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94

Apparently you're not the first person to notice this; in 1895, a German nose specialist called Richard Kayser found that we have tissue called erectile tissue in our noses (yes, it is very similar to the tissue found in a penis). This tissue swells in one nostril and shrinks in the other, creating an open airway via only one nostril. What's more, he found ...


37

This is natural phenomenon called the nasal cycle. It is discussed in this paper by Telles et al. (1994), among many others. The nostrils are used on an alternating cycle of about 2-3 hours, controlled by the autonomic nervous system. If you notice alternating congestion, that also seems to be coupled to the nasal cycle (Hasegawa and Kern 1977, 1978). ...


30

For the same reason that when you urinate or use the toilet, you have to exert pressure and urine or faeces just does not simply leak out when you stand up. The urethra seals shut when the urethral sphincter muscles relax. Similarly Sphincter ani externus muscle seals shut in the anal canal when there is no antagonistic force. So water can't just simply ...


17

In "Guns, Germs, and Steel" Jared Diamond includes quite a bit on this topic. His conclusion is that Europeans, and old world humans in general were much more exposed to their farm animals, often living in the same buildings. This allowed a much greater number of diseases to jump from animal to human, forcing us to development immunity against these ...


14

There is at least one important exception - it is generally thought that syphilis came to Europe from the Americas.


12

As others have said, this phenomena is called the nasal cycle, a process controlled by the autonomic nervous system that alternants congestion between your nostrils. Mentalfloss of all places has an article about this that explains: ...it makes our sense of smell more complete. Different scent molecules degrade at different rates, and our scent ...


10

Usually, nothing happens if you eat silica gel. In fact, you eat it all the time. Silica is added to improve flow in powdered foods. It occurs naturally in water, where it may help confer resistance against developing senility. Silica is just another name for silicon dioxide, the main component of sand. Mayby you think if silica is harmless to eat, why do ...


9

The female breast is composed primarily of fat and connective tissue plus lobules and ducts for milk production and delivery. The pectoralis muscles form a thin layer beneath the breast, as seen in the figure in the link. An athletic female can enlarge the size of the pectoralis muscle and the laterals muscles, just as male athletes can enlarge their "pecs" ...


7

As you point out human beings (and other organisms) have hundreds of retroviruses and many can be seen in the human genome, some of which appear to be the remains of deactivated viruses, others which may be active. Most retroviruses are not pathogenic - they don't cause disease. This is because many retroviruses replicate slowly, budding and secreting ...


6

Life is generally distinguished from non-life by metabolism and growth. As such, a fetus is alive. The reference to "not...until 26 weeks gestation" that you've heard likely refers to viability.* With the most aggressive medical care, this is the approximate age when a fetus may be able to survive outside the womb. The term human from a biologic ...


5

They don’t meet. Some framework: Spinal nerves contain motor, sensory, and autonomic fibers. Each of these have different pathways. Spinal nerves don’t go to the brain. Rather, they synapse in the spinal cord with other neurons which in turn go to the brain (sometimes requiring one more synapse). In the case of motor neurons, we talk about upper and ...


5

They would die. Let's imagine that we perfectly cut a person down the middle. That would mean cutting the spinal cord in half, probably damaging the tissue so much that the remaining half wouldn't work well. The liver would be gone. The intestines and bladder would just be open. The heart would have to be adjusted to the left. The surgery would probably ...


4

Oxidation does not mean inflammation. But oxidation can be a cause of inflammation. Oxidation processes are part of normal cell metabolism (mostly in mithocondria). They lead to reactive oxygen species ($O_2^-$, $H_2O_2$ and $OH-$) which can trigger inflammation via activation of some transcription factors: NF-κB, AP-1, p53, HIF-1α, PPAR-γ, ...


4

As stated in wiki "The major histocompatibility complex (MHC) is a set of cell surface molecules encoded by a large gene family in all vertebrates which controls a major part of the immune system. MHC molecules mediate interactions of leukocytes, also called white blood cells (WBCs), which are immune cells, with other leukocytes or with body cells. MHC ...


4

A haplotype is commonly defined as ...a group of genes within an organism that was inherited together from a single parent. -- Nature Scitable This definition of haplotype applies whether it is just a few genes or all of the genes on an entire chromosome$^1$. In the case of the major histocompatibility complex, it is a group of more than 200 genes on ...


3

I suspect that what you are actually looking for is the following: - 1 gram of fat = 9 kcal - 1 gram of protein = 4 kcal - 1 gram of sugar = 4 kcal - 1 gram of alcohol = 7 kcal Those are general and inexact values. They're just often used to give a rough idea of the amount of energy we get from different types of food.


3

The existence of membrane potential is just that: as long as they are alive, cells try to keep their cytosol different from the outside soup, mainly by expelling sodium ions. There is a longer story, with cells pumping other ions in or out, or leaking ions due to the imbalance, but resting membrane potential really revolves around sodium. There is an ...


3

Yes, in all clinical situations where you need pure vasoconstriction without heart rate acceleration (mostly valid for iv administration route). The classical example would be in the operative setting. If the patient is in a hypotensive state due to hypnotic drugs, opiates, etc. and has atherosclerosis, you will prefer a drug that will reverse the ...


3

Answers in comments are correct. The tail effect of hypnotic drugs combined to opiates given for pain relief will make you feel really tired just after surgery. But if you are referring to a more long-term effect, such as feeling tired for several days after surgery, then several factors combine: psychological stress physical deconditioning: inpatients ...


2

Fatigue on exercise is proportional to unmet demand for oxygen and glucose (sugar/fuel). In people who are "fat": They typically do less exercise. Therefore their cardiovascular system is not conditioned with the heart being able to cope with increased exercise i.e. it is unable to beat more efficiently and instead must beat A LOT more faster to cope ...


2

Bianconi et al. 2013 give an estimated lower bound of 3.72 × 10^13 (which, by the way, is approximately the geometric mean of 10^13 and 10^14). However, from the table in their Supplemental Information (where estimates for about fifty different types of cells are added up), it is clear that the vast majority of these are the erythrocytes, also known as red ...


2

To understand what a membrane potential is, you should understand the units for -80mv. The negative sign is relative to the observer, yourelf, to the inside of a cell. From your perspective, the inside has an excess of negative ions. On the outside of the cell, there is an excess of positive ions. Unlike electricity, where charge separation is quantified ...


2

We shampoo our hair because of sebum. In humans, sebaceous glands are are most numerous on the face and scalp, with (on the scalp at least) several glands plus a hair follicle making up a pilosebaceous unit. Each gland secretes sebum, initially a colorless and odorless fatty substance (plus dead cells) that spreads from the scalp outward over the hair, but ...


2

There is a nice video which can give you a comprehensive answer. Also you can find references in the description below the video: Why Do We Have Two Nostrils? (by Vsauce) link: https://www.youtube.com/watch?v=eiAx2kqmUpQ


2

I don't think it would harm you: apparently silica gel is a widely-used food additive. According to Wikipedia: Silica gel, also referred to as silica aerogel or hydrated silica, has FDA GRAS (generally recognized as safe) status, meaning it can be added to food products without needing approval. Silica is allowed to be added to food in the US at up to 2% ...


2

Why can't we just create a pill that does have all the necessary components? I'm assuming you mean micronutrients (vitamins & minerals). A day's worth of macronutrients (energy and building-block providing chemicals - proteins, fats, sugars) are already very abundant and dense - a pill containing a day's worth would be the size of an egg. ...


2

This is in the discussion for quite a while. I have found no scientific studies which back the claims of kinesio tape. A review article (from which the quote below is taken) found no clinically important results which support the claims of the tape. The results about range-of-motion were inconsistant and it is not clear if the changes found were beneficial ...


2

Yes, the difference is "only" in the 3D structure. This makes some differences when proteins change their shape, antibodies which recognize conformational epitopes are usually not well suited for lab work, as proteins are often denaturized here. The different epitopes are also called linear epitopes (for the sequencial) and discontinous epitope (for the ...


2

For animals to check the amount of energy used for a certain behavior you can use a RESPIROMETER. It basically calculates the oxygen consumption. In your case you could calculate for writing a sentence vs speaking the same sentence. Regarding your second question: At least in birds more than the type of sound (the frequency modulation) what matters for ...



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