Questions tagged [muscles]

The contractile tissue of animals derived from the mesodermal layer of embryonic germ cells.

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84 views

Limit of muscle atrophy [closed]

I read that lack of action leads to muscle atrophy , I experienced same when I had a cast for hand fracture. So how far this atrophy go, who decides minimum size of muscle due to lack of activity, for ...
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Energy efficiency of muscles and animals as a whole

When human or animal do some work, they use energy from their food. What is known about overall efficiency of this process? Say a horse is turning a winch and does 10,000 kJ of work. How much more ...
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Need / consumption of magnesium

Does doing sports makes a human require more magnesium and – if any – how strong is this effect? Do athletes take magnesium supplements (e.g. pills of magnesium carbonate) because they build muscles ...
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Bone fracture cause [closed]

I had bone fracture twice in the same arm. So I had first bone fracture in right forearm with 45 degree break on two bones, after 3 months of that fracture while I was climbing a slope I fell and I ...
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The link between muscle mass and muscle strength and how to train for each [closed]

I'm getting into my fitness and am beginning to see an increase in muscle mass. However, I look at people like Bruce Lee, Elliott Hulse, Mohammad Ali and Wim Hof who are capable of incredible strength ...
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687 views

Are there genetic causes underlying the difference in circumference of the upper arm and foream?

Is there any genetic reason for the difference in size between the upper arm and lower arm (i.e., the forearm)? In most women, it seems that the upper arm is larger in circumference than the forearm. ...
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123 views

Does the speed of muscle contraction within a single sarcomere differ between people?

Of course the number of muscle cells can be different person to person. But within a single sarcomere, are we all the same? Would the frequency of the protein motor binding and release cycle ...
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365 views

How is the Force of Contraction Applied to the Tendons by the Muscle's Individual Fibers?

Image and question have been updated for clarity! The image above is a side view of a semi-transparent skeletal muscle. The dark red lines represent individual fibers, the blue lines represent ...
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How to contract sternocleidomastoid muscle by thought?

If I do not turn my head, how can I contract ( or tighten) the sternocleidomastoid muscle ( like we can intensely tighten muscle in limbs)?
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212 views

Why does lactate build up prevent a further increase in the speed of an athlete?

This question was triggered by an exam question that I was doing on the following paper (Q2 part (b)(i)): http://qualifications.pearson.com/content/dam/pdf/A%20Level/Biology/2013/Exam%20materials/...
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814 views

Are tergo-sternal muscles of cockroach involved in blood circulation?

Tergosternal muscles help in the blood circulation in a cockroach as well as in movement of the wings for flying. I came across a question that claims that these muscles are used in blood circulation ...
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1answer
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Why are successful human rock climbers so dissimilar to Hominidae primates who spend extended time periods climbing? [closed]

In rock climbing, the sport considers the Ape Index when evaluating the factors critical for success. However, the majority of successful climbers are lithe and slim with less than 8% body fat. As ...
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1answer
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Mechanism of Myosin Head Bending in Cross Bridge Cycle Power Stroke Phase

What is the mechanism of bending of myosin head during the power stroke of the cross-bridge cycle of the muscle contraction? Does this have anything to do with the protein's 3-D structure i.e. folding ...
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What neuro-motor diseases cause the lower esophageal sphincter (LES) to malfunction?

Please note: This question is neither homework nor seeking medical advice. I'm simply asking for a factual, objective, biological explanation of the various neuro-motor diseases/illnesses that can act ...
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What is coffee effect on muscles ? On sport performances?

Since coffee is a vaso-restrictor does it have any impact on sport performances ? I mean does it go against natural way the body works (sending more blood to muscles due to the increasing needs) or ...
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Why do some cells like myofibrils have multiple nuclei?

I see that myofibrils (muscle cells) contain not one, but multiple nuclei. Why is this so? Do all the nuclei participate in cell division?
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3answers
561 views

Why are our muscles limited to 7 Hertz?

I have heard from a (usually very knowledgeable) friend before, that a human can only tap his fingers 7 times per second. I generalized this to "our muscles are limited to 7 hertz" When my wife ...
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What makes delayed onset muscle soreness stop occurring?

If someone lifts weights or takes a long jog after not doing it for a while, they can experience delayed onset muscle soreness (DOMS). However, when they return to the same exercise days afterwards, ...
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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
5k views

What is difference between High quality and low quality proteins [closed]

I have seen in news that some bodybuilder died of taking steroids; when I went through details I learned that "low quality proteins" contributed to their death. I have studied about linkages in ...
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1answer
6k views

Location of t tubule in muscle

Why do mammalian skeletal muscles have t-tubules at the junction of the anisotropic and isotropic band, whereas non-mammalian muscles and cardiac muscles have it at Z-line? What could have been the ...
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346 views

How can skeletal muscles in the human body be modeled as levers? [closed]

From what I understand, human arms can be thought of as third class levers, so that the distance from your elbow to the place where the muscle attaches is effectively the distance to the fulcrum, so ...
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1answer
329 views

What is the difference between a “semi-contracted” muscle and a “contracted” muscle?

I read on http://www.spine-health.com/glossary/muscle-tension: Muscle tension refers to the condition in which muscles of the body remain semi-contracted for an extended period. What is the ...
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110 views

How do our muscles get tired?

I know one of the main reason why our muscles get tired is because there is too much lactic acid, but how does this lactic acid negatively affect the action of myosin on actin?
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255 views

What is the difference between muscle tension and muscle tightness?

Is there any difference between muscle tension and muscle tightness? I want to study the relation between forearm muscles tightness/tension and tendinopathy (specifically, medial and lateral ...
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1answer
118 views

What makes us “tired” in the gym that forces us to rest? [closed]

If I'm doing push ups or any other of gym exercise, I can do 10 in a row, but each one I do I feel more "tired", but if I rest for 5 minutes, I'm much "full of energy". Please explain me exactly what ...
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Muscle contraction/extension percentage during normal ranges of motion

What is the typical percentage range/limits of extension/contraction during normal ranges of motions for muscles? Assuming a rest length in a typical relaxed state. I'm mostly interested in humans ...
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2k views

8 abdominal muscles but 10 pack

Simple question, how is it possible that there are people who appear to have 10 pack abdominal muscles while the human body has only eight?
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1answer
106 views

What is the state of actin-myosin in my biceps after I have flexed my arm?

When I'm starting to flex my arm, the myosin and actin slide over each other in a ratchet like mechanism. When I've totally flexed my arm, are the actinomyosin left in this contracted state? Since ...
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1answer
867 views

How does motor nerve innervation determine type of muscle fibre?

Muscle fibres are of two types - type I and type II. They differ from each other in various properties. Even the underlying biochemical processes are different to suit their function (slow vs fast) ...
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275 views

How does the ATPase stain for muscles revert on changing the pH?

Muscle sections are stained with ATPase to differentiate between types of fibres and to display the ckecerboard pattern. But it is done at two different pH. The staining is reversed at acidic/basic pH....
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557 views

How do legs of tiny insects/spiders like mosquito/Opiliones work?

I think I understand how legs of humans work. We have bones to which muscles are attached. Muscles can only contract / relax. By the combination of many different muscles we can make complex movements:...
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1answer
52 views

Which of the response is faster? voice or hand action?

After taking certain stimuli and making the the decision to do certain action, which one response (output) (out of 2 possible output-ways, voice and hand-movement) would act faster? For example lets ...
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Myoblasts Formation

Myoblasts arise from mesenchymal stem cells (MSCs), and are precursors to myocytes. In muscles, in the basement membrane, there are also present satellite cells which can divide to generate muscle ...
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How does gold chloride stain neuromuscular junctions?

Gold chloride is used in muscle biopsies to stain the NMJ. What is the substrate that it binds to?
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2answers
19k views

What is the difference between endomysium and sarcolemma [closed]

They both are lining of muscles so how can we differentiate these two? Please answer in simple terms.
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1answer
267 views

How do sarcomeres coordinate contraction?

As can be seen from the figure if myosins from both sides apply equal force then how does muscle contract? And also how do actins resist tearing? Is there any kind of coordination between different ...
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1answer
1k views

Are glands in human made up of muscles?

I came across this idea while reading an excerpt of my textbook $-$ Muscles move eye lid , tongue, beat the heart, popel food through gut, discharge wastes, squeeze out secretion from the glands ...
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Are myosatellite cells myoblasts or do they differentiate into myoblasts?

Can satellite cells immediately fuse to a myotube/myofiber (meaning it is a myoblast already) or do they differentiate into a myoblast first and then fuse to myotubes/myofibers?
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1answer
611 views

When a muscle contracts, but not all the muscle fibers are activated, what happens to the remaining muscle fibers?

I understand how motor neurons work, but I would like clarification on what exactly is going on when a muscle contracts. For the sake of simplicity, let's just use the bicep as an example. If I do a ...
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In a sarcomere, during contraction, is chemical energy turned into elastic energy and then mechanical energy?

I'm familiar with the cross bridge cycle and how the sarcomere contracts, but I have two related questions. I’ve read that when the myosin head cocks, it’s similar to a spring-loaded mousetrap. But is ...
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Long-Term EMG studies

I am having trouble differentiating onset/offset of muscle activation. Is there anyone in the field has a specific way to set the threshold for both time and magnitude?
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1answer
657 views

Storage of energy in muscles vs fat depos [closed]

How does the body control, where consumed energy (fat, glucose) is stored? And what is its strategy? More specific: 1) How does the body control storing glucose in muscles and not as (subcutan) fat? (...
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1answer
44 views

Physical activity in fasted state: Glucose for brain vs muscles [closed]

Let's consider this scenario: You do sports in the morning in a fasted state (i.e. without consuming any calories after waking). Your brain of course needs glucose and your liver probably still has ...
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1answer
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What are the binding sites (or receptors) of cortisol?

I am in the process of a OCR GCSE Case Study, and my question is "Do the benefits of anabolic steroids outweigh the risks, which has an obvious conclusion. I need to know the scientific name, or a ...
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2k views

How does the muscle return to its resting state after muscle contraction?

I know that when ADP binds to the myosin head, it moves along and as it does so, it releases the ADP. The ATP attaches to the myosin head and releases the myosin head from the actin filament. Then the ...
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1answer
1k views

What causes humans to be physically weak compared to animals like gorillas?

Animals like gorillas seem to have a physical fitness and muscle mass that don't depend as strongly on how much exercise they get, compared to humans. E.g. gorillas living in the wild sleep and rest a ...
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1answer
10k views

What is the difference between muscle fascicle and muscle bundle?

In the photo above (given by Bio teacher), the muscle bundle is shown to be as a bundle of fascicles, but in most web definitions I've seen, the two terms are used interchangeably. What is the correct ...
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Abdominal muscles during inspiration/inhalation

During inspiration I am aware that the diaphragm and the external intercostal muscles contract, thus increasing the volume of the thoracic cavity. However, I read on my textbook that during ...
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How is recruitment of multiunit smooth muscle cells fine tuned if they are innervated by varicosities?

In my physiology textbook (Silverthorn) and on wikipedia it says that: Multiunit smooth muscle tissues innervate individual cells; as such, they allow for fine control and gradual responses, much ...