobe
- the occipital lobe them interprets the info
what determines the characteristics of vision impairment
- the location of the lesion in the visual pathway
what does damage to one eye or optic nerve cause? why?
= blindness of the innervated eye
- bc there is no crossover yet, so it will only effect the info from that eye
what does damage to the optic chiasm cause? why?
- blindness in both eyes
- the optic chiasm is the point of crossover, so info from both eyes is in the same spot
- therefore damage to this spot will effect both eyes
what does damage to the occipital lobe or optic tract cause
- loss in the contralateral visual field
ex. if damage was to the R occipital lobe, that lobe contains all the L visual field info = loss of left visual field (in both eyes bc half of each eye contains L visual field info)
describe the pathway of sound transmission
- sound transmissions cause vibrations of the ear drum & bones
- the auditory info travels via the vestibulocochlear nerve to the brainstem
- at the brainstem, the neurons split
- 2 neurons go to the contralateral temporal lobe
- 1 goes to the ipsilateral temporal lobe
what can lesion in the temporal lobe cause
- some hearing impairment in both ears, but more in the contralateral ear (since most of the info goes to that one)
- failure to locate sounds
where is broca’s and wernicke’s area found?
- both on the L hemisphere
- broca’s = L frontal lobe
- wernicke’s = L temporal lobe
what is aphasia
- inability to express or comprehend language
what are 2 types of aphasia
- expressive aphasia
2. receptive aphasia
what causes expressive aphasia
- damage to broca’s area when the L frontal lobe is damaged
what does expressive aphasia result in
- inability to speak or write fluently
- poor articulation
what is the fancy word for poor articulation
- dysarthria
what causes receptive aphasia
- damage to wernicke’s area when the L temporal lobe is damaged
what does receptive aphasia result in
- inability to read or understand spoken words
what is dysaphasia
- partial impairment in the ability to express or comprehend language
what is global aphasia
- damage to both broca’s and wernicke’s area
- combo of expressive & receptive aphasia
what causes global aphasia
- wide-spread L hemisphere damage
ex. stroke
what 4 nerves are involved in spoken language
- facial (5)
- glossopharyngeal (tongue & pharynx) (9)
- accessory (11)
- hypoglossal (12)
what is cerebral dominance
- when some cerebral functions are isolated to one hemisphere
what is the L hemisphere often dominant for?
- language
- logical thinking
- analytical skills
what is the R hemisphere often dominant for
- artistic abilities
- spatial relationships
what does wide-spread damage to the R hemisphere often cause
- impairs artistic abiltiies & spatial relationships
- behavioral problems
__% of right-handed individuals are L hemisphere dominant for language
99
__% of left-handed people are R hemisphere dominant for language, __% left hemi dominant; what does this mean
- 40%
- 15%
= in most left-handed individuals hemispheric dominance is incomplete
what are the pros and cons to incomplete hemispheric dominance
pro =if have stroke, may not lose all language ability
con = greater risk of dyslexia or impairment of language ability
