Lab Quiz

The neuromuscular junction is found between which two structures? Axon terminal of motor neuron and motor end plate Axon terminal of motor axon and T-tubule Cell body of motor neuron and myofibril Dendrite of motor neuron and sarcoplasm

Axon terminal of motor neuron and motor end plate

What does the epimysium surround? Bundle of 2-3 fascicles Entire muscle Single muscle cell Single fascicle

Entire Muscle

Based on your knowledge of the microscopic anatomy of muscle tissue, how would you conclusively identify cardiac muscle tissue from a cross-sectional view? I would confirm the presence of a single, centrally located nucleus in the cells. I would confirm the absence of a multiple, peripherally located nuclei in the cells. I would confirm the presence of a single, peripherally located nucleus in the cells. I would confirm the absence of stippling (i.e., many, small dots) in the sarcoplasm of the cells.

I would confirm the presence of a single, centrally located nucleus in the cells.

In the sliding filament mechanism, which event occurs first? Influx of potassium into the sarcolemma Binding of myosin to actin Power stroke of the crossbridge Influx of calcium into the sarcoplasm

Influx of calcium into the sarcoplasm

Which of the following descriptions characterizes skeletal muscle tissue? It contains striated cells. It contains uninucleate cells. It contains intercalated discs. It contains spindle-shaped cells. It contains branched cells.

It contains striated cells.

What is the region of the sarcolemma across from the axon terminal at the neuromuscular junction? Fascicle Triad Motor end plate Transverse tubule

Motor end plate

What does the thick filament do during a muscle contraction? Stabilizes the Z-disc Pulls on the thin filament Forms a stationary wall for the thin filament to pull against Blocks the actin active site

Pulls on the thin filament

What will glycerin do to skeletal muscle fibers? Increases calcium permeability Adhere myosin heads to actin active sites Block actin active sites Remove ions and ATP so actin active sites are exposed

Remove ions and ATP so actin active sites are exposed

What is the smallest functional unit of a muscle contraction? Sarcomere Myofibril Myofilament T-tubule

Sarcomere

Which structure stores calcium? Thin filament Sarcoplasmic reticulum T-tubule Mitochondrion

Sarcoplasmic Reticulum

What does the perimysium surround? Single sarcomere Single muscle cell Single fascicle Entire muscle

Single Fasicle

Which structure allows the action potential to travel deep into the interior of the cell to each contractile organelle? T-tubule Sarcolemma Sarcoplasm Myofibril

T-tubule

Predict the effect of adding ATP and ions to the H-band of glycerinated muscle fibers. The H-zone would widen. The H-zone stays the same. The H-zone would narrow.

The H-zone would narrow.

Which of the following statements describes the microscopic appearance of skeletal muscle tissue? The cells are long and striated. The cells are short and oblong shaped. The cells are branched. The cells have one to two nuclei.

The cells are long and striated.

The endomysium of a muscle fiber is composed of loose connective tissue while the perimysium is composed of dense irregular connective tissue. What can you conclude about the function of the endomysium versus the function of the perimysium based on the tissue differences? The endomysium is under high levels of physical stress due to contraction of the muscle. The endomysium is effective at separating muscle fascicles. The endomysium only needs to form an electrical conduction pathway with the muscle fiber. The endomysium only needs to electrically insulate the muscle fiber.

The endomysium only needs to electrically insulate the muscle fiber.

Explain the functional significance of the T-tubules of the sarcolemma and the terminal cisternae of the sarcoplasmic reticulum. The increased surface area provides space for more ligand gated ion channels, thus increasing the effectiveness of acetylcholine binding. The abundance of each structure increases the rate of ATP production. The increased surface of both structures increases the speed and efficiency with which the end-plate potential leads to sarcomere contraction. The T-tubules and terminal cisternae enhance the chemical attraction between myosin and actin.

The increased surface of both structures increases the speed and efficiency with which the end-plate potential leads to sarcomere contraction.

Which description is true of skeletal muscle fibers? They contain 1-2 nuclei. They are long and cylinder shaped. They have faint or no striations. They are branched.

They are long and cylinder shaped.

When muscle contraction occurs, what happens to the thick and thin filaments? They shorten in length as does the sarcomere. They separate from each other, which causes the sarcomere to lengthen. They bind to the Z discs, which causes the sarcomere to lengthen. They slide past one another, which causes the sarcomere to shorten. They remain separated and do not move during the shortening of the sarcomere.

They slide past one another, which causes the sarcomere to shorten.

What structure consists of myosin? Thick filament Thin filament Perimysium Endomysium

Thick filament

Part complete What is the main component of the A band of the myofibril? Thin filaments Actin filaments Thick filaments Elastic filaments

Thick filaments

The boundaries of a sarcomere are formed by ________. thick filaments Z discs H zone M line thin filaments

Z discs

Acetylcholine is released from the axon terminal of a motor neuron and it acts as ________. an inhibitory chemical a catalyst a neurotransmitter an action potential

a neurotransmitter

A neuromuscular junction is a junction between a_________ and a ___________. sarcoplasm; T-tubule bulbous end of axon; skeletal muscle fiber dendrite of an axon; myofibril dendrite of an axon; skeletal muscle fiber bulbous end of axon; cell body of axon

bulbous end of axon; skeletal muscle fiber

The active sites on the actin filaments are exposed by ________. acetylcholine potassium sodium calcium

calcium

Which ion is responsible for exposing the active sites on actin? hydrogen sodium potassium calcium chloride

calcium

Exposing skeletal muscle fibers to ________ removes ions and ATP from the cells and disrupts the troponin-tropomyosin complex such that it can no longer block the active sites on the actin molecules. glycerin chloride calcium acetylcholinesterase sodium

glycerin

A muscle action potential travels deep into the interior of the cell via invagination of the sarcolemma called ______________. motor axons terminal cisternae T-tubules myofibrils the sarcoplasm

myofibrils

Acetylcholine is a(n) _________ released from the axon terminal of a motor neuron. mineral vitamin enzyme ion neurotransmitter

neurotransmitter

The functional unit of a muscle contraction is the ____________. muscle fiber sarcomere myofilament T-tubule myofibril

sarcomere