8b.) Consciousness Flashcards
What is consciousness?
- Hard to define
- Related to awareness of external environment and internal states
What is arousal?
Emotional state associated with some kind of goal seeking behaviour or avoidance of noxious stimuli
Consciousness requiers two neural components to be functioning normally and connected to each other; what are these two components?
Cerebral cortex
Reticular formation
Where do conscious thoughts arise?
Cerebral cortex
What is the role of the reticular formation
Circuitry that keeps cortex awake (particularly the reticular activating system in the brainstem)
Where does reticular formation receive inputs from?
Cerebral cortex and sensory systems
What fibres connect the cortex and reticular formation?
Reciprocal excitatory projection fibres connect the cortex & reticular formation creating a positive feedback loop
What type of feedback loop is seen between the cortex and reticular formation?
Positive feedback loop
When are positive feedback loops seen?
When there is a binary outcome e.g. sleep/awake, ovulating/not ovulating, clotting/not clotting etc…
Outputs from the reticular formation, to the cortex, occur via three major relay nuclei:
- State the neurotransmitter which the reticular formation uses to communicate with each of the relay nuclie
- State the relay nuclei and also state the transmitter used
Reticular formation sends cholinergic (excitatory) projections to the following relay nuclei:
- Basal forebrain nuclei: send excitatory cholinergic fibres to cortex (ACh)
- Hypothalamus: send excitatory histaminergic fibres to cortex (Histamine)
- Thalamus: sends excitatory glutamatergic fibres to cortex (glutamate)
![](https://s3.amazonaws.com/brainscape-prod/system/cm/301/614/332/a_image_thumb.png?1581079432)
Alongside projecting to the cortex via 3 relay nuclei, does the reticular formation project anywhere else?
Yes, it also sends projections down the cord (responsible for maintaining muscle tone)
Summarise the outputs from the reticular formation
- Excitatory to cortex
- Cholinergic excitatory fibres to relay nuclei
- Relay nuclei use different neurotransmitters to excite cortex
- Also has excitatory fibres projection fibres down spinal cord to maintain muscle tone
What is the reticular formation?
Population of specialised interneurones in brainstem which receives numerous inputs from sensory system & cortex- which regulates arousal. Has widespread outputs to thalamus, hypothalamus, basal forebrain nuclei (which then project to cortex)and spinal cord.
Clinically, what is used to assess consciousness?
GCS score
Describe the 3 components of the GCS (Glasgow Coma Scale) and state the scores which can be given for each
- Eye opening (scored 1-4)
- Motor response (scored 1-6)
- Verbal response (scored 1-5)
Eye opening is one of the components assessed in the GCS score; for each score that can be given suggest what it indicates
Eye opening scored 1-4:
- 4= spontaneous eye opening- suggests normal cortical and brainstem function
- 3= response to speech- suggests slightly diminished cortical function but still functioning brainstem
- 2= response to pain- suggests impaired cortical function but brainstem preserved so that reflex opening can occur
- 1= no response- suggests severe damge to brainstem +/- cortex
![](https://s3.amazonaws.com/brainscape-prod/system/cm/301/615/376/a_image_thumb.png?1581080411)
Motor response is one of the components assessed in the GCS score; for each score that can be given suggest what it indicates
Motor response is scored 6-1:
- 6= obeys commands- suggests normal function with working connections from auditory system to brainstem/cord
- 5= localises to stimuli- suggests diminished higher cortical function but still connetions working from sensory to motor cortex
- 4= withdraws to pain- suggests there is still a physiological reflex response to stimuli
- 3= flexor response to pain- suggests a lesion above the level of the red nuclei (this response is semi-physiological)
- 2= extensor response to pain- suggests a lesion below the red nuclei (this response is not physiological at all)
- 1= no response to pain- suggests severe damage to brainstem +/- cortex
![](https://s3.amazonaws.com/brainscape-prod/system/cm/301/615/643/a_image_thumb.png?1581082346)
Verbal response is one of the components assessed in the GCS score; for each score that can be given suggest what it indicates
Verbal response scored from 5-1:
- 5= orientated in time/place- suggest normal cortical function
- 4= confused conversation- suggests diminished higher cortical function but language centres are still functioning adequetely
- 3= inappropriate words- suggests language centres have been damaged
- 2= incomprehensible sounds- sugests cortical damage with brainstem mediated groans
- 1= no reponse suggests severe dmage to brainstem +/- cortex
![](https://s3.amazonaws.com/brainscape-prod/system/cm/301/617/686/a_image_thumb.png?1581082315)
What does an electroencephalogram do?
Measures combined activity of thousands of neurones in a particular region of cortex
![](https://s3.amazonaws.com/brainscape-prod/system/cm/301/617/880/a_image_thumb.png?1581082409)