PSYC 211 Chapter Notes - Chapter 8: Superior Colliculus, Muscle Spindle, Two-Streams Hypothesis
22 Aug 2013
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Document Summary
Spinal cord has some autonomy, particular kinds of somatosensory stimuli can elicit quick responses via neural connections in spinal cord; reflexes are simplest level of motor integration, e. g. patellar reflex takes 50 milliseconds. If weight added, muscle lengthens, increases firing rate of muscle spindle afferent neurons, which increases firing rate of buttons that stimulate alpha motor neurons. Gamma motor system: rate of firing determines degree of contraction. When active, they become shorter and more sensitive to changes in muscle length. Adjustable sensitivity simplifies role of brain in controlling movement, since more control in spinal cord means fewer messages sent to/from brain. If muscle spindle contracts faster than muscle as a whole, then there will be afferent activity. By establishing rate of firing in the gamma motor system, brain controls length of muscle spindles and indirectly the length of the entire muscle. Polysynaptic reflexes: afferent axons from golgi tendon organ are detectors of muscle stretch.
