A local electrical change that triggers a wave of excitation that travels rapidly along the fiber and initiates processes leading to muscle contraction (shortening).
The ability of the muscle cell to stretch under tension.
The ability for a muscle to return to its original resting length after being stretched.
Voluntary striated muscle that is usually attached to one or more bones.
An involuntary muscle that does not contain Z discs, sarcomeres, T tubules, or striations but is the only muscle capable of mitosis and hyperplasia.
Involuntary muscle that is limited to the heart and is composed of myocytes that join through intercalated discs. Has large mitochondria and no terminal cisternae.
A collective term for several hereditary diseases in which the muscles degenerate, weaken, and are gradually replaced by fat and fibrous scar tissue.
An autoimmune disease in which antibodies attack the neuromuscular junctions and bind ACh receptors together in clusters. (Usually occurs in women between the ages of 20 and 40.)
An acute, often fatal disease characterized by spasmodic contraction of voluntary muscles, especially those of the neck and jaw, and caused by the toxin of the bacillus Clostridium tetani, which typically infects the body through a deep wound. Also called lockjaw.
A disorder usually caused by brain damage occurring at or before birth and marked by muscular impairment.
Ends of the sarcoplasmic reticulum, where calcium is released, in response to action potential, to initiate muscle contraction.
T tubules are extensions of the ______________ in skeletal muscle.
Cytoplasm of a muscle fiber.
These penetrate throughout the muscle fiber to spread the electrical impulse (action potential) and are necessary to initiate a concentration.
Surrounds the myofibril and stores calcium.
motor end plate /neuromuscular junction
The Ach binds with receptors on the ___________________of a muscle cell.
A nerve cell forming part of a pathway along which impulses pass from the brain or spinal cord to a muscle or gland.
Unfused myoblasts that remain throughout the muscles that are available to divide to repair a small number of damaged muscle fibers.
Active transport pumps calcium back to SR where it binds to____________.
A regulatory protein associated with tropomyosin that acts as a calcium receptor.
A protein in smooth muscle that activates the myosin light chain kinase.
A huge springy protein that makes up elastic filament.
Filaments that connect the thick filament to the Z disc structure and that stabilize and help the sarcomere recoil.
____________and_____________are contractile proteins that do the work of shortening the muscle.
___________and____________are regulatory proteins that act like a switch that starts and stops shortening.
The dark middle band of fibers, made up of the entire length of the thick filaments and a portion of the thin filaments.
The outer portion of fibers that are made up of thin filaments.
This zone/band disappears during muscle contraction. It is a portion of the A band that contains only thick filaments.
Seperate sarcomeres from one another; passes through the I band.
The chemical messenger/ligand in the neuromuscular junction or motor end plate.
The end of nerve fiber at the neuromuscular junction or motor end plate.
The sarcolemma has tubular infoldings called______________, which penetrate through the cell and emerge on the other side.
motor end plate
The region of a sarcolemma adjacent to the axon terminals at a neuromuscular junction.
An enzyme in the sarcolemma and basal lamina of the muscle fiber in the synaptic region; responsible for degrading ACh and stopping the stimulation of the muscle fiber.
One motor neuron and all the muscle fibers it stimulates.
The segment from one Z disc to the next.
A type of spastic paralysis that blocks glycine in the CNS.
Flaccid paralysis can be caused by_________________.
Blocks glycine (inhibitory neurotransmitter) release in the spinal cord and causes overstimulation of the muscles and is caused by toxin of clostridium tetani bacteria.
Pesticides contain______________________that bind to acetylcholinesterase and prevent it from degrading Ach. This leads to spastic paralysis and possible suffocation.
This chemical carries the stimulating message across the neuromuscular junction.
myosin light chain kinase
Calmodulin activates _______________________, which adds a phosphate group to a small regulatory protein on the myosin head.
When the muscle has no time to relax between stimuli so twitches fuse into smooth prolonged contraction.
The phenomenon occurring when the tension of muscle twitches progressively increase as the frequency of stimulus increases.
Tetanus in which each stimulus causes a contraction to be initiated when the muscle has only partly relaxed from the previous contraction.
The type of muscle contraction where the muscle contracts but exhibits no change in length.
A_________________________contraction goes against gravity and shortens the muscle.
An________________________contraction resists the return from gravity and lengthens the muscle.
Fast twitch fibers use_____________respiration.
The most efficient means of ATP production.
Myosin converts ATP to _____.
Creatine kinase obtains Pi from this phosphate-storage molecule.
A single-chain, iron-containing protein found in muscle fibers, structurally similar to a single subunit of hemoglobin and having a higher affinity for oxygen than hemoglobin of the blood.
_______________lowers the pH of the sarcoplasm, which inhibits the enzymes involved in contraction, ATP synthesis, and other aspects of muscle function.
ATP and CP are collectively called the _________________because they provide nearly all the energy used for short bursts of intense activity.
To make a muscle contract more strongly, the nervous system can activate more motor units. This process is called_____________.
The process by which multiple or repeated stimuli can produce a response in a nerve, muscle, or other part that one stimulus alone cannot produce.
A quick cycle of contraction and relaxation.
Calcium is released from the sarcoplasmic reticulum when an action potential opens gated ion channels located in the ________________.
A junction between two nerve cells, consisting of a minute gap across which impulses pass by diffusion of a neurotransmitter.
After the power stroke has occurred during skeletal muscle contraction, ATP must bind with the _____________ in order for the acto-myosin cross-bridge to be released.
A regulatory protein that lies in the groove of F actin and, in relaxed muscle, blocks the myosin-binding active sites.
An integral membrane protein that responds to the binding of acetylcholine, a neurotransmitter.
A myofilament about 11nm in diameter composed of bundled myosin molecules.
A myofilament about 5 to 6nm in diameter composed of actin, troponin, and tropomyosin.
Round, amorphous bodies scattered through the cytoplasm of smooth muscle fibers; they appear to be points of attachment for myofilaments.
The hole between cell membranes of cardiac myocytes where substances can flow.
Rate and depth of respirations increase during and after exercise to restore__________________.
Hold tension in smooth muscle and are connected by dense bodies and plaques on the intracellular side in place of Z-discs.
Sequester or store Ca++ at rest.
A myofibril within the thin filament that provides binding sites for myosin to cross link to.
Connect the thick filament to the Z disc structure, stabilize and help sarcomere recoil.
_________________is when: the body stiffens 3-4 hours after death, contraction occurs because ATP is also necessary for relaxation, the sarcoplasmic reticulum deteriorates and releases calcium, and myosin-actin cross bridges form due to calcium release.
True or False: During muscle twitch, the latent period is the segment after contraction is completed.
The twitch that is rich in enzymes for phosphagen and glycogen lactic acid systems.
__________twitch is resistant to fatigue, is involved in postural muscles, is adapted for aerobic respiration and displays higher levels of mitochondria.
In phosphagen systems, high energy phosphate groups can be stored for future ATP production by combining with ______________.
The thick myofilament consists of many molecules of this protein.
The head of myosin attach to actin to form a______________.
The ability of the muscle cell membrane to respond to stimuli with electric changes.
A protein with a long shaftlike tail and a globular head that constitutes the thick myofilament.
Invaginations of the sarcolemma where ACh receptors are especially concentrated.
The energy storage molecule in skeletal muscle fibers.
The strength of contraction is related to the size of the _________________and how many of them are activated at the same time.
Short term energy uses____________________fermentation. (uses glucose to produce ATP)
Long term energy uses _________________respiration. (uses oxygen to produce ATP)
___________twitch fibers use only aerobic cellular respiration and are resistant to muscle fatigue. (more mitochondria)(small in size)
Fast____________fibers use both aerobic cellular respiration and anaerobic glycolysis and are used during all types of activities.(intermediate in size)
Fast twitch fibers fatigue quickly, have low amounts of myoglobin, blood capillaries and mitochondria and use______________respiration. (large in size)
Smooth muscle has a __________________mechanism that allows myosin to remain attached to actin without using ATP. (this mechanism uses aerobic respiration)