Tag Info

New answers tagged

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

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 ...


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 ...


2

We humans are not perfectly symmetrical. Some organs exist only on one side of the body which are critical for life.That said you can however live without half your brain (if you call that state living) and some other organs also have distributed function over thier surface.


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 ...


13

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


14

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 ...


0

GnRH-secreting neurons are not fully independent. To date, their most studied regulators are kisspeptin-secreting neurons. During childhood, kisspeptin-secreting neurons are off, due to GABAergic higher level structures and to lack of free leptin. So both brain and body fat have a word on it. Caveat: most of the evidence is circumstantial (for example, ...


1

Yes it can. Usually this is through an increased rate of suicide or the inability to look after yourself due to the level of pain you are in. It is so common that there are so many medical departments that have the sole job of pain management. Pain itself is not designed to kill you (in fact the very opposite as highlighted excellently by Cuana), but as ...


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 ...


1

The most popular method of getting fat in the first place involves exerting yourself as little as possible. This leads to the muscles and metabolism failing to become conditioned for strenuous activity, ie. remaining very untrained. Therefore, a person who became fat in this manner is mentally and physically unprepared for intense activity, for the simple ...


2

If you are speaking especially of the stomach, it actually makes no difference because the extremely low pH of the stomach allows very few bacterial organisms to survive. Often, Helicobacter pylori can however be present. Whether dissolved oxygen makes a difference to it is, to my knowledge, unknown. However, pure water does not stay long inside the stomach ...


1

It's for control, coordination and balance. From a mathematical point of view, parallel lines won't intersect and thus line A won't affect line B unless they intersect and thus would hardly influence the other unless and an external force is applied to any of the lines. This is also why corpus callosum connects the left and the right side of the brain.


1

Firstly we must acknowledge there is a difference between being thin and being fit. An unfit thin person will also tire more quickly than a fit person, performance is not always directly related to weight. This is due to the "use it or lose it" nature of fitness. In addition to the factors mentioned by Deepanjali Dwivedi it is often the case that overweight ...


2

If you have no medical background at all, you will need a general text that teaches more than just digestive physiology. That is because you need to understand the function of other systems that have an influence over the digestive system (for example, the peripheral nervous system). Here are a few good general references to get you started: Physiology by ...


1

This may shed light on why the teenagers response to dopamine changes. Quote from reuniting website There's much still to learn, but it looks like a number of reward circuitry events occur after climax that have the potential to desensitize us for a time. First, androgen receptors decline after ejaculation, and take up to seven days to normalize. ...


3

Fat people have a large amount of body cells which need a large supply of oxygen from the blood.Heart beats at some constant rate and it has some upper limit to which it can supply blood. In fat people the same sized heart and same volume of blood needs to be circulated throughout the body and this becomes difficult during exercise or rather cells of the ...


4

Pathogen identification procedure is not necessarily standardised due to differences in resources available to each country but there are certainly several characterised and accepted approaches used to identify a disease causing pathogen. The predominant techniques used to identify pathogens relies upon conventional clinical microbiology-based approaches, ...


1

I remember something from the anatomy lecture saying that one nostril picks up one, the other other kinds of molecules depending of the molecule's size and other attributes. Meaning speed is important: if you breathe in through the nose right now, you'll probably feel the air coming in faster from one side than the other. And still if i remember correctly ...


7

It might be better to consider the sampling technology, economic and logistical issues with this question as well as the tech behind the tests. First, some tests still will want a few milliliters of blood - e.g. cell counts for specific cell types. Then there is the need to create and stock many different kinds of sample collection devices and train the ...


1

No. Some structures in the body are ever present from birth to death. The first things which come to mind are nerves, the eyes, the auditory hairs in the ears and the list goes on.....


8

As Chris said it's a matter of a low concentration for a small amount of time. Most people clean up their vomit rather than leave it to sit. Most people who vomit also have recently eaten something which triggers the reflex but also dilutes the acid or may neutralise it. To further add to Chris' answer. Even heartburn or gastro-oesophageal reflux disease, ...


2

They are vital if not incredibly useful in many other mammals but not humans. People have tried to look for a role and seen that they activate in times of stress or anxiety. However this probably only serves to heighten both stress and anxiety as you now also don't smell that great either. There is no identifiable role in humans apart from causing a variety ...


6

I was first thinking of voting to close the question because it was too broad, but in reconsideration I think the answer of showing why it is too broad would constitute a proper answer in this case. First of all, the term disease is one of the most general terms for a problem in medicine. The only term that could be higher up is "medical condition." It ...


3

We have two nostrils for the same reason we have 2 ears and 2 eyes. Having 2 nostrils means an odor molecule coming from one direction will have higher concentration in one nostril than the other, so we can determine what direction the smell is coming from, and allows us to find food or avoid predators more effectively. While humans no longer rely on smell ...


3

The main minerals in tap water are calcium and magnesium, which determine the hardness of water. The main minerals in mineral waters are calcium, magnesium, sodium, chloride, carbonate and sulfate. Tap water from different regions and various brands of mineral water can contain very different amounts of minerals, so it is impossible to make a general ...


5

There are two aspects to your question. First, organisms have some kind of symmetry. The field of evolutionary developmental biology has some theories on why our anatomy is the way that it is. So, we have two eyes, two halves of our nose and two nostrils, one "tube" that becomes the path from our mouth to anus, etc. Our nostrils are just part of that ...


29

First of all, it is corrosive. People which are bulimic often get problems with their teeth getting damaged by the permanent exposure to the acidic stomach fluids. See the paper for more information: Bulimia and tooth erosion Then it is a matter of concentration. According to Wikipedia, the concentration of the acid in the stomach is around 0.5% which is ...


2

I'm not a medical professional, so this isn't exhaustive or guaranteed 100% accurate: You can live a (*mostly) normal life without your: appendix tonsils spleen gallbladder pancreas portions of your liver (pieces can be removed and it will regenerate) portions of your small or large intestines both lungs (one is needed) both kidneys (one is needed) ...


4

They are actually different. INTERVERTEBRAL FORAMINA is actually spaces between adjacent vertebrae which gives passage for spinal nerves to exit. Whereas, VERTEBRAL FORAMINA forms vertebral canal. Source: Organization of the Nervous System: An introduction for students in the Human Anatomy Course


6

The woman running bit is obviously a myth but that is genius.. Other than that the length of the umbilical cord has been found to be highly variable depending on each individual. Characterizing it as just long would therefore not be right. According to Wikipedia, The umbilical cord in a full term neonate is usually about 50 centimeters (20 in) long ...


5

Apparently, both are true. ...Individual differences exist in both odorant production and odor perception. The biological basis for the inability to produce the metabolite in detectable quantities is unknown, but the inability to smell the odor is associated with a single nucleotide polymorphism (rs4481887) within a 50-gene cluster of olfactory ...


8

Identical twins have, despite the name, neither identic fingerprints nor identic genetic fingerprints. Fingerprints: According to the papers listed below the fingerprints show higher similarities (the "structure" is the same), but they can be distinguished and are not the same. On the similarity of identical twin fingerprints Can identical twins be ...


1

So it seems to me that signs of stress would be high levels of both of these things. Yes. Wikipedia claims [1] the same: Stressors [...] activate the HPA axis, though via different pathways. [...] Stressors that are uncontrollable, threaten physical integrity, or involve trauma tend to have a high, flat diurnal profile of cortisol release (with ...


1

I can make a rough analogy in terms of digital media storage. Our memories exist as a relationship between our perceptions and our sensations. Computers store input readily. However, humans store memories perceptually. This means who we are and how we remember an event permanently changes our recollection. If you look at the progression of lossy video ...


1

I am not sure whether I grasped the gist of your question appropriately, but let me provide some clarifications. $\text{Nerve}$ is simply a collection of axons. Therefore, all the spinal nerves are just bundles of assorted nerve axons. Now, the origin of nerve is slightly ambiguous as far as its meaning is considered. It can mean the physical origin, ...


2

This question is related to the question: Why are some things transparent and others opaque? Being able to see something requires that it is opaque and that sufficient light illuminates it. UV and shorter wavelengths are not as prevalent as visible light on earth. The world would appear too dark to see if we used UV and shorter wavelengths. This is ...


2

Electroencephalography has a good time resolution (milliseconds) but poor spatial resolution (several centimers). The usual estimated figure is that at least 50000 neurons need to fire simultaneously so that the activity can picked up by EEG. The answer provided by @Jeremy Kemball is not very accurate. The reason why the spatial resolution of EEG is poor is ...


0

Human skin is made up of three layers [1]: Epidermis; it contains no blood vessels; it has 5 cellular layers (starting from surface): stratum corneum stratum lucidum stratum granulosum stratum spinosum stratum germinativum Dermis; it is separated from the above by the basal membrane; made up of connective tissue (with blood vessels and nerve endings) ...


5

Factors that can lower body temperature: low environment temperature low metabolic rate hypothyroidism I couldn't find any relevant study addressing the Japanese people situation, but: There is significant variation in metabolic rate in humans, independent of differences in body size, body composition, age, and gender. Although it has been generally ...


1

This entire post is taken from odd thinking: http://skeptics.stackexchange.com/questions/10309/do-japanese-people-have-a-lower-body-temperature-than-caucasians There may be a difference, depending on whether you are talking about internal or skin temperatures. This study compared 9 Japanese men to the results of a similar study done in Ohio with Caucasian ...


1

You're confusing an emergent system with a determined system. Your cells have programming which emerges as the form you see. You are using determinism to decide what your form should be. Determinism gives one reaction for every action. Biology is emergent, not deterministic. The biological mechanisms which are responsible for healing exist in a different ...


1

Many examples of animals which have more difficulty maintaining their population size than humans exist. This is partially why some species go extinct. The Tasmanian Devil is at high risk for extinction from a genetic predisposition for cancer onset by infection. Your premise that humans are unhealthy is not sound. Humans are long lived, genetically diverse ...



Top 50 recent answers are included