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The patellar reflex, also called the knee reflex or knee-jerk, is a stretch reflex which tests the L2, L3, and L4 segments of the spinal cord. Many animals, most significantly humans, have been seen to have the patellar reflex, including dogs, cats, horses, and other mammalian species.
Knee jerk or patellar reflex — a kick caused by striking the patellar tendon with a tendon hammer just below the patella, stimulating the L4 and L3 reflex arcs. Moro reflex , a primitive reflex — only in all infants up to 4 or 5 months of age: a sudden symmetric spreading of the arms, then unspreading and crying, caused by an unexpected ...
Reflex arc demonstrated. When a reflex arc in an animal consists of only one sensory neuron and one motor neuron, it is defined as monosynaptic, referring to the presence of a single chemical synapse. In the case of peripheral muscle reflexes (patellar reflex, achilles reflex), brief stimulation to the muscle spindle results in contraction of ...
The patellar reflex (knee jerk) is an example of the stretch reflex and it is used to determine the sensitivity of the stretch reflex. Reflexes can be tested as part of a neurological examination, often if there is an injury to the central nervous system. To test the reflex, the muscle should be in a neutral position.
A stretch reflex is the contraction of a muscle in response to its lengthwise stretch. Biceps reflex (C5, C6) Brachioradialis reflex (C5, C6, C7) Extensor digitorum reflex (C6, C7) Triceps reflex (C6, C7, C8) Patellar reflex or knee-jerk reflex (L2, L3, L4) Ankle jerk reflex (Achilles reflex) (S1, S2)
The Jendrassik maneuver to reinforce knee-jerk. The Jendrassik maneuver is a medical maneuver wherein the patient clenches the teeth, flexes both sets of fingers into a hook-like form, and interlocks those sets of fingers together. The tendon below the patient's knee is then hit with a reflex hammer to elicit the patellar reflex. The elicited ...
Reflex circuits vary in complexity—the simplest spinal reflexes are mediated by a two-element chain, of which in the human body there is only one, also called a monosynaptic reflex (there is only one synapse between the two neurones taking part in the arc: sensory and motor). The singular example of a monosynaptic reflex is the patellar reflex.
Westphal's sign is the clinical correlate of the absence or decrease of patellar reflex or knee jerk. Patellar reflex or knee jerk is a kind of deep or stretch reflex where an application of a stimulus to the patellar tendon such as strike by a solid object or hammer caused the leg to extend due to such stimulus causes the quadriceps femoris muscle to contract.