|MadSci Network: General Biology|
Hello, thank you for your question about the height and the gender of persons and their heart rates. The answer to the first part of your question is no. Consider: Normal blood pressure is about 120/80 mmHg, or “millimetres of Mercury”. What does that mean: It means that if you apply that pressure to a column of Mercury (In a glass tube, say), you can lift the column by 120mm. Now blood does not consist of Mercury (however, older blood pressure measuring devices did, hence the use of the unit), it consists almost exclusively of water. 1 mm of Mercury exerts the same pressure as 1.36 cm of water. That means, the normal human blood pressure will propel our blood to a height of 163 cm (in systole). Since our brains are usually not more than 30 – 40 cm above our heads, the normal pressure is able to bring blood to brains of large and small people alike several times over. In fact, under normal circumstances, there is a mechanism in the arteries of the brain that dampens down the excess pressure so that the brain is not subject to excessive blood pressures. The condition you describe is sometimes relevant in certain diseases of the brain, but is irrelevant with respect to height. The second part of the question is a bit trickier. One has to ask, what does “men” and “women” mean here? Heart rate is extremely dependent on life stile, physical fitness, smoking or non-smoking, to name a few, so the answer may show differences over historic times and different world regions. In Western societies, women have a somewhat higher resting HR. For example, in ref. , you’ll find this in a sample small of age-matched, healthy men and women – the measurements were used as baselines for the evaluation of several physiologic parameters pertaining to blood pressure regulation. The women came up with a resting HR of 65, the men with 52 bpm.  Convertino A (1998) Am J Physiol (Regul Integr Comp Physiol) 275 : p 1909. The URL for access to the article online is: http://ajpregu.physiology.org/cgi/content/abstract/275/6/R1909?ijkey=f9a678b73d33bd490df1b017333f077801a6f75b&keytype2=tf_ipsecsha
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