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17

The "normal" visual acuity in the Anglosphere is the 20/20 vision which means that on a Snellen chart characters with 8,86 mm height can be read conveniently from a distance of approximately 6 m. Now there are many known people who have very sharp eyes, having the doubled acuity of 20/10. This means they can discern characters of only 4,43 mm height from ...


16

Short answer Visual acuity decreases with age. Your son's age is within the age range that visual acuities are best. Acuity starts to decrease from about age 45. Background Visual acuity (visual resolution) first increases from birth up until around 4-6 years. Note that in the following graph better acuities are represented by lower numbers (logMAR ...


14

This phenomenon has been demonstrated in studies [1][2] which show a significant increase in urine output in the cold. The latter study shows the biggest increase is when a person is initially exposed to the cold rather than when they continue to be exposed or rewarmed up. In the study, the average urine out was 157 mL/hour when a person was initially ...


10

A gene being dominant does not necessarily imply the gene is also common. An easy counterexample is Huntington's disease. The gene is dominant, and only one mutant allele of huntingtin would result in development of the disease. However, the allele prevalence of the mutant is low in the general population. In the absence of a selective advantage of green ...


10

You might need to demote your single-celled 'lords' to 'squires'. They're not essential to an individual's life. You wouldn't die (dispensing with the "how" right off the bat.) You'd be just fine if no bacteria reentered your body. Your fecal output would be greater; you would derive somewhat less nutrition from your food, you would need to take vitamin K, ...


6

Cold-induced diuresis, where kidneys relieve blood pressure by increasing urine production. http://en.wikipedia.org/wiki/Cold-induced_diuresis The blood pressure is thought to be increased by vasoconstriction due to the cold. One source that supports that theory: Sun, Z. American Journal of Physiology -- Regulatory, Integrative, and Comparative Physiology, ...


6

Overdiagnosis and overtreatment are intertwined. There is debate about how to best describe the problem, but narrowly defined, overdiagnosis occurs when increasingly sensitive tests - or changing definitions - identify abnormalities that are minor, non-progressive, or likely to resolve on their own, and that, if left untreated, will not cause symptoms or ...


5

You might expect identical twins to have the same fingerprints as twins have virtually indistinguishable DNA. The distinguishing nature of physical characteristics of a person is due to both the inherent individual genetic diversity within the human population as well as the random processes affecting the development of the embryo. The same would then be ...


5

The answer is of interest not only in sleep but also the perceptions of patients under anesthesia, comatose states, etc. Our senses aren't 'dimmed' in sleep. There is no effective way to turn off our senses. The best way to explain what happens in sleep is that at some point (the last point, actually), our cognitive processing of sensations changes. That ...


5

I found an interesting article that dealt with anxiety and micturition. There are no proven or accepted view on this. There are a few theories as to how this happens. I am quoting it: There are several beliefs for what causes frequent urination from anxiety, and the likelihood is that all of these factors play a role: Muscle Tension – This is one ...


3

The pectoralis muscle attaches to the top to the inner half of the clavicle, just underneath the biceps on the inner part of your arm and the breastbone (a.k.a the sternum) which is found in the middle of your ribs. See below: So taking that in account the pectoralis muscle helps bring your arm closer to your body (adducts your arm), pulling it forward in ...


3

It's all about chemical reactions in your body triggered by your brain. Lot's of researches and documents confirmed this is what happens when you face a stressful situation. Stress -> hypothalamus -> sympathetic nerves -> Epinephrine (Adrenaline) -> more urine flow Domino neural connectivity (Thinking) => Domino Chemistry (Body reaction = stress and ...


3

In BACK INJURIES IN THE YOUNG ATHLETE, a paper by three Harvard Medical School/Children's Hospital orthopedic surgeons in the Division of Sports Medicine, there is more than enough evidence that back pain is common in young athletes of both sexes: Back injuries in the young athlete are a significant phenomenon, estimated to occur in 10% to 15% of ...


3

According to the Mayo Clinic website: As you age, the tissue structures and muscles supporting your eyelids weaken. The skin may start to sag, and fat that is normally confined to the area around the eye (orbit) can move into the area below your eyes. Also, the space below your eyes can accumulate fluid, making the under-eye area appear puffy or ...


3

The lighter crescent-shaped part at the base of the nail is called the lunula. It is a normal part of the nail matrix, and indicates nail growth. The faster your fingernails grow, the more obvious the lunula. Absence of the lunula without any other abnormalities of the nail is not uncommon, and while it can indicate anemia or malnutrition, it is often ...


3

I doubt you are going to be satisfied with any answer since the authorities on the matter can't test the many hypothesis and don't all agree. Around the time of homo erectus (1.89 million years ago), hominids began walking upright on a more permanent basis but this wasn't the only evolutionary event. Additionally, hominids began growing taller now as well ...


3

Preamble. There is a lot of misunderstood science here and you are more than right for questioning the lecturers interpretation of these energy values; something the other answers do not discuss. The problem arises from a dodgy reference and a lot of conjecture. In summary. Light and sound cannot be compared energetically in a biological context. Our ears ...


3

ANF (Atrial Natriuretic Factor more commonly known as ANP - atrial natriuretic peptide) squeezes (vasoconstricts) the efferent arteriole. This means the pressure in the glomerulus is higher (like if you squeeze the end of a hose) and so more fluid is squeezed out i.e. the glomerular filtration rate (GFR) is higher. It also dilates the afferent which means ...


2

Basically there is every variation under the sun possibly but I have structured my answer so that the more common variations are earlier. On average a woman loses around 30-40 ml of fluid, this is a combination of mucous, secretions, endometrial tissue and around 50% blood. Because of this it is a slightly darker colour than just regular old blood. This of ...


2

The thunder chimp's answer summarized the answer very well. To try to pull things together a bit, if you have seven minutes, check out this video. It shows a man chasing down a kudu. They both run for 8 hours, until the kudu literally collapses and the man calmly walks up to it and slays it. The video shows the evolutionary adaptions that the man has - he ...


2

No it isn't necessary to breathe in CO2 from the atmosphere. For the buffer system your brain detects the amount of CO2 (H+ which is an indicator of excess or too little CO2) and adjusts your breathing automatically to compensate so that your blood's pH stays normal. No outside CO2 is needed. Your kidneys also play a similar role but the lungs are what ...


2

He may have extreme acuity, or he may even have an extra cone type that allows him to see extra colors (and more color attunement may allow easier reading of those particular plates). But, you won't know anything for sure by asking on here. Take him to an ophthalmologist and let us know what the doc says! If you aren't 40+ and have 20/20 vision and he's ...


2

Digitalis (which was by the way originally synthesized from Digitalis Purpurea) has two mechanisms of action: The action by which digoxin improves contractility appears to be inhibition of the sarcolemmal Na$^+$K$^+$-ATPase "pump", normally responsible for maintaining transmembrane Na$^+$ and K$^+$ gradients The major therapeutic electrical effect ...


2

The hippocampus helps to solidify the pattern of connections that form a memory but the memory itself depends on the solidification of connections between the individual brain cells". This refers to the phenomenon called Long Term Potentiation which regulates synaptic strength between neurons. Certain patterns of firing (high frequency) causes the post ...


2

Mostly no. For example, if a non-diabetic person were to be injected with a small amount of insulin, the pancreas would halt its own production of insulin and, if the dose was too large, begin producing glucagon, which stimulates the liver to produce more glucose to match the dose of insulin. If these periodic doses continue, the size of the islets in the ...


2

Yes it is possible but in most cases it will not occur as the body simply halts production. The most infamous manifestation of this is in adrenal insufficiency. That's where when we take glucocorticoids (e.g. prednisolone used in management of lots of inflammatory diseases like asthma and autoimmune diseases) for a prolonged period at high dose. This causes ...


2

Haemophiliac females are rare but they can survive just like affected males do. However, the case is slightly more complicated in women because of menstruation. I could not find an article from any medical journal but this site seems authentic enough for a reference.


1

No, mammals need not take in CO2 from atmosphere. The body's homeostatic function will maintain its composition by checking the amount of CO2 released out by lungs. So certainly animals would survive if put in a CO2 free atmosphere.


1

Screening is the process of testing the population enmasse to check for the presence of risk factors for a disease or to detect the early form of a disease. Usually the tests that are used in screening are not highly effective in excluding people who do not have the disease (low negative predictive value). Instead the goal of screening is to identify as ...


1

A quick search through the Internet, as well as any textbook, will reveal that the lining of the uterus (endometrium) created thickened during every menstruation cycle is rich in nutrients, and requires a constant blood supply, in order to accommodate a fetus. Therefore, maintaining the lining would be more costly to the body than rebuilding it every month; ...



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