Questions tagged [physiology]

The study of the normal function of living organisms and their anatomical parts and the means by which their normal functioning is achieved.

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1answer
391 views

Is there any evidence for secondarily poikilothermic vertebrate? [closed]

Is it possible that an endothermic physiology can evolve into an ectothermic (poikilothermic) physiology? I have a non-scientific gut feeling that it is irreversible. Whales and dolphins are evolved ...
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Do animals exhibit handedness (paw-ness?) preference?

I have been observing my cat and found that when confronted with an unknown item, she will always use her front left paw to touch it. This has me wondering if animals exhibit handedness like humans ...
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Where does extra blood come from to fill your muscles during exercise?

Let's say I go to the gym and lift some weights an hour. During this time my arms will grow due to the "pump" -- the extra blood rushing in to feed the muscles. For example, I've measured about 2-3 ...
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10answers
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Why are there no organisms with metal body parts, like weapons, bones, and armour? (Or are there?)

Reading this question, Why are there no wheeled animals?, I wondered why no organisms seem to make use of the tensile and other strengths of metal, as we do in metal tools and constructions. I am ...
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1answer
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What is itching?

What exactly at the molecular level is itching? What physiological function does itching serve, if any? I cant remember the reference but a PLCb3 null mice lost the itch phenotype, so presumably it is ...
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1answer
799 views

Body size, what are the evolutionary trade-offs?

Background Considering just the "Kingdom Animalia" branch of organisms. It is clear that bigger does not necessarily mean better - there is large variation in body size... From the 94 µm long ...
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3answers
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What causes feeling of feet falling asleep to be delayed?

This answer explains the sensation of extremities "falling asleep" as a result of sustained pressure on a nerve. The answer links to an external web page that says that the feeling "quickly goes away ...
11
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1answer
338 views

Were dinosaurs 'hot-blooded' or 'cold-blooded'?

Were dinosaurs hot-blooded or cold-blooded? NOTE: The popular term 'hot-blooded' means having an internally maintained average body temperature, which is generally more than that of the surroundings, ...
3
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1answer
818 views

What is the biological potential for vision of wavelengths outside the human visual range?

Humans eyes have evolved to perceive light only between approximately 350-700nm, because that form of light is most common to our lifes. Other animals can perceive lights with slightly different ...
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3answers
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Why do we get runny noses in the cold?

The most annoying thing for me about being cold is a runny nose. Is there an advantage to having a runny nose when cold? What does having a runny nose achieve?
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1answer
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How is ATP involved in muscle contraction?

The sliding filament mechanism as explained by my text does not elaborate on how ATP is involved in the cross bridge binding and contraction process. How does muscle contraction utilize ATP? In my ...
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2answers
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Why does the affinity of haemoglobin for oxygen decrease at high altitudes?

My class 12 NCERT book says, Pg 226 The body compensates low oxygen availability by increasing red blood cell production, decreasing the binding affinity of haemoglobin and by increasing breathing ...
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2answers
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What actually happens when my leg 'falls asleep'?

Most people have experienced the temporary loss of feeling and tingling in their leg resulting from sitting in an abnormal position for a short while. Usually you get a loss of feeling in your leg ...
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4answers
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Why is the brain dependent on glucose?

The strict dependence of the (human) brain on glucose has always been puzzling to me. While ketones can substitute for a portion of the brain's energy needs, it cannot substitute completely: blood ...
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3answers
465 views

How are long time periods measured in biological systems?

Biological systems are pretty good at measuring fairly long times, for example, menstrual cycles (month), or puberty (years). Counting days or years seems to be implausible, and chemical concentration ...
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2answers
2k views

Why do small organisms make faster movements than big organisms?

I hesitated to ask this question because it seems so obvious and intuitive. However, I am not able to explain this tendency. Background It seems to me that small organisms make faster movements than ...
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5answers
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Why do the humans become sleepy after meals?

I don't know about all the mankind, but I know enough people, who becomes sleepy after their meals. Also, I'm not sure, what kind of food do they consume, but I personally get sleepy almost from any ...
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How is membrane capacitance related to the increased speed of saltatory conduction?

Here is the original question which inspired my question. As explained by the answers there, the reason saltatory conduction in myelinated neurons is faster than non-myelinated conduction is because ...
19
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3answers
625 views

Are human fetuses more likely to be male? [duplicate]

Question: From a physiological point of view, when sex is determined in a human fetus, is it equally likely to be male or female? Studies in this area typically measure age at birth, where the data ...
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1answer
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How did the huge dinosaurs cope with gravity and loads on bones, etc.?

It's very costly to be a huge animal. Your mass grows in cube when you scale up, but you still only have two/four legs to support the same weight. This increases the pressure that your body needs to ...
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2answers
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Is the 'fluttering feeling' when under stress neurological or physical?

I'm sure that everyone is familiar with the sensation commonly known as "butterflies in the stomach". It is commonly experienced during periods of anxiety or stress (e.g. before high stakes job ...
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2answers
1k views

Inductance in cell

In an animal cell, especially neuron and in particular its axon, while there is electrical resistance and capacitance mechanism in the cell, which play essential roles in the cable theory model of ...
6
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1answer
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How are arms different than legs?

Ok, this is a bit of a tangent question, but it came up yesterday and I didn't know the answer: How are arms and legs defined physiologically? For example, we say humans have two arms and two legs, ...
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What causes "ear rumbling"?

The video Ear rumbling happens below the range of human hearing demonstrates that the "ear rumbling" sound is actual sound and can be recorded by a sensitive microphone near the ear. What is it ...
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1answer
622 views

How does regurgitated food go to the 3rd stomach chamber instead of going to the 1st?

Ruminants are known for their regurgitation of food; the food goes through the 1st and 2nd stomach chambers, then returns to the oral cavity in cuds. The cuds then come back into the stomach, but this ...
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1answer
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Elevated position effect on recovery times from upper respiratory infections at rest?

In nursing school, they advice for people with upper respiratory infections to be in a slightly elevated position at the head region when sleeping. My intuition of the reason is that the lymphatic ...
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335 views

Is there any evolutionary/physiological advantage to multi-lateral symmetry?

Just wondering ; I get the impression a large number of multicellular organisms are multi-lateral in their physical structure. Why would evolution/mutation have retained multi-lateral symmetry in an ...
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1answer
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How fast can a human run?

I'm a runner (cross country) and I'm always amazed at how fast Olympic sprinters are. There's a lot of hype about those in the 100-meter dash being the fastest in the world, and we're constantly ...
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Is it correct to use the terms multinucleate and syncitia interchangeably?

If you see the skeletal muscle,it is having several nuclei and is said to be "multinucleate".Similarly the cardiac muscle is also having several nuclei yet it is specifically termed"...
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How much heat can a human sustain?

For how long can a human sustain a temperature of 180 degrees Fahrenheit (82oC) without damage in a confined place? For instance, suppose a person is sitting in a steam-filled room, without external ...
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2answers
8k views

Can food swallowed when a person is upside down reach the stomach?

If a person positions him/herself upside down and swallows food, will it reach the stomach against gravity? If so how?
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1answer
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If targeting a certain daily water intake, do you have to compensate for beverages that promote diuresis?

Please forgive my ignorance on the topic and I hope this is a "on topic" question here. It was a toss up between this SE and Physical Fitness SE but I want a more scientific answer. I came at a ...
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356 views

Why is thrombin time (TT) normal range longer than prothrombin time (PT)?

Reference range for the TT is longer than that of the PT.
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What's the mechanism for being mentally tired?

I notice that after long tests, or long periods of critical thinking, my body and mind feel noticeably tired. Why does this happen? Are the neurons in my head not firing as quickly, or is there just a ...
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1answer
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What is the human energy consumption by organ?

The human brain uses about 25% of the human body's metabolic energy. How are the other 75% spent, in terms of portioning to its various systems? I thought this could be answered by a simple search, ...
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Is there any use of CO₂ in human body?

We all know CO₂ as a waste product of metabolism . Does CO₂ have any helpful role , apart from having a role in pH of blood ?
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2answers
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Why do some mammals not have testes in a scrotum?

Coming from an evolutionary approach, Is the only purpose of a scrotum to regulate the temperature of the testes? Knowing all mammals are warm blooded, shouldn't all mammals have testes in a scrotum?...
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Why do we urinate more when we are nervous?

This question is a result of my personal experience... But I guess that is common for many of us. My school timing is 8:00 am to 1:30 pm (usually). During normal school days I typically urinate one ...
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Should we induce fever to assist healing?

I am currently reading "The Fundamentals of Anatomy Physiology" 10th edition, and have found it an incredibly interesting book. I have just been reading about the lymphatic system, and the various ...
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6answers
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What is the cause of muscle cramps?

According to Wikipedia, muscle cramps are caused by the inability of myosin fibers to break free from the actin filaments during contraction, resulting in a prolonged contraction. A lack of ATP would ...
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The genetic and physiological origins of laughter?

This Wikipedia article defines laughter in many terms, such as... "a visual expression of happiness, or an inward feeling of joy" and "a part of human behavior regulated by the brain, helping ...
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1answer
272 views

Does stress physically age our body?

Going by the assumption that stress eventually triggers a flight/fight response, and the subsequent realization that flight/fight puts the body in a system of readiness to use it's available resources ...
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How is the blood volume of a living organism measured without killing it?

How is the blood-volume of an organism measured without killing it? Note:The blood-volume of an organism is defined as the total volume of blood present inside that organism.
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Do animals exist with an uneven total number of digits?

I recently finished reading Contact by Carl Sagan. In the book they talk about a pattern in the transcendental number like pi or e, and comment that it is found in base 10 or however many fingers the ...
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1answer
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Can an organism exist as a single cell but come together as multi-cellular during certain times?

I am trying to remember a particular segment from a BBC special, about a single celled species. However, at certain times all the individual cells came together to form a structure, not unlike a ...
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1answer
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Why doesn't ovulation occur in both ovaries simultaneously?

I know that in human body ovulation takes place at only 1 ovary every month. But development of a follicle depends on FSH levels in the blood, and since both the ovaries are exposed to the same blood ...
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1answer
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Relationship between nerves and axons

I just wanted to get a realistic viewpoint of our nervous system. I understand arteries and veins, but I wanted to know how similar our nervous system is to that? I understand we have neurons (...
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2answers
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Why does an electrical shock freeze up muscles?

Why is it when someone comes into contact with an electrical supply that their body freezes up and is unable to move away from the electrical source? Can someone explain this through a physiological ...
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1answer
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Is the swimming pool water harmful to frogs who jump in? If so, how?

Here is an odd question: Frogs have permeable skin. Indeed, via capillary action, frogs absorb water through their skin. Chlorine is in principle a harmful substance. I am sure what percentage of ...
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What is the function of the Hyoepiglottic ligament?

The hyoepiglottic ligament (ligamentum hyoepiglotticum) is an elastic band that connects the epiglottis to the hyoid bone. Although I can find information about the clinical significance of this ...