Muscle Tissue Flashcards
What is acetylcholine?
ACh - The neurotransmitter released at a neuromuscular junction.
The characteristic that allows muscles to pull on bones and organs to create movement is called:
contractility
How does muscle contraction occur?
The overlapping of myofilaments increases, shortening the overall sarcomere.
What type of muscle cells have a fusiform shape and taper to a point at the end?
Smooth
What does the sliding filament theory describe?
Muscle contraction
Name three characteristics of cardiac muscle cells.
They contract with regular rhythm, they are resistant to fatigue, and they contract nearly in unison, it is rich in myoglobin, it has large stores of glycogen, it uses aerobic respiration almost exclusively
What is acetylcholinesterase?
The enzyme that breaks down acetylcholine.
What is the enzyme that breaks down acetylcholine?
acetylcholinesterase
What is a motor unit?
All of the muscle fibers innervated by a single motor nerve fiber.
Tell whether cardiac, smooth, and skeletal muscle are voluntary or involuntary
Cardiac: involuntary; smooth: involuntary; skeletal: voluntary
When muscles stretch and recoil, they recoil to a shorter length. What is this property called?
Elasticity.
What type of contraction involves the development of tension but no change in length?
Isometric
What type of contraction involves the development of tension with a change in length
Isotonic
How do smooth muscle myocytes differ from cardiocytes?
Smooth muscle myocytes have no T tubules while cardiac muscles do.
What is the portion of a myofibril from one Z disc to another?
Sarcomere
The step in which muscle fiber develops tension and may shorten is called what?
Contraction
List the steps of muscle relaxation in order:
1: The nerve signal ceases. 2: AChE breaks ACh down. 3: Active transport pumps in the sarcoplasmic reticulum begin to pump calcium back into cisternae. 4: Calcium releases from troponin. 5: Tropomyosin covers the myosin binding sites.
Describe some characteristics of smooth muscle.
Has no T-tubules, has little SR, is uninucleated, typically slow to contract and slow to relax
What is the difference in electrical charge between one point and another?
electrical potential
What is a feature unique to cardiac muscle?
intercalated discs
What occurs during the relaxation phase of muscle contraction?
Myosin releases the thin filaments; calcium levels in the sarcoplasm fall; muscle tension declines
What is the continuous, forceful contraction in a muscle with no relaxation between stimulii?
Complete tetanus
What is the quick up-and-down voltage shift from negative to positive called, and what is it caused by?
Action potential, caused by the movement of Na and K across the cell membrane.
Which membranous structures conduct impulses through the sarcoplasm to stimulate the release of calcium?
T-tubules
What causes the opening of ion channels, resulting in the initial movement of Na and K across the plasma membrane at the neuromuscular junction? If continued, this can trigger an action potential at the neighboring sarcolemma?
end-plate potential
What affects twitch strength?
How stretched the muscle was just before stimulation; temperature of the muscle; muscle fatigue; stimulation frequency
What is myosin ATPase?
An enzyme located in the myosin head that hydrolyzes ATP
How do resistance exercises cause muscle growth?
They increase the size of myofibrils.
In which type of muscle can excitation be non-electrical?
Smooth muscle
Which muscle tissue resists fatigue and frequently exhibits tetanus?
Smooth Muscle
Fibers well adapted to aerobic respiration are called what -twitch fibers?
Slow twitch
What is a thick filament composed of in myofibril?
pairs of myosin molecules intertwined together
What is the indented region of a sarcolemma that participates in the neruomuscular junction called?
Motor end plate
What is the name of the red pigment that stores oxygen needed for muscular activity?
myoglobin
Which three situations lead to muscle fatigue in long-duration exercises?
Electrolyte loss, fuel depletion, and central fatigue
Where is calcium stored in a skeletal muscle cell?
sarcoplasmic reticulum
An overstretched or over contracted muscle will result in what?
A weak contraction
In which type of contraction does a muscle shorten as it maintains tension?
Concentric
In which type of contraction does a muscle lengthen as it maintains tension?
Eccentric
When a muscle is at rest, which molecule blocks the active sites on the actin molecule?
Tropomyosin
On a myogram, what is the time between the stimulus and the twitch?
latent period
When acetylcholine binds to its receptors on the motor end plate, an ion channel opens, allowing which ions to diffuse quickly into the cell?
Sodium
What is the change in membrane potential with the entry of sodium ions called?
Depolarization
Which fibers are adapted for a quick response?
Fast glycolytic
How does the action potential move deep into the muscle cell?
T-tubules
Which structures coordinate contractions in cardiac muscle cells
Gap junctions
Pockets within the sarcolemma of smooth muscle that contain calcium channels
caveolae
During what period of a muscle twitch does a muscle fiber shorten and generate force?
contraction
