What happens to anatomical structures (i.e. muscles) when a person rises from a chair?
547093
Standing up involves a number of muscles because you have to lift you body from the sitting position.Muscles are in two groups each group works antagonistic to the other. \nThere are three main muscle groups of the thigh: the quadriceps; the adductors; and the hamstrings. The quadriceps muscles extend the knee joint and move the leg forwards. \n But I think it's easier to explain what happens if we consider the thigh muscles into two groups anterior muscles and posterior muslces. The anterior group the will contain the flexors of the thigh (the thigh is in a flexed position when you lift it) as well as the abductors (abduction is when the thighs are brought together). And the posterior would contain the extensors (extension is the opposite of lexion that is when you return the leg from the lifting position) as well as the adductors ( adduction is when you move the thighs apart). \nWhen sitting the posterior muscles are somehow relaxed and the anterior group of muscles are some how contracted because the hip is in a flexed position and the femoral head is medial and slightly outwards. when standing up the posterior group slightly contracts and the anterior group relaxes because the thigh is extended the femoral head is rotated slightly inwards.\nIn anatomy the muscles are said to contract when they are reduced in size and relaxed when they are increased in size that is when the innervation is intact!\nIf you are at a science lab try using the anatomy models to observe the actions you will see the movements more clearly.
191680
By emergency I'm assuming like a danger situation... as in that Fight or Flight respnse.\n\nYour body releases epinephrine, aka adrenaline.  This has a variety of affects on different systems, striated muscle has an exciting effect, whereas smooth muscle tends to be relaxed by it.\n\nIn the pressence of "adrenaline" you find that you move a bit faster or can possess the super strength of a mother flipping a car to save her child trapped underneath.  Your heart rate increases, blood flow increases, blood pressure drops.  Hope this is helpfull for you.
284554
I believe that you are proposing to sit on the chair with your legs on the rungs and use your hands to lift up on the edge of the seat in order to lift the chair off the floor.\n\nThe short "scientific" answer is that this has never been done and even your own attempts have failed, right?  Science learns a great deal from empirical studies, cut and try.  Only one person must succeed to prove it can be done.\n\nScientists then go on to seek a reasonable explanation for what is observed.  Grasping and pulling on the edge of the seat produces a force that drives your body down into the seat.  What is needed is a force that pulls the chair up and away from the floor.  You could use your arms to pull up on a rope above you or your legs to push down on the floor below you.  Scientists would tell you that you must carefully define your system boundary.  When the system boundary includes only you and the chair (but not the room) you can only bend the chair but not lift it.  When the system boundary also includes the room, you can exert a force on the room (floor or ceiling) and move the chair relative to the room.\n\nThis is a great question to study how application of forces may be studied.  it applies in much more complicated configurations that are even harder to think about.
624942
You lose the ability to control voluntary movements. Depending on the amount and place of damage it may eventually effect your lungs and or heart. Keep in mind your heart is a muscle and you chest wall is full of muscles that allow you to inhale and exhale. As for your muscles that control movement they become flaccid . Anything that is considered to function by voluntary or involuntary movement may be affected depending on the kind of damage. Keep in mind only your physician can determine the extent of damage that will occur depending on diagnosis. Hope to have helped.
68834
A proper description would take too long (and I am not in the mood).\nGeneral info about direct and indirect flight musculature: you should be able to find in any university level physiology text book. \nIf you want more specific info, search for articles using either pubmed (should be accessible to everybody) or if your university has a subscription for Web of Science you can look there. Start looking for review articles if you don't already know something about the subject.
1151599
The skeletal system is the base for all of the other systems, in your question, muscles are directly attached to bone by tendons and ligaments.  The nerves then run around and through our muscles so when a thought to move is made then the nerve is sent from the brain to the nerves then they send it to the muscle creating a movement.
226533
A simple was to state it: The sensation that you react to, like a pinprick, or sudden shortening of your tendon (like when you slip) sends a message along the sensory axon.  This communicates with a motorneuron in your spinal cord, which immediately sends a signal to a muscle-so that you jerk your hand back from pain, or move your leg to catch yourself before you fall.  The whole sequence doesnt involve your brain at all, its all done in your spinal cord- a single synapse.
970442
A few hours after a person or animal dies, the joints of the body stiffen and become locked in place. This stiffening is called rigor mortis. Depending on temperature and other conditions, rigor mortis lasts approximately 72 hours. The phenomenon is caused by the skeletal muscles partially contracting. The muscles are unable to relax, so the joints become fixed in place. \nMore specifically, what happens is that the membranes of muscle cells become more permeable to calcium ions. Living muscle cells expend energy to transport calcium ions to the outside of the cells. The calcium ions that flow into the muscle cells promote the cross-bridge attachment between actin and myosin, two types of fibers that work together in muscle contraction. The muscle fibers ratchet shorter and shorter until they are fully contracted or as long as the neurotransmitter acetylcholine and the energy molecule adenosine triphosphate (ATP) are present. \n\nHowever, muscles need ATP in order to release from a contracted state (it is used to pump the calcium out of the cells so the fibers can unlatch from each other). ATP reserves are quickly exhausted from the muscle contraction and other cellular processes. This means that the actin and myosin fibers will remain linked until the muscles themselves start to decompose. \nRigor mortis can be used to help estimate time of death. The onset of rigor mortis may range from 10 minutes to several hours, depending on factors including temperature (rapid cooling of a body can inhibit rigor mortis, but it occurs upon thawing). Maximum stiffness is reached around 12-24 hours post mortem. Facial muscles are affected first, with the rigor then spreading to other parts of the body. The joints are stiff for 1-3 days, but after this time general tissue decay and leaking of lysosomal intracellular digestive enzymes will cause the muscles to relax.
351685
umm...I doubt that is how it would happen to a normal human, because obviously that dummy didnt have she muscle structure (and tightness) of the muscles in a normal human's arms...it might be a factor that the dummy was unproportionally weighted vertically (from head to butt to toes) if that makes any sense.
656787
A newly dead human being, or any other animal, will sink when placed in water.  After the gases of decomposition build up in the chest and abdomen, however, the body will inflate, rise like a hydrogen-filled balloon, and pop to the surface, sometimes dragging with it surprisingly heavy weights that a murderer might have thought sufficient to keep it down.   With the passage of time and further decomposition, however, the body cavities eventually rupture, the gas escapes, and the corpse goes down again, this time for good.\n\nThere is one notable exception:  sometimes, due to air caught in the clothing, a body will stay on the surface for several hours before sinking.
155675
This is definitely a strange sensation -- you get up out of your seat, and all you feel from one foot is an uncomfortable tingling. Or you wake up in the middle of the night, and you can't move your arm at all. And then, as your body part "wakes up," the strange tingling intensifies. Just what is going on here?\n\nUsually, you feel this familiar sensation after you've been putting pressure on part of our body -- sitting on a foot, sleeping on an arm, etc. When you apply this pressure for a prolonged period of time, you actually cut off communication from your brain to parts of your body. The pressure squeezes nerve pathways so that the nerves can't transmit electrochemical impulses properly. Nerve impulses carry sensation information from nerve endings in the body to the brain, as well as instructions from the brain to the parts of the body. When you interfere with this transfer by squeezing the nerve pathways, you don't have full feeling in that body part, and your brain has trouble telling the body part what to do.\n\nThis pressure can also squeeze arteries, stopping them from carrying nutrients to body cells. Without these nutrients, the nerve cells may behave abnormally, which can further interfere with communicating bodily sensations.\n\nDue to both these factors, the information transmitted from the body part becomes somewhat jumbled, and the brain receives strange messages. Some nerve cells don't transmit any information and others start sending impulses erratically. This causes you to feel a strange tingling sensation, which actually serves an important function. Your foot falling asleep for 10 minutes doesn't pose any health threat, but if you were to cut off circulation for an extended period of time -- several hours -- you could suffer serious nerve damage. The initial tingling sensation tells you that you might want to readjust your position.\n\nOnce you do move your foot, stretch your legs, or roll over off your arm, the nerve impulses begin to flow properly again. You don't regain feeling right away, however. There is a certain amount of re-adjustment time before the nerves transmit impulses correctly again. This increases the intensity of the tingling, causing the familiar "pins and needles" sensation.\n\nIf this has ever happened to you, you know that there are actually a few distinct sensations you go through as your body part "wakes up." The tingling may be followed by a more uncomfortable burning sensation, before your body part finally returns to normal. This happens because the nerves in your body are made up of separate long nerve cells that carry different sorts of impulses. These nerve fibers have different surrounding structures. Some nerve fibers have thicker "insulation" around them and so take longer to begin transmitting impulses properly after they've been squeezed. The fibers that transmit pain and temperature information are relatively thin, so you feel the tingling situations pretty quickly. Motor control fibers are thinner than the ones carrying touch information, so you can move the body part before you've regained complete feeling in it. Eventually, all the nerve fibers return to normal and you regain full use of the sleeping body part.
38377
It comes from the muscle having a spasm.
183737
It is infront of you.  If you were a mannequin, you will fall forward.  The reason you do not is that your muscles act as guy wires to keep you from falling over.
193418
Heisenberg notwithstanding, I have never observed my chair turn into energy, even as a transient state, no, not even for an instant.  It must be when I'm not looking.\n\nEnergy, if unused as work, turns into mass... in my case, a mass of fat around the middle.
1105071
most likely a stool of some sort so you could rest your pelvis on it. or we would not need chairs because we could basically kneel a lot easier.
615328
Physiological changes that occur in the human body in motion as a result of rapid increase of speed. Rapid acceleration and surges in acceleration are felt more critically than are gradual shifts.\n\nRiders of roller coasters are especially subject to the effects of acceleration because of the high-speed drops, turns, and inversions of the coaster. Acceleration forces are measured in units of gravitational acceleration, or g. One g is a force equivalent to the weight of the coaster on the surface of the earth. A force of 3 g, for example, is equivalent to an acceleration three times that of a body falling near the Earth.\n\nThree kinds of acceleration stress are distinguished--positive, negative, and transverse--according to the position of the body with relation to the direction of acceleration.\n\nPositive acceleration stress occurs when the direction of acceleration is along the long axis of the body from head to foot, experienced, at 1 to 2 g, by a general feeling of heaviness in the seat, hands, and feet.\n\nNegative acceleration stress occurs when the direction of acceleration is from feet to head, causing a slight displacement of the internal organs in the abdomen and chest and a rush of blood to the face accompanied by the feeling of congestion. The average endurable times for negative stress are a few seconds at 5 g, 15 seconds for 4.5 g, and around 30 seconds for 3 g.\n\nTransverse acceleration stress occurs when the direction of acceleration is sideways with relation to the long axis of the body. Accelerations up to 6 g directed across the body produce sensations of increased pressure on the part of the body that supports the weight.\n\nAT THIS POINT IN THE RIDE . . . the coaster approaches the vertical loop, entering at a high rate of speed. Entry may create a heavy force on the riders as high as 5 g, but only for a few seconds--any longer and riders may blackout from acceleration stress. Modern vertical loops are tear-shaped, clothoid loops that have a tighter curve at the top, where the velocity is smaller, than at the exit and entry points at the bottom. The larger radius at the bottom of the loop reduces centripetal acceleration, thereby lowering the overall g-forces, which naturally increase by 1 g owing to gravitation. Often the designer will adjust the radius at the top of the loop to create a centripetal force of 2 g, allowing the riders, after subtracting the value of gravitation (1 g), to experience normal weight levels while upside down. The queasiness associated with looping rides is owing to some internal organs floating upward, counter to their natural hanging position.
399528
Yeah, sound like sciatica. A trapped nerve in the base of the spine. Lean with your back against something solid, like a wall & lift your body weight off the floor an inch or two with your arms straight. If the pain goes, it's probably sciatica.\nI've had it for 30 years. No problem if you know what you're dealing with.\nLie on your back, feet on the floor, knees up & gently move your legs from side to side about 10 times. It releases the trapped nerve.