starting at the neuromuscular junction and ending with muscle contraction describe in detail events?
406206
I answered that same question yesterday:\nThe impulse reaches the terminal end of the motor neuron and breaks open the synaptic vesicles, releasing the neurotransmitter acetylcholine into the synaptic cleft.\nACh then binds to receptor molecules in the motor end plate of the muscle fiber.\nThe action potential is started in sarcolemma and passes along the membrane until it reaches the sarcoplasmic reticulum releasing calcium. Calcium diffuses in sarcoplasm and binds to the troponin in the thin filaments.\nThe binding sites on the actin molecules are freed, allowing\nthe heads of myosin (thick filaments) to attach on the binding sites forming the cross-bridges connections.\nThe cross-bridges shift their angle causing the thin filaments to slide over the thick filaments; this produces the contraction.\nATP is needed for the last step. ATP is bound to myosin; calcium activates ATP breakdown into ADP and phosphate.\nPart of the energy produced is used to move bridges, the other part is released as heat, increasing the body temperature.\nMore ATP breaks the bond between thick and thin filaments in the cross bridge; calcium returns to thesarcoplasmic reticulum and the thin filaments return to their original position, closing off the binding site to cross bridges and causing the muscle to relaxe.
1103467
An orgasm is a physiological event that occurs at the highest point in sexual excitement and is usually associated with a wave of intense pleasure. During orgasm, both males and females experience involuntary muscle contractions. In males, contractions of the muscles of the prostate, vas deferens and seminal vesicles induce emission (movement of semen into the urethra) and ejaculation. Females experience rhythmic contractions of the vagina and uterus, thought to facilitate the transportation of sperm. Also called climax .
861069
A muscle (or even a few fibers of a muscle) that involuntarily (without consciously willing it) contracts is called a "spasm." If the spasm is forceful and sustained, it becomes a cramp.\nA muscle cramp is thus defined as an involuntarily and forcibly contracted muscle that does not relax.
632748
The sets of muscles that have the finest control have the fewest muscle fibers per motor unit.  This makes sense because when a neuron depolarizes all of the muscle fibers it is connected to depolarize and contract.  This is refered to as a "All-or-None" response.  Muscle fibers don't contract half way.  So if you want precise control over your muscles you have to have a lot of neurons innervating it.
922767
when a cramp occurs, go to the middle of the belly of the muscle. \n\nPlace your fingers about 2 inches apart, in the middle of the muscle, with your fingers and hands parallel with the muscle.\n\nPush the middle parts of the muscle towards each other, as though you were trying to shorten the muscle. Dig in a bit, be quite firm about this. \n\nKeep it up until the pain stops. Keep repeating this on any muscle or part of the muscle that is cramping.\n\nThis can give almost immediate relief. You may be surprised at how fast this works!\n\nIf you are still unsure of what I am saying, attend a "Touch for Health" weekend seminar, where you will learn this technique. (It's called "unblocking the muscle"). See www.tfhka.org or your local health food store for details.
311533
I believe the external stimulation would trigger a contraction.  I am basing that on the fact that the muscle fibers are stimulated directly by the electrical current\nfrom the voltage source.\n\nRecruitment of fibers occurs opposite the standard.  Type II, fast twitch fibers, are recruited first and Type I, slow twitch, are second.  Normally the pattern is Type I then Type II when needed.\n\nThe change in charge at the muscle, which is a great conductor of electricity, causes the Ca++ release normally triggered by ACh or another neurotransmitter.\n\nCouldn't find a source to back me up, try an advanced physiology textbook. I did find this link below that has similar information.
471751
a synapse is also called a junction. it's a space between neurons where neurotransmitters are released. to transmit information from one neuron to another, the neurotransmitters travel through the cell body of the neuron and are released though the axon. after chillin in the synaptic gaps they are received from the dendrite of another neuron. i'm assuming you know what an action potential is? anyway as it travels through the nueron it can't really leave so it lets the neurotransmitters escape and go to another neuron. if the action potential is great enough you react to the stimulus. if it doesn't reach the threshold then you don't.
911826
It’s pretty much where excitatory and inhibitory signals are summated.  If there is enough stimulation to reach threshold the neuron fires an action potential here.  This is basically the first domino of a whole line.  Once it goes the signal travels down the rest of the axon, but this is where it starts.
525919
The combination of a single motor neuron and all the muscle fibers it innervates is called a motor unit. Synapse takes place at the motor end plate.
269825
arm muscles mostly\nthey work by contraction and expansion directed by brain synapses
633434
During muscle contraction the strands of collagen are stretched as the muscle shortens. This stretching deforms the terminals of the Ib afferent axon, opening stretch-sensitive cation channels. As a result, the axon is depolarized and fires nerve impulses up to the central nervous system via the spinal cord. The action potential frequency signals the force being developed within the muscle.\n\nThis sensory feedback plays an important role in spinal reflexes and in the central control of muscle contraction. Specifically, it is postulated that because a Golgi tendon organ exists in serial connection with muscle fibers, it can measure the tension that each muscle contraction builds up. The Ib afferent axon synapses with interneurons within the spinal cord and also relays information to the brain. One of the main spinal reflexes receiving an input from the Ib afferent is the autogenic inhibition reflex, which is involved with the regulation of the force profile of on-going muscle contractions.\n\nThe ascending pathways to the cerebellum are the dorsal and ventral spinocerebellar tracts and are involved in the cerebellar regulation of movement.
1108804
This search:\n\nhttp://www.google.com/search?sourceid=navclient&ie=UTF-8&rls=RNWE,RNWE:2004-20,RNWE:en&q=%22Z+line%22+actomyosin\n\nmay help you, eg:\n\nhttp://72.14.235.104/search?q=cache:tdm7-RoSXMIJ:www.dentistry.leeds.ac.uk/biochem/thcme/muscle.html+%22Z+line%22+actomyosin&hl=en&ct=clnk&cd=4\n\nAccording to this one:\n\nhttp://72.14.235.104/search?q=cache:ea3xzJMj0nsJ:www.neuro.wustl.edu/neuromuscular/mother/myosin.htm+%22Z+line%22+actomyosin&hl=en&ct=clnk&cd=11\n\n"Z-line: Capping proteins inhibit polymerization at the most active, barbed (plus) end \nOther actin filament associated proteins \nActin bundling proteins: Plastins  \nα-actinin"\n\nand that leads to another 2 links....\n\n:-)
353806
T-tubules transmit nerve impulses throughout the muscle.  Think of it this way.  Your biceps muscle is composed of many different muscle cells working together.  When your brain tells your biceps to contract, does it send individual nerves to every single muscle cell?  No it doesn't (I guess that really isn't an obvious answer).  This is where the T-tubules come in.  They transmit electrical impulses from one muscle cell to another.  This way, only some muscle cells need to be activated by a nerve--the rest will be signaled through the T-tubule network, so that all of the muscle cells will contract together.\n\nSo what happens when you block the T-tubules?  Your muscle doesn't work so well anymore.  You might still get cell-to-cell communication (I'm not sure), but even if you did, it would be slow so that the muscle fibers would not contract synchronously.\n\nAddendum: It's been 6 or 7 years since I last studied physiology, so I think you should listen to the professor, not me!
583718
Calcium is the cellular messenger that actually initates contraction through a process called excitation-contraction coupling. While the process differs slightly in cardiac, skeletal and smooth muscle cells, the basic process is the same. Contraction is due to an extenal stimulus that is faciliated on the dihydropyridine receptor (DHPR) of the sarcolemma (cell membrane). The DHPR activates the ryandoine receptor (RyR), which is in the endoplasmic reticulum (SR) inside the cell. The RyR is a channel that allows calcium stored within the SR to be released from the SR and into the cytosol of the muscle cell. This calcium interacts with Troponin in the contractile apparatus of the cell, causing the cell to contract. Contraction of the cell will continue until the calcium in pumped out of the cystosol and back into the SR by the SERCA calcium pump. Then the process is primed to fire again to cause the cell to contract.
1153271
When muscles are stimulated, sodium flows into muscle cells & then potassium flows out. The muscle cell then has a pump (called the Na+-K+ ATPase) that is in charge of pumping the sodium back out of the cell and the potassium back in. During heavy exercise, this pump cannot keep up - so too much potassium ends up outside the cell. This is hyperkalemia.
49397
depolarization which stimulates adjacent Na+ and K+ gates to open, thus starting an action potential in the muscle cell
965444
The third class (see link for illustration).  The articulation is at one end, the resistance at the other, and the muscle is between, evidently close to the articulation.