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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. A stimulus initiates a neural signal, which is carried to a synapse. The signal is then transferred across the synapse to a motor neuron, which evokes a target response. These neural signals do not always travel to the brain,[4] so many reflexes are an automatic response to a stimulus that does not receive or need conscious thought.[5]

Many reflexes are fine-tuned to increase organism survival and self-defense.[6] This is observed in reflexes such as the startle reflex, which provides an automatic response to an unexpected stimulus, and the feline righting reflex, which reorients a cat's body when falling to ensure safe landing. The simplest type of reflex, a short-latency reflex, has a single synapse, or junction, in the signaling pathway.[7] Long-latency reflexes produce nerve signals that are transduced across multiple synapses before generating the reflex response.

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The myotatic or muscle stretch reflexes (sometimes known as deep tendon reflexes) provide information on the integrity of the central nervous system and peripheral nervous system. This information can be detected using electromyography (EMG).[8] Generally, decreased reflexes indicate a peripheral problem, and lively or exaggerated reflexes a central one.[8] A stretch reflex is the contraction of a muscle in response to its lengthwise stretch.

Newborn babies have a number of other reflexes which are not seen in adults, referred to as primitive reflexes. These automatic reactions to stimuli enable infants to respond to the environment before any learning has taken place. They include:

Many of these reflexes are quite complex, requiring a number of synapses in a number of different nuclei in the central nervous system (e.g., the escape reflex). Others of these involve just a couple of synapses to function (e.g., the withdrawal reflex).Processes such as breathing, digestion, and the maintenance of the heartbeat can also be regarded as reflex actions, according to some definitions of the term.

In medicine, reflexes are often used to assess the health of the nervous system. Doctors will typically grade the activity of a reflex on a scale from 0 to 4. While 2+ is considered normal, some healthy individuals are hypo-reflexive and register all reflexes at 1+, while others are hyper-reflexive and register all reflexes at 3+.

Some might imagine that reflexes are immutable. In reality, however, most reflexes are flexible and can be substantially modified to match the requirements of the behavior in both vertebrates and invertebrates.[9][10][11]

A good example of reflex modulation is the stretch reflex.[12][13][14][15] When a muscle is stretched at rest, the stretch reflex leads to contraction of the muscle, thereby opposing stretch (resistance reflex). This helps to stabilize posture. During voluntary movements, however, the intensity (gain) of the reflex is reduced or its sign is even reversed. This prevents resistance reflexes from impeding movements.

Background: Semmelweis reflex is a human behavioral tendency to stick to preexisting beliefs and to reject fresh ideas that contradict them (despite adequate evidence). We aim to familiarize the readers with the term that not only has a significant historical background but also grave clinical implications.

Methods: A keyword search for "Semmelweis reflex," "Belief perseverance," "handwashing," and "Idea rejection" was conducted using PubMed Central, MEDLINE, and Google SCHOLAR. Literature published in paper-based journals and books was also searched. All manuscripts pertaining to these keywords were thoroughly analyzed for this review.

Conclusions: The age-old prejudice that is Semmelweis reflex is explored in this review. With careful and thorough study design, scientific rigor, and critical self-analysis of the manuscript, one can avoid being victimized by this reflex. The dual edged nature of this reflex lays unveiled when its importance is highlighted in the prematurely accepted medical failures. Understanding that any new idea goes through the grill of being critically analyzed and perceived encourages the scientist to hold on to the original thought as it may rather be practice changing.

The gastrocolic reflex is a physiological reflex that controls the motility of the lower gastrointestinal tract following a meal. As a result of the gastrocolic reflex, the colon has increased motility in response to the stretch of the stomach with the ingestion of food. The gastrocolic reflex allows room for the consumption of more food via control over peristalsis and movement of ingested food distally toward the rectum. Myoelectric recordings demonstrate the reflex in the large intestine that shows a spike in electrical activity within minutes of food consumption. The gastrocolic reflex initiates and controls migrating motor complexes throughout the colon. These motor complexes act cyclically during the digestion process and can be broken up into four phases.

Alteration in the gastrocolic reflex has been a suspected etiology in patients with irritable bowel syndrome (IBS). Patients with IBS have demonstrated a stronger colonic response to the gastrocolic reflex. These patients may experience a strong urge to defecate following ingestion of a meal and may experience symptoms like abdominal distension, flatulence, pain, and tenesmus.[3][4] Furthermore, alternations in the gut microbiome can cause a downstream effect that alters the enteroendocrine cells' ability to sense and carry out paracrine functions, thus indirectly affecting the motility of the colon.

Profound gastrocolic reflex has been implicated in the idiopathic variant of dumping syndrome (DS). Although abdominal pain is present in both DS and IBS, systemic signs including palpitations, hypotension, dizziness, diaphoresis often accompany DS. Another key difference in the presentation of DS is that they often present with protein-calorie malnutrition due to increased excess nutritional loss in diarrhea.[5]

Both IBS and DS are caused by profound gastrocolic reflex, whereas poor gastrocolic reflex results in constipation. Neuronal dysfunction may lead to impaired gastrocolic reflex and poor gut motility. Diabetic patients with neuropathy often have gastroparesis resulting in delayed gastric emptying and also impaired gastrocolic reflex leading to constipation.[6]

The gastrocolic reflex is multisystemic in origin. The reflex involves the autonomic nervous system, the enteric nervous system, and cells of the GI tract that regulate endocrine functions. Signals from the central nervous system communicate with the enteric nervous system and vice versa controlling peristalsis. The enteric nervous system proves to be paramount and is demonstrated by the morbid effects of enteric nervous system neuropathies; this is in contrast with the importance of vagal and sympathetic inputs, which have shown not to carry as much of an effect if these connections become interrupted.[14]

When food gets introduced into the stomach, a coordinated response via stretch receptors, neuropeptides, and the enteric nervous system activate the gastrocolic reflex, which in turn increases the motility in the colon to make room for more food. Migrating motor complexes induce food bolus movement through slow waves and faster segments of increased electrical activity, know as spike waves; this is very similar to how the stomach and small intestine move food. The large bowel also employs stronger, more frequent contractions known as mass movements in response to signals from mechanical stretch receptors in the stomach and the products of digestion in the small intestine. The enteric nervous system controls these mass movements and is most active in the transverse and left colon, which helps move food toward the rectum for defecation, which is the reason behind the urge to defecate following ingestion of a meal.[17][2]

A colon transit study may be employed to test for the functionality of the gastrocolic reflex. The gold standard for measuring colon transit time utilizes a radiopaque indicator that is easy to do and relatively low cost. The only downside to this test is that it subjects the patient undergoing radiation exposure. Another test utilized is radionuclide scintigraphy. This is done using a labeled radioisotope and viewed through a specialized camera. The patient swallows a labeled radioisotope, and it gets followed throughout transit through the GI tract; this approach exposes a lesser degree of radiation. Both of these transit studies are usually for research purposes and less often used in clinical practice. Colonic manometry and bead expulsion are more frequently used to assess the contractility and motility of the colon. Colonic manometry is a more common modality in children with colonic dysmotility, encopresis, and abdominal pain. They record various colonic motor contractions and guide the further courses of treatment, including the need for surgical interventions.[18] Lastly, a test that uses wireless motility capsules has been considered.[19]

The gastrocolic reflex has correlations with the pathogenesis of irritable bowel syndrome. The act of food consumption can provoke an overreaction of the gastrocolic response due to heightened visceral sensitivity seen in IBS patients, resulting in abdominal pain, constipation, diarrhea, bloating, and tenesmus. It is also a known fact that ondansetron decreases the tonic response to stretch, giving evidence toward its use in providing relief for patients with IBS. Commonly prescribed medications to treat overreactive gastrocolic response include antispasmodics, tricyclic antidepressants, and SSRIs. Antibiotics and probiotics have also been utilized to restore normal colonic flora, which in turn helps regulate the response of integral components of the reflex. 2351a5e196