Ras

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Ras

  1. 1. The Reticular Activating SystemFriday, 11 January 2013
  2. 2. In topic 2 - Brain Structures and Processes we will learn about many areas of the brain and their functions. We will learn how they communicate (neurons and neurotansmitters) and control bodily functions. However to understand normal waking consciousness in particular attention, we need to jump ahead and look at the Reticular Activating System and the role of the Thalamus.Friday, 11 January 2013
  3. 3. The reticular activating system Is a network of neurons extending in many directions from the reticular formation in the brainstem to different parts of the brain and spinal cord Functions include: • Arousal, e.g. regulates by increasing or decreasing • Alertness, e.g. regulates wakefulness and attention • Selective attention, e.g. regulates what we choose to attend to, directs specific cortical areas to focus on relevant information Evidence for these functions includes: • Destroying the RAS causes a coma resembling sleep • Electrical stimulation of RAS instantly awakens sleeping animalsFriday, 11 January 2013
  4. 4. Thalamus Is a small structure on the top of the brain stem that filters and relays incoming sensory information (except smell) to relevant cortical areas. Information moves from cortical areas to lower brain structures, the spinal cord and out to the peripheral nervous system. Function: • Plays a role in attention by actively filtering incoming sensory information, giving more weight to and emphasising certain information. • Regulates arousal through connection with the RAs. • Closes pathways of incoming information during sleep, preventing information from reaching the brain as it restsFriday, 11 January 2013

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