How do  reflexes differ from other motor actions?

Topic: How do  reflexes differ from other motor actions?


Reflexes are quick, involuntary, stereotyped reactions of glands or muscles to stimulation. Reflexes required stimulation they are not spontaneous action like muscle for example tic, but responses to sensory input. Reflexes are quick they generally involve  in only a few interneurons, or none and minimum synaptic delay. There are three main reflexes actions sensory, motor and relay. These different types of neurons work together in a reflex action. A reflex action is an automatic (involuntary) and rapid response to a stimulus, which minimizes any damage to the body from potentially harmful conditions, such as touching something hot. Reflex action are therefore essential to survival of many organisms, reflex action follows the general sequence and does not involve the conscious part of the Brain.. This is why the response is so fast. A gamma motor neuron of the spinal cord innervates each end and stimulates it contraction. This maintains tension and sensitivity of the intrafusal fiber preventing it from going slack like an unstretched rubber band when a muscle shortens. Spinal motor neurons that supply the extrafusal muscle fiber are called alpha motor neurons.( Saladin 2020) pg 482-484



sensory neurone

Relay neurone

Motor neurone




Critical Thinking


Most of us have had our reflexes tested with a little rubber hammer a tap of the elbow or the knee. Produces and uncontrollable jerk of the leg. In most reflex arcs the integrating center includes one or more interneurons. Synaptic events in the integrating center determine whether the different neurons issue s signal to the muscles. The more interneurons there are the most complex the information processing can be, but with more synapses, there is a longer delay between input and out put. many somatic reflexes involve stretch receptors called muscle spindles embedded in the muscle these are located among the body’s proprioceptors, these sense organs are specialized to monitor the position and movement of the body parts. The function of muscle spindles is to inform the brain of muscle length and body movements. This enable the brain to send motor commands back to the muscles that control muscle tone, posture, coordinate movement, and corrective reflexes for example, to keep one’s balance spindles specially aboundant in muscle that required fire control. Hands and foot muscles have 100 or more spindles per gram of muscle, where there are relatively few in large muscle with coarse movements and more at all in the middle- ear muscle. A muscle spindle is a bundle of usually seven or eight small modified muscle fiber enclosed in an elongated fibrous capsule about 5to10mm long. spindles are especially concentrated at the end of a muscle near it tendon.(fig 13.24) pg 483.



Saladin,K(2020)Anatomy and Physiology The unit of forms and function(9thed) McGraw Hill Education.

Reflex actions – The nervous system – GCSE Biology (Single Science) Revision – BBC BitesizeLearn about the nervous system which includes the central and peripheral nervous systems with BBC Bitesize GCSE Science.BBC Bitesize