Questions tagged [muscles]
The contractile tissue of animals derived from the mesodermal layer of embryonic germ cells.
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If the Z-line is pulled from both sides , how does it move to shorten the sarcomere?
When I was considering muscle contraction as a whole, this issue came to mind.
Which side should the Z-line of myofibrils shift to when it is being pulled by actin filaments on both sides to which it ...
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What does happen to the ADP on the myosin head that cannot bind to the actin due to velocity of contraction?
One of the explanation of decrease muscle force when speed of contraction increases is that some myosin heads "don't have time" to bind to the actin filaments. As explain here for example.:
&...
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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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Why is the sinoatrial node in the right atrium?
Is it just an evolutionary remnant? If so, why would it have been disadvantageous for humans to have it in the left atrium?
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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 ...
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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 ...
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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 ...
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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)...
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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 ...
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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 ...
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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 ...
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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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Do people with higher body hair growth (eg. Women with hirutism) need more protein? [closed]
Hair is protein. Does that mean that the body of a woman with hirutism is using more than usual protein to make hair and thus she needs more for building and repairing muscles?
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Why does hypocalcaemia cause increased muscle contraction?
Calcium is needed for muscle contraction, so how does hypocalcaemia cause increased sustained contraction?
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Are changes in flexibility from stretching due to changes in the nerves or the muscles?
For many people, stretching repeatedly over a period of time improves their flexibility. I want to know whether this improvement commonly seen is due to a change in the nerves or the muscle’s material ...
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Why is muscle force more dependent on cross-sectional area than on fiber length?
I was looking up why smaller animals are proportionally stronger than larger animals. The answer that comes back everytime is that muscle force depends on the number of muscle fibers, which is ...
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Do multiple axons innervate a single skeletal muscle fiber?
The typical text-book illustration of innervation of muscle fibers shows branches at a single position along the fiber. Does any given muscle fiber have more axons that innervate it though, given that ...
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Are there any detrimental effects to long term electrical muscle stimulation?
I know that different types of electrical stimulation can be used in fields such as physical therapy to get muscles to contract. However, these electrical stimulation sessions are not prolonged and ...
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Can the human body store protein?
I am interested to know if a human body can store protein.
Absolutely for the bodybuilders, does it really matter if they divide their protein consumption during the day or eat all of it in one meal ...
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Why do muscle spindles send impulses at a constant rate when the muscle is at rest?
According to my book, the sensory neuron around the muscle spindle is sending impulses at a constant rate, while the entire muscle itself is relaxated (at rest).
So when the muscle stretches the ...
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