PHIS 206 Lecture Notes - Lecture 10: Golgi Tendon Organ, Withdrawal Reflex, Muscle Spindle
2 May 2018
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Lecture 10: Reflexes and Smooth Muscle
Muscles have Sensors
• Muscle spindle
o Monitor muscle length
o Kinda sensor in muscle (manipulates itself to be same length as muscle) -- main
job is to detect how long the muscle is → can’t give good info about how long
muscle is unless it is the same length as muscle
• Golgi Tendon organ
o Monitor muscle force
o In series with muscle it protects, monitors how hard muscle is pulling
• These two sensors are not offering info about environment, its more of a feedback
• They evoke spinal reflexes (spinal because it does not need your head)
Stretch Reflex
• Protects muscle from becoming too long
• Important for balance and posture
• Involves spindle → when you hit your patellar tendon, your leg kicks because your
muscle gets slightly long very quick which makes you kick so the muscle gets shorter
(cause the muscle got too long too quickly) → the muscle in the front contract, the
muscles in the back relax so the leg can kick and fix the length
• When people have too many excited spindles all the time any change in muscle length
will cause contraction (I think?)
• Golgi tendon organ prevents you from tearing your muscle off your bone, if you are
putting too much force on your muscle, it shuts off your muscle so you drop everything
Withdrawal Reflex
• Pain or touch triggers reflexive muscular action
• Actions are opposite on opposite sides of the joint
o Thermal pain receptor in finger
o Afferent pathway
o Integrating center (spinal cord)
o Efferent pathways
o Effectors (response)
o Ascending pathway to brain
• Components of a reflex arc:
o Receptor
o Afferent pathway
o Interpreting center
o Efferent pathway
o Effector
• We flex on the side of the stimulus (“get us away from this threat”)
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