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Year 13 Biologists Sensing Activity


It was like going back in time … some 30 years ago, John Harris and I were attending undergraduate physiology practical classes on a Friday afternoon in the labs at Sutton Bonington, and last Friday afternoon, the A2 Biologists, accompanied by Mr Ormerod and Dr Wastie, visited the neurophysiology laboratories at The University of Nottingham, School of Biosciences at the Sutton Bonington campus. The purpose of their visit was to reinforce a part of the A level syllabus which focusses on reflex responses and electrical activity in neurones.

Led by Dr John Harris (now Assistant Professor of Neurophysiology), students were taken through the principle of reciprocal inhibition in antagonistic muscle groups. Dr Carl Stevenson helped the students attach surface electrodes to the correct position on their lower legs, checked that the equipment provided a suitable recording of the electrical activity in the muscles of the lower leg and that the students understood what they recorded. Students were quickly interpreting results traces as they lifted their toes from the floor while keeping the heel in contact with the ground, then made the opposite movement.

With the basics sorted out and students readily interpreting results, the electrodes were used to investigate the simplest functional circuits in the human nervous system, reflex pathways which are activated by muscle stretch. When a tendon, which attaches a muscle to bone, is hit by a tendon hammer this causes a brief stretch in the muscle itself; the muscle reacts by rapidly shortening (i.e. contracting), causing the limb to jerk forwards or backwards.

For this part of the work, the electrical activity from the ankle extensor, medial gastrocnemius, was measured as the subjects knelt with the recording leg on a stool with the foot swinging freely over the edge. Once these control readings had been taken, the students were asked to perform the rather scary-sounding ’Jendrassik’s manoeuvre’, ably demonstrated by Dr Alan Waterfall.

The subject had to clench their teeth, flex both sets of fingers into a hook-like form, interlock the fingers together and then try to pull their hands apart. The subject’s Achilles tendon is hit with a reflex hammer to elicit the ankle jerk reflex.

Students were challenged to compare the data they obtained from both investigations and suggest explanations for the response they saw. Dr Harris explained that our data was excellent and that we had generated ‘perfect’ results! When the elicited response is compared with the reflex result of the same action when the maneuver is not in use, often a larger reflex response will be observed when the patient is occupied with the maneuver. While the exact mechanism for this response is as yet unknown, it is thought that the manoeuver may prevent the subject from consciously inhibiting or influencing their response to the hammer.

Throughout the afternoon, Dr Sara Kelly, a lecturer in neurophysiology and admissions tutor for Biosciences was also on hand to answer questions about the University, interview processes and the work undertaken at Sutton Bonington. “Awesome, thanks, Miss!”

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