TPR 11 - Muscular and Skeletal Systems Flashcards
Skeletal muscle vs. cardiac muscle vs. smooth muscle.
1) Skeletal = voluntary muscle; role is to contract in response to conscious intent; STRIATED
2) Cardiac = found only in the wall of the heart; STRIATED; no control; innervated only by ANS
3) Smooth = found in the walls of all hollow organs such as the GI tract, urinary tract, etc.; no conscious control - innervated only by ANS
Skeletal muscles provide voluntary movement of the body stimulated by ___.
somatic motor neurons
Muscles are often attached to the bone by___.
Tendons, which are strong connective tissue formed primarly from collegen.
Flexing versus extending.
Skeletal muscles can move a joint by flexing (reducing the angle of the joint) and extending (increasing the angle of the joint).
Abducting versus adducting.
Abducting is moving away from the body’s midline.
Adducting is moving toward the body’s midline.
Origin versus insertion.
The point on the bone where the muscle attaches is called the ORIGIN and the point where the muscle attaches on the bone more distant from the center of the body is the INSERTION.
Which of these movements require contraction: abducting, adducting, origin, insertion…
They ALL require contraction. Muscles cannot expand with force. Muscles can only CONTRACT (get shorter) to cause force on bones and movement.
Contraction of the triceps have the (same/opp) effect on the lower arm as the contraction of the bicep.
The opposite effect.
Muscles that are responsible for movement in opp directions are termed _____, while muscles that move a joint in the same direction are ___.
Antagonistic and synergistic. Example of antagonistic: biceps and triceps. Bicep curl: biceps = flexor; triceps = extensor.
Do antagonistic muscles receive stimulation by neurons that release diferent neurotransmitters?
No. All skeletal muscles are innervated by somatic motor neurons which release ACh at the neuromuscular junction. The difference in regulation is not the type of signal but rather the timing of the signal (frequency of stimulation, and thus amount of NT release)
Muscle is composed of connective tissue that holds the muscle fibers (myofibers) together called:
fascicles.
Skeletal muscle cells are mutinucleate ___, formed by the fusion of individual cells during development. They are innervated by a single nerve ending, and stretch the entire length of the muscle.
Mutinuclate syncyitia.
The myofiber has a cell membrane called the ___ that is made of plasma MB and an additional layer of polysacharride and collagen.
Sarcolemma
Fascicles versus myofiber versus myofibrils.
Fascicles are bundles of muscle cells. Myofiber are muscle cells and are multinucleate. Myofibrils are smaller units in a myofiber responsible for generating contractile force of skeletal muscle.
The proteins in the myofibrils of myofiber that generate contraction are…
Actin and myosin.
Actin polymers form?
Thin filaments.
Myosin polymers form?
Thick filaments.
Sarcomeres.
Overlapping arrenangement of bands of thick and thin filaments, bound by two Z lines.
Z lines, I bands, A bands, H zone.
Z lines - line that seperates one sarcomere from next
I Band - The regions of sarcomere composed of only thin filaments
A Band - The full length of thick filaments; includes both the overlapping regions of thick/thin and the region with only thick filaments.
H zone - sarcomere region consisting of only thick filaments
I Band
The regions of sarcomere composed of only thin filaments
H Zone
Sarcomere region consisting of only thick filaments
Hefty zone.
A band
The full length of thick filaments; includes both the overlapping regions of thick/thin and the region with only thick filaments.
Go through the steps of the contractile cycle. Note which parts require ATP.
1) The myosin head is bound to ATP and is in its low energy configuration.
2) The myosin head hydrolyzes ATP to ADP and Pi, and is in its high energy configuration. ADP + TroPi are bound. Note myosin has ATPase activity.
3) The myosin head binds to actin, foming a CROSS BRIDGE
4) relreasing ADP and Pi, myosin returns to low energy configuration, sliding the actin chain toward the center of the sarcomere. This is the POWER STROKE.
5) Binding of a new ATP is necessary for the release of actin by the myosin head.
Troponin-tropomyosin complex.
Complex that prevents contraction when Ca2+ is not present.
When troponin binds Ca2+, troponin undergoes a conformational change that moves tropomyosin out of the way, so that myosin heads can attach to actin and filament sliding can occur.
Tropomyosin.
A long fibrous protein that winds around the actin polymer blocking all the myosin binding sites.
Troponin.
A globular protein bound to the tropomyosin that can bind Ca2+. When troponin binds Ca2+, troponin undergoes a conformational change that moves tropomyosin out of the way, so that myosin heads can attach to actin and filament sliding can occur.
Which has ATPase activity? Myosin or actin?
Myosin.
The ___ is the synapses between an ___(synaptic knob) and a ____.
Neuromuscular junction is the synapse between a axon terminus and a myofiber. NMJ is not a single point, but rather a long trough of the cell membrane so the neuron can depolarize a large region of the postsynaptic membrane.
The postsynaptic membrane of a myofiber cell membrane is known as.
The motor end plate.
Impulse transmission at the NMJ is typical of chemical synaptic transmission. An AP arrives at the axon term, triggering opening of ___ channels; the resulting increase in ___ triggers the ___ of acteylcholine. Binding of ACh results in a postsynaptic ___ influx, which depolarizes the postsynaptic membrane.
An AP arrives at the axon term, triggering opening of Ca2+ channels; the resulting Ca2+ increase triggers the release of Ach. The postsynaptic MB contains ACh receptors, which are ligand gated Na+ channels.
Binding of ACh results in a postsynaptic Na influx, which depolarizes the postsynaptic membrane, depolarizaton is known as the end plate potential.
End Plate Potential (EPP)
The depolarization of the postsynaptic membrane of a myofiber.
ACh will continue to stimulate the post-synaptic receptors until its destroyed by ___.
Acetylcholinesterase, which hydrolyzes ACh to choline plus acetyl unit.
When a sufficient end plate potential occurs, the threshold is reached, and __ channels open in the postsynaptic membrane, initiating an action potential in the muscle cell. The AP here is propagated as in neurons
Na+ channels open.
How are teh APs in neurons and muscle cells (myofibers) similar/different?
They are pretty much the same. Neurons EPSP + IPSP add up, and if a threshold is reach Na+ channels open. For muscles, a sufficient end plate potential is required before Na+ channels open.
APs only occur at the cell surface. Myofibers are thick. How do we get to all the fibers?
We have deep invaginations in the cell membrane called TRANSVERSE TUBULES, which allow the AP to travel into the thick cell.
Sarcoplasmic reticulum.
A specialized endoplasmic reticulum. As the AP spreads along the T tubules, it triggers changesin the SR, opening Ca2+ channels. Ca2+ ions stored in the interior of the SR flow through open channels in the SR into the cytosol and bind to the tropoinin complex, initiating contraction of the muscle fiber.
The smallest measurable muscle contraction is known as:
Muscle twitch. A twitch results from the activation of one motor neuron
Motor unit and recruitment.
A motor unit is a group of myofibers innervated by the branches of a single motor neuron. A
The nervous system can increase the force of contraction in two ways:
1) motor unit recruitment (activating more motor neurons)
2) frequency summation - a second contraction that occurs immediately after the first and builds on it
Frequency summation.
Each contraction ends with SR returning the Ca2+ to low resting levels. If a 2nd contraction occurs fast enough, there is insufficient time for the Ca2+ to be sequestered, and the 2nd contraction builds on the first. This may happen just right after the refractory period.
A rapidly repeating series of stimulations results in the strongest possible contraction, known as ___.
Tetanus.
Length-tension relationship.
A muscle contracts most forcefully at an optimum length. This corresponds to the sarcomere length of 2.2 microns, where a max degree of overlapp occurs between actin and myosin thinn/thick filaments.
