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In biology, a reflex, or reflex action, is an involuntary, unplanned sequence or action [1] and nearly instantaneous response to a stimulus. [2] [3] 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.
Joints are controlled by two opposing sets of muscles called extensors and flexors, that work in synchrony for smooth movement.When a muscle spindle is stretched, the stretch reflex is activated, and the opposing muscle group must be inhibited to prevent it from working against the contraction of the homonymous muscle.
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.
However, actions controlled by polysynaptic reflex loops are still faster than actions which require perceptual processing. [30]: 171, 578 While the actions of short-loop reflexes are fixed, polysynaptic reflexes can often be regulated by instruction or prior experience. [31]
A common example of reciprocal innervation, is the effect of the nociceptive (or nocifensive) reflex, or defensive response to pain, otherwise commonly known as the withdrawal reflex; a type of involuntary action of the body to remove the body part from the vicinity of an offending object by contracting the appropriate muscles (usually flexor ...
The autonomic nervous system is regulated by integrated reflexes through the brainstem to the spinal cord and organs. Autonomic functions include control of respiration, cardiac regulation (the cardiac control center), vasomotor activity (the vasomotor center), and certain reflex actions such as coughing, sneezing, swallowing and vomiting.
There are many various reflexes that can occur simultaneously during a startle response. The fastest reflex recorded in humans happens within the masseter muscle or jaw muscle. The reflex was measured by electromyography which records the electrical activity during movement of the muscles. This also showed the response latency, or the delay ...
The righting reflex is not exclusive to humans. A well-known righting reflex in cats allows them to land on their feet after a fall. As a cat falls, it turns its head, rotates its spine, aligns its hindquarters, and arches its back to minimize injury. [18]