Reflexes
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Reflexes

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    Reflexes Reflexes Presentation Transcript

    • REFLEXES
    • Actions performed automatically in response to a stimulus without conscious thought or decision are called reflex actions or reflexes.
      • Simple reflex actions are handled by the spinal cord without involvement of the brain.
      • Other reflexes are carried out in various relay centers in the lower brain or brainstem , but no conscious thought is involved.
      • Reflex actions carried out by the spinal cord occur automatically, but at the same time as the reflex occurs, sometimes a signal is sent to the brain by a connecting interneuron. When this happens, a stimulus is processed by the spinal cord as an arc and a response is sent back to the periphery, but a signal is also sent to the brain for interpretation and additional reaction .
    • Examples of each of these are:   a. Knee jerk response (simple/spinal cord only)
    • b. Sneezing – one of the reflex centers in the medulla (involves brainstem activity only)
    • c. Hand on a hot stove – a simple reflex pulls the hand away (spinal cord arc only, no brain involvement) followed by a reaction due to an interneuron connection to the brain from the spinal cord.
    • **optional
      • The systems described above represent the simplest units of the nervous system and are called reflex arcs . There are 5 parts to these:
      •   1. Sensory receptor(s) is/are stimulated.
      • Sensory neuron(s) send(s) message to the spinal cord.
      • ** Interneuron(s) in CNS transmit the message to one or more motor neurons.
      • Motor neurons transmit the message to the effector.
      • Effector (muscle) is stimulated.