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29/07/2018
Arousal & wakefulness
The Reticular System
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CNS
Consists of:
Brain
Spinal cord
Receives input from sensory neurons.
Directs activity of motor neurons.
Association neurons maintain homeostasis.
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3. Arousal
Non specific arousal of the cerebral cortex to incoming sensory information.
This requires that Sensory information flows from the brain stem to the cortex.
Part of this pathway is the
Reticular Activating System.
It plays a major part in keeping us awake & alert & allowing us to sleep.
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7. RAS - the attention centre in the brain
The key to "turning on your brain," ? the centre of motivation.
It is connected at its base to the spinal cord where it receives information projected directly from the ascending sensory tracts.
It runs all the way up to the mid-brain.
As a result, the Reticular Activating System is a very complex collection of neurones that serve as a point of convergence for signals from the external world and from interior environment.
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Connections
RAS generates dynamic effects on the activity of the cortex, including the frontal lobes, and the motor activity centres of the brain.
It plays a role in determining whether a person can learn & remember things well, whether or not a person is impulsive or self-controlled, whether or not a person has high or low motor activity levels & whether or not a person is highly motivated or bored easily.
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9. A centre of balance for systems
When functioning normally, it provides the neural connections that are needed for the processing and learning of information, and the ability to pay attention to the correct task. 
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RAS in brief
Stimulated from all of the sensory systems & feeds stimuli through the brain stem to the cerebral-cortex.
The cerebral-cortex feeds stimuli back to the RAS which conveys stimuli to the muscular system
The muscular system in turn feeds back to the RAS.
The RAS appears to have an activating or deactivating effect that allows us to sleep and wake – It is less active when a person falls asleep, as sensory input to the cortex decreases.
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11. Communicating with dynamic systems--- examples
The RAS
Communicating with dynamic systems--- examples
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14. Neural Pathways from Retina
Think about stimuli that might contribute to waking you from sleep
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Optic Nerves
AVIOD STIMULATION OF BOTH EYES AT THE SAME TIME
- A little more useful info to take with you to skills re pupil assessment
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Smell (olfaction)
sensory neurons located within pseudostratified epithelium.
The axon projects up into olfactory bulb of cerebrum.
Think about visual stimuli that might contribute to waking you from sleep
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Ears and Hearing
Sound waves travel in all directions from their source.
Waves are characterized by frequency and intensity.
Frequency:
Measured in hertz (cycles per second).
Greater the frequency the higher the pitch.
Intensity:
Directly related to amplitude of sound waves.
Measured in decibels.
Sounds all around us my not play a part of our conscious recognition but are processed by our RAS. Think about our relaxation experiment
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18. Brain/Brain stem need O2 & glucose
Blood flow to the brain is maintain at about 750 ml/min. This is regulated in respect of the brains metabolic demands & mean arterial B/P.
The mean arterial pressure ranges between 60mmhg and 160mmhg:
Increase C02 & H+ concentrations both increase cerebral blood flow, as does a decreased 02 concentration.
This help to keep us aroused during stress
Lack of blood supply & 02 will affect the ability of the RAS to respond
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Melatonin study
hormone produced in the brain by the pineal gland,
?involved in the control of sleep & in the correction of some sleep problems.
Low doses of melatonin helped healthy young adults and elderly insomniacs to fall asleep faster. It also helped older people awaken less frequently
Melatonin: A Sleep-Promoting Hormone, Irina V. Zhdanova, Harry J. Lynch, and Richard J. Wurtman, Sleep, Volume 20, Number 10, 1997
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Other conditions
Have a think about attention deficit disorder
Low motivation
‘Slow learners’
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