Consciousness And Sleep Flashcards
What is arousal?
Emotional state associated with an aim or to avoid something
What is consciousness?
Awareness of internal and external environments
What is responsible for consciousness?
Cerebral cortex
Reticular formation
What is the reticular formation?
Group of specialised interneurones in the brainstem
How do the cerebral cortex and reticular formation relate to each other?
Stimulate each other in a positive feedback loop
What sends inputs to the reticular formation?
Sensory neurones
Cerebral cortex
What are the outputs of the reticular formation delivered to?
Thalamus
Hypothalamus
Basal forebrain nuclei
Spinal cord
What do the neurones from the reticular formation to the thalamus release as their neurotransmitter? What effect does it have?
Glutamate, excitatory
What do the neurones from the reticular formation to the hypothalamus release as their neurotransmitter? What effect does it have?
Histamine, excitatory
What do the neurones from the reticular formation to the basal forebrain nuclei release as their neurotransmitter? What effect does it have?
Acetylcholine, excitatory
What do the neurones from the reticular formation to the thalamus, hypothalamus and basal forebrain nuclei form?
Reticular activating system RAS
What do the neurones from the reticular formation to the spinal cord form?
Reticulospinal tracts
What is a common side effect of antihistamines and anticholinergic drugs? Why?
Drowsiness
Because they inhibit the effects of neurones from the reticular formation to the hypothalamus and basal forebrain nuclei
What are the methods used to assess consciousness?
Glasgow coma scale GCS
Electroencephalogram EEG
How does the Glasgow coma scale work?
Give points based on different aspects of patient’s condition
Add up points to get total scare
Higher score means are more conscious
How does an EEG measure consciousness?
Measures activity of neurones in the cerebral cortex
What happens to neurones in the brain if inputs from the somatosensory system are reduced?
Fire action potentials in a synchronised manner
What are the stages of sleep?
Eyes open
Eyes closed
REM sleep
Stage 1
Stage 2
Stage 3
Stage 4
What is seen on an EEG when a person has their eyes open?
Beta waves
What is seen on an EEG when a person has their eyes closed?
Alpha waves
What is seen on an EEG when a person is in REM sleep?
Beta waves
Why are beta waves seen on an EEG when a person is in REM sleep?
Because cerebral cortex gives inputs to visual system
Hence similar EEG appearance to having eyes open
What is seen on an EEG when a person is in stage 1 sleep?
Alpha waves
Occasional theta waves
What is seen on an EEG when a person is in stage 2 and 3 sleep?
Theta waves
Occasional sleep spindles, K complexes
What do sleep spindles represent?
Activity of the thalamus trying to return to awake state
What is seen on an EEG when a person is in stage 4 sleep?
K complexes, now called delta waves
How do the waves on an EEG change in appearance from beta to alpha to theta to delta? Why?
High frequency to low frequency
Low amplitude to high amplitude
Due to neuronal synchronisation
How many stages of sleep does a person pass through?
Pass through all stages in order, multiple times
What is the mechanism of sleep?
Inhibition of reticular activating system
Inhibition of positive feedback loop between the reticular activating system and the cerebral cortex
Inhibition of the thalamus by reducing inputs from the somatosensory system
What initiates REM sleep?
Groups of neurones in the pons
How is REM sleep initiated?
Strong inhibition of the thalamus
Inhibition of lower motor neurones by glycnergic neurones
Where do the glycinergic neurones that inhibit the lower motor neurones arise from?
The reticular formation
How do the glycinergic neurones from the reticular system reach the lower motor neurones?
Travel down reticulospinal tracts in the spinal cord
What is the purpose of inhibiting lower motor neurones during REM sleep?
Loss of muscle tone
To prevent muscle movements during dreaming
What are the functions of sleep?
Healing
Removal of waste products
Energy conservation
Memory consolidation
What are some examples of sleep disorders?
Insomnia
Narcolepsy
Sleep apnoea
What is the most common sleep disorder?
Insomnia
What is insomnia?
Sleeplessness
- difficulty falling asleep
- falling asleep but only for a short time
What causes insomnia?
Hormone shifts e.g. menopause, hyperthyroidism
Mental disorders e.g. depression, anxiety
What is narcolepsy?
Decreased ability to regulate sleep-wake cycles
What causes narcolepsy?
Dysfunction of neurotransmission in neurones responsible for sleep
What is sleep apnoea?
Pauses in breathing or shallow breathing during sleep
Leads to hypoxia
Wakes the patient up
What causes sleep apnoea?
Blockage of airways
What are some examples of consciousness disorders?
Brain death
Coma
Locked in syndrome
What is brain death?
Complete loss of brain function
What does brain death look like on an EEG?
Flat EEG
What is a coma?
State of unconsciousness
Person cannot be awakened
What causes coma?
Injury to cerebral cortex or reticular activating system
Due to drug poisoning or hypoxia usually
What does a coma look like on en EEG?
Various patterns
What is locked-in syndrome?
Patient is aware but cannot move, can only move their eyes
What causes locked in syndrome?
Poisoning, drugs
Brainstem stroke
Trauma
What does the EEG look like with locked-in syndrome?
Normal
