G05--> Consciousness Flashcards
what is consciousness?
awareness of one’s self and one’s place in the environment with the ability to respond appropriately to environmental stimuli
Consciousness results from what important functions of the brain
memory, learning, self from non self and re entry (Where mechanisms located in thalamocortical system)
what is a coma?
Non-sleep LOC lasting for extended period of time (unlike syncope)
what are the levels of unconsciousness?
- Lethargic –> patient can be fully aroused
- Obtunded –> patient can not be fully aroused
- Stuporous—> sleep like status
- Comatose –> no purposeful response
Describe the ascending reticular activating system of the ascending arousal system responsible for consciousness
Cell groups in the reticular formation of the midbrain receive collateral connections of ascending pathways (spinothalamic tract, spinal tract of V, solitary tract, vestibular and cochlear nuclei, olfactory and optic system)and project via 2 branches to higher centers of the cerebral cortex
what are the two projected branches to higher cortical centers
- To thalamus –> activating and modulating thalamic relay nuclei and intralaminar nuclei
- To the lateral hypothalamic area –> which is joined by ascending output from hypothalamic and basal forebrain cells
What would happen to the patient if either of these pathways are lesioned?
the thalamus, midbrain or cerebral hemispheres can impair consciousness
The brainstem plays an important role for what?
condition of consciousness, attentive vigilance and wake-sleep rhythm
Thalamic relay neurons have 2 physiological states: describe each one
- Transmission Mode –> wakefulness and awareness
a. resting potential is near firing threshold
b. cholinergic input from pons and basal forebrain is present
c. EEG shows desynchronized pattern -> low voltage and high frequency
(look at the notes for the image of the EEG)
what is the second physiological state
- Burst Mode –> deep sleep and coma
a. neurons hyperpolarized by inhibitory GABA from reticular formation input
b. EEG shows synchronized wave pattern –> high voltage and low frequency
what is a coma?
a deep state of unconsciousness; unable to move or respond to environmental stimuli
what are some common causes of coma?
head injury or complications to another disease (Brain tumor or increased intracranial pressure)
Supratentorial mass lesion (epidural hemorrhage, subdural hemorrhage)
Subtentorial lesions (brain stem infarction, brain stem tumor, cerebellar hemorrhage)
Metabolic and diffuse cerebral disorders (anoxia or ischemia, concussions, infection)
always has to be on both sides!
what symptoms do you see on examination of a coma patient?
not opening eyes, not obeying commands and not uttering understandable words
Where is the lesion in a vegetative state?
cortex/higher centers
complete loss of higher brain function (cortex) however maintain breathing and circulatory functions
Can spontaneous movements occur?
yes they can occur such as eye opening to painful external stimuli but are unable to respond to commands, to speak or respond meaningfully to environmental stimuli