Dictionary > Patellar reflex

Patellar reflex

Definition
noun, plural: patellar reflexes
A stretch reflex wherein the anterior muscles of the thigh contracts by reflex as a response to a smart tap on the patellar tendon while the leg hangs loosely at a right angle with the thigh
Supplement
A stretch reflex is a reflex reaction characterized by muscle contraction due to the stimulation of the muscle proprioceptors. When the muscle is stretched, the body reacts by resisting the stretch by reflex. Some of the stretch reflexes are jaw jerk reflex, biceps reflex, brachioradialis reflex, triceps reflex, patellar reflex, and ankle jerk reflex.
A patellar reflex is a form of stretch reflex involving the L2, L3, and L4 segments of the spinal cord. It is applied in neurological examination to determine the status of the nerves in those regions. The test is done by striking the patellar tendon with a reflex hammer while the leg hangs loosely at a right angle with the thigh. This elicits a reflex reaction involving the anterior muscles of the thigh. The muscle contracts leading to the oscillation of the leg once, and then rests. The absence of this reflex may be an indication of a neurologic problem or an underlying medical condition such as lower motor neuron lesion. This reflex though is absent during sleep. Too many leg oscillations following the tap may be an indication of a cerebral disease.
Synonym(s):

  • knee jerk
  • knee phenomenon
  • knee reflex
  • knee-jerk reflex
  • patellar tendon reflex
  • quadriceps reflex

See also:

  • stretch reflex


    You will also like...

    Gibberellins and Gibberellic Acid
    Gibberellins and Gibberellic Acid

    This tutorial describes the role of gibberellin family in plants. Find out the effects of gibberellin on plant growth an..

    Geological Periods
    Geological Periods

    Geological periods is a study guide that cites the different geological periods on Earth's timeline. Each has a brief ov..

    Growth Patterns
    Growth Patterns

    This tutorial describes the sigmoid curve, annual plant growth, tree growth, human growth, and insect growth as the grow..

    Hormone Production
    Hormone Production

    Hormones are chemical messengers produced by specialized glands and they were produced by switching on the genes designe..

    Biological Cell Defense
    Biological Cell Defense

    Organisms employ different strategies to boost its defenses against antigens. Humans have an immune system to combat pat..

    Human Neurology
    Human Neurology

    Human Neurology deals essentially with the nervous system of humans. It also features the various theories put forward b..