9) The Reticular Formation and Consciousness Flashcards
Define Arousal
Emotional State associated with a goal or avoidance of noxious stimuli
Define Consciousness
Awareness of both external world and internal state
What two neural components are required for Consciousness ?
Cerebral Cortex + Reticular Formation
> Connected by Reciprocal Excitatory Projections, forming a Positive feed back Loop
When is positive feedback loop seen between Cerebral Cortex and Reticular Formation ?
It is seen where there is a binary outcome. e.g. Sleep / Awake, Ovulating / Not Ovulating
What is the Reticular Formation ?
Interneurones in the grey matter which when activated allows for consciousness
How does the RF relay information to the cortex ?
3 routes
Basal Forebrain Nuclei => Sends Excitatory Cholinergic Fibres to the Cortex
Hypothalamus => Sends Excitatory Histaminergic Fibres to the Cortex
Thalamus => Sends Excitatory Glutaatergic Fibres to the Cortex
Where else does RF relay to aside from Cortex ?
Spinal Cord, controls muscle tone
How can you assess Consciousness ?
GCS, Glasgow Coma Scale
Max = 15
Min = 3
What is assessed in GCS
Eye Opening 4 - Spontaneous Eye Opening 3 - Response to Speech 2 - Response to Pain 1 - No Response
Motor Response 6 - Obeys Command 5 - Localises to Stimuli 4 - Withdraws to Pain 3 - Flexor Response to Pain 2 - Extensor Response to Pain 1 - No response to Pain
Verbal Response 5 - Oriented to time / place 4 - Confused Conversation 3 - Inappropriate Words 2 - Incomprehensible Sounds 1 - No response
How can you measure activity of Neurones in the Cortex
Electro Encephalogram
Describe the different stages of sleep. 6 Stages
Awake Eye Open
=> beta waves, irregular 50hz
Awake Eye Shut
=> alpha waves, regular 10 hz
Stage 1
=> Background alpha interspersed by theta waves (5hz)
Stage 2 / 3
=> Theta interspersed with sleep spindles and K Complexes
Stage 4
=> Delta Waves, Regular 1Hz
REM sleep
=> EEG similar to beta waves, dreaming occurs
What is the neural mechanism of Non - REM Sleep
> Deactivation of RF, loss of PF between cortex and RF therefore reduced Cortical Activity
Inhibition of Thalamus
What initiates REM Sleep ?
Initiated by Neurones by the Pons
What happens to the body during REM Sleep ?
> Decreased muscle tone - Glycinergic inhibition of LMNs
Eye movements and other CNs
Autonomic Effects e.g.Penile Erection, loss of thermal regulation
List 3 common sleeping disorders
Insomnia => Can’t Sleep most likely an underlying psychiatric disorder
Narcolepsy => Problems in Neuro transmission unable to maintain awaked state
Sleep Apnoea => Compression of airway during sleep, so they wake up. Occurs in people with fat necks
