Day 12: Skeletal Muscle Contraction

When a muscle fiber contracts, which parts of the sarcomere maintain a constant length throughout contraction?

A band

In a muscle there are concentric layers of connective tissues. From deep to superficial these connective tissue layers are the _____, the _____, and the _____.

Blank 1: endomysium Blank 2: perimysium Blank 3: epimysium

The three connective tissue layers surrounding the individual components of a muscle are the: _____, _____, and _____.

Blank 1: epimysium Blank 2: perimysium Blank 3: endomysium

At maximal contraction of a muscle fiber, the thin filaments are pulled into the ______ zone which disappears.

H

In a relaxed muscle fiber there are no thin filaments overlapping the thick filaments in the ______ zone.

H

In a sarcomere, the ______ zone (or band) is the light, central region of the A band.

H

When viewed under a light microscope, the light bands, called ______ bands, contain only ______ filaments.

I; thin

The ______ line is a thin, transverse, protein meshwork structure in the center of the H zone of a sarcomere.

M

Deep invaginations of sarcolemma are called ______.

T-tubules

Once started, a muscle impulse will travel along the sarcolemma and into the muscle fiber via the ______.

T-tubules

When calcium ions bind to troponin, which of the following then occurs?

The myosin-binding sites on actin are exposed.

True or false: A single myofibril runs the length of the muscle fiber.

True

True or false: In the absence of calcium, troponin attaches to tropomyosin to hold it in place on the surface of the F actin strand.

True

True or false: Skeletal muscle is usually attached to the skeleton, but it is also found at the openings between the digestive tract and the external environment and the urinary tract and the opening to the external environment.

True

What is a facicle?

a bundle of muscle fibers

The arrival of a nerve impulse at the synaptic knob of a motor neuron causes synaptic vesicles to release ______ into the synaptic cleft.

acetylcholine

Contraction of a muscle fiber requires that the myosin heads in the thick filament bind to active sites on ______ molecules within the thin filaments

actin

Each myosin head in a thick filament can bind to the protein in a thin filament called ______.

actin

Which of the following proteins are found in a thin filament?

actin

The connective tissue layers in muscle provide protection, distribution sites for blood vessels and nerves, and a means of ______ to the skeleton.

attachment

Functionally, troponin provides a binding site for ______ ions.

calcium

The cyclic events of "attach, pivot, detach, return" continue as long as ______ ions remain bound to the troponin.

calcium

A muscle fiber is what level of organization in the body?

cellular

The long tails of the myosin molecules in the thick filaments point toward the ______ of the filament.

center

Sarcoplasm is another term for skeletal muscle ______.

cytoplasm

In a muscle, the perimysium is composed of what type of connective tissue?

dense irregular

Muscle tissue demonstrates the property of _____ when it is done contracting and returns to its resting length.

elastisity

The connective tissue layer that surrounds an entire muscle is called ______.

epimysium

Muscle cells are said to have what characteristic because they can respond to stimulation from the nervous system?

excitability

The synaptic knob of the neuron is a(n) ______ of an axon.

expanded tip

In a transverse section of a muscle, you can see that each skeletal muscle is actually composed of many ______, which are bundles of muscle fibers.

fascicles

In a muscle, the perimysium surrounds ______ muscle cells.

fascicles of

A skeletal muscle cell is also called a muscle ______.

fibers

Each myosin strand has a free ______ and an attached tail.

head

What part of a myosin molecule does ATP bind to?

head

The act of shivering is an example of skeletal muscle performing what function?

heat production

When a nerve impulse reaches the end of an axon of a neuromuscular junction, calcium flows ______ the synaptic knob.

into

Because muscle cells require a huge amount of ATP in order to contract, they have a large number of which organelle?

mitochondria

In a motor unit, a single ______ neuron typically controls numerous muscle fibers in a muscle.

motor

Neurons that stimulate muscle contraction are called ______ neurons.

motor

Skeletal muscle contraction is controlled by ______ neurons.

motor

Upon release from the synaptic knob, acetylcholine attaches to receptors on the ______.

motor end plate

A motor unit is composed of a single ______ and all of the muscle fibers it controls.

motor neuron

Match each muscle unit with the connective tissue layer that surrounds it. Instructions -muscle -fascicle -muscle cell endomysium epimysium perimysium

muscle ----> epimysium fascicle ----> perimysium muscle cell ----> endomysium

The sarcoplasm of a skeletal muscle fiber contains hundreds to thousands of long, cylindrical structures called ______ that extend the length of the cell.

myofibrils

Muscle fibers contain cylindrical structures called myofibrils, which are composed of ______.

myofilaments

Myofibrils are made of ______.

myofilaments

Myofibrils consist of bundles of short ______.

myofilaments

Termination of the nerve impulse at an NMJ results in the passive sliding of ______ back to their original state.

myofilaments

Muscle cells store oxygen bound to a ______ molecule.

myoglobin

Thick filaments are assembled from bundles of the protein called ______.

myosin

Thick myofilaments are composed of bundles of ______ protein molecules.

myosin

After the cross bridges are formed, ATP is required to detach the ______ and complete the sequence of cyclic events.

myosin heads

Synaptic knob, motor end plate, and synaptic cleft are parts of a ______.

neuromuscular junction

While observing skeletal muscle tissue under the microscope you note that it appears striated. You tell your lab partner this is because ______.

of the arrangement of myofilaments in each sarcomere

The connective tissue layer that surrounds each muscle fascicle is called ______.

perimysium

An internal membrane complex in skeletal muscle cells that is similar to the smooth endoplasmic reticulum of other cells is called the sarcoplasmic ______.

reticulum

After stimulation of ACh receptors, a muscle impulse spreads quickly along the ______ and into the muscle fiber along T-tubules.

sarcolemma

The motor end plate is a specialized region of the ______.

sarcolemma

Within a myofibril, each ______ shortens as the muscle fiber contracts.

sarcomere

A contracting skeletal muscle fiber typically shortens as all of its ______ shorten in length.

sarcomeres

Within a myofibril, Z discs separate the functional contractile units known as ______.

sarcomeres

The cytoplasm of a skeletal muscle cell has a specific name and is known as ______.

sarcoplasm

At the end of muscle contraction, calcium ions are moved back into the ______ reticulum by ATP-driven ion pumps.

sarcoplasmic

During the development of skeletal muscle cells, some myoblasts do not fuse and instead become ______ cells.

satellite

If a skeletal muscle is injured, surrounding ______ cells may be stimulated to differentiate and assist in its repair and regeneration.

satellite

Approximately 40-50% of your body weight is _____ muscle.

skeletal

Attached to the skeleton and surrounding the openings of the urinary and gastrointestinal traces are locations of ______ muscle.

skeletal

Maintenance of posture and production of heat are functions of ______ muscle.

skeletal

The ______ filament theory explains how muscle fibers shorten during contraction.

sliding

The attachment of ACh to the receptor on the motor end plate causes the receptor to open, allowing ______ ions to enter the muscle fiber.

sodium

A nerve impulse travels through an axon to its ______.

synaptic knob

The expanded tip of an axon is called a ______.

synaptic knob

The motor end plate has folds and indentations to increase the membrane surface area adjacent to the ______.

synaptic knob

A neuromuscular junction contains a(n) ______.

synaptic knob, motor end plate, synaptic cleft

A thick cordlike structure that attaches a muscle to a bone is called a(n) ______.

tendon

As a result of ACh stimulation, calcium ions are released from the ______ of the sarcoplasmic reticulum.

terminal cisternae

The epimysium of a muscle surrounds ______.

the entire skeletal muscle

The H band (or H zone) is more lightly shaded because only ______ filaments are present.

thick

in a sarcomere, the M line serves as an attachment site for the ______ filaments and keeps them aligned during contraction and relaxation.

thick

In a muscle cell at rest, the myosin heads of a thick filament point ______ the sarcomere.

toward the ends of

The deep invaginations of the sarcolemma that extend into the sarcoplasm of skeletal muscle fibers as a network of narrow membranous tubules are called ______.

transverse tubules

As the troponin changes shape (due to binding calcium), it moves the ______ molecule to which it is attached, thus exposing the active sites on the G-actin molecules.

tropomyosin

When a muscle fiber is in a relaxed state, the ______ molecules cover the G-actin active sites, preventing interaction between thick filaments and thin filaments.

tropomyosin

Calcium ions bind to what protein in a thin myofilament?

troponin

If the sarcoplasm of a muscle cell is flooded with calcium ions, to which protein will they bind?

troponin

Upon release from the terminal cisternae, some calcium ions bind to ______ causing it to change shape.

troponin

Each myosin protein molecule in a thick filament consists of ______ strands.

two

Thick filaments are about ______ the diameter of thin filaments.

two times