Susan
  • Member for 7 years, 4 months
  • Last seen more than 1 year ago
What do you see when your eyes are closed?
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37 votes

This is called a phosphene — the experience of perceiving light in the visual cortex without light actually entering the eye. This commonly happens due to stimulation of the retinal ganglion ...

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Is there anything that is completely non-toxic to humans at any dose?
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33 votes

I’ll answer this theoretically, since that’s how it has been posed. And if we’re ignoring practicalities, we may as well posit that the substance in question will be introduced directly into the ...

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Why is menstruation in wild animals not a disadvantage to organismal survival?
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31 votes

Thanks to the other answer for pointing me in the right direction with some references. It seems that two biologists in the early 1990s had a back-and-forth over this topic in The Quarterly Review of ...

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Why should a tumor look like a crab?
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16 votes

Such projections are more formally known as spiculations. Most commonly, we talk about spiculations with respect to the radiographic appearance of malignant breast and lung lesions. This paper* ...

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What is the biological reason for a burst appendix being potentially lethal?
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16 votes

Necessary conditions In order for the process culminating in appendiceal rupture to begin, there must first be proximal obstruction of the lumen (the inside cavity of the appendix) that prevents ...

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Do biological facts determine when a human fetus is considered alive and human?
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15 votes

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 ...

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How does myopia develop, exactly?
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9 votes

What is myopia? Myopia, a.k.a. near-sightedness, is a refractory error. Refraction is the process by which the optical system focuses images of objects on the retina, which are then transmitted to ...

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Does THC excretion increase if urine volume increases?
8 votes

This question asks about the urinary excretion of THC. Before answering the question I think you're getting at, I'll first note that cannabinoids (of which THC is one) are primarily metabolized by ...

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Biological origin of shuddering during sleep
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7 votes

These are called hypnic jerks, also known as hypnagogic jerks or sleep starts. They are normal part of the wake-to-sleep transition. Hypic jerks consist of non-periodic myoclonic movements, generally ...

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Counterintuitive action of Vitamin D?
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6 votes

There are two pieces to this question: a) How does bone resorption (movement of Ca/Phos out of bone into the blood) result in net improvement in bone structure? Bones are constantly remodeling, ...

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Can rapid eye blinking induce epileptic seizures?
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6 votes

“Self-induction” in photosensitive epilepsy is a well-described and fascinating phenomenon. Photosensitivity itself is rare, occurring in only ~5% of patients with epilepsy.1 Among this group it has ...

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Which literature/study/myth spurred the idea that urine is sterile?
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5 votes

But why does this mantra persist; where does it come from? Behind this line of inquiry is a fascinating observation about the disconnect between the laboratory and the clinic. The basic answer, from ...

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Why can't you just take a vitamin? Why you need a healthy diet on top of that?
5 votes

I think the piece of missing information here is the distinction between macronutrients and micronutrients. The info from Mayo clinic quoted in the another answer addresses some reasons why whole ...

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What is the difference between clinical and non-clinical depression, and is there a term for different severity of the bipolar disorder?
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5 votes

I think the main question here is: Is there a term…which describes a bipolar disorder of lesser severity[?] Yes. There are a couple ways to think about this, but you’re clearly accustomed to ...

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Where do the 31 spinal nerves start/meet?
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5 votes

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 ...

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Hydrophobia Outside of Rabies?
4 votes

You are correct that hydrophobia is often considered pathognomonic of rabies. However, I offer for your consideration: Hydrophobia as a rare presentation of Cotard's syndrome: a case report.1 ...

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Vitamins that could help "make us smarter"?
4 votes

Are there vitamins that make us smarter? Vitamins are micronutrients required in small quantities for normal human metabolism. Extra high (supra-physiological) doses do not generally result in ...

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Why is gastric lavage considered to be helpful only if a patient comes to a hospital within 1 hour of a toxic ingestion?
4 votes

Gastric lavage only washes out ("lavages") the stomach ("gastrium"). Gastric emptying time is generally ~60-120 min, probably on the lower end of that for ingested liquids. After that amount of time, ...

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What percent of the population has some form of synesthesia?
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3 votes

The phenomenon Synesthesia is a neurological phenomenon in which a stimulus in one sensory or cognitive pathway triggers an experience in another. Some hallmarks:1 It tends to be developmental, ...

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What is refractory proteinuria?
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3 votes

The article itself1 defines what the authors mean by both proteinuria and refractory: ...progressive proteinuria, with [urine protein-to-creatinine] values ranging from 0.6 at initial evaluation ...

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To get Standard ECG from PhysioNet?
3 votes

As another answer suggested, it's a matter of choosing a database that has all of the leads. The St Petersburg INCART 12-lead Arrhythmia Database (incartdb) contains all 12 signals. Here is the ...

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Can ovulation and menstruation occur simultaneously?
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3 votes

Ovulation and menstruation don’t happen in normally cycling women at the same time. A basic outline of the hormonal cycle that triggers these events will make this clear. Proliferative (a.k.a ...

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What are the highest and lowest possible pH, paCO2 and HCO3 in the blood of living human?
3 votes

As discussed in the comments, there are theoretical and practical problems with arriving at such data. There have been controlled experiments using canines, but you have specifically stated your ...

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Which process is needed to complete male reproductive development?
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3 votes

Regarding option C: Although it is correct that testosterone is converted into DHT, it is the former, not the latter, which is responsible for differentiation of the mesonephric (a.k.a. Wolffian) ...

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What is the mechanism of reflex arcs?
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2 votes

Withdrawal reflex You asked specifically about the withdrawal reflex and the receptors that trigger this. The initiation of the reflex arc is determined at the level of the nociceptors (pain-...

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What studies are there showing the effectiveness of any substance on canine hypertension?
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1 votes

Check out this consensus statement (PMID 17552466): J Vet Intern Med. 2007 May-Jun;21(3):542-58. Guidelines for the identification, evaluation, and management of systemic hypertension in dogs and ...

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