Spinal Reflexes Flashcards
Occur without direct involvement of higher brain centers.
Spinal Reflexes
Provide the nervous system with information about the length of a muscle.
Muscle Spindles
Provide the nervous system with information about the tension in a muscle.
Tendon Organs.
Modified skeletal muscle fibers in muscle spindles that are enclosed in connective tissue capsules. Mostly noncontractile, but have contractile regions at their ends. Receptive surface of the spindle.
Intrafusal Muscle Fibers
Effector fibers of the muscle.
Extrafusal Muscle Fibers
Endings of large axons that wrap around the muscle spindle center. Stimulated by both rate and degree of stretch.
Anulospiral Endings
Smaller axons that supply the spindle ends. Stimulated by degree of stretch.
Flower Spray Endings
Innervate the contractile regions of intrafusal muscle fibers. Arise from small motor neurons in the ventral horn of the spinal cord.
Gamma Efferent Fibers
Innervate the extrafusal muscle fibers.
Alpha Efferent Fibers
Stimulated the extrafusal muscle fibers to contract.
Alpha Motor Neurons
Descending fibers of mother pathways synapse both motor neurons so that motor impulses are simultaneously sent to the large extrafusal fibers and to muscle spindle intrafusal fibers.
Alpha-Gamma Coactivation
Causes muscle contraction in response to increased muscle length to make sure that muscles stay at the length set by the brain. Important for maintaining muscle tone.
Stretch Reflex
A stretch reflex that prevents knees from buckling when you are standing upright.
Patellar Reflex
Occurs when branches of afferent fibers from muscle spindles synapse with interneurons that inhibit motor neurons controlling antagonistic muscles.
Reciprocal Inhibition
All stretch reflexes are these types
Monosynaptic and Ipsilateral.
Reflexes that involve motor activity on the same side.
Ipsilateral
Cause muscles to relax in response to tension. Help prevent muscles and tendons from tearing when they are subjected to potentially damaging stretching force.
Tendon Reflexes
Occurs when motor neurons in spinal cord circuits supplying contracting muscles are inhibited and antagonist muscles are activated.
Reciprocal Activation
Initiated by a painful stimulus. Causes automatic withdrawal of the threatened body part from the stimulus.
Flexor Reflex
Flexor reflexes are these types.
Ipsilateral and polysynaptic
Occurs when incoming afferent fibers synapse with interneurons that control the flexor withdrawal response on the same side of the body and with other interneurons that control extensor muscles on the opposite side.
Crossed-Extensor Reflex
Elicited by gentle cutaneous stimulation.
Superficial Reflexes
A superficial reflex that occurs when stroking the skin of the lateral abdomen above, to the side, or below the umbilicus and induces a reflex contraction of the abdominal muscles.
Abdominal Reflexes
A superficial reflex that occurs when stroking along the lateral aspect of the plantar surface of the foot, causing the toes to flex downward.
Plantar Reflex
