Stretch Reflexes • 1. Stretching of the muscle activates a muscle spindle • A muscle spindle is a bundle of specialized skeletal muscle fibers that act as sensory receptors • 2. An impulse is transmitted by afferent fibers to the spinal cord • 3. Motor neurons in the spinal cord cause the stretched muscle to contract • 4. Reflexes Reflex - Rapid, involuntary Motor Response to Stimulus Reflexes may: - Inborn (Intrinsic) or Learned (Acquired) - Involve only Peripheral Nerves & Spinal Cord - Involve Higher Brain Centers as Well. 3. Reflex Arc 5 Components of Reflex Arc - Receptor - Site of Stimulus - Sensory Neuron - Transmits Afferent Impulse to CNS Materials rubber reflex hammer, penlight Procedure Part 1: Knee Jerk 1. Find a partner. You will act as each other's subjects.2. Have your subject sit on a desk with his or her legs crossed. The subject's upper leg should remain relaxed. Upload your study docs or become a Course Hero member to access this document Continue to access End of preview. The Reflex Action and the Reflex Arc Reflex actions are quick and involuntary responses to external stimuli. Reflexes take place with the help of receptors, sensory neurons, associated neurons, motor neurons and effector neurons (muscles or glands). The nerve JIBA/ATED 2019; 9(2):84-95 A. Kağnıcı & Ö. Sadi 87 Reflex action is a sudden and involuntary response to stimuli. It helps organisms to quickly adapt to an adverse circumstance that could have the potential to cause bodily harm or even death. Pulling our hands away immediately after touching a hot or cold object is a classic example of a reflex action. 2. Briefly state the event that proceeds a