Chapter 6: The Muscular System

What creates the alternating light and dark bands that provides the striation pattern on skeletal muscle tissue?

A & I bands

(T/F) The striations seen in skeletal muscle are actually alternating dark A and light I bands

True

(T/F) When a muscle fiber contracts, the I bands nearly disappear, and the A bands move closed together but do not change the length

True

(T/F) Cardiac and skeletal muscle both possess striations

True

(T/F) Cardiac muscle fibers are joined by special gap junctions called intercalated discs; these discs allow heart activity to be closely coordinated

True

(T/F) The neurotransmitter used by the nervous system to activate skeletal muscle cells is acetylcholine

True

(T/F) The sarcoplasmic reticulum wraps like a sleeve around the myofibril and stores and releases calcium

True

What is acetylcholine?

a neurotransmitter that stimulates skeletal muscles to contract

The mechanical force of contraction is generated by

a sliding of thin filaments past thick filaments

What must occur first to trigger the skeletal muscle to generate an action potential and contract?

acetylcholine binds to receptors on the sarcolemma and allows pass of sodium ions into the cell

What enzyme breaks down acetylcholine into acetic acid and choline to prevent continued contraction of the muscle fiber?

acetylcholinesterase

Enzyme that breaks down acetylcholine (ACh)

acetylcholinesterase (AChE)

During skeletal muscle contraction, to what do myosin heads bind?

actin filaments

Electrical current that travels the length of the sarcolemma that results in the contraction of the muscle fiber

action potential

What is the unstoppable electrical current that travels down the length of the entire surface of sarcolemma?

action potential

What is covered by the endomysium

an individual muscle fiber

Muscles that perform opposite actions to one another are termed

antagonists

Neurotransmitters are release upon stimulation from a nerve impulse from the

axon terminals of the motor neuron

The sarcoplasmic reticulum stores this chemical

calcium ions

Why are calcium ions necessary for skeletal muscle contraction?

calcium ions trigger the binding of myosin heads to actin filaments

Muscle tissue composed of branching cells and intercalated discs

cardiac

Muscle tissue found only in the heart

cardiac

Striated involuntary muscle tissue found in the heart is

cardiac

Striated involuntary muscle tissue is classified as ______ muscle

cardiac

The arrangement of fascicles in orbicularis oris is

circular

Muscle tissue has the ability to shorten when adequately stimulated, a characteristic known as:

contractability

The heads of the myosin myofilaments are called when they link the thick and thin filaments together during skeletal muscle contraction

cross bridges

According to the sliding filament theory, how does muscle contraction occur?

myosin heads form cross bridges and pull thin filaments, causing them to slide

The point of muscle attachment to an immovable or less movable bone is knows as the:

origin

Which of the following is an example of an isometric contraction?

pushing against an immovable wall

What organelle wraps and surrounds the myofibril and stores calcium?

sarcoplasmic reticulum (SR)

Muscle tissue that is multinucleate

skeletal

Muscle tissue that maintains posture, body position, and stabilizes joints

skeletal

Voluntary muscle tissue

skeletal

Which type of muscle tissue contracts most quickly upon stimulation?

skeletal

Muscle tissue that activates arrector pili muscles to stand hairs on end

smooth

Muscle tissue that dilates and constricts the pupils of our eyes

smooth

Performs very slow, sometimes rhythmic, contractions

smooth

Chemical that enters a muscle cell upon excitation

sodium ions

What must rush into a muscle cell to promote its depolarization?

sodium ions

Creatine phosphate functions within the muscle cells by

storing energy that will be transferred to ADP to resynthesize ATP as needed

Gap between the axon terminals and the plasma membrane of ta neighboring muscle cell

synaptic cleft

The gap between the axon terminal of a motor neuron and the sarcolemma of a skeletal muscle cell is called the

synaptic cleft

The condition of skeletal muscle fatigue can be best explained by

the inability of the muscle to contract even if it is being stimulated

A skeletal muscle twitch differs form a tetanic contraction in that

the muscle twitch is a brief and jerky movement, while the tetanic contraction is prolonged and continuous

Which of the following is composed mostly of the protein myosin?

thick filaments

(T/F) Depolarization of a skeletal muscle cell leads to the opening of more channels that only allow potassium entry

False

(T/F) Smooth muscles stabilize joints of the skeleton

False

Specific neurotransmitters that stimulate skeletal muscles cells

acetylcholine

A smooth, sustained contraction, with no evidence of relaxation, is called

fused, or complete, tetanus

What does anaerobic glycolysis require to make ATP?

glucose ONLY

Skeletal muscle, as a whole, can generate different amounts of force, and different degrees of shortening, in response to stimuli. What is this concept called?

graded response

What are the 3ish functions of the muscular system?

is responsible for body movements, maintains posture, stabilizes joints, and generates heat

Contractions in which muscles shorten and produce movement are known as

isotonic contractions

A motor neuron and all of the skeletal muscle fibers it stimulates are termed a

motor unit

One neuron and all the skeletal muscles it stimulates is known as a:

motor unit

An inherited disease that causes muscles to degenerate and atrophy is known as

muscular dystrophy