The straightening reflex , also known as the Labyrinthine straightening reflex, is a reflex that corrects the orientation of the body when taken from the normal upright position. It is started by the vestibular system, which detects that the body is not erect and causes the head to return to its original position while the rest of the body follows. Perception of head movement involves the body feeling the linear acceleration or the force of gravity through the otolith, and the acceleration of the angle through the semicircular canal. Reflexes use a combination of visual system input, vestibular input, and somatosensory input to make postural adjustments as the body shifts from its normal vertical position. This input is used to create what is called a copy of the eference. This means the brain makes comparisons in the cerebellum between expected posture and perceived posture, and corrects the difference. Reflexes can be affected by different types of balance disorders. Straightener reflexes have also been studied in non-human mammals, especially cats. Proper reflection takes 6-7 weeks to perfect.
Video Righting reflex
Overview
Vestibular System
The vestibular system consists of the inner ear organ forming a "labyrinth": the semicircular canal, otolith, and cochlea. The section below is a description of the vestibular system, because it is very important to understand the straightening reflex. Sensory information from the vestibular system allows the head to return to position when disturbed when other parts of the body follow. The semicircular canal (brown, see picture) is arranged at an angle to the horizontal plane of the head when it is in a normal vertical position. Each channel has a broad base, called the ampulla, which shadows special sensory hair cells. The fluid in these canals surrounds the hair cells, and travels through them as the head moves to gather information about motion and body position. Hair cells are covered by tiny sensory hairs called stereocilia, which are sensitive to displacement forces because the body moves in different positions. When the head is moved, the force moves the hair cells forward, which sends signals to the afferents and to the brain. The brain can then decide which muscles in the body need to be active to repair itself.
The semicircular canals have superior, posterior, and horizontal components. Studies have shown that the horizontal canal is most correlated with agility, as indicated by some mammals. The curvature and size of these canals seem to affect agility, and probably because of the environment in which animals navigate, such as two-dimensional landscapes compared to three-dimensional space (ie, air, trees, or water).
Otolith has two components: utricle and saccule. Both are made up of the same sensory tissue that contains hair cells, which are covered by an agar layer and an above-mentioned autolithic membrane. Embedded in this membrane is a crystalline calcium carbonate, called otoconia, or "ear stone". When the head is tilted forward or backward, autoconia moves the hair cells in the same way as the semicircular canal fluid movements and causes depolarization of the hair cells. Signals from these cells are also transmitted along with afferent fibers and to the brain.
Signal Transduction
The vestibular afferent signals are carried by hair cells of type I or type II, which are distinguished by larger amounts of stereocilia per cell in type I cells than in type II cells. The nerve fibers attached to these hair cells carry signals to the vestibular nucleus in the brain, which is then used to obtain information about body position. Large-diameter afferent fibers carry information from type I and type II hair cells, and regular afferent fibers carry signals from Type II hair cells. A semicircular canal encodes a head velocity signal, or angular acceleration, while autoconia encodes a linear acceleration signal and a gravitational signal. Regular afferent signals and irregular afferent signals travel to the vestibular nucleus in the brain, although irregular signals are at least twice as sensitive. Because of this, it has been questioned why humans have common afferent signals. Studies have shown that common afferent signals provide information about how long the head or body movements take place, and the irregular afferent signals occur when the head is moved harder, like a fall.
Maps Righting reflex
Function
Straightening reflexes involve complex muscle movements in response to stimuli. When shocked, the brain can evoke an anticipatory posture adjustment, or series of muscle movements, involving the function of the midbrain. However, the mechanism of origin has not been explained. The data support the formation of these movements from spinal circuits connected to additional motor areas, basal ganglia, and reticular formations.
Reference frame
The visual input for proper refining straightening functions is felt in the form of a frame of reference, which creates a space representation for comparison with expected orientation. Three types of reference frames are used to view the vertical orientation; they are consistently updated and quickly adaptable for processing vestibular input changes.
Allocentric reference template
The allocentric reference framework describes a visual frame of reference based on the arrangement of objects within an organism's environment. To test the use of the allocentric reference framework, the "trunk-and-frame" test, in which the subject's perception of virtual objects in a changing environment, can be used to cause the slope of the body as a trusting subject to correct for shift.
The egocentric reference frame
The egocentric frame of reference refers to the proprioceptive reference frame using the body position of the organism in space. This frame of reference relies heavily on somatosensory information, or feedback from the body's sensory system. Muscle vibrations can be used to change the subject's perception of the location of their body by creating abnormal somatosensory signals.
Geocentric reference frame
Geocentric reference frames involve visual inputs to help detect environmental verticality through gravitational pull. The soles of the feet contain receptors in the skin to detect gravity, and play a big role in standing or walking balance. Abdominal organs also contain receptors that provide geocentric information. The "Roll-tilt" test in which the subject body is mechanically moved can be used to test the function of geocentric reference frames.
Path
The straightening reflex can be described as a three-neuron arc system consisting of primary vestibular neurons, vestibular core neurons, and target motorneuron. Input from the vestibular system is received by the sensory receptors in the hair cells of the semicircular canal and otolith, which are processed in vestibular nuclei. The small brain is also active at this time to process what is called a copy of the eference, which compares the expectations of posture to how it is oriented at the time. The difference between the expected posture and the actual posture is corrected for through the motorneurons in the spinal cord, which controls the muscle movement to straighten the body.
This automatic postural adjustment can be explained in two reflexes similar to the straightening reflex: vestibulo-ocular reflex (VOR) and vestibulocollic reflex (VCR) . VOR involves eye movement when the head is turned to remain fixed on the stationary image, and the VCR involves control of the neck muscles for head orientation correction. During VOR, the semicircular canal sends information to the brain and improves eye movement in the opposite direction of head movement by sending excitatory signals to motor neurons on the opposite side of the head rotation. Neurons in otoliths not only control these signals to control eye movement, but also signals for correction of head movement through the neck muscles. Reflex straightens using VOR and VCR as it brings the body back into position. Visual information under the control of this reflex creates greater stability for more accurate postural correction.
Test to improve reflex function
Vestibular function can be tested through a series of visual acuity tests. The static visual acuity test investigates the patient's ability to view objects remotely by placing the subject at a certain distance from the letters mounted on the screen. The dynamic visual acuity test involves the patient's ability to control eye movements by following the letters that appear on the screen. The difference between these two test results is the patient's fixation capability and the efficiency of the vestibuloocular reflex (VOR).
Vestibular reflexes can also be examined using a tilt body experiment. Patients with vestibular disorders can be through the Dix-Hallpike maneuver, where the patient sits with elongated legs and turns the head 45 degrees. The patient is then asked to lie on the table and check for nystagmus, or uncontrolled eye movement. Nystagmus in the patient shows vestibular system dysfunction, which can cause dizziness and inability to complete the straightening reflex.
The proprioceptive ability test is important in testing to improve reflex function. A therapist may ask the patient if he knows where a particular leg or joint is without seeing it. These tests are often performed on uneven surfaces, including sand and grass.
More recently, vestibular reflexes have been investigated using a foot rotation experiment. Foot and foot rotation tests can be used to investigate changes in neuron activity in the labyrinth, or inner ear. When the head is turned when the legs and feet are turned 90 degrees, the vestibular signal causes the brain to block movement toward rotation. At the same time, it activates the muscles on the opposite side in an attempt to correct the displacement.
Plasticity
Because visual input is essential in proper aligning reflex function, visual impairment can be detrimental. Blind patients can rely on vestibular input where visual input is not available, and the visual cortex can be rewired to accommodate other senses to take control. Developmentally blind patients have larger parts of the brain dedicated to vestibular and somatosensory inputs than patients with normal visual function. Recently blind patients should establish new connections where visual input is used, and vestibular therapy may improve this ability. This principle, called neuroplasticity, is a growing interest for researchers today.
Disorders
Many inner ear disorders can cause dizziness, which leads to dysfunctional straightening reflex action. A common inner ear disorder can cause vertigo in the patient, which may be an acute or chronic symptom. Labyrinthitis, or inflammation of the inner ear, can cause an imbalance that must be overcome through therapeutic exercise. Labyrinthectomy, or removal of the inner ear organs, is an operation performed for patients with inner ear disorders whose vertigs are debilitating. Imbalances result from the procedure, but therapy can help to overcome the symptoms.
Vertigo positional paroxysmal benign
Benign paroxysmal positivity vertigo, or BPPV, is a disorder caused by the breaking of otoconia pieces from otolith. Otoconia floats freely in the inner ear fluid, causing disorientation and vertigo. This disorder can be tested for using nystagmus tests, such as Dix-Hallpike maneuvers. This disorder can disrupt the reflex function of straightening as symptoms of vertigo and disorientation prevent proper postural control. Treatments for disorders include antihistamines and anticholinergics, and disorders often disappear without surgical removal of free otoconia.
Diseases MÃÆ' Â © niÃÆ'¨re
Disease MÃÆ' Â © niÃÆ'¨re is considered a balance disorder involving fluid buildup in the inner ear. This can be caused by a number of factors, including head injury, ear infections, genetic predisposition, chemical toxicity, allergies, or syphilis. Syphilis may cause some patients to develop the disease later in life. The disease is characterized by pressure in the ears, ringing in the ears, and vertigo. It also causes nystagmus, or uncontrolled eye movement. There is no known treatment for this disorder, although symptoms can be treated. These include water pills to dilute ear fluids, eat a low-salt diet, and take anti-nausea medication.
Other causes of reflex aligning disorder
Vestibular and balance disorders can have a number of contributing factors. Dietary factors such as high-salt diet, high caffeine intake, high sugar intake, monosodium glutamate (MSG) intake, dehydration, or food allergies can contribute to vertigo symptoms and should be avoided in patients with balance disorders. Other disorders may have vertigo symptoms associated with them, such as epilepsy, migraine, stroke, or multiple sclerosis. Infectious diseases such as Lyme disease and meningitis can also cause vertigo.
Straighten out reflexes in animals
Reflex straightening is not exclusive to humans. The famous buffer reflex in cats allows them to land on the soles of the feet after falling. When the cat falls, it turns its head, rotates its spine, aligns its hind legs, and arches its back to minimize injury. Cats achieve a free fall to achieve this, which is much lower than humans, and they can touch the ground in a relaxed body shape to prevent serious injury.
However, bats possess the unique anatomy of the vestibular system. Their balance system, at a 180 degree orientation opposite to humans, allows them to perform strong feats while flying in the dark. The ability of this pair to function vestibular with sensory echolocation to hunt prey. However, they do not have a straightening reflex that is similar to most mammals. When exposed to zero-G, bats do not undergo a series of straightening reflexes that most mammals do to improve orientation because they are used to resting upside-down.
References
Source of the article : Wikipedia
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