Category Archives: Outreach and Education

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The physiology of stress

Stress is a popular word in our society and is thought to be the biggest contributor to workplace sickness and depression. But what exactly is it?

Living in the human zoo, we are constantly exposed to stressors, especially those deemed unnecessary on a survival level such as consumerism and the pursuit of happiness. Stress is usually linked to just the mind – anger, upset and irrationalities – but it actually affects our entire body (HSE, 2016).

According to recent statistics, the total number of working days lost due to stress in 2015/2016 alone was 11.7 million (HSE, 2016) with a strong association found between unemployment and suicide (NHS Behind the Headlines, 2015). As well as affecting mental health, stress is also linked to chronic pain, a condition that affects just under 28 million adults in the UK (Fayaz. A, et.al., 2016).

Stress is defined as a physiological or biological response to a stressor. The stress response system is a common pathway across organisms, which is designed to temporarily assign energy currency from areas of the body considered useless in a stressful situation to other areas in the body that are beneficial for survival.

Whilst such components are considered an adaptation, when exposed to chronic stress (where the body is exposed to long periods of stress psychologically and/or physiologically) these components can cause all kinds of life-effecting issues such as high blood pressure, decreased immune function, or fertility issues.

There have been numerous studies considering how stress plays a part in debilitating conditions of the body and mind focusing on the physiological pathways of the stress response, such as the HPA, sympathetic nervous system, amygdala, and hypothalamus. What does the future hold for us humans living in a crowded and highly-pressured society?

Some experts focus on a need for pharmacologic interventions, whilst others look for longer term solutions such as psychotherapy. One interesting piece of research I have come across focuses on the idea that encouraging an understanding of stress, coping methods, and the impacts on health within individuals will advance the treatment of stress (Segerstrom. S et.al., 2012).

The Physiological Society’s annual theme ‘Making Sense of Stress’ is looking to contribute toward public engagement and education about the effects of stress, and research across the globe looking to alleviate chronic stress and its related ailments.

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Tune in as we go LIVE this Tuesday, 21 February at 18:00 GMT, (or in person if you’re in London) for a panel and discussion chaired by Geoff McDonald, former Global VP of Human Resources at Unilever and one of the leaders of minds@work, and featuring neuroscientist Professor Stafford Lightman and occupational psychologist Professor Gail Kinman.

Post by Jessica Suter, Undergraduate of The Open University and Events Manager for Eaton Park Science Day

References:

Fayaz, A., Croft, P., Langford, R. M., Donaldson, L. J. and Jones, G. T. (2016) ‘Prevalence of chronic pain in the UK: a systematic review and meta-analysis of population studies.’, BMJ open, British Medical Journal Publishing Group, vol. 6, no. 6, p. e010364 [Online]. Available at: http://www.ncbi.nlm.nih.gov/pubmed/27324708 (Accessed 29 November 2016).

Health and Safety Executive (2016) ‘Statistics – Work-related stress, anxiety and depression statistics in Great Britain (GB)’, HSE [Online]. Available at: http://www.hse.gov.uk/statistics/causdis/stress/ (Accessed 29 November 2016).

McLannahan, H. (2004) “Chapter 3: Stress” SK277 Book 4: Life’s Challenges,  in The Open University. (eds), Plymouth, Latimer Trend and Company Ltd, pp. 79-113

NHS Choices (2015) ‘Unemployment and job insecurity linked to increased risk of suicide – Health News – NHS Choices’, Department of Health [Online]. Available at: http://www.nhs.uk/news/2015/02February/Pages/Unemployment-linked-to-increased-risk-of-suicide.aspx (Accessed 29 November 2016).

Segerstrom, S. C. and O’Connor, D. B. (2012) ‘Stress, health and illness: Four challenges for the future’, Psychology & Health, vol. 27, no. 2, pp. 128–140 [Online]. Available at: http://www.tandfonline.com/doi/abs/10.1080/08870446.2012.659516 (Accessed 29 November 2016).

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Making sense of stress in the wild

Imagine leaning forward over the edge of a precipice. Lurching back to safety, you picture the forest hundreds of metres below. Is your heart racing? Are your palms sweating? Our body’s stress response to an ever-changing environment enables us to survive and flourish.

Physiologists play a crucial role in developing our understanding of the mechanisms involved. To highlight the exciting work that they do, our 2017 theme is ‘Making Sense of Stress’. Follow the conversation on Twitter using #YearOfStress.

Launching the theme will be Dr Kimberley Bennett’s talk, ‘Making sense of stress in the wild’, at the Association for Science Education’s (ASE’s) Annual Conference on 6 January 2017. Read a teaser to her talk below!

Coping with stress is a major issue in modern society, but it’s easy to forget that wildlife experiences stress too. Without enough water, plants wilt and die and whole crops fail; without the right habitat, a small population of rare animals dwindles and dies out, causing extinction of the species; a whole coral reef bleaches when the water temperature gets too high, causing catastrophe for the ecosystem, and massively increasing flooding risk for people living by the coast. We really need to pay attention to stress in the wild because the consequences can herald disaster.

Stress is the biological response to a major challenge, whether it’s at the whole organism or cell level. A gazelle in the Serengeti chased by a lion experiences the same stress responses that we do – a surge of adrenaline and cortisol that cause increased heart rate and blood pressure and a release of glucose. These changes make sure there is enough fuel and oxygen to cope with increased demand at the tissue and cell levels. Sudden change or mismatch in the supply of oxygen and fuel leads to increased production of reactive molecules called ‘free radicals’ that can damage cells. If the temperature gets too hot too fast or if the acidity of the cell changes too much, proteins (the molecules that catalyse reactions, transport substances and provide structure) can fall apart or unravel. So cells have to increase their defence mechanisms too. Cellular defences include antioxidants that mop up the free radicals, and heat shock proteins, which refold damaged proteins and stop them forming a sticky mess inside the cell.

The old adage that what doesn’t kill you makes you stronger is often true: short term ‘good stress’ builds up these defences and makes organisms better able to deal with stress later on. However, sometimes defences can be overwhelmed or can’t be maintained for long periods. The organism then experiences the same sorts of problems as people under chronic stress: lower immunity, altered metabolism, anxiety and tissue damage (like ulcers). In wildlife, this can have major consequences for breeding success or even survival. By affecting whether organisms survive and thrive, stress dictates which individuals contribute to the next generation. Stress shapes population dynamics, lifestyle and adaptations, and is therefore a powerful agent of natural selection.

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I work on seals, top marine predators that are used to stress as a normal part of their existence. Their individual and population level health is an indicator of ecosystem health. Seals are air breathing mammals that feed underwater, but need to come to the surface to breathe, and to come ashore to rest, breed and moult. Diving on a single breath hold means they need to conserve oxygen; to do this, blood flow is restricted mostly to the heart and brain, so that other tissues may experience free radical production while oxygen levels are low. On land, seals need to fast, often while they are doing energy-demanding activities i.e. shedding and replacing hair, producing milk, defending pups or territory, or undergoing rapid development. Injury and infection can occur from skirmishes or trampling. Seals may have to reduce their defences to deal with all these demands on their energy when food is not available. In addition to their ‘lifestyle stressors’, seals face stress from competition for access to fish, disturbance on haul out or displacement from foraging grounds as a result of human activity, and the accumulation of contaminants in their blubber.

We need to understand natural and man-made causes of stress in wild populations, distinguish good stress from bad stress, and understand how multiple stressors at the same time can create problems. That means we have to have effective tools to measure stress and its consequences in organisms that can’t tell us how they feel. But can we measure stress responses in wildlife? What do they mean in context? And can they help in managing stress in the wild?

I will address all these questions and more at the ASE’s Annual Conference on Friday 6 January 2017, as part of the annual Biology in the Real World (#BitRW) lecture series. Please drop by the Knight Building, LT 135, at the University of Reading, at 1.30pm to find out more!

Dr Kimberley Bennett, Abertay University

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Danger! High Voltage!

Standing between school students and their weekends was always going to be a tough gig, but it was #PhysiologyFriday and we were determined to put on a show. Together with Orla and Ioannis, PhD students from the University of Reading, I arrived at East Ham Town Hall and was greeted by over 200 excited students and their teachers.

Our mission was to deliver an engaging session around electricity and pass on an innovative human-human interface educational resource that the students had won as part of a Physiological Society competition, The Science of Life 2016. After a brief introduction to human electricity and how we can detect it, we took the students on a journey from the first electroencephalogram (EEG) to the potential of neuroprosthetics in treating paralysis. We then tackled a live demonstration of the kit and the students were intrigued to see the interface in action.

 

Surely, one human cannot control another’s arm using only their brain activity? The wonders of neuroscience said it should be possible, but we sensed some doubters in the audience. Using the human-human interface Ioannis was going to harness his brain power to move Orla’s arm against her wishes……

Thankfully the demonstration was up to scratch with the students requesting several encores, and even asking for the voltage to be turned up! Normally the complexities of electrophysiology remain in the lab due to expensive and static equipment, however this kit gave us the ability to be mobile and take the dark art of electrophysiology to young minds keen to explore neuroscience. It was well worth it. The students left school for the weekend with a sense of excitement and thirst to learn more. Orla, Ioannis and I left East Ham Town Hall feeling that we had sparked the interest of the next generation of physiologists.

Dr Mark Dallas

@drmarkdallas

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Myth-busting: Do heart cells really have their own ‘pulse’?

By Dr. Andy James, University of Bristol

The comedian, Jake Yapp, has been presenting on BBC Radio 4’s website a series of short comic histories of science entitled, “Everything We’ve Ever Known About …” Informative and entertaining, these are invariably funny. A recent edition concerned the heart, neatly covering the development of our understanding of heart function through the millennia, from the ancient Egyptians to the present day – where Jake concludes by commenting that if you isolate a heart muscle cell it will have its own pulse. Actually, strictly speaking, a pulse is the increase in pressure within the arteries as a result of beating of the heart. ‘Rhythm’ is a better word.

http://www.bbc.co.uk/programmes/p04bwbxl/player

It’s a commonly held misconception, even amongst specialists in cell biology, that all heart muscle cells have their own rhythm that synchronises when the cells couple together (meaning they join and allow electricity to flow between them). Beautiful as this idea is, it simply isn’t true. The heart’s rhythm originates as electrical activity in a specialised area of the heart known as the sinus node- the heart’s physiological pacemaker. The heart muscle cells of the sinus node generate rhythmic electrical activity so that, when isolated, they contract regularly.

In the intact heart, a conduction system ensures that the electrical activity is passed to the chambers to produce a well-coordinated contraction. Many of the cells of the conduction system would also beat when isolated. But the cells from the walls of the chambers that produce the pressure to – as the English anatomist, William Harvey, would have it – propel the blood, do not. Chamber cells only need to receive the signal, but not generate it themselves.

The persuasive and attractive idea that all heart muscle cells show their own rhythm may have arisen from attempts to maintain heart muscle cells for several days in a petri dish. Heart muscle cells from adult mammalian hearts do not generally multiply under these conditions and while it is possible to keep the cells alive for a short time, after a few days, the cells die. However, cells from embryonic, or even neonatal, hearts do multiply in culture. They often show rhythmic contractions and, yes, they synchronise once they form connections with their neighbours.

So do heart cells really have their own pulse? It depends! Cells from adult hearts are programmed to behave in a fixed way- as a pacemaker cell, a conducting cell or a contractile cell from a chamber wall. Cells from immature hearts, on the other hand, retain the ability to change their properties and tend to develop pacemaker-like function in the petri dish.

Horse or Human: who will win the race?

Place your bets now! Because tomorrow, on 11 June, the 36th annual Horse vs Man Marathon will take place in Llanwrtyd Wells, Wales, where humans will test their mettle against horses on 22 miles of mountainous terrain. Who will win this year?

On flat terrain, it would be a no-brainer: horses clearly have a significant advantage over humans. With their lean and muscular physique, thoroughbreds can reach speeds of up to 55 mph, while the world’s fastest human, Usain Bolt, lags behind with a top speed of only 27 mph. So how do horses reach such impressive speeds? We can find some clues by studying their anatomy and physiology.

The first proper studies began over 200 years ago, after the death of a particularly special racehorse, Eclipse, who was never beaten throughout his racing career from 1769 to 1770. His extraordinary success prompted the founding of the Royal Veterinary College in 1791 and ever since then, veterinary scientists have been making great strides in finding out what it is that allows horses to run so fast. It turns out that several factors play a role, including a big heart and the ability to increase heart rate to a remarkable degree:

 

Horses’ ability to increase the amount of blood pumped by the heart around the body to the muscles makes all the difference in a race, and that is helped by the spleen, which contains a store of oxygen-carrying red blood cells that are released into the bloodstream during exercise. They have other tricks up their sleeve too:  compared to humans, they have a far greater tolerance of increased body temperature and blood acidity, both of which go up fast during intense exercise.

We can find other clues to horses’ speed in their long and light-weight legs, which have very springy tendons that save energy needed to move quickly. So where does the muscular power come from?  The leg muscles aren’t in the lower legs as humans’ are, but tucked up close to the body, connected to the lower legs by very long tendons, which also generate  ‘springiness’. As with all four-legged animals, the muscles in the back, neck and abdomen also contribute to the ability to gallop. The quickest racehorses have lots of fast twitch fibres in these muscles, helping them to generate more energy for movement via both aerobic and anaerobic respiration.

Also unlike humans, the stride in galloping directly controls the timing of breathing: the huge weight of the hindgut acts like a piston on the lungs at the front, sucking in the maximum amount of air possible and then expelling it rapidly, as the torso moves with each step. This neat trick means that horses can move large volumes of air in and out of the lungs very quickly, helping to maintain their performance for longer.

And, of course, no racehorse is complete without its rider – who also plays a key role in the horse’s performance. Have you ever wondered why jockeys ride crouching over the horse, rather than sitting upright? Well, this is known as the ‘monkey crouch’ and was invented by Americans in the 1890s in order to improve horse speeds. This position separates the stride of the horse from the rider i.e. as the horse moves forward, the rider moves back, and vice versa. In this way, the rider takes up some of the effort required to move forward, enabling the horse to save some much needed energy for the race.

But what about humans? How can we possibly measure up to all this? By levelling the playing field, to something less level – which is exactly what the Horse vs Man Marathon has done, by holding the race on mountainous terrain. This gives humans a fighting chance – so while it’s true that horses have dominated the Marathon so far, there have been two occasions when a human has won the race. How come?  On rough hilly ground, the horses’ ability to reach and maintain their peak speed is severely reduced. Humans are much lighter, so the changes in direction needed on rough ground take less energy than for the much larger horses.

If we look at the cases where humans have won the race, one factor immediately jumps out, and that is: hot weather. It’s not immediately clear why that favours humans. Our ability to sweat, which cools us down in hot weather, is shared with horses. But, being smaller, we have relatively more skin to sweat from than do horses, and that may be a greater benefit than horses’ greater tolerance of high body temperature. And humans can take on extra fluid during the race, replacing that lost in sweat, without having to stop – something their equine competitors can’t do.

So, who will win tomorrow? The weather forecast predicts maximum temperatures of 19°C, so the human participants will have to draw on all of their abilities, to be in with a chance of winning.

Who will you place your bet on?