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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.
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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.
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 ...
English: Explicative diagram of reflex arc; the journey takes energy and nerve impulse of a stimulus by two or more neurons.The spinal cord(3) receives sensory impulses of the body(2)- here his finger and sent to the central nervous system (afferent pathways(4), which sends impulses to the spinal motor (efferent(5)that sends turn-here the bodies arm muscle through spinal nerves(6).
In a reflex arc, an action potential never travels to the brain for processing and so results in a much quicker reaction. When a stimulus (pain) is encountered, the signal from that stimulus will travel up the sensory neuron to the spinal column.
A list of reflexes in humans. Abdominal reflex; Accommodation reflex — coordinated changes in the vergence, lens shape and pupil size when looking at a distant object after a near object. Acoustic reflex or attenuation reflex — contraction of the stapedius and tensor tympani muscles in the middle ear in response to high sound intensities.
The simplest reflex is initiated by a stimulus, which activates an afferent nerve. The signal is then passed to a response neuron, which generates a response. Reflexes are found with varying levels of complexity in organisms with a nervous system. A reflex occurs via neural pathways in the nervous system called reflex arcs.