Welcome back, chaps. I’m writing this is the car, on the way back from a lovely (if sadly cut-short) weekend in Suffolk. But you’ll hear more about that tomorrow. (EDIT: Just brought to my attention: Don’t worry! It’s nothing sinister. Just a lot to get done before the start of a working week meant that we had to leave early in the morning!)
So, where did we get to yesterday? Ah yes, we were at the Royal Institution, we’d just gluttoned ourselves into a sticky toffee stupor, and, looking at the clock, it was time to get moving for the night’s lecture. In fact, no sooner had I asked the waiter for the bill but the bell was rung for the 15 minute warning – we needed to get ourselves seated upstairs in the lecture hall. No time to find our cocktail companions for later – we needed to get moving! Apparently, we passed Angharad and Paul in a blur – they were having a quick pre-talk drink in the Time&Space bar. But it’s all right – they found us on the stairs and so we made our way into the lecture hall together.
My one criticism of the Royal Institution’s lecture theatre is that it is not kind to the tall. Not a problem for me (as I am a short arse) but not so good for Paul or the even taller Ben. But the lads did not complain, bless ‘em (especially as Ben managed to land himself by the aisle, so he could stretch his legs out there).
Before the talk started, I saw Rebecca and her friend Chantal come in and seat themselves at the opposite side of the theatre – I saw Rebecca looking around, and then wave jovially when she caught sight of us. There would be time for introductions and chat in the bar after the talk.
The night’s lecture was the monthly Friday Evening Discourse: an event exclusively for members and their guests (of which I had brought three, hurrah!) Every last-Friday-of-the-month, a guest speaker is invited to talk about their subject for a maximum one hour (it is timed and signalled by a bell), and this is followed by a 15-minute Q&A session, open to the audience. I have been to some fantastic FEDs since I joined the RI at the beginning of the year, including one about the nature/nurture debate, and a presentation about the therapeutic effects of Lithium.
But this month, it was “Rhythms of the Body”, a talk presented by Prof. Stafford Lightman from the University of Bristol He took us through a brief definition of bio-rhythms, and the various different cycles that living creatures follow (annual, seasonal, lunar/tidal, and of course the daily 24-hour cycles shared by so many organisms) – heliotropes, a group of flowering plants, will faithfully follow a 24-hour cycle of blooming and closing, even if kept in complete darkness.
Next, he went on to explain the underlying cortisol fluctuations that keep us human beings in a happy circadian rhythm. It used to generally be accepted that cortisol levels fluctuated evenly throughout the day, linking to energy levels (plotted, the projected cortisol levels resemble the familiar bell-curve). However, scientific analysis has revealed that cortisol levels fluctuate throughout the day, coming in regular pulses (spikes on a graph), with the pulses getting bigger during the main part of the day, then dying down again at night. These cortisol levels pulse due to a delayed response to neural pulses – Lightman helpfully gave the analogy of a cranky old shower (we’ll ignore the fact that he confused Mr Burns and Homer Simpson on his slides). Imagine you’re in the shower: it’s too cold, so you turn the heat up. But there is a delay, so you turn it up again. When the first increase-signal gets through, great, the shower is at the perfect temperature, but soon the second increase-signal gets through and suddenly the shower is too hot. So you turn the heat down a bit. But again, because of the delay, it remains hot, so you turn it down again. Guess what happens – first it’s perfect, but soon it overshoots (you impatient thing) and it’s too cold again. Repeat ad infinitum. Cortisol pulses in a similar way through a hypothalamus-pituatary-adrenal pathway (involving AVP, CRH, ACTH and finally cortisol), giving us the characteristic spikes.
Cortisol is an anticipatory hormone, and so overall it averages out as that bell-curve over a 24-hour cycle. This anticipation prepares you to act in times of stress and situations involving threat – as a mouse without cortisol, you wouldn’t be prepared to run if the cat was looking at you funny. But you can’t be in a sustained state of anticipation: the mathematics of the feedback/feedforward loop forbid this, as with a sustained high level of cortisol, the oscillating effect cannot occur.
This might explain the desensitisation effect observed in those suffering from continual high levels of stress (such as Post Traumatic Stress Disorder, and the recently defined Prolonged Duress Stress Disorder) who need stronger stimuli in order to become engaged emotionally and psychologically.
Cortisol also spikes up in response to stress – and since there is a delay, we can feel the effects of cortisol for some time after the stress-inducing event has actually occurred. So hopefully it’s apparent that interruptions to regular cortisol levels will have an impact on our circadian rhythm: I’m sure we’ve all experienced the effects of stress on our sleeping pattern, and the subsequent effect on our energy levels. Eventually, the circadian rhythm will reassert itself, but you won’t feel top notch in the meantime. And I’m sure we all know that chronic stress can lead to serious physical ill health.
So the circadian rhythm is important, and cortisol levels help to regulate that. So why are we so cruel to our circadian rhythms? Shift-work, staying up late… It’s not good for you. Abnormal cortisol patterns are linked to depression and anxiety, chronic fatigue, memory problems, hypertension…
This was probably the shortest talk I’ve ever been too, but that was by no means a bad thing – it meant we had plenty of time for the Q&A sessions. And a lot of interesting questions were asked: about links to depression, about the change in cortisol fluctuations as we age, about whether or not stress is good for us. Even I asked a question, about the circadian rhythm and Seasonal Affective Disorder: if heliotropes can flower in darkness, why do I need a lightbox to see me through the winter months? And are their any flowers with SAD? Rebecca followed with an interesting question about the increase in the occurrence of breast cancer in women who do shift work and therefore work at odd hours (and therefore disrupt their circadian rhythms).
Overall, a thoroughly interesting talk. And how better to follow this up by returning to Time&Space (this time to their bar and lounge) to discuss the talk over cocktails?
We cosied ourselves away on a couple of sofas with Angharad, Paul, Rebecca and Chantal. Time&Space do some fantastic cocktails, so it’s definitely worth a look in, even if you’re not going for a lecture. I managed to get through a Pink Mojito, a Dragon Fly and a Grand Mimosa. Unfortunately, Rebecca and Chantal had to take off around 10:30pm, but Ben and I stayed chatting with Angharad and Paul until we were pretty much asked to leave… We caught a black cab back to Streatham, and crawled into bed, tipsy and content.
A final shout out must go out to Angharad and her wonderful new shoes. That is all I have to say. Yes, they are that good that they need their own mention 🙂
Image credits: ultra cute rat from http://www.desicolours.com, Time&Space bar from RIGB website, and lecture hall was my own