Convergent nonsense.

Evolution Appears to Converge on Goals -- But in Darwinian Terms, Is That Possible?
Denyse O'Leary July 27, 2015 10:39 AM 

Very different life forms frequently converge on eerily identical patterns of development (convergent evolution). That is odd if evolution is purely undirected and unplanned. There isn't enough time, given the history of the universe.

Talk to the Fossils.jpgAnd, as I've noted before, the welter of data coming back from paleontology, genome mapping, and other studies are changing paleontology from a discipline dependent on grand theories to one more like human history, dependent on identified facts.

A century or so ago, British anatomist St. George Mivart noted that Darwin's theory of evolution "does not harmonize with closely similar structures of diverse origin" (convergent evolution). There is more evidence for Mivart's doubts now than ever.

According to current Darwinian evolutionary theory, each gain in information is the result of a great many tiny, modest gains in fitness over millions or billions of years, due to natural selection acting on random mutations. The resulting solutions should then follow inheritance laws, in the sense that the more similar life forms are according to biological classifications, the more similar their genome map should be.

That just did not work out. Different species can have surprisingly similar genes. For example, kangaroos are marsupial mammals, not placentals. Yet their genes are close to humans. Researchers: "We thought they'd be completely scrambled, but they're not."

Kangaroos? Shark and human proteins, meanwhile, are also "stunningly similar." Indeed, sharks are genetically closer to humans than they are to aquarium zebrafish. Researchers: "We were very surprised... "

Sharks? But does all this not raise a serious question? The popular science literature claims that a near identity between the human and chimpanzee genome is irrefutable evidence of common descent. Why then do we hear so little about any of these findings, which muddy the waters? Why are science writers not even curious?

There is also the question of how easily a life form can "evolve" a complex solution to a difficult problem. Birds are said to have evolved ultraviolet vision at least eight times.

Similarly, whether large bird and mammal brains arise from common descent or convergent evolution is actually uncertain. Two distantly related groups of reptiles are thought to have given rise to mammals and birds, both featuring a much higher brain to body weight ratio than in their ancestors. Paleontologist R. Glenn Northcutt writes that the matter is "contentious and unresolved," because brains rarely fossilize.

It's not just mammals and birds. Two different species of deadly sea snake, with "separate evolutions," were found to be identical. Dolphins and insects, we are told, share components of a hearing system.

The smartest invertebrates, the molluscs (including squid, octopuses, and cuttlefish), seem to have evolved brains four times. From one study we learn, "The new findings expand a growing body of evidence that in very different groups of animals -- and mammals, for instance -- central nervous systems evolved not once, but several times, in parallel."

Cambridge paleontologist Simon Conway Morris's Map of Life website provides many other examples of convergence, listing, for example, the convergent evolution of foul smelling plants ("Love me, I stink"), convergence in sex (love-darts), eyes (camera-style eyes in jellyfish), agriculture (in ants) or gliding (in lizards and mammals).

Convergent evolution is evidence that evolution can happen. But the Darwinian model does not seem to be the right one. The life forms appear to be converging on a common goal.

That said, the problem presented for Darwinism by convergent evolution has hardly penetrated the world of pop science writers, high school teachers, politicians, judges, theologians, and entertainers. Mere evidence could not compete with a position so compelling as Darwin's.

Alternatively, however, there is the position taken by many great physicists: The universe is about information and consciousness, not matter. A sense of the results having been directed would not, then, be surprising. 
For more on that, consult William Dembski's Being as Communion.

See the rest of the series to date at "Talk to the Fossils: Let's See What They Say Back."

The Divine Law and blood X

Call It a Bloodless Coup
Date: April 1, 2013

Hopkins uses some 60,000 units of blood products a year. “That alone,” says Steven Frank, “justifies prudence.”  

Hopkins uses some 60,000 units of blood products a year. “That alone,” says Steven Frank, “justifies prudence.”

Though some form of the “bloodless surgery” that lowers the need for transfusions has been around almost two decades, a new body of clinical research looks to cement its hold at Johns Hopkins and extend it to more patients. Also, new work suggests now may be the time to rethink assumptions about blood-banking. 

“We’re seeing that we can do a lot more with less blood during surgery and afterward,” says anesthesiologist Steven Frank, medical director of The Johns Hopkins Hospital’s umbrella program for bloodless medicine and surgery. “Our aim is to reduce transfusions by 10 to 20 percent throughout our medical system. 

“The tactics we use don’t only benefit those who traditionally refuse transfusions for personal concerns about contamination or, like the Jehovah’s Witnesses, for religious beliefs. We’ve come to see bloodless surgery as best practice for more patients in general.”  

What drives the new goal, Frank says, are four landmark studies—the most recent including Johns Hopkins data. All the trials followed large numbers of patients during hospital stays, comparing survival based on whether or not their hemoglobin levels had been boosted by transfusions. The trials varied in details, though all involved very sick people experiencing blood loss. 

“The bottom line,” says Frank, “was that patients held to a lower hemoglobin reading before getting transfusions* did just as well or better than those transfused at a traditional higher triggering point. So we see no advantages in routinely giving extra blood. All you do is introduce cost and risk.

“Transfusions aren’t necessarily benign,” he adds. Transfused patients are two to three times more likely to get acquired infections. Also, receiving donor blood sparks antibodies that work against future transfusions.

Just-out work from Hopkins adds another consideration: the blood supply. Yes, worldwide shortages exist in banked blood. But banking itself warrants a second look. Blood banks’ equivalent of a “sell by” date—six weeks—is likely off, Frank says. He and colleagues show that blood starts becoming “stale” after three weeks. Red blood cell membranes stiffen, which can slow passage in capillaries. That likely explains transfused patients’ slightly higher risk of cardiac complications.

One remedy, however, lies in reducing blood bank demand. 

 So the hospital program goes beyond modern tactics that recycle blood lost during surgery, shrink operating fields through robotics or beef-up patients’ presurgical red cell count. Tactics are increasingly patient-tailored. And research continues on best practice. A large hospital database, for example, showed Frank’s team how a simple $9 IV-based device that one Hopkins critical care unit used halved blood loss during testing.

The benefits of blood conservation, Frank says, are clear: They lower risk. They lower cost. And they improve outcomes. 

Outcome of Patients Who Refuse Transfusion After Cardiac Surgery: A Natural Experiment With Severe Blood Conservation FREE

Gregory Pattakos, MD, MS; Colleen G. Koch, MD, MS, MBA; Mariano E. Brizzio, MD; Lillian H. Batizy, MS; Joseph F. Sabik III, MD; Eugene H. Blackstone, MD; Michael S. Lauer, MD

ABSTRACT

ABSTRACT | METHODS | RESULTS | COMMENT | ARTICLE INFORMATION |REFERENCES

Background Jehovah's Witness patients (Witnesses) who undergo cardiac surgery provide a unique natural experiment in severe blood conservation because anemia, transfusion, erythropoietin, and antifibrinolytics have attendant risks. Our objective was to compare morbidity and long-term survival of Witnesses undergoing cardiac surgery with a similarly matched group of patients who received transfusions.

Methods A total of 322 Witnesses and 87 453 non-Witnesses underwent cardiac surgery at our center from January 1, 1983, to January 1, 2011. All Witnesses prospectively refused blood transfusions. Among non-Witnesses, 38 467 did not receive blood transfusions and 48 986 did. We used propensity methods to match patient groups and parametric multiphase hazard methods to assess long-term survival. Our main outcome measures were postoperative morbidity complications, in-hospital mortality, and long-term survival.

Results Witnesses had fewer acute complications and shorter length of stay than matched patients who received transfusions: myocardial infarction, 0.31% vs 2.8% (P = . 01); additional operation for bleeding, 3.7% vs 7.1% (P = . 03); prolonged ventilation, 6% vs 16% (P < . 001); intensive care unit length of stay (15th, 50th, and 85th percentiles), 24, 25, and 72 vs 24, 48, and 162 hours (P < . 001); and hospital length of stay (15th, 50th, and 85th percentiles), 5, 7, and 11 vs 6, 8, and 16 days (P < . 001). Witnesses had better 1-year survival (95%; 95% CI, 93%-96%; vs 89%; 95% CI, 87%-90%; P = . 007) but similar 20-year survival (34%; 95% CI, 31%-38%; vs 32% 95% CI, 28%-35%; P = . 90).

Conclusions Witnesses do not appear to be at increased risk for surgical complications or long-term mortality when comparisons are properly made by transfusion status. Thus, current extreme blood management strategies do not appear to place patients at heightened risk for reduced long-term survival.

Red blood cells (RBCs) not only are in short supply but are also associated with increased morbidity and reduced survival after cardiac surgery.1- 3 Jehovah's Witness patients (Witnesses) hold beliefs that disallow blood product transfusion and therefore offer a natural experiment in severe blood conservation. Their beliefs encourage the use of a number of blood conservation practices, including preoperative use of erythropoietin and iron and B-complex vitamins, hemoconcentration, and minimal crystalloid use; intraoperative use of antifibrinolytics and cell-saver and smaller cardiopulmonary bypass circuits; and postoperative liberal use of additional operation for bleeding along with tolerance of low hematocrit levels postoperatively. Although some of these practices may be beneficial to all cardiac surgical patients, others are associated with well-documented morbidity,4- 6 and their effect on long-term survival is uncertain.

Although prior investigators compared immediate postoperative outcomes between Witnesses and non-Witnesses,7- 16 comparisons of long-term survival are lacking. Comparison is hampered, however, by impossibility of randomization to religious preference or blood transfusion, typical of any natural experiment. We have therefore used propensity-based comparative effectiveness tools17- 19 to compare morbidity and long-term survival of Witnesses undergoing cardiac surgery with a propensity-matched group of patients who received transfusions.

Outcomes in cardiac surgery in 500 consecutive Jehovah's Witness patients: 21 year experience.

Vaislic CD1, Dalibon N, Ponzio O, Ba M, Jugan E, Lagneau F, Abbas P, Olliver Y, Gaillard D, Baget F, Sportiche M, Chedid A, Chaoul G, Maribas P, Dupuy C, Robine B, Kasanin N, Michon H, Ruat JM, Habis M, Bouharaoua T.
Author information
Abstract
BACKGROUND:
Refusal of heterogenic blood products can be for religious reasons as in Jehovah's Witnesses or otherwise or as requested by an increasing number of patients. Furthermore blood reserves are under continuous demand with increasing costs. Therefore, transfusion avoidance strategies are desirable. We describe a historic comparison and current results of blood saving protocols in Jehovah's Witnesses patients.
METHODS:
Data on 250 Jehovah's Witness patients operated upon between 1991 and 2003 (group A) were reviewed and compared with a second population of 250 patients treated from 2003 to 2012 (group B).
RESULTS:
In group A, mean age was 51 years of age compared to 68 years in group B. An iterative procedure was performed in 13% of patients in group B. Thirty days mortality was 3% in group A and 1% in group B despite greater operative risk factors, with more redo, and lower ejection fraction in group B. Several factors contributed to the low morbidity-mortality in group B, namely: preoperative erythropoietin to attain a minimal hemoglobin value of 14 g/dl, warm blood cardioplegia, the implementation of the Cornell University protocol and fast track extubation.
CONCLUSIONS:
Cardiac surgery without transfusion in high-risk patients such as Jehovah Witnesses can be carried out with results equivalent to those of low risk patients. Recent advances in surgical techniques and blood conservation protocols are main contributing factors.

PMID: 23013647 [PubMed - indexed for MEDLINE] PMCID: PMC3487917 Free PMC Article

Comparisons of cardiac surgery outcomes in Jehovah's versus Non-Jehovah's Witnesses.

Stamou SC1, White T, Barnett S, Boyce SW, Corso PJ, Lefrak EA.

Author information

Abstract

Jehovah's Witnesses is a Christian faith whose members will not accept blood or blood products under any circumstances on the basis of religious grounds. To date, no comparative studies have evaluated the outcome of open heart surgery in Jehovah's Witnesses compared with patients who accept the transfusion of blood products. The present study was conducted to systematically compare the operative mortality and early clinical outcome after open cardiac surgery in Jehovah's Witnesses versus non-Jehovah's Witnesses. From January 1990 to July 2004, 49 Jehovah's Witness patients underwent cardiac surgery, and their data were compared with those of a contemporaneous control group of 196 non-Jehovah's Witnesses. Logistic regression analysis was used to compare operative mortality, postoperative intensive care unit care, and hospital length of stay between the 2 groups, controlling for preoperative risk factors. The Jehovah's Witnesses were matched in a 1:4 ratio to the non-Jehovah's Witnesses using propensity scores. No significant differences were identified in unadjusted stroke (p = 0.5), acute myocardial infarction (p = 0.6), new-onset atrial fibrillation (p = 0.106), prolonged ventilation (p = 0.82), acute renal failure (p = 0.70), and hemorrhage-related reexploration (p = 0.59) rates between the 2 groups. On multivariate analysis, Jehovah's Witnesses had operative mortality (odds ratio 0.66, 95% confidence interval 0.12 to 3.59, p = 0.63), intensive care unit stay (odds ratio 1.36, 95% confidence interval 0.46 to 3.97, p = 0.58), and postoperative length of stay (odds ratio 1.43, 95% confidence interval 0.92 to 2.20, p = 0.16) comparable to those of the non-Jehovah's Witnesses, after controlling for preoperative risk factors through matching. In conclusion, cardiac surgery in Jehovah's Witnesses is associated with clinical outcomes comparable to those of non-Jehovah's Witnesses by adhering to blood conservation protocols.

PMID:

 

17056333

 

[PubMed - indexed for MEDLINE]

Safety of cardiac surgery without blood transfusion: a retrospective study in Jehovah's Witness patients.

El Azab SR1, Vrakking R, Verhage G, Rosseel PM.

Author information

Retraction in

• Notice of retraction. [Anaesthesia. 2010]

Abstract

The aim of this retrospective study was to compare the utilisation of blood products and outcomes following cardiac surgery for 123 Jehovah's Witnesses and 4219 non-Jehovah's Witness patient controls. The study took place over a 7-year period at the Amphia Hospital in Breda, the Netherlands. A specific protocol was used in the management of Jehovah's Witness patients, while the control group received blood without restriction according to their needs. Patients' characteristics were comparable in both groups. Pre-operatively, the mean (SD) Euro Score was higher in the Jehovah's Witness group (3.2 (2.6) vs 2.7 (2.5), respectively; p < 0.02). Pre-operative haemoglobin concentration was higher in the Jehovah's Witness group (8.9 (0.7) vs 8.6 (0.9) g.dl(-1), respectively; p < 0.001). The total cardiopulmonary bypass time did not differ between groups. The requirement for allogenic blood transfusion was 0% in the Jehovah's Witness group compared to 65% in the control group. Postoperatively, there was a lower incidence of Q-wave myocardial infarction (2 (1.8%) vs 323 (7.7%), respectively; p < 0.02), and non Q-wave infarction (11 (9.8%) vs 559 (13.2%), respectively; p < 0.02) in the Jehovah's Witness group compared with controls. Mean (SD) length of stay in the intensive care unit (2.3 (3.2) vs 2.6 (4.2) days; p = 0.26), re-admission rate to the intensive care unit (5 (4.5%) vs 114 (2.7%); p = 0.163), and mortality (3 (2.7%) vs 65 (1.5%); p = 0.59), did not differ between the Jehovah's Witness and control groups, respectively.

Comment in

• Safety of cardiac surgery without blood transfusion: a retrospective study in Jehovah's Witness patients. [Anaesthesia. 2010]

PMID:

 

20402872

 

[PubMed - indexed for MEDLINE]

Comparison of outcome in Jehovah's Witness patients in cardiac surgery: an Australian experience.

Bhaskar B1, Jack RK, Mullany D, Fraser J.

Author information

Abstract

INTRODUCTION:

Despite the advances in modern medicine, cardiac surgery remains associated with significant amounts of blood transfusion and is responsible for nearly 20% of all transfusions in Australasia. Progressive advances in perfusion technology and perioperative supportive management have made it possible for members of the Jehovah's Witnesses (JW) religious group to undergo open cardiac operations with remarkable safety. This study systematically compares the operative mortality and early clinical outcome after cardiac surgery in JWs.

METHODS AND MATERIALS:

Data was obtained from the cardiac surgery and intensive care unit databases from January 2002 to December 2005. A total of 5353 patients who underwent cardiac surgical procedures including coronary artery bypass grafting with cardiopulmonary bypass (n=4041) and valvular heart surgery (n=2287) were assessed in this study. Of the 5353 patients 49 patients refused blood and blood products because of their religious beliefs. Models were constructed to determine the association between JWs and non-JWs and three outcomes: (1) operative mortality, (2) postoperative variables and (3) length of stay in intensive care unit. Propensity scores were computed from these models and used to match JWs with non-JWs.

RESULTS:

There were minimal differences in the baseline patient demographic characteristics between the two groups. Haemoglobin and haematocrit levels were higher in JWs both before (13.7g/dL vs 12.8g/dL; P=0.01, and 40.0% vs 39.2%; P=0.08) and after (10.8g/dL vs 9.9g/dL; P=.003, and 34.0% vs 30.9%; P=.001) surgery. Jehovah's Witnesses experienced significantly less bleeding, almost half compared to the control group, with 

CONCLUSION:

This study concurs with the international published data that outcomes for JW patients who undergo cardiac surgery are similar to those who receive transfusion. Every appropriate opportunity to reduce the use of allogeneic blood products.

Copyright © 2010 Australasian Society of Cardiac and Thoracic Surgeons and the Cardiac Society of Australia and New Zealand. All rights reserved.

PMID:

Even Darwinists admit that there is legitimate cause for doubt re:the Cambrian explosion

BioEssays Article Admits "Materialistic Basis of the Cambrian Explosion" is "Elusive"
Casey Luskin June 24, 2009 12:51 PM 

A recent paper in BioEssays, "MicroRNAs and metazoan macroevolution: insights into canalization, complexity, and the Cambrian explosion," admits the lack of a "materialistic basis" -- that is, a plausible materialistic explanation -- of the Cambrian explosion. As the article states:

Thus, elucidating the materialistic basis of the Cambrian explosion has become more elusive, not less, the more we know about the event itself, and cannot be explained away by coupling extinction of intermediates with long stretches of geologic time, despite the contrary claims of some modern neo-Darwinists.
(Kevin J. Peterson, Michael R. Dietrich and Mark A. McPeek, "MicroRNAs and metazoan macroevolution: insights into canalization, complexity, and the Cambrian explosion," BioEssays, Vol. 31 (7):736 - 747 (2009).)

The authors give no indication that they themselves support intelligent design (ID), and it seems they are still hopeful for a "materialistic" explanation for the Cambrian explosion, but they nonetheless give a witty nod to some observations and arguments made by ID proponents:
Beginning some 555 million years ago the Earth's biota changed in profound and fundamental ways, going from an essentially static system billions of years in existence to the one we find today, a dynamic and awesomely complex system whose origin seems to defy explanation. Part of the intrigue with the Cambrian explosion is that numerous animal phyla with very distinct body plans arrive on the scene in a geological blink of the eye, with little or no warning of what is to come in rocks that predate this interval of time. The abruptness of the transition between the ''Precambrian'' and the Cambrian was apparent right at the outset of our science with the publication of Murchison's The Silurian System, a treatise that paradoxically set forth the research agenda for numerous paleontologists -- in addition to serving as perennial fodder for creationists. The reasoning is simple -- as explained on an intelligent-design t-shirt.
Fact: Forty phyla of complex animals suddenly appear in the fossil record, no forerunners, no transitional forms leading to them; ''a major mystery,'' a ''challenge.'' The Theory of Evolution -- exploded again (idofcourse.com).
Although we would dispute the numbers, and aside from the last line, there is not much here that we would disagree with. Indeed, many of Darwin's contemporaries shared these sentiments, and we assume -- if Victorian fashion dictated -- that they would have worn this same t-shirt with pride.
(Kevin J. Peterson, Michael R. Dietrich and Mark A. McPeek, "MicroRNAs and metazoan macroevolution: insights into canalization, complexity, and the Cambrian explosion," BioEssays, Vol. 31 (7):736 - 747 (2009), internal citation numbers removed, emboldened emphasis added.)


While their article then directly goes on to admit the "elusive" state of any "materialistic basis" of the Cambrian explosion, it doesn't really offer any explanation for the Cambrian explosion other than a vague mention of the open niche hypothesis and adaptive radiation. The rest of the article focuses on explaining the overall loss of phyla and body plans since the Cambrian, rather than the explosive emergence of new body plans in the Cambrian explosion. At some point, however, neo-Darwinism must account for the origin -- an abrupt one at that -- of new body plans, not merely the inability to evolve new ones in post-Cambrian times (what they call the "canalizing" of development). It would seem that after this article, the explanation for the origin of the phyla in the Cambrian explosion is no less "elusive" than before it.

Now Europe peers into the abyss.

Europe Bans Animal -- Not Human -- Cloning
Wesley J. Smith September 19, 2015 5:40 AM 

I am always amazed at how there is a great anger in Europe against technologies like plant GMOs, but far less outrage over the prospect of human genetic modification, in the early stages of implimentation. From The Indpendent story:

The genetic manipulation of human IVF embryos is set to start in Britain for the first time following a licence application by scientists who want to understand why some women suffer repeated miscarriages.

If the research licence is granted by the Government's fertility watchdog it will be only the second known occasion in the world where the chromosomes of human embryos have been genetically manipulated using a revolutionary gene-editing technique called Crispr/Cas9.

Meanwhile, Europe has banned farm animal cloning. From the Science Insider story:

The European Parliament today voted to ban the cloning of all farm animals as well as the sale of cloned livestock, their offspring, and products derived from them. The measure, which passed by a large margin, goes beyond a directive proposed by the European Commission in 2013, which would have implemented a provisional ban on the cloning of just five species: cattle, sheep, pigs, goats, and horses.

The supporters of the ban cited animal welfare concerns, claiming that only a small percentage of cloned offspring survive to term, and many die shortly after birth.

The ban does not cover cloning for research purposes, nor does it prevent efforts to clone endangered species.

Continuing with the theme of this post, human cloning has not been similarly banned throughout Europe.

Indeed, while there is a protocol against allowing a cloned baby to be born, and some countries like Germany outlaw creating human cloned embryos, others like Great Britain-which even permits the use of animal eggs in cloning attempts-allows the human cloning research to proceed full speed ahead.


Sometimes I think that in the minds of some, animals matter more than humans.

Darwinism Vs. the real world. XII

The Human Body Continues to Give Evolutionary Biologists High Blood Pressure

Howard Glicksman September 18, 2015 4:27 PM | 

Editor's note: Physicians have a special place among the thinkers who have elaborated the argument for intelligent design. Perhaps that's because, more than evolutionary biologists, they are familiar with the challenges of maintaining a functioning complex system, the human body. With that in mind, Evolution News & Views is delighted to present this series, "The Designed Body." Dr. Glicksman practices palliative medicine for a hospice organization.

Let's review what this series of articles has shown so far about human life. The body is made up of trillions of cells, each of which must control its volume and chemical content while receiving what it needs to live, grow and work properly. Since the body is made up of matter, it is subject to the laws of nature, which demand that it have enough energy to do what it needs to do to survive.

To get enough oxygen to meet its metabolic needs, the lungs must have fast enough airflow, large enough volume and efficient enough gas exchange in addition to having enough hemoglobin in the blood. Since it is the blood in circulation that provides the cells with what they need, the body must also make sure it has enough water, sodium and albumin to maintain enough blood volume. Moreo4ver, since blood has mass, it needs the heart to pump it throughout the body against forces like inertia, friction and gravity that naturally prevent it from moving anywhere. To do this adequately, the heart must have a properly working electrical system, which is dependent on having the right amount of potassium in the blood, and enough coronary blood flow, proper valve function and sufficient ventricular relaxation and contractility.

Having enough of whatever is needed to follow the rules set down by nature also requires being able to take control and each of the systems the body uses has a sensor, an integrator and an effector to get the job done right. And since life doesn't take place inside a vacuum or within the imaginations of evolutionary biologists, when it comes to living and dying, real numbers have real consequences. This means that to survive within the laws of nature, life must make sure that each of its numerous chemical and physiological parameters must stay within a certain range.

We've already looked at how the blood volume and cardiac output are properly maintained. But it is possible for both of these parameters to be normal and death can still take place due to an abnormal blood pressure. How does that happen?

Blood pressure is the force which blood applies against the walls of a chamber or blood vessel through which it is moving. Think of it like the pressure that can be felt as water rushes through a garden hose. Since blood flows from the heart through the arteries to the capillaries in the tissues, and back again through the veins, this means that there are many different blood pressures throughout the cardiovascular system. However,the blood pressure used in clinical practice is understood to be the force of blood exerted against the walls of the brachial artery that is located in the upper arm. In other words, the blood pressure is synonymous with the force the blood applies against the walls of the large systemic arteries.

When it comes to measuring blood pressure, it is important to understand the cardiac cycle and how blood flows within the arterial system. Systole makes up one-third of the cardiac cycle during which the left ventricle pumps blood through the aortic valve into the aorta and from there into the large arteries. As this blood is added to what is already present within the brachial artery, this causes the blood pressure to rise to a maximum. This is called the systolic pressure (SP).Diastole makes up two-thirds of the cardiac cycle, during which the left ventricle relaxes and fills with blood.

Once pumped out of the left ventricle, the blood travels down narrowing vessels until it meets resistance in the arterioles. Some of the blood flows through to the capillaries while some rebounds back towards the heart where it again meets resistance, this time from the closed aortic valve. The blood then continues to ping-pong back and forth between the arterioles and the closed aortic valve during diastole, allowing some of it to pass into the capillaries. By the time diastole ends and systole is about to begin, the blood pressure within the brachial artery has dropped to a minimum and is called the diastolic pressure (DP). In other words, at the end of diastole there is still a lot of blood within the large arteries.

The blood pressure is measured by pumping up a pressure cuff, placed around the upper arm, high enough to block the blood flow in the brachial artery. While slowly releasing the pressure, the doctor uses a stethoscope to listen for the first sound of turbulent blood flow (SP) and then its total disappearance (DP). The blood pressure is measured in units called millimeters of Mercury (mmHg)and is usually expressed as the SP/DP, such as "120/60." Since systole lasts for one-third of the cardiac cycle and diastole, two-thirds, it is possible to calculate the mean arterial pressure (MAP) as 1/3 SP + 2/3 DP. So the MAP for a BP of 120/60 would be 80 mmHg (1/3 (120) + 2/3 (60)).

It is important to remember that the blood pressure represents the driving force that moves blood throughout the circulatory system to feed the cells what they need to live, grow and work properly. This means that, in general, blood flow is directly related to blood pressure. It is the MAP that is often used when considering blood flow because it represents the average blood pressure. Like all matter, blood is affected by natural forces such as inertia and gravity, which must be overcome by the pumping heart to move it where it needs to go. Just as friction slows the movement of an object on the ground, blood flow meets its counterpart, called vascular resistance in the blood vessels. In particular, the vascular resistance that is generated by the peripheral arterioles is called the peripheral vascular resistance (PVR).

Inertia, vascular resistance and gravity are the three main forces that prevent blood from going where it needs to go in the body. The body must generate enough blood pressure to maintain enough blood flow throughout the circulation. The three main factors that affect the blood pressure are the cardiac output, the total blood volume and its distribution within the circulation, and the peripheral vascular resistance. The harder and faster the heart pumps, the more blood enters the arterial system and the higher the blood pressure, and vice versa.

The total blood volume is dependent on how much water and sodium is in the body. The systemic arteries usually contain about 12 percent of the body's blood while the veins have about 60 percent. So, the more water and sodium in the body, the more blood volume, and when the body shifts more of it from the systemic veins into the arteries, the higher the blood pressure and vice versa. The vascular resistance applied to blood flow by the peripheral arterioles causes less blood to go into the capillaries and more to stay inside the arteries. So more peripheral vascular resistance results in higher blood pressure and less peripheral vascular resistance, lower blood pressure.

It is the laws of nature that demand that each cell have enough energy and nutrients to live and do what it is supposed to do inside the body. However, it is these same laws that the body must overcome by having enough arterial blood pressure to get enough blood flow to its cells and provide them with what they need. In other words, as clinical experience has shown, too low of a blood pressure is a big problem. Since blood vessels are made of tissue that can withstand only so much pressure, too high of a blood pressure is just as bad. Next time we'll look at how the body takes control of its blood pressure to be able to survive within the laws of nature.