Phylogenetic Generalized Least Squares
The relationship between log and log was analyzed using PGLS in the Analysis of Phylogenetics and Evolution package within R according to established procedures . For each of these models, a measure of phylogenetic correlation, Î» , was estimated by fitting PGLS models with different values of Î» and finding the value that maximizes the log likelihood. The degree to which trait evolution deviates from Brownian motion was accommodated by modifying the covariance matrix using the maximum likelihood value of Î», which is a multiplier of the off-diagonal elements of the covariance matrix . All models were compared on the basis of Akaike’s Information Criterion as a measure of model fit . The probability that any given model is actually the best fit out of those tested was measured by its Akaike weight , calculated as the likelihood of the model divided by the sum of the likelihoods of all other models .
Giraffe Have This Huge Problem Of Having A Head That Is 2 M Away From The Heart So In A Really Big Animal How Does It Get Blood Up Thereprof Graham Mitchell Centre Of Wildlife Studies In Onderstepoort South Africa
The giraffe has an extremely high blood pressure , which is twice that found in humans. The heart can beat up to 170 beats per minute when a;giraffe is running, but a resting/normal heart rate is around 40-90 beats per minute.
It was previously thought that a giraffe had a really big heart, but recent research has revealed that there isnt room in the body cavity for this. Instead, the giraffe has a relatively small heart and its power comes from a very strong beat as a result of the incredibly thick walls of the left ventricle.
The right ventricle pumps the blood a short distance to the lungs, and the muscle is about 1 cm thick.;The left ventricle has to pump the blood all the way up to the head against the hydrostatic pressure of the blood already in the long vertical artery. A giraffes heart has evolved to have thick muscle walls and a small radius giving it great power to overcome this pressure.
The thickness of the muscle wall is related almost directly to the length of the neck. For every 15 cm increase in the length of the neck the left ventricle wall adds another 0.5 cm thickness.
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What Is Blood Pressure
Blood pressure refers to the pressure against the walls of arteries during the time the heart contracts and empties itself of blood as well as during the time the heart relaxes and fills with blood.
When the heart contracts, this is known as systole, and the systolic pressure is the maximum pressure against the walls of the arteries. When the heart relaxes, it is known as diastole, and diastolic pressure is the minimum pressure against the walls of the arteries.
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Giraffes Blood Never Floods The Brain
Because of all these special features, giraffes are well-adapted to their high blood pressure. So really they dont suffer the what we normally think of consequences for high blood pressure. In another mammal such a level of blood pressure would leave both the heart and blood vessels seriously ruptured.
Obviously, the source of the high blood pressure in giraffes is the small heart. It needs such a high blood pressure to be able to push blood from the heart all the way to the brain.;;However, the high blood pressure isnt just an issue for an upstanding giraffe. It gets worse when the animal bends over to have a drink. The blood pressure from the heart tends to increase due to the effects of gravity. What saves the giraffe are the special valves in the neck blood vessels. As soon as the giraffe bends, the valves close to stop the blood from flooding the brain.
Also, the giraffe also has the rete mirabile, a webbed collection of tiny blood vessels. Any excess blood that returns to the brain while the giraffe is bending is absorbed when these vessels expand. The blood, therefore, never floods the brain.
Clearly, the giraffe doesnt just have high blood pressure, but mechanisms to deal with it too.
Heroes Should Be Medium
Water animals have no problem with gravity. The external hydrostatic pressure of the water compensates for any gravitational effects . The cardiac output pressure in fish is 2550 mmHg; nevertheless, they do not experience orthostatic problems . For terrestrial animals, gravity does pose a problem. A water column of 1 m translates to a hydrostatic pressure difference of 73 mmHg! A human of 1.70 m in size and a systolic blood pressure of 120 mmHg at the level of the heart will have a systolic blood pressure of approximately only 70 mmHg in the brain and 190 mmHg within the toes. This simple calculation also explains why the heart is usually located in the middle of the body . As outlined above, early terrestrial animals generated a systolic blood pressure of only less than 3040 mmHg to avoid pulmonary oedema. For this reason, amphibians and reptiles always have a horizontal body posture . You will never meet a crocodile standing on its hind legsas it is often depicted in comics. The crocodile would feel dizzy rather quickly.
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What Kind Of Monitoring Will Be Required For My Dog
The treatment goal for a dog with hypertension is a systolic pressure of 140mmHg or less, and a diastolic pressure of 90mmHg or less. Periodic laboratory testing will be required to monitor for side effects of medication and progression of disease.
Potential complications of hypertension in the dog include:
- congestive heart failure
- retinal degeneration and subsequent blindness
- bleeding into the eye
How Is Blood Pressure Measured
Measuring blood pressure in your dog is very similar to having your own blood pressure measured. In general, your dog will be taken to a quiet room and gently laid on his side, giving him time to calm down. If your veterinarian is using a Doppler method of measurement, they will usually shave a small patch of fur on the underside of your dogs metacarpal or metatarsal and a small probe will be taped in place. An appropriate-sized cuff will then be placed above this area and inflated, just like your own doctor would do. As the cuff is deflated, your veterinarian will listen for the pulsing sound of the blood to be heard, at which point the systolic blood pressure will be recorded .
“Measuring blood pressure in your dog is very similar to having your own blood pressure measured.”
Generally, several measurements will be taken over a period of a few minutes, with the results being averaged out.
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How Is Hypertension Typically Treated In Dogs
The treatment of dogs with hypertension depends upon the underlying cause, if there is one. If the dog develops a serious complication related to hypertension like acute kidney failure or bleeding into the eye, there may be a need for hospitalization. In general, once any underlying condition is appropriately managed, medication and nutrition are important to normalizing blood pressure.
“The treatment of dogs with hypertension depends upon the underlying cause, if there is one.”
Medications that are commonly used to manage hypertension in dogs include angiotensin converting enzyme inhibitors, angiotensin II receptor antagonists , beta blockers, diuretics, and calcium channel blockers. Additional medications may be required depending upon the response to initial therapy. Therapeutic nutrition is generally accepted as an important part of long-term management.
What Are The Signs Of Hypertension
The signs of hypertension include:
- sudden blindness, bleeding inside the globe of the eye, and persistently dilated pupils
- detached retinas
- nervous system signs like depression, head tilt, seizures, disorientation, wobbly or uncoordinated movements , circling, weakness or partial paralysis, or short, rapid, back-and-forth movements of the eyes
- increased drinking and urinating with the progression of chronic kidney disease
- blood in the urine
- bleeding in the nose and nasal passages
- heart murmurs or abnormal heart rhythms
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The Giraffes Circulatory System
In the results published in the Journal of Comparative Biochemistry and Psychology, the researchers wanted to find out why and how the giraffe has such a long neck.;With its long neck the giraffe is able to browse for leaves in trees and also regulate its body temperature apart from maintaining a high level of vigilance.;The researchers were concerned with the fact that the head of a giraffe is more than 2 meters away from the heart. Just how is it able to get blood to the brain?
In previous studies, it had been shown that the giraffe has a blood pressure that is twice as high as that in other mammals. But it was mistakenly assumed that this was due to the animal having a gigantic heart.;The current research found that the size of the giraffes heart is smaller than that in a mammal of a similar size. The heart is a supercharged powerful machine that leads to the high blood pressure.
Taking A Pets Blood Pressure
Measuring a pets blood pressure is often done the same way as it is with humans. An inflatable cuff is placed on the dogs leg or tail, and standard blood pressure measuring instruments check the pressure. One difficulty can be keeping the dog still long enough to get an accurate reading, and thats important.
Veterinarians have to calculate another number when taking a dog or cats blood pressure called MAP or Mean Arterial Pressure. A dogs or cats MAP is calculated by dividing the diastolic pressure + 1/3 by the systolic pressure diastolic pressure.
|118.7 +/- 3.10|
* Some variation depending on breed.
If your pet has already been diagnosed with, and is being treated for, hypertension, ;your veterinarian will need to treat the underlying condition that caused the high blood pressure. They will probably also want to measure your pets blood pressure every three months moving forward. The vet may also suggest performing other tests, such as a complete blood count, blood chemistry panel and a urinalysis, every six months.
For most of us our pets are part of the family, so make sure they get a regular annual check-up with their; veterinarian. Dont ignore your vets advice, or at least get a second opinion before you make a potentially life and death decision on your fur-babys behalf.
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The Giraffe Has Another Trick To Avoid Heart Failure: The Electrical Rhythm Of Its Heart Differs From That Of Other Mammals
And the giraffe has another trick to avoid heart failure: the electrical rhythm of its heart differs from that of other mammals. In giraffes, the ventricular-filling phase of the heartbeat is extended, Natterson-Horowitz found. This allows the heart to pump more blood with each stroke, allowing a giraffe to run hard despite its thicker heart muscle. “All you have to do is look at a picture of a fleeing giraffe,” Natterson-Horowitz says, “and you realise that the giraffe has solved the problem.”
Natterson-Horowitz is now turning her attention to another problem that giraffes seem to have solved: high blood pressure during pregnancy, a condition known as preeclampsia. In people, this can lead to severe complications that include liver damage, kidney failure and detachment of the placenta. Yet giraffes seem to fare just fine. Natterson-Horowitz and her team are hoping to study the placentas of pregnant giraffes to see if they have unique adaptations that allow this.;
Doppler Ultrasound Blood Pressure Monitor
To measure blood pressure with the Doppler, an ultrasonic probe is placed over the artery and a pressure cuff is placed distal to the transducer. The operator then inflates the pressure cuff to a suprasystemic pressure that extinguishes the Doppler signal. Systolic blood pressure is determined by listening for return of the pulse signal as the cuff slowly deflates .11,12,22,26
Figure 1. In addition to pressure cuffs, components of a Doppler ultrasound blood pressure monitoring system include ultrasound gel to enhance contact between the probe and skin, the Doppler unit and the 8-MHz transducer probe, and a sphygmomanometer to measure pressure. Pediatric probes are preferred due to their higher sensitivity with small vessels. Photo credit: Katrina Lafferty, CVT, VTS. .
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Why Frogs Are Not Good Runners
A low systemic blood pressure is the reason why early land animals are unable to deliver a sustained high physical performance. The adaptive changes in the microcirculation of low-pressure animals explain why these animals are not good runners.
Early air-breathing animals, i.e. lungfish and some amphibians, have the largest erythrocytes of all vertebrates. With a diameter of 4050 µm, their erythrocytes are much larger than those of humans . Several studies have analysed the size of the red blood cells of vertebrates and found two trends in which the lungfish/amphibians instituted a major evolutionary transition . From the earliest fish, the agnathans , to the most recent bony fish , the erythrocyte diameter has decreased from 2012 µm. The terrestrial vertebrates show the same tendency. From the earliest terrestrial vertebrates, the amphibians, to mammals, the size has declined from a diameter of 50 µm to a diameter of 57 µm . As a side note, on this evolutionary path, the erythrocyte nucleus was removed in mammals but not in birds.
However, a denser capillarization comes with a price tag. To maintain an adequate blood flow in a vascular system with a high resistance, a higher blood pressure is needed. According to the HagenPoiseuille law, a reduction of the vessel radius increases vascular resistance to the 4th power ! In fact, the resistance at the tissue level was estimated to be 10-fold higher in mammals than in some amphibians .
Oscillometric Blood Pressure Monitor
Automated oscillometric monitors use an inflating cuff to detect oscillations produced by blood flow and these oscillations are used to determine blood pressure.7,22,27 There are significant disadvantages associated with use of oscillometric monitors in exotic animal patients. First, automated monitors take readings at a minimum of every minute. Changes can develop rapidly in critically ill exotics so the intermittent nature of the information obtained can be a problem during periods of cardiovascular instability. 8 Additionally, oscillometric monitors tend to be most unreliable when the information is needed most:; as blood pressure falls, the instrument may fail to obtain any readings at all.1,3,48,9,27 Oscillometric techniques can also fail to obtain measurements with rapid heart rates , small patient size, and hypothermia.9,27
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The Giraffe Has A Normal Sized Heart But Thick Ventricular Wall
The reason why the heart is so powerful is its small radius, which is enclosed by thick walls. Its blood vessels also have thick walls to ensure they dont rupture due to the high blood pressure.
Unlike other mammals, giraffes have an internal mechanism that enables them to either shrink or expand their blood vessels. In this way, they are able to efficiently increase or decrease the volume of the circulatory system.
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The Primordial Ocean Within Us: Invention Of The Kidney
We will begin our journey towards personal happiness with the fish, which evolved 500350 million years ago . As already well illustrated by Homer W. Smith , one of the major novel inventions of the fish was its capability to actively stabilize its internal milieu. Remarkably, the relative ionic composition of the extracellular fluid is virtually identical in fish as well as in all subsequent animal species .
Extracellular electrolyte concentration of the major inorganic ions in vertebrates in comparison to the salt concentration of the ocean
Chronological overview. From fishes, two major continuous separate evolutionary pathways can be traced which lead either to mammals or to birds . Both branches show similar phenotypic stages of development . However, as evidenced by the different anatomy of the lung, the evolution of both branches was separate, even though similar developments occurred . The position of each animal klades indicates the approximate time point of the last most common ancestor . Each transition of the geological ages was accompanied by mass animal extinctions and a subsequent rise in novel animal klades . Examples for monotremes and are the platypus and kangaroo.
In summary, from our early days as fish, we have taken the primordial ocean with us. The kidney was developed to maintain a standardized internal milieu within us.
Which Animal Will Never Sleep
Bullfrogs are thought to be animals that can survive without sleeping for months at a time. While they shut their eyes and go on to rest, they remain alert during these periods. According to research even while resting these huge amphibians were awake enough to respond to painful stimuli and show respiratory changes.
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