Muscular System

Which of the following motor units would allow for greater muscular control?

a motor unit made up of a motor neuron and five muscle fibers

Creatine phosphate

acts as an energy reserve in muscle tissue.

The muscle that works in opposition to another muscle is the __________.

antagonist

The biceps brachii muscle and the triceps brachii muscle

are antagonists

Actin myofilaments

are attached to Z lines at one end of the sarcomere

In skeletal muscle contraction and relaxation, Ca2+

are returned to the sarcoplasmic reticulum by active transport.

A condition known as flaccid paralysis

arises because acetylcholinesterase levels are artificially low.

Extensibility is the ability of skeletal muscle to

be stretched

Which of the following is NOT a typical effect of aging on the muscular system?

increase in the number of myofilaments in each fiber

The __________ is the end of a muscle attached to a bone undergoing the greatest movement.

insertion

In a resting cell, K+ ions have a higher concentration __________ the cell, which results in the net movement of K+ __________ of the cell.

inside; out

Which of the following muscles most likely contain motor units that are relatively small (motor neurons that innervate only a small number of muscle fibers each)?

intrinsic hand muscles

A single motor neuron and all the skeletal muscle fibers it innervates is called a __________.

motor unit

Connective tissue that surrounds the fasciculi is called __________.

perimysium

The normal resting cell membrane is the most permeable to

potassium ions

For any given movement, the __________ is a muscle in a group that plays a major role in the desired movement

prime mover

An anterior thigh muscle that extends the leg is the __________.

quadriceps femoris

Elasticity is the ability of skeletal muscle to

recoil to its original resting length

The characteristic that allows muscles to have a slow, smooth, sustained contraction is

recruitment of motor units

Excitability is the ability of skeletal muscle to

respond to a stimulus

The __________ is the functional unit of skeletal muscle because it is the smallest portion of the skeletal muscle capable of __________.

sarcomere; contracting

The __________ is the smooth ER of a muscle fiber and stores calcium ions.

sarcoplasmic reticulum

Contractibility is the ability of skeletal muscle to

shorten with force

Muscles that work together to cause movement are called __________.

synergists

The condition in which a muscle remains contracted between stimuli without relaxing is called a/an ___________.

tetanus

The primary muscle(s) responsible for elevating the ribs during inspiration is/are

the external intercostals.

The specific molecules that provide calcium-binding sites on actin are __________ molecules.

troponin

The __________ is attached to bones via tendons.

whole skeletal muscle

What are the relative concentrations of Na+, K+ and dissolved proteins in the intracellular solution (i.e., cytosol) as opposed to concentrations in the extracellular fluid?

↓ Na+, ↑ K+, and ↑ dissolved proteins inside the cell

Acetylcholine

- is the neurotransmitter at the neuromuscular junction - is broken down by acetylcholinesterase - binds to receptors on the muscle cell membrane - causes an influx of sodium ions into the muscle cell when bound to its receptor

Dr. Davis, your anatomy and physiology instructor, is conducting a field trip, and notices a dog approaching a fire hydrant. Always alert to instructional opportunities, he excitedly says, "Now watch as the dog utilizes his__________ and __________ muscles to lift his leg."

gluteus maximus; tensor fascia latae

The hip muscle commonly used as a site for injection is the __________.

gluteus medius

The anterior hip muscle that flexes the thigh is the __________

iliopsoas

Caffeine aids in the movement of calcium ions across cell membranes by both making it easier for the Ca2+ channels to open and by holding the channels open longer. How would the administration of caffeine to a muscle fiber affect its contraction?

- caffeine would increase the strength of the fiber's contraction - caffeine would allow more cross-bridges to form in the fiber - at high enough levels, caffeine would cause the muscle fiber to contract without a signal from the associated motor neuron

Muscle fibers

- have a relatively high metabolic rate - depend upon large amounts of O2 - contain large numbers of mitochondria - preferentially aerobic respiration

Pull-ups are easier to do with the hands supinated than with the hands pronated. An explanation for this is

- the briceps brachii is attached to the radial tuberosity - the biceps brachii supinates the forearm - if the forearm is pronated, the biceps brachii is ineffective in flexing the forearm - the brachialis is a much smaller muscle than the biceps brachii

Arrange the following events in the correct order that they occur during skeletal muscle contraction. 1) Calcium ions move along their concentration gradient. 2) Action potential occurs in cell membrane. 3) Ion channels open in sarcoplasmic reticulum. 4) Action potential moves along T tubules. 5) Actin to myosin cross-bridges form.

2,4,3,1,5

Most types of nerve gas exert their effect by inactivating acetylcholinesterase. One of the antidotes for nerve gas is atropine, which is also a poison. Although it may seem strange to have one poison counteract the effects of another poison, which of the following suggestions might be accurate for the effect that atropine has on the neuromuscular junction?

Atropine attaches to receptor sites for acetylcholine on the muscle cell membrane.

What ensures that one action potential in the neuron yields only one action potential in the skeletal muscle fibers of the stimulated motor unit and therefore only one contraction per fiber?

Enzymatic breakdown of acetylcholine by acetylcholinesterase

During muscle contraction, the actual length of the actin and myosin molecules changes

FALSE

The ____________ consists of only actin myofilaments.

I band

Which of these muscles is NOT a fixator of the scapula?

Latissimus dorsi

The myosin myofilaments are anchored in the center of the sarcomere by the __________.

M line

Which of the following statements is FALSE?

The concentration of NA+ is higher inside the cell than outside

Which of the following muscles are used to elevate the larynx?

The hyoid muscles

What would happen if the cell membrane suddenly became impermeable to potassium ions (K+)?

The cell would become more positively charged

Curare is a poison used by South American Indians. It is known to bind to ACh receptors, preventing the binding of ACh. What effect would curare have on muscle function?

The muscle fibers would not contract, because the NA+ channels, which cause depolarization of the muscle fiber membrane, are never signaled to open

The actin myofilaments are attached to the __________.

Z disks

Aerobic respiration

can use fatty acids and amino acids to generate ATP

A high-energy molecule that can be quickly used to produce ATP is __________.

creatine phosphate

A chemical that is considered an acetylcholine antagonist

decreases or prevents the activity of acetylcholine

The major abductor of the upper limb is the __________.

deltoid

Cardiac muscle

is under involuntary control.

Which of the following characteristics would establish conclusively that muscle tissue being examined was skeletal muscle tissue?

many nuclei per cell

The __________ is a group of muscle fibers surrounded by perimysium

muscle fascicle

A _________ is a single muscle cell.

muscle fiber

The muscles of domesticated chickens represent the differences between fast-twitch and slow-twitch muscle fiber well. Chickens do not fly long distances but rather have burst of flight so they can quickly move away from danger. The muscles for flight (breast muscles) are lighter in color than the muscles for walking and running (leg muscles). Which types of muscle fibers are found in each area?

muscles for flight are composed of fast-twitch muscle fibers and muscles for walking and running are composed primarily of slow-twitch muscle

If someone winks at you, they are using their

orbicularis oculi

In a neuromuscular junction,

the presynaptic terminal is separated from the postsynaptic terminal by the synaptic cleft.

Organophosphates cause spastic paralysis because

they prevent the muscles from relaxing

A muscle fiber will not respond to a stimulus until that stimulus reaches

threshold level