Muscle Tissues

During muscle contraction ______________

sarcomeres become shorter

Muscle fibers belonging to the same motor unit ______

are controlled by the same motor neuron

During muscle contraction ____________

myofibrils become shorter

Where in a skeletal muscle fiber could you find Nebulin?

at the core of thin filaments

A single motor neuron will trigger contraction of __________

many muscle fibers

During muscle contraction _______________

muscle fibers become shorter

Cardiac muscle cells _______________

do not have terminal cisternae

A muscle (organ) is surrounded by ___________

the epimysium

The amount of tension produced by an individual muscle fiber depends on __________

the number of pivoting cross-bridges

Which of the following is a component of thin filaments in skeletal muscle fibers?

Nebulin

What triggers activation of ligand-gated Na+ channels at the neuromuscular junction?

binding of acetylcholine

During muscle contraction, a power strokea follows after ___________

ADP and phosphate are released from the myosin head

Once Ca2+ is removed from the sarcolemma, myosin heads in thick filaments come to a complete stop. Which one of the following statements best describes the status of those myosin heads?

myosin heads remain energized, with their ADP and phosphate binding sites occupied

What are the components of thick filaments in skeletal muscle fibers?

myosin

What is acetylcholine doing at the neuromuscular junction?

it promotes depolarization at the motor end plate due to activation of Na+ channels

Which of the following is a component of thin filaments in skeletal muscle fibers?

tropomyosin

At the sarcomere, Ca+2 ions will bind to________

troponin

Muscle fibers undergoing intense and frequent contractions ______

will produce large amounts of pyruvate and lactate from glucose

Cardiac muscle cells _________

do not have triads

Which one of these elements will shorten following contraction of a muscle fiber?

myofibrils

A bundle of muscle fibers (or fascicle) is surrounded by_________

the perimysium

After death, metabolism shuts down and ATP runs out. As a result, calcium pumps at the sarcoplasmic reticulum stop, so Ca+2 ions diffuse out into the sarcoplasm. What do you think will be the consequences for the muscles of this persons body?

due to increased Ca2+ concentration, sarcomeres will enter a contraction cycle. Then, because of the lack of ATP, myosin heads will be unable to detach from actin, so muscles will become stiff

A structure composed by terminal cisternae surrounding a T-tubule is known as ______

triad

Motor unit refers to_____

a more or less large group of muscle fibers that is controlled by the same motor neuron

Which specific event will induce a myosin head to do a power stroke?

release of ADP

Upon arrival of an action potential, the terminal cisternae release Ca2+ into the______

sarcoplasm

The Z line is the point where __________

consecutive sarcomeres meet

In smooth muscle cells, actin filaments are attached to ___________

dense bodies

Which one of these elements will shorten following contraction of a muscle fiber?

sarcomeres

During moderate activity a skeletal muscle fiber will_________

use both anaerobic and aerobic metabolic pathways (i.e., glycolysis and citric acid cycle) to produce ATP

One of these proteins is not part of thick or thin filaments, but is always attached to them. Which one is it?

titin

One of these proteins prevents binding of actin to myosin in the absence of calcium. Which one is it?

tropomyosin

Energy to produce creatine phosphate in a skeletal muscle fiber may come from_______

citric acid cycle

In skeletal muscle cells, myofibrils are surrounded by________

the sarcoplasmic reticulum and T-tubules

Resting skeletal muscle fibers produce_______

ATP, glycogen, and creatine Phosphate

Which one of these structures is present in smooth muscle cells?

thin filaments

In cardiac muscle cells, action potentials are triggered_____

by ions moving between neighboring cells, via gap junctions

In order to reach a muscle fiber, blood vessels must get through _____

the epimysium, perimysium and endomysium

Which one of these structures is present in all cardiac muscle cells?

T-tubules

Smooth muscle tissue ___________

has thin filaments attached to dense bodies and to the plasma membrane

Which of the following is a component of thin filaments in skeletal muscle fibers?

troponin

Muscle contraction is triggered by Ca+2 ions binding to________

troponin

During the muscle contraction cycle, myosin heads return to the cocked or energized position after__________

ATP binds to myosin heads and is hydrolyzed to ADP and phosphate

Energy to produce creatine phosphate in a skeletal muscle fiber may come from _________

aerobic metabolism

Collagen fibers in tendons originate at the_______

epimysium, perimysium and endomysium

Skeletal muscle cells are multinucleated because _____________

they originate from multiple myoblast that fuse together into a single cell

Muscle fibers within a motor unit_____

contract all at the same time

Voltage-gated calcium channels located at the triads release Ca2+ into the sarcoplasm, triggering the contraction of neighboring sarcomeres. What is the stimulus that activates these channels?

a sudden surge in the cells membrane potential (or voltage across the plasma membrane) to more positive values

What sources of energy will a muscle fiber use during peak activity?

Anaerobic metabolism of glucose, aerobic metabolism in mitochondria using both pyruvate and fatty acids as substrate, and creatine phosphate

The role of a neuromuscular junction is_________

to allow an action potential to spread from an axon terminal to the sarcolemma of a muscle fiber

Action potentials are transmitted to the triad via ______

transverse tubules

Contraction of the sarcomere will end after__________

Ca2+ is sequestered by the sarcoplasmic reticulum