Questions tagged [muscles]

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

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152 views

Hand-eye coordination in 3D space

A simple daily event has amazed me and triggered this question. I have read and heard about hand-eye coordination. It quite straightforward when you e.g. want to open a door or play Xbox. In this case ...
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3k 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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3k 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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738 views

Why a continuous supply of energy is needed to support a weight?

What motivates this question is the apparent discrepancy between the concept of Work in physics and in physiology. Work in physics is defined as the dot product of the force applied to move a certain ...
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Trying to differentiate between the three muscle tissues with small pictures

For an assignment I have to differentiate the three types of muscle tissues in these three pictures . I'm having difficulty seeing the striations and branches etc. because the pictures are so small. ...
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What are the max angles of human eyeball rotation?

How much can our eyeballs rotate towards the nose, away from it, towards the top and bottom?
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Why Doesn’t Hypercalcemia Cause Muscle Spasms?

If you have more calcium in the cell, wouldn’t more attach to troponin and initiate muscle contraction? Why does hypercalcemia cause muscle weakness instead of spasms?
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Slow-oxidative fibres vs fast-glycotic fibres

Why do slow oxidative muscle fibres contain more mitochondria compared to fast-glycolytic muscle fibres?
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What is a myotube?

If I understand correctly, the following images show the main components in a human skeletal muscle: From Life: The Science of Biology: From Human Physiology/The Muscular System in wikibooks: ...
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Mechanism of redirected blood

I've read several fitness articles mentioning redirected blood flow to muscles that are in use. However, they never mention how it works. Is it local and specific to the muscles in use? Or, for ...
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653 views

Function of Smooth Muscles in the skin

I understand that the overall function is voluntary movement, but is it the same in the skin? Is the main function in the skin movement or is there a greater function? Could anyone could provide this ...
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Before I move my arm the brain sends signals - what causes the brain to send signals? [closed]

Please tell me what causes the brain to send signals, how does the brain send signals? can you tell me what happens between the point when you make an intention to pick up a glass of water, and before ...
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315 views

What is the connection between exercise and muscle growth

From a physiological perspective, all that is done during exercise is the expending of energy in the form of ATP to fuel muscle contraction and extension. When I looked up why muscle grow due to ...
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147 views

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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Can muscles work as brakes?

When I walk downhill I lose potential energy. If I descend 100m in, say, 10 minutes I lose potential energy at a rate of about 114J/s (114W). Where does the energy go? Not into kinetic energy ...
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160 views

What is the point in the Neuromuscular Junction?

Surely a direct connection (i.e. an electrical synapse) between motor neurone and the sarcolemma would allow for much faster neuromuscular transmission? It is my understanding that chemical synapses ...
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Doesn't the sarcomere contract during isometric contraction?

During muscle contraction, the lenght of the sarcomere changes, length of myocyte changes and so does the length of muscle. However, if the length of muscle is not changing length as in isometric ...
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Correlation between muscle size and absolute strength

Is there a linear connection between muscle size and the power it can produce? If not, why? And what is the true correlation if any, can it be described with an appropriate function? What other ...
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79 views

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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881 views

Why is the ingestion of salt and water beneficial to muscle cramp

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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Why fingers in human fists get folded in absence of neural stimuli?

Background: I noticed that the fingers in our fist tend to get folded in absence of neural stimuli. The same thing happens in case of our hands and legs. Question: What is the mechanism behind this ...
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390 views

Why do athletes see a dip in performance in their thirties?

I have noticed a lot of athletes hit their prime when they are in their 20s and that by the time they reach their 30s they are past it and start to decline. Great athletes tend to prolong their ...
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100 views

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

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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54 views

Partial muscle fibre contraction

I'm being taught that: a muscle fibre spans the entire length of the muscle, from the originating tendon to the inserting tendon. The question is, can a muscle fibre contract only partially? Say, if ...
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Are there specific theories as to what causes cold[-water] muscle cramps?

The field of what might cause cramps is quite contested with a lot of controversy around the heat/dehydration cramps, but I find it surprising that no specific theories appear to have been proposed (...
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377 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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Is there any stem cell or biogel method that exist for muscle and tendon lengthening?

Is there any stem cell or biogel method that exist for muscle and tendon lengthening? It is known that height surgery is limit to six inches with two surgeries and three inches each, it is also true ...
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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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Why is there a mass limit on biological powered flight?

So, this is a thing I never fully understood. There are a lot of reasons for a flying creature to be limited in mass (though I'm unsure if I'm familiar with all of them), from energy consumption to ...
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240 views

Is the ACh receptor more permeable to sodium ions?

The AChR is permeable to sodium and potassium ions only and has a reversal potential of 0mV. However the Nernst potentials for sodium and potassium ions is ~ +60mV and -88mV respectively. Taking a ...
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84 views

Does tremor frequency generally increase as Parkinson's disease progresses?

I've been trying to research this question, but most if not all the on-line journals require costly subscription, and the studies that are posted look at tremor frequency with regards to other factors....
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Involuntary twitches and apnoea during early phases of sleep

I assume most people either experienced or have seen people with the following phenomenon: in the early phases of sleep sometimes involuntary twitches occur that usually accompany the pause of ...
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Are there free electrons in muscles, hair, or skin?

Electric shock occurs upon contact of a (human) body part with any source of electricity that causes a sufficient current through the skin, muscles, or hair. In metals many electrons are said to be ...
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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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Why we have to damage our muscles to build them?

I know that new muscle cells are made when actin fibers are disrupted. My hypothesis is that muscle mass is limited, from birth, and that nutrients (protein) are only directed to grow muscle when ...
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519 views

How do muscles help erect the spine?

Muscles of the spine help to support it against gravity. For example, the multifidi interweave throughout the vertebrae and, as I understand, sort of reinforce the spine. So let's suppose muscles help ...
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908 views

How do muscle relaxants work?

Do they act directly on the muscle and actually relax muscle tissue and ease spasms, or do they just prevent your brain from receiving signals that inform you of tight muscles? In the latter case, ...
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367 views

How is breathing involuntary if the muscles that control it are skeletal?

How is breathing involuntary if the muscles that control it are skeletal? Breathing is involuntary. However, the muscles that control it are skeletal: intercostal muscles and the diaphragm. Are there ...
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4k views

What happens when we stretch?

From the wikipedia page on stretching: Stretching is a form of physical exercise in which a specific muscle or tendon (or muscle group) is deliberately flexed or stretched in order to improve the ...
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385 views

Do muscles still hold glycogen reserves if there is no carbohydrate input

Afaik skeletal muscles take glucose from the blood to store it localy as glycogen, to be used in the case of intensive exercise. Does this still happen if the calorie input is exclusively made up ...
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378 views

Attachment of muscles during molting in insects

Normally, insects' muscles are attached to their exoskeleton but what happens to this attachment when they are moulting? Sorry if this is an extremely silly question but I have wondered about it for ...
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614 views

Need of Creatinine Phosphate

In muscle cells most of the ATP's phosphate is with creatinine phosphate. So why is the displacement of the phosphate group done ? Is it because creatinine phosphate would give it's phosphate more ...
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101 views

Text/resource with information on all skeletal muscles and their motor units

Something analogous to an encyclopedia on baseball players with a list of all thier stats would be ideal. I'm not looking for just generic muscle names, locations and illustrations. Good answers ...
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How does an electrical impulse spread in a muscle fiber spread from the motor end plate?

Does this impulse in skeletal muscle spread much in the same way it does in neurons, with an initial potential change that spreads to its immediate surroundings and is then re-amplified or is it the ...
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298 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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419 views

At what levels of muscle energy intake does catabolism start?

From my own reading, there are three ways used by the body to produce energy: Alactic anaerobic (direct degradation of ATP and creatine phosphate for regeneration of ATP) Lactic anaerobic (breakdown ...
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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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How does isometric contraction work?

What exactly happens to myosin during isometric contraction? I suspect that either myosin heads just "freeze" in the middle of crossbridge cycle, or go through full crossbridge cycles repeatedly at ...
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Why do hand/fore-arm muscles "lock up" after very high-powered effort?

Inspired from Why does it hurt the next day after doing significant exercise? with its excellent answer: In climbing, you can put tremendous load on the hand/fore-arm muscles (specifically, flexor ...
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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?