Muscle Test

The following events happen in this sequence:

1. Action potential arrives at the axon terminal. 2. Calcium ions enter the axon terminal. 3. Synaptic vesicles fuse to the membrane of the axon terminal. 4. Acetylcholine is released into the synaptic cleft. 5. Acetylcholine binds to receptor sites on the motor end plate. 6. Motor end plate becomes depolarized. 7. Action potential is initiated on the sarcolemma. 8. Action potential propagates along the sarcolemma and down the T Tubules. 9. Calcium ions are released from the terminal cisternae. 10. The muscle cell contracts.

These things occur in the following order:

1.An action potential arrives at the axon terminal 2. Acetylcholine is released from the axon terminal into the synaptic cleft. 3.The motor end plate is depolarized. 4.The depolarization triggers an action potential which propagates along the sarcolemma and the T tubules. 5. The sarcomeres contract.

Which of the following is the dark band seen on the myofibrils

A band

The area where actin and myosin overlap

A-Band

The post-synaptic reaction on the sarcolemma is short in duration. Which of the following explanations describes why the reaction of the sarcolemma is short in duration?

ACh diffuses out of the synaptic cleft and AChE acts to breakdown the ACh in the synaptic cleft

Which of the following events most directly occurs due to an action potential generated by the motor neuron?

ACh is released at the synapse.

The characteristic muscle stiffness associated with rigor mortis is due to the inability of myosin filaments to detach from the active site on actin filaments. What molecule is essential for this detachment?

ATP

What is required to occur to allow myosin to detach from actin

ATP

Vesicles in the synaptic terminal contain

Acetylcholine

Action potential propagation in a skeletal muscle fiber ceases when acetylcholine is removed from the synaptic cleft. Which of the following mechanisms ensures a rapid and efficient removal of acetylcholine?

Acetylcholine is degraded by acetylcholinesterase.

The neuromuscular junction is a well-studied example of a chemical synapse. Which of the following statements describes a critical event that occurs at the neuromuscular junction?

Acetylcholine is released by axon terminals of the motor neuron.

Tamara's muscle weakness and fatigue becomes progressively worse over the course of the day. This is a hallmark sign of myasthenia gravis, an autoimmune disorder that affects the ability of a motor neuron to communicate with a muscle fiber. What synaptic events must happen first for excitation to occur?

Acetylcholine is released from the axon terminal and diffuses across the synapse to bind to a receptor in the surface of the motor end plate.

The injection that dramatically improved Tamara's symptoms was Tensilon, an acetylcholinesterase inhibitor. What is acetylcholinesterase, and why was this injection effective in relieving Tamara's symptoms?

Acetylcholinesterase is the enzyme that clears acetylcholine from the synapse. Inhibiting this enzyme will enable acetylcholine to be available for a longer period to bind to receptors.

More efficient use of glucose molecules for ATP production

Aerobic respiration

Used for long term, light-to-moderate exercise

Aerobic respiration

Used fro strenuous exercises

Anaerobic respiration

The binding of the neurotransmitter to receptors on the motor end plate causes which of the following to occur?

Binding of the neurotransmitter causes chemically gated sodium channels to open in the motor end plate (junctional folds of the sarcolemma) and sodium enters the cell.

What moves troponin and tropomyosin on the actin so that cross bridges can form?

Ca ions

What must be released from the SR in order for myosin to bind to actin?

Ca ions

Ca++ is stored in specialized pockets of the sarcoplasmic reticulum called

Cisternae

Which connective tissue layer wraps the entire muscle?

Epimysium

The perimysium surrounds a bundle of muscle fibers called a

Fascicle

Which of the following produces ATP from glucose anaerobically

Glycolysis

The part of the sarcomere that contains thick filament but no thin filaments is the

H band

The area where actin and myosin do not overlap and only actin is found is called the

I Band

Areas of a sarcomere with just actin

I band

The region of the sarcomere that always contains thin filaments is the

I band

The area where actin and myosin do not overlap and only actin is found is called the

I-Band

Myasthenia gravis is an autoimmune disorder that results in the production of antibodies that either block or cause the destruction of the ACh receptor. Why do you think that Tamara's symptoms become worse as the day progresses?

In the morning, the neuronal reserves of acetylcholine are larger, allowing for sufficient neurotransmitter release and resulting in effective muscle signaling. As the day progresses and the stores of acetylcholine become depleted, muscle function becomes progressively worse.

What is the type of contraction in which the muscle does NOT change length?

Isometric

Why is control over leg muscles LESS precise than control over the muscles of the eye

Many muscle fibers are controlled by a single motor neuron

What structure most directly stimulates a skeletal muscle fiber to contract?

Motor neuron

Myofibrils bundled together form

Muscle Fiber (cell)

How does the muscle fiber becomes positively charged during depolarization?

Na ions flood into the cell

Why do bodies go into rigor after death?

No ATP to release myosin from actin

Inadequate calcium in the neuromuscular junction would directly affect which of the following processes?

Release of acetylcholine from the synaptic vesicles

What is the functional unit of the muscle fiber (cell)?

Sacromere

The repeating functional units seen in the myofibrils are

Sarcomeres

Since each myofibril is attached at either end of the muscle fiber, when sarcomeres shorten, the muscle fiber

Shortens

When acetylcholine reaches receptors on the sarcolemma of muscle fibers, ____ channels open

Sodium (Na)

Calcium entry into the axon terminal triggers which of the following events?

Synaptic vesicles fuse to the plasma membrane of the axon terminal and release acetylcholine.

Action potentials travel along the sarcolemma and reach the interior of the cell though

T tubules

Action potentials travel long the sarcolemma and reach the interior of the cell through

T tubules

infoldings of the sarcolemma called

T tubules

Sodium and potassium ions do not diffuse in equal numbers through ligand-gated cation channels. Why?

The inside surface of the sarcolemma is negatively charged compared to the outside surface. Sodium ions diffuse inward along favorable chemical and electrical gradients.

Which of these statements about skeletal muscles is FALSE?

Their fibers branch.

Myasthenia gravis is a disease resulting from an autoimmune attack on the ACh receptors of the motor end plate. Binding of antibodies to the ACh receptors results in generalized muscle weakness that progresses as more ACh receptors are destroyed. Which of the following medications would help alleviate the muscle weakness?

a drug that binds to and inactivates acetylcholinesterase (neostigmine)

Sarcomere is best defined as __________.

a repeating unit of striated muscle

Acetylcholine receptor

a type of chemically-gated ion channel located on the junctional folds of the muscle fiber.

Calcium channel

a type of voltage-gated ion channel located on the axon terminal.

sodium channels

a type of voltage-gated ion channel located on the sarcolemma of the muscle fiber.

Neurotransmitter that is released from the axon terminal to cross the synaptic cleft

acetylcholine

Vesicles in the synaptic terminal contain

acetylcholine

In a neuromuscular junction, synaptic vesicles in the motor neuron contain which neurotransmitter?

acetylcholine (ACh)

The cytoplasm of the neuromuscular terminal contains vesicles filled with molecules of the neurotransmitter

acetylcholine.

Thin Filaments are also called

actin filaments

Thin filaments are also called

actin filaments

Which filaments =moves during muscle contraction?

actin or thin

The most important factor in decreasing the intracellular concentration of calcium ion after contraction is

active transport of calcium into the sarcoplasmic reticulum.

Creatine phosphate

acts as an energy reserve in muscle tissue

During the recovery period the body's need for oxygen is increased because

additional oxygen is required to restore energy reserves.

A resting muscle generates most of its ATP by

aerobic metabolism of fatty acids

Decreased blood flow to a muscle could result in all of the following except

an increase in intracellular glycogen.

After heavy exercise, if energy reserves in a muscle are depleted, ________ occurs.

an oxygen debt

Makes ATP faster

anaerobic respiration

Active sites on the actin become available for binding after

calcium binds to troponin.

In response to action potentials arriving along the transverse tubules, the sarcoplasmic reticulum releases

calcium ions

Branching, striated muscle tissue is called

cardiac

Ca ++ is stored in specialized pockets of the sarcoplasmic reticulum called

cisternae

Contraction where the muscle shortens

concentric

Contraction where the muscle shortens and does work

concentric

Fatigued muscles signify __________.

decreased pH

When the muscle cell becomes positively charged, it has been ____

depolarized

Contraction where the muscle lengths and does work

eccentric

Individual muscle fibers are covered by which connective tissue?

endomysium

Muscle fibers are directly surrounded by which thin layer of connective tissue?

endomysium

The capillaries that wrap around each muscle fiber are located within the __________.

endomysium

The outer connective tissue layer surrounding a group of fascicles is called

epimysium

Synaptic vesicles contain neurotransmitters that are released by ________ when the action potential arrives.

exocytosis

What means of membrane transport is used to release the neurotransmitter into the synaptic cleft?

exocytosis

Action potentials travel the length of the axons of motor neurons to the axon terminals. These motor neurons __________.

extend from the brain or spinal cord to the sarcolemma of a skeletal muscle fiber

A group of muscle fibers are called

fascicles

Which of the following would not lead to increased oxygen consumption?

increased anaerobic respiration by muscle cells

A weight-lifter strains to lift a heavy weight and there is no movement of the person's arms holding on to the weight. This type of contraction is called a(n) ________ contraction.

isometric

Contraction of muscles that do not change length

isometric

Which of the following is a function of skeletal muscle?

maintain body temperature, produce movement, and maintain posture

Synaptic vesicle

membranous sac located in the axon terminal that contains neurotransmitter.

Organelle of ATP production

mitochondria

When acetylcholine binds to receptors at the motor end plate, the sarcolemma becomes

more permeable to sodium ions.

Acetylcholine crosses the synaptic cleft and binds to the receptors on the

motor end plate

Receptors for acetylcholine are located on the

motor end plate

A nerve that stimulates a muscle fiber

motor neuron

A motor neuron and all fibers it stimulates

motor unit

All the muscle fibers and the single motor neuron that innervates them are called a __________.

motor unit

One neuron and all the muscle cells it contains is called

motor unit

One nueron and all the muscle cells it controls is called

motor unit

Interactions between actin and myosin filaments of the sarcomere are responsible for

muscle contraction.

Myofribrils bundled together form

muscle fiber (cell)

In an isotonic contraction,

muscle tension exceeds the load and the muscle lifts the load.

The ability of a muscle to stay in a slightly contracted state is

muscle tone

In which of the following would the motor units have the fewest muscle fibers?

muscles that control the eyes

Muscle cells are made up of

myofibrils

Muscle cells are made up og

myofibrils

Thick filaments are also called

myosin filaments

Cross-bridges are portions of

myosin molecules

Each skeletal muscle fiber is controlled by a motor neuron at a single

neuromuscular junction.

Acetylcholine

neurotransmitter that stimulates skeletal muscle contraction.

What starts the 'relaxation' phase after a muscle contraction

no impulse sent down motor nueron

Why does muscle fatigue occur?

not enough ATP

Fascicles are covered by a layer of connective tissue called

perimysium

The advantage of having many nuclei in a skeletal muscle fiber is the ability to

produce large amounts of muscle proteins.

Which of the following is a function of skeletal muscle?

produce movement, maintain posture, and maintain body temperature

Muscle is responsible for all the following EXCEPT...

production of vitamin D

During anaerobic glycolysis,

pyruvic acid is produced oxygen is not consumed carbohydrate is metabolized ATP is produced.

A patient takes a medication that blocks ACh receptors of skeletal muscle fibers. What is this drug's effect on skeletal muscle contraction?

reduces the muscle's ability for contraction

The cell membrane in muscle cells is referred to as the

sarcolemma

The cell membrane of the muscle cell is called

sarcolemma

The plasma membrane of a skeletal muscle fiber is called the

sarcolemma.

Functional, repeating unit of all myofibrils

sarcomere

The basic functional unit of a skeletal muscle is the

sarcomere

The repeating unit of a skeletal muscle fiber is the

sarcomere.

Myofibrils are made up of repeating sub-units called

sarcomeres

The basic functional unit of skeletal muscle is the

sarcomeres

In response to an action potential along the transverse tubules, the __________ release(s) calcium ions into the sarcoplasm.

sarcoplasmic reticulum

Within the fiber, calcium ions are stored in the

sarcoplasmic reticulum

A high blood concentration of the enzyme creatine phosphate (CPK) usually indicates

serious muscle damage

How is acetylcholine (ACh) removed from the synaptic cleft?

simple diffusion away from the synaptic cleft and acetylcholinesterase (AChE; an enzyme)

What are the three types of muscle tissue

skeletal, cardiac, smooth

Movement of the eyeball would be controlled by ____ motor units

small

Which type or muscle tissue do NOT contain sarcomeres?

smooth

Involuntary muscle(s)

smooth and cardiac

The space between the axon terminal and the muscle fiber

synaptic cleft

The narrow space between the synaptic terminal and the muscle fiber is the

synaptic cleft.

At each end of the muscle, the collagen fibers of the epimysium, perimysium, and endomysium, come together to form a

tendon

Muscles are held to bones by

tendons or aponeuroses

The contraction of a muscle exerts a pull on a bone because muscles attach to bones by

tendons.

The action potential on the muscle cell leads to contraction due to the release of calcium ions. Where are calcium ions stored in the muscle cell?

terminal cisterns (cisternae) of the sarcoplasmic reticulum

An infection by the bacterium Clostridium tetani can cause the disease called

tetanus.

Acetylcholinesterase

the enzyme that breaks down acetylcholine in the synaptic cleft

Acetylcholine binds to its receptor in the sarcolemma and triggers __________.

the opening of ligand-gated cation channels

Synaptic cleft

the space between the axon terminal and junctional folds.

Which of the following best describes the term Z line?

thin filaments are anchored here

The action potential is conducted into a skeletal muscle fiber by

transverse tubules.

The release of Ca ions triggers the movement of

troponin/ tropomyosin complex

When an action potential arrives at the axon terminal of a motor neuron, which ion channels open?

voltage-gated calcium channels