L10 - Reticular Formation Flashcards
Arousal
Emotional state associated with a goal of avoidance of something noxious
Consciousness
Awareness of internal and external states
Involves the cerebral cortex and reticular formation
Reticular formations
Diffuse network of neurones in the brainstem
Positive feedback loop
Monominergic projections ascend from the reticular formation to the cerebral cortex and activate the cortex
Pyramidal cells descend from the cerebral cortex to the reticular formation and activate the reticular formation
Inputs to the reticular formation
Somatosensory system - sensory neurones
Cortex
Outputs of the reticular formation
Basal forebrain nuclei
Hypothalamus
Thalamus
Basal forebrain nuclei
Send projection to the cortex
Stimulate the release of acetylcholine
Excitatory
Hypothalamus
Project to the cerebral cortex
Stimulate the real ease of histamine
Excitatory
Thalamus
Projections to the cerebral cortex
Stimulates the release of glutamate
Excitatory
Reticular activating system
Ascending projections to the basal forebrain nuclei, hypothalamus and thalamus
Glasgow coma scale
Highest score - 15
Lowest score - 3
Eye opening
Motor response
Verbal response
EEG
Electroencephalogram
Measures activity in groups of 1000s of neurones
- high temporal resolution - fast
- low special resolution - hard to localise neurones as electrodes spaced out
EEG when awake
50 Hz
A lot of external sensory input prevents neurones from synchronising therefore irregular
Beta waves
- also seen in REM
Stage I - closed eyes
10Hz
Decreased external sensory input
Neurones firing more in synch
Alpha waves
Stage II/III
Background alpha waves
Sleep spindle - caused by thalamus
K complex
Sleep spindle
When sleeping there is negative feedback on the thalamus but there can be sudden, unpredictable excitability of thalamus that causes sleep spindles
K complexes
Insight into intrinsic rate of cerebral cortex
Stage IV
K complexes
Delta waves
Decreased frequency and high amplitude as neurones are in synch
Sleeping
Pass around 6 cycles of sleep from stage 4 to REM
Inhibit the reticular activating system, thalamus and positive feedback loop
Removal of sensory inputs
REM
Dreaming
- Cortex provides the sensory input
- Paralysed except for the occulomotor muscles of the eyes as inhibitory projections inhibit LMNs (glycinergic)
- EEG similar to person that is awake but difficult to arouse due to inhibition of thalamus
- essential for life
- autonomic effects are seen e.g. penile erection and loss thermoregulation
Pons
Neurones in the pons activate REM sleep
Nocturnal bruxism
Grinding of teeth during sleep
Functions of sleep
Energy conservation
Muscle repair
Memory consolidation
Clear neck of extracellular debris
Sleep disorders
Insomnia - symptom
Narcolepsy
Sleep apnoea
Cause of insomnia
Anxiety
Stress
Depression
Caffeine
Narcolepsy
Neurones releasing less orexin
Genetic defect in the orexin gene
Obstructive sleep apnoea
Neck tissue compressed the trachea and pharynx
Narrowing the airways
Wake up several times during the night
Coma
Widespread cortical and brain stem damage with various EEG patterns
Unarousable
Unresponsive to stimuli
No sleep wake cycle detected
Persistent Vegetative state (PVS)
Like coma but with spontaneous eye opening
Sleep - wake cycle detectable
