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Spinal Cord and Reflexes
Published in Nassir H. Sabah, Neuromuscular Fundamentals, 2020
A reflex is a largely involuntary and stereotyped action that occurs relatively fast in response to a certain stimulus. An example is the flexion reflex discussed below and which results in rapid withdrawal of a limb, such as the hand, upon touching a hot object. A large number of reflexes can occur in the body under physiological conditions, which could involve glands, internal organs, the autonomic nervous system, the somatic nervous system, the brain, or the spinal cord. An example of a purely endocrine reflex that involves endocrine glands without mediation of the nervous system is the regulation of glucose level in the blood. Thus, an increase in the level of glucose in the blood causes the pancreas to release more insulin, which allows more glucose to enter cells, thereby reducing glucose level in the blood. Some reflexes can be conditioned through learning, so that the reflex action is elicited by a stimulus other than the natural stimulus for the reflex.
The cases
Published in Chris Schelvan, Annabel Copeman, Jacky Davis, Annmarie Jeanes, Jane Young, Paediatric Radiology for MRCPCH and FRCR, 2020
Chris Schelvan, Annabel Copeman, Jacky Davis, Annmarie Jeanes, Jane Young
Clinical manifestations depend on the site and extent of the lesion. There may be complete loss of motor, sensory and reflex function below the affected level. Involvement of the sacral roots leads to bowel and bladder dysfunction.
Fatigue as a physiological problem: experiments in the observation and quantification of movement and industrial labor, 1873-1947
Published in History and Technology, 2023
Charles Scott Sherrington (C.S.S.) would be knighted in 1922, and win the Nobel Prize for ‘Physiology or Medicine’ ten years after that. He was the author of numerous papers on the neurophysiology of reflexes, and in The Integrative Action of the Nervous System (1906) he famously described the ‘reflex arc’. This is a shortcut in the nervous system of even primitive vertebrates that allows bodily reflexes, such as withdrawal of a limb from pain, to occur far faster, since in those cases sensory nerves bypass the brain stem and activated motor neurons in the spinal cord. More immediately pertinent to his factory visit, in that book Sherrington first defined ‘proprio-ception’, where receptors positioned throughout the muscular tissues and accessory organs (tendons, joints, blood vessels) provide feedback to the organism on its posture, position, and movement.4 After cycling from Oxford to Birmingham in 1915, as a well-established physiologist and one of the pioneers of neurophysiology, he volunteered to spend three months working in the VickersMaxim munitions factory.