A&P chapter 9

During muscle contraction, ATP supplies energy for

Myofilament movement

Name the connective tissue that separates a skeletal muscle into fascicles

Perimysium

An electrical impulse traveling along the sarcolemma and into the transverse tubules causes calcium ions to diffuse from the ______into the_______

Sarcoplasmic reticulum; sarcoplasm

What happens to the A band in a contracted muscle

The A bands do not change length

What is the I band?

The area with thin filaments only; no thick filaments

The functional unit of muscle contraction is

The sarcomere

People with myasthenia gravis have a deficiency of

acetylcholine receptors

A gluteal gait, in which a person walks with a waddling limp, is usually caused by a disorder of the

gluteus medius, gluteus minimus

Both acetylcholine and norepinephrine can affect

smooth muscle contraction

transverse tubules

transmit muscle impulses into the cell interior.

The striations seen in skeletal muscles consist of alternating dark bands called the _________bands , and light bands called the _______bands.

A; I

As strenuous activity begins, muscle cells first use the ______molecules present in their cytoplasm as their source of energy. The supply of this molecule, however, is limited. It must be produced by other means in order for exercise to continue.

ATP

Tawanda finishes a sprint and suffers great pain in her calf muscles. Her muscle cramps are most likely due to a temporary deficit of

ATP

Myosin heads directly use __________ to transition to their __________ conformation, which enables them ready to bind to actin.

ATP; energized

The chemical used at the junction with a skeletal muscle cell is

Acetylcholine

What is the first event in muscle fiber contraction

Acetylcholine is released from the end of the motor neuron

Neurotransmitters

Acetylcholine molecule

Location of binding sites for myosin

Actin

How does an electrical impulse travel into the interior of a muscle fiber

By way of transverse tubules

1. The layer of connective tissue that closely surrounds a skeletal muscle is called the

Epimysium

which muscle group is composed of mainly slow twitch (typeI) fibers

Erector spinae muscles of the back

cardiac muscle

Excites itself

The presence of calcium in the sarcoplasm is directly responsible for______

Exposing the binding sites on actin

As exercise continues, the cells now begin to use______ as a fuel to produce ATP. Initially, the anaerobic pathway called______ uses this fuel to produce 2 ATP and 2 molecules of pyruvic acid.

Glucose; glycolysis

In a recording of a muscle twitch, the delay between the time a stimulus is applied and the time the muscle responds is called the

Latent period

Site of ATP production

Mitochondrion

Location of receptors for neurotransmitters

Motor end plate

A weightlifter uses muscles so the muscles exert more than 75% of their maximum tension, this stimulates

Muscle fibers developing new filaments of actin and myosin.

An example of a partial but sustained contraction would be

Muscle tone

The electrical impulse that moves over the surface of a muscle fiber and into the T-tubules results from increased membrane permeability to what ion?

Sodium

The point of communication between a motor neuron and a muscle fiber is called a

Synapse

Define muscle tone

The state of partial contraction of resting muscles

What is the name of the neurotransmitter used at a skeletal neuromuscular junction

acetylcholine

Myofibrils are composed of

actin and myosin

myasthenia gravis is

an autoimmune disorder

The muscle that opposes a particular action is called

antagonist

A muscle fiber exposed to a series of stimuli of increasing frequency combines individual twitches (summation) which results in

complete sustained contraction.

If there was a high concentration of acetylcholine within the synaptic cleft, but little to no response at the motor end-plate, you would expect ________________ to be the responsible neuromuscular-blocking agent.

curare

What is the A band?

length of the myosin filament

Site of ATP production

mitochondria

The antidote that holds the most promise to counteract the effects of tubocurarine is one that _________________________.

modifies acetylcholine receptors so that they bind acetylcholine stronger than tubocurarine

At a neuromuscular junction, the muscle fiber membrane folds, forming a

motor end plate

Place in order, from largest to smallest, the components of a skeletal muscle

muscle, fascicle, muscle fiber, myofibril, myofilaments

The characteristic reddish brown color of skeletal muscle comes from which substance

myoglobin

Forms cross bridges

myosin

Botulinum toxin causes muscle paralysis because

no acetylcholine enters the synaptic cleft

Facial wrinkles, such as glabellar or "frown" lines, appear with aging as a result of natural, repetitive muscle contractions. Botox® helps alleviate the appearance of these wrinkles by _________________.

relaxing the facial muscles that cause the wrinkles

Plasma membrane of muscle fiber

sarcolemma

The striated appearance of skeletal muscle results from the

sarcomere organization

creatine phosphate

supplies energy for the synthesis of ATP

Acetylcholine (ACh) is released from motor neurons and enters the

synaptic cleft

Space between axon and muscle fiber

synaptic cleft

A muscle that assists the agonist is a(n)

synergist

Blocks myosin binding sites

tropomyosin

Calcium ions bind to _____ in order to initiate a muscle contraction

troponin

In what type of muscles does some of the calcium needed for contraction come from the extra cellular fluid?

Cardiac muscle and visceral smooth muscle

The structures that connect cardiac muscle cells are

Intercalated discs

Which of the following best describes the role of calcium in muscle contraction

It binds to troponin, moving tropomyosin, so that myosin heads can bind to actin.

Describe the role of acetylcholinesterase in stimulation of a muscle fiber

It is the enzyme that breaks down acetylcholine in the synaptic cleft, ending stimulation of the muscle fiber

The binding of the chemicals to the muscle cell causes a electrical impulse to travel across the sarcolemma and down the _____tubules

Transverse

The triangle of auscultation, commonly used to hear sounds of respiratory organs, is located near the border of the

Trapezius and latissimus dorsi

In order for a skeletal muscle fiber to contract, calcium must bind to_____

Troponin

If little or no oxygen is available, pyruvic acid is converted to_______. If, however oxygen is available the pyruvic acid molecules enter the aerobic respiration pathways

Lactic acid

The chemicals then bind to receptors located on the _______, a specialized area of the sarcolemma

Motor end plate

At this neuromuscular junction, a ________releases a type of chemical called a neurotransmitter.

Motor neuron

Provides stimulation to the muscle fiber

Motor neuron axon

In order for muscle contraction to occur, cross- bridges for between

Myosin and actin

During the contraction cycle, what is the result of ATP binding to myosin

Myosin heads release from the binding sites on actin

Acetylcholine causes an end plate potential by triggering the

Opening of sodium channels

At what level of organization is a skeletal muscle such as the biceps brachii

Organ

2.Another layer of connective tissue, called the_______, extends inward from the epimysium and separates the muscle tissue into groups of muscle fibers. These groups are called ________.

Perimysium; fascicles

Functions of the muscles include

Pumping blood

At neuromuscular junctions, acetylcholine binds to

Receptors in the muscle fiber membrane

Which of the following is not true

Red fibers have fewer mitochondria than white.

The discoloration and swelling that occurs with a muscle strain is due to

Ruptured blood vessels

Muscle fibers are basically a collection of

Sarcomeres

Compared to skeletal muscle, smooth muscle is ______ to contract and _______to relax

Slower; slower

These chemicals diffuse across a small gap between the neuron and muscle fiber called the

Synaptic cleft

What is the name of the space between a motor neuron and a muscle fiber at the neuromuscular junction

Synaptic cleft

Storage of neurotransmitters

Synaptic vesicles

What happens to the H zone in a contracted muscle

The H zones shorten

What happens to the I bands in a contracted muscle

The I bands shorten

What is the H zone?

The area with thick filaments only; no thin filaments

Location of binding sites for calcium

Troponin

The amount of oxygen needed to repay the oxygen debt includes the amount of oxygen that muscle cells need to resynthesize ATP.

True

Transverse tubules (T-tubules) are invaginations of the sarcolemma of a muscle cell

True

Thin filaments connect and extend from either side of a _______. These thin filaments are composed largely of the myofilament ________.

Z disc; actin

As long as oxygen is available, the oxidation of each glucose molecule using ______ metabolism will produce, in total,______ATP molecules

aerobic; 30

The muscle that causes an action is the

agonist

An action, such as flexing the knee, is caused by the contraction of a muscle acting as an ______ and is opposed by a muscle acting as an ______.

agonist and antagonist

If it were possible to move the terminal cisternae further away from the T-tubules. It would

interfere with the signal required for the release of calcium from the sarcoplasmic reticulum

Fibers of muscles whose motor neurons are severed

may be replaced by fat or fibrous connective tissue

A threshold stimulus is the

minimum strength of stimulation required to contract a muscle fiber

Threadlike bundles of thick and thin filaments

myofibril

Functional unit of contraction within muscle fiber

sarcomere

cytoplasm of a muscle fiber

sarcoplasm

Site for storage of calcium

sarcoplasmic reticulum

Regina began an exercise program six months ago, and the muscles of her upper limbs and lower limbs are more prominent. Exercise can lead to formation of new muscle by

stimulating skeletal muscle cells to release IL-6, which stimulates satellite cells to divide, producing more muscle cells.

Which of the following describes smooth muscle contraction but not skeletal muscle contraction

Hormones can inhibit muscle contraction

Hundreds of mutations have been identified in RyR1 that contribute to multiple muscular diseases. Assume that a new mutation was discovered that causes this receptor to continually remain open. Based on what you know about the function of this receptor, how would you expect this new mutation to impact contraction?

this mutation will increase levels of calcium in the sarcoplasm, which will induce continued muscle contraction

Channel formed by invagination of plasma membrane

transverse (T) tubule

When myosin heads form cross bridges during muscle contractions, they bind to binding sites found on _______, a component of thin filaments.

Actin

Choose the correct statement about muscle contraction

Actin filaments slide along side myosin filaments

The two types of myofilaments are thin filaments, composed primarily of the protein _______. And thick filaments composed of ________.

Actin; myosin

Describe how action potentials travel from the sarcolemma into the interior of the muscle fibers, resulting I. The release of calcium ions into the sarcoplasm.

Action potentials travel along T tubles

What are intercalated discs that are found in cardiac muscle

Complex membrane junctions that include desomones and gap junctions

Which of the following statements describes myofibrils

Comprised of thick and thin filaments

4. Therefore, as described, layers of _________ enclose and separate the various parts of a skeletal muscle.

Connective tissue

The muscle that adducts and flexes the arm is the

Coracobrachilias

In order to produce ATP, the muscle cells next start to use__________, also present in the cytoplasm, to form new ATP. This is done by moving a phosphate and it's energy from this molecule to ADP, forming new ATP.

Creatine phosphate

What happens to each sarcomere during contraction

Each sarcomere shortens

3. Each muscle fiber within a fascicle is surrounded by a thin covering called a

Endomysium

Rigor mortis occurs after death because

detachment of crossbridges does not occur due to the lack of ATP