Questions tagged [muscles]

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

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T-tubules in Muscle Cells

I understand that T-tubules are common to striated muscles such as skeletal and cardiac muscles (with smooth muscle cells having caveolae) but what precisely (if any) is the difference in the T-...
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When mice move their lips, they always purse them. Why?

This is common in many rodents I see, from rats to squirrels, and it even appears in a variety of humans. The topside and underside flesh spurts out. These movements appear to be involuntary. What is ...
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Muscle contraction and closing in of z line/disc

I have studied that during a contraction of myofibril, the globular heads of myosin attach to actin filaments and pull them towards the centre of the sarcomere pulling the z line/disc as well. What I ...
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The amount of heat produced in muscles. A wrong answer

I'm trying to find how energy is released during muscle contraction. Seeing how no work is being produced, the issue is, after working out how much heat was theoretically produced by the heaviest ...
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What happens to the gamma motor neuron during too much contraction of a muscle?

Suppose a muscle is contracting too much, so we need a reflex to stop it from contracting too much. Contraction of a muscle causes the muscle spindle to go slack, hence the Ia axons and II-axons do ...
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To where exactly does the sarcoplasmic reticulum release its calcium when stimulated?

I`m reading through medical physiology (2nd ed) by Boron & Boulpaep. On page 240 when describing the mechanism behind muscle activation, they write the following: After depolarization of the L-...
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Why is the ordinary cardiac muscle’s target value of the action potential 0mV?

Why do some excitable cells have a target of 0mV for the action potential, even with a slight overshoot? Excitable cells such as muscles and nerves have the ability to rapidly change their membrane ...
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Micro-intradermal spasms in the legs after exercise [closed]

Heyo ! When i'm doing physical effort that involves and then rest, I feel small and suddle of what feels like contraction all over my legs (but not feet); It stops by itself after a few minutes and ...
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How are the muscles of some dead animals still able to function for an extended period of time without oxygen?

I found this video on youtube that features several butchered and sometimes cooked animals that are still able to move despite of this. Some of these animals have been dead for several hours already ...
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What is the linear force in a bicep compared to the force at the hand?

So I know that like most joints, the bicep applies a force near to the pivot (the elbow) and creates a rotational torque in the elbow, this moving the lever, your forearm and hand. Due to the biceps ...
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What keeps a muscle fiber in tension?

Someone in massage therapy told me that muscles require some chemical reaction to relax, and that magnesium helps with that. Looking into it, every source online I've found states that muscles relax ...
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Estimating Weight of Human Skeletal Muscle?

Is there a way to measure the weight of skeletal muscle? I understand body fat and lean body mass can be measured by: skin fold calipers, electrical impedance, table lookup based on formula of weight,...
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Fibrosis vs stenosis vs sclerosis

I can't figure out the key distinguishing factors between these three and I keep seeing them being used almost interchangeably. For example aortic valve fibrosis and aortic valve stenosis. As much as ...
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What is the actual molecular mechanism for muscle relaxation?

A number of my students asked what happens to the sliding filaments when muscles relax. For example, in an individual sarcomere, do all myosin heads release all at once or one/few at a time? More ...
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Would muscles still twitch if the applied potential is reversed?

In Galvani's experiment with frog legs, he applies an electric potential across the muscles of a frog which causes the leg muscles to contract. What would happen if the polarity was reversed (I do not ...
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Simultaneous activation of myosin kinase (MLCK) and myosin phosphatase (MLCP)

Reading about smooth muscle cells, I stumbled upon this sentence in Guyton & Hall, Textbook of Medical Physiology (14th ed): When the myosin kinase and myosin phosphatase enzymes are both ...
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Are the muscles of all animals mechanically similar?

For instance, is the skeletal muscle of an elephant made of the same balance of fibers and cells as the skeletal muscle of a hippopotamus? I recognize that slow- and fast-twitch muscles are a thing, ...
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What are the mechanical properties of human skeletal muscle?

TL;DR: I need more information on the mechanical properties of human skeletal muscle; if you have such information, please give it to me. I'm writing something on how much more effective (or otherwise)...
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Biological reason for "deadlift face"?

Always when I deadlift at the maximum load, my face looks more or less like this: or this: The same applies for when I do other heavy-weight exercises. But what biological mechanism causes that? ...
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What benefit do cardiomyocytes accrue by requiring calcium induced calcium release (relative to skeletal myocytes)?

According to 2 sources I've read, in contrast to skeletal myocytes, cardiac myocytes need calcium to diffuse in to result in contraction. One source says that they need large amounts of calcium to ...
Robert S's user avatar
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Impact of increased sodium conductance at a neuromuscular junction

If trans-epithelial Na+ transport were to increase at the synapse(please consider both pre and post-synaptic membrane situations) in a neuromuscular junction, how would that manifest itself? My guess ...
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How long does it take for a new muscle fiber to be connected to motor neuron?

When new muscle fibers are formed through hypertrophy, how long does it take for motor neurons to connect to the new muscle cells in order to be able to control them? After taking a break from ...
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Is the nervous message sent by an eyelash being flexed sent all the way to the brain?

Since the reflex to close the eyelid once an eyelash is touched seems very fast, does the signal from the neuron detecting the touching travel all the way to the brain, get processed then back to the ...
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Looking for literature on hand-head movement coordination (not hand-eye)

sports scientists and kinesiologists, I'm a linguist working on sign languages and I'm looking for papers that discuss motor coordination of hand and head movements and potential constraints on such ...
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What is the relationship between muscle energy consumption, the period over which the contraction occurs and the mechanical work performed?

I'm asking this question with some basic knowledge of physics and general fitness. Suppose you are lifting a still object with mass $m$ from height $h_1$ to height $h_2$ with an arbitrary (straight or ...
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What are the roles of ATP and ADP in muscle contraction?

I've always known that the hydrolysis of ATP generates ADP, P, and energy, so I'd assume that if energy is necessary in a given process, ATP hydrolysis should occur (or another exothermic process). ...
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Why doesn't muscle strength depend on its length?

In case of tug of war the more people participate the more strength they represent. And in case of muscles - the longer it is, the greater the number of myosin heads bind to actin when muscles ...
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Why does bicep activate during dead hang?

Hanging from a bar causes my bicep to feel much harder than when simply holding my arm straight above my head relaxed, without a bar. This was slightly surprising to me: I used to assume that since ...
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Do animal muscles atrophy slower than humans?

Suppose I consider the silver back gorilla as an example. I cannot imagine ever seeing one in the wild intentionally doing something akin to weightlifting like humans solely for the purpose of ...
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Most optically transparent muscle phantom?

I am trying to use Schlieren imaging techniques to visualize how a sound wave propagates through muscle tissue. In the past, when needing to experiment with muscle we would use an agar based muscle ...
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Does alcohol really helps to get substances get faster into the bloodstream? [closed]

I saw the video where Arnold Schwarzenegger cooks some protein cocktail and adds Austrian Schnapps to the mix, saying that it's to make everything get faster to the blood. Is it true or some kind of a ...
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What mammals can rotate and move their ears the most?

I found out that rabbits can rotate their ears 270 degrees, and also move them up, down and independently. Are there any other mammals that can control their ears' position that well, or even better?
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What does the term 'glycogen mobilisation' mean?

I read that glycogen is a mobilised store of glucose: Glycogen is a readily mobilized storage form of glucose. It is a very large, branched polymer of glucose residues (Figure 21.1) that can be ...
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Does Krebs cycle occur in fast glycolytic muscle fibres?

They have mitochondria. So they can have aerobic respiration. (?) Does Krebs cycle occur in their mitochondria?
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Why Can't Muscles Push When They Return To Their Original Length?

I understand that muscles can only contract and shorten and thus can only pull, but why can't a muscle push when it relaxes and returns to its initial length?
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What stops myosin during muscle relaxation?

I understand that when the muscle is relaxed tropomyosin blocks myosin binding sites on actin filaments thereby preventing muscle contraction. What I am concerned with however, is whether myosin ...
Positron12's user avatar
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Does ATP production increase with oxygen availability?

I'm not a biologist so pardon any ignorance on my part. I'm working on a speculative evolution project and I'm looking to understand how the partial pressure of oxygen effects the maximum aerobic ...
Zac Walton's user avatar
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3 answers
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Biological Neural Network Training for Babies [closed]

I am concerned by the fact that babies cant walk because the muscles in their limbs arent developed and tuned to give directional control, it takes years before babies gain mobility and dexterity. So ...
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What is the difference between a myofibril and a myoblast? (In skeletal muscle)

I read that a muscle fibre (myofiber) is formed when myoblasts fuse. https://teaching.ncl.ac.uk/bms/wiki/index.php/Skeletal_muscle#:~:text=The%20multinucleate%20feature%20is%20established%20in%...
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Question on thick filaments

In this photo, I know that the arrows pointing towards the M-line of sarcomere on actin filaments are due to the power strokes of myosin heads. However, what I don't understand are the arrows on the ...
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Summation on muscles

I am learning myology and encountered 2 problems in tetanus and summation: Unfused tetanus is just a continual summation of twitches if I am not mistaken. However, is it a MUST for summation / ...
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what powers power strokes

I am wondering what really powers the myosin head to undergo the power stroke to push the actin filaments towards the M-line. I have 2 thoughts: when ATP in the myosin head gets hydrolyzed, the ...
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What inhibits linkage between actin and myosin filaments

What is the mechanism behind the inhibition for cross-bridge linkage between actin and myosin filaments in the binding-tilting cycle? There are 2 possible ways that are in my mind: a. Tn-I (tropnin-I)...
234ff's user avatar
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Why didn't more muscles evolve the endurance of heart muscle? [closed]

The heart is a muscle capable of both the quick contraction of white muscle cells, and also the endurance of red muscle cells. Why haven't more muscles in the body adapted the same combo of abilities? ...
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Pectoralis muscles as push muscles vs pull muscles

Pectoralis muscles are the adductors, flexors of arm in addition to medial rotators of arm. How does this action translate in to acting as helping in push ups or in bench press? I am having trouble ...
rasdocus's user avatar
1 vote
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Suspensory ligaments: why are they ligaments?

Don't ligaments connect bone to bone? In the eye for example, the suspensory ligaments connect the ciliary muscle to the lens, which obviously aren't bones. Is this just one of those instances where ...
Ally's user avatar
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In a skeletal muscle contraction, what happens after ACh binds to the nicotinic iontropic receptors on sarcolemma?

Does the bound ACh becomes unbound and then gets hydrolysed by acetylcholinerase?
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Are “tremors” and “ tetanic contractions” the same thing?

Do these two expressions have the same meaning? 1- Tetanic contractions in the skeletal muscles 2- Rythmic shaking of the hands (These two expressions are supposed to be two symptoms of Parkinson’s ...
user261947's user avatar
4 votes
1 answer
175 views

What happens to eyeball when you push your eye muscles harder? [closed]

I have myopia and I read that the rays of light intersect before the retina. When I can not see clearly I can push somehow my eye muscles and can see a bit clearly. The object gets clear but moves ...
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Humans best at long distance running: purely physiological or is it a function also of ability to pace?

I have read that although certainly other land animals are much faster over short distances, a human can run down any other animal over time, so that if a human is hunting like a gazelle, etc. ...
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