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62 Cards in this Set

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  • Back
3 Types of Muscle
1) Skeletal Muscle: aka voluntary muscle
-its role is to contract in response to conscious intentions, striated (microscopic appearance)
2) Cardiac Muscle: found only in the wall of the heart, striated (microscopic appearance)
3) Smooth Muscle: found in the walls of all hollow organs (i.s., GI tract, urinary system, uterus, etc.)
-no conscious control over cardiac or smooth muscle because they are innervated only by the autonomic nervous system
Can skeletal muscle alone move the body?
Not alone. Skeletal muscle requires the framework of the bones of the skeleton for movement to occur.
Tendons
Strong connective tissue formed primarily of collagen
What effect does expansion of skeletal muscle have on the two bones the muscle is connected to?
None. Muscle can only contract to cause force on bones and movement.
Flexing
One way skeletal muscles can move a joint, by reducing the angle of the joint
Extending
One way skeletal muscles can move a joint, by increasing the angle of the joint
Abducting
One way skeletal muscles can move a joint, by moving away from the body
Adducting
One way skeletal muscles can move a joint, by moving towards the body
Which of the movements: flexing, contracting, abducting, or adducting involve contraction of skeletal muscle?
All of them. It is the only way to move bones and joints: by contracting skeletal muscles.
Does flexing the elbow bring the hand closer to or farther from the shoulder?
Flexing decreases the angle of a joint. If the elbow is flexed, the hand will be closer to the shoulder.
Origin
Where muscle attaches to the bone.
Insertion
The point where the muscle attaches on the bone more distant from the center of the body
What, involving the origin and insertion, happens when a muscle contracts?
The insertion is brought nearer to the origin.
Elbow joint by the biceps brachii
Origin of muscle: Shoulder joint
Insertion: in the bones of the lower arm
-Contraction of the biceps brings the insertion (lower arm) closer to the origin (the shoulder)
Different muscles are necessary for flexion and extension of a joint because...
Muscles can only contract.
Triceps Brachii
For the elbow, the muscle on the back of the upper arm
-Responsible for extension
Where is the origin of the triceps muscle?
The origin of the triceps is the point of attachment nearer the center of the body, or the shoulder, on the opposite side of the biceps attachment.
Do both the biceps and triceps contract vigorously simultaneously to cause movement?
Usually, no. Muscles that oppose each other's action are usually regulated by the nervous system in the opposite manner, so that one relaxes while the other contracts.
Antagonistic
Muscles that are responsible for movement in opposite directions.
Synergistic
Muscles that are responsible for movement in the same direction.
Triceps Brachii
For the elbow, the muscle on the back of the upper arm
-Responsible for extension
Where is the origin of the triceps muscle?
The origin of the triceps is the point of attachment nearer the center of the body, or the shoulder, on the opposite side of the biceps attachment.
Do both the biceps and triceps contract vigorously simultaneously to cause movement?
Usually, no. Muscles that oppose each other's action are usually regulated by the nervous system in the opposite manner, so that one relaxes while the other contracts.
Antagonistic
Muscles that are responsible for movement in opposite directions.
Synergistic
Muscles that are responsible for movement in the same direction.
When forearm extends...
Biceps extend and triceps contract
Fascicles
Connective tissue that holds the contractile tissue together in bundles
-allow flexibility within the muscle
Myofibers
Many fine muscle fibers
-within each bundle
Syncytia
A large multinucleate cell, typically formed by the fusion of many smaller cells during development (e.g., a skeletal muscle cell), or formed by nuclear division in the absence of cellular division
Do antagonistic muscles receive stimulation by neurons that release different neurotransmitters?
No. All skeletal muscle is innervated by somatic motor neurons which release acetylcholine at the neuromuscular junction. The difference in regulation is not the form of the signal that is sent to the muscle, but the timing of the signal.
Sarcolemma
Myofiber has this cell membrane that is made of the plasma membrane and an additional layer of polysaccharide and collagen
Myofibrils
Within each skeletal muscle cell (myofiber) there are many smaller units of these
-responsible for the striated appearance of skeletal muscle and generates the contractile force of skeletal muscle
Actin and Myosin
The proteins in the myofibril that generate contraction.
actin- polymerizes to form thin filaments
myosin- polymerizes to form thick filaments in the middle of each sarcomere
Myofibril
Composed of many sarcomeres aligned end-to-end
Z-lines
-A sarcomere is bound by two of these
-thin filaments (actin) attach to each Z line and overlap with thick filaments (myosin) in the middle of each sarcomere
-thick filaments are NOT attached to the Z lines
What creates the contraction at the sarcomere?
Overlapping regions of thick (polymerized myosin) and thin (polymerized actin) filaments in each sarcomere
Sliding filament model of muscle contraction
Within each sarcomere, actin and myosin filaments overlap w/ each other.
-contraction occurs when the thin and thick filaments slide across each other, drawing the Z lines of each sarcomere closer together and shortening the length of the muscle cell
During muscle contraction, do the thin and hick filaments shorten?
No. The thin and thick filaments slide across each other to shorten the sarcomere without themselves changing in length.
What powers filament sliding?
ATP hydrolysis
-myosin is an enzyme that uses the energy of ATP to create movement
H Zone
A Band
Z line
M line
H zone: the separation between two thin filaments
A Band: end to end of the thick filament
Z line: boundary lines of the sarcomere
M line: mid-sarcomere
Cross Bridge in muscles
The result of a myosin head attaching to a specific site on an actin molecule
-when actin and myosin are attached, myosin and actin are said to be connected by a *cross bridge
When the angle between the head and tail decreases...
Contraction occurs.
4 Steps of the Contractile Cycle with ATP involvement
1)Binding of the myosin head to a myosin binding site, aka *cross bridge formation [myosin has ADP and P bound]
2) The *power stroke, in which the myosin head pulls the actin chain past itself and ADP is released
3) Binding of a new ATP molecule is necessary for the release of actin by the myosin head (key!)
4) ATP hydrolysis occurs immediately and the myosin head is cocked like the hammer of a gun (PR analogy). Another cycle begins when the myosin head binds to a new binding site.
Contraction is dependent on the levels of _____. Howcome?
Ca2+, because the troponin-topomyosin complex prevents contraction when Ca2+ is NOT present.
Tropomyosin
A long, fibrous protein that winds around the thin filament (actin), blocking all myosin binding-sites
Troponin
Binds Ca2+. Undergoes a conformational change that moves tropomyosin out of the way, so myosin heads can attach to actin and filament sliding can occur.
What protein is responsible for ATP hydrolysis during muscle contraction?
Myosin is the protein with the ATPase activity.
In the absence of actin, which step in ATP hydrolysis by myosin is prevented, the hydrolysis of ATP or the release of ADP?
The release of ADP is prevented in the absence of actin (release of ADP occurs in the process of pulling the actin chain past itself).
If troponin-tropomyosin is added to myosin and actin filaments in a test tube along with ATP, the hydrolysis of ATP will be sensitive to...
The concentration of calcium.
Neuromuscular Junction
This is the synapse (junction between two nerve cells) between an axon terminus (synaptic knob) and a myofiber.
-Not a single point. A long trough or infolding of the cell membrane
Why is the axon terminus elongated to fill the long synaptic cleft?
To allow the neuron to depolarize a large region of the postsynaptic membrane @ once.
Which neurotransmitter is at the neuromuscular junction?
ACh (acetylcholine)
What is the postsynaptic membrane known as?
The motor end plate
Impulse Transmission is typical of chemical synaptic transmission. What does impulse transmission entail?
An action potential arrives at the axon terminus, triggering the opening of voltage-gated Ca2+ channels in the presynaptic membrane
-the resulting influx of Ca2+ causes exocytosis of vesicles containing ACh
-the postsynaptic membrane contains ACh receptors, which are ligand-gated sodium channels
-ACh diffuses across the synaptic cleft to reach its receptor
-Binding ACh to its receptor results in a postsynaptic sodium influx, which depolarizes the postsynaptic membrane
Why is the axon terminus elongated to fill the long synaptic cleft?
To allow the neuron to depolarize a large region of the postsynaptic membrane @ once.
Which neurotransmitter is at the neuromuscular junction?
ACh (acetylcholine)
What is the postsynaptic membrane known as?
The motor end plate
Impulse Transmission is typical of chemical synaptic transmission. What does impulse transmission entail?
An action potential arrives at the axon terminus, triggering the opening of voltage-gated Ca2+ channels in the presynaptic membrane
-the resulting influx of Ca2+ causes exocytosis of vesicles containing ACh
-the postsynaptic membrane contains ACh receptors, which are ligand-gated sodium channels
-ACh diffuses across the synaptic cleft to reach its receptor
-Binding ACh to its receptor results in a postsynaptic sodium influx, which depolarizes the postsynaptic membrane
Why is the axon terminus elongated to fill the long synaptic cleft?
To allow the neuron to depolarize a large region of the postsynaptic membrane @ once.
Which neurotransmitter is at the neuromuscular junction?
ACh (acetylcholine)
What is the postsynaptic membrane known as?
The motor end plate
Impulse Transmission is typical of chemical synaptic transmission. What does impulse transmission entail?
An action potential arrives at the axon terminus, triggering the opening of voltage-gated Ca2+ channels in the presynaptic membrane
-the resulting influx of Ca2+ causes exocytosis of vesicles containing ACh
-the postsynaptic membrane contains ACh receptors, which are ligand-gated sodium channels
-ACh diffuses across the synaptic cleft to reach its receptor
-Binding ACh to its receptor results in a postsynaptic sodium influx, which depolarizes the postsynaptic membrane