A & P 10

The characteristic of muscle that allows it to be passively stretched is:

extensibility

Which are possible functions of skeletal muscles?
a: Maintenance of posture
b: Both highly coordinated and localized simple movements
c: Temperature regulation
d: Support of certain body organs
e: Regulation of the movement of material through certain body tracts

a, b, c, d, e

A skeletal muscle cell can be several inches long. The property of muscle tissue that allows an impulse to travel down the entire length of the cell membrane is:

conductivity

The spring-like property that returns muscle to its original length after a contraction ends is:

elasticity.

In general, a skeletal muscle is composed of:
a: connective tissue sheaths
b: nerves
c: arteries
d: veins
e: muscle fibers

a, b, c, d, e

Which is a correct listing of the hierarchy of a skeletal muscle’s components, beginning with the smallest?
a: Myofibrils
b: Muscle fiber
c: Fascicle
d: Skeletal muscle

a, b, c, d

Which is the correct order of the connective tissue layers of a skeletal muscle, beginning with the outermost first?
a: Endomysium
b: Epimysium
c: Perimysium

b, c, a

The structure responsible for attaching muscle to bone is a

tendon.

A flat, thin structure made of dense connective tissue that serves to attach a muscle to a bone (or to another muscle) is a(n):

aponeurosis.

The neurons that stimulate muscle contraction are called _____ neurons.

motor

The multiple nuclei in skeletal muscle cells are the result of the:

fusion of myoblasts.

The membranous network that wraps around myofibrils and holds relatively high concentrations of calcium is known as the:

sarcoplasmic reticulum.

Invaginations of the muscle cell membrane that extend deep into the cell are known as the:

T-tubules.

Which are the reservoirs that store the calcium required for muscle contraction?

Terminal cisternae

Which protein makes up the thick filaments?

Myosin

Which is not a protein found in thin filaments?

Sarcomyosin

Each thick filament contains about ______ protein molecules (each molecule has two heads and two braided tails).

200

A skeletal muscle cell contains hundreds to thousands of _________, which are complex organelles; they are cylindrical in shape–about 2 micrometers in diameter and as long as the cell.

myofibrils

What is the letter associated with the dark bands in a sarcomere?

A

Which letter is associated with the line that is a thin protein structure that serves as an attachment site for thin filament ends?

Z

Which letter is associated with a zone (in a relaxed muscle) that is a little more lightly shaded because only thick filaments are present?

H

Which letter is associated with the light band and contains thin filaments only?

I

Which of the myofilaments of a muscle fiber has the active sites to which the heads of the thick filaments will bind?

Actin

A sarcomere is defined as the distance from one _____ to the next adjacent ____ . (The same answer fills in both spaces.)

Z disc

Myoglobin is a molecule within muscle cells that can bind:

oxygen

A typical skeletal muscle cell contains approximately _____ mitochondria.

300

The presence of mitochondria and myoglobin facilitate _________ respiration in muscle cells.

aerobic

One feature that helps provide fast energy to a muscle cell is the presence of granules containing the complex carbohydrate:

glycogen

A motor unit consists of:

a single motor neuron and the multiple muscle fibers it controls.

A motor unit within the powerful quadriceps muscle would:

generally contain several hundred fibers.

Fibers from one motor unit:

are dispersed throughout most of the muscle.

The narrow space that separates the motor neuron and the skeletal muscle fiber in a neuromuscular junction is called the:

synaptic cleft.

Which structures are reservoirs that store acetylcholine?

Synaptic vesicles

When an impulse arrives at the knob of the motor neuron, calcium:

enters through voltage-gated channels and triggers the release of transmitter.

The way acetylcholine is released from a neuron is:

through exocytosis when a vesicle fuses with the membrane.

Acetylcholine exerts its effect by:

binding to receptors at the motor end plate.

Which is the neurotransmitter that causes the release of calcium ions from reservoirs within the muscle cell and thereby initiates the steps of contraction?

Acetylcholine

The calcium ions involved in skeletal muscle contraction bind to a(n)______ subunit.

troponin

An end plate potential is an event that involves a gain of:

positive charge for the cell, as sodium rapidly enters.

The action potential of a muscle fiber occurs:

along the sarcolemma and down the T-tubules.

The repolarization of the action potential involves the opening of:

voltage-gated K+ channels.

Which sequence correctly lists the changes that allow the thick and thin filaments to slide past one another in skeletal muscle contraction?

Attach – pivot – detach – return

During which phase of the crossbridge cycle is ATP split into ADP and Pi?

Immediately preceding the resetting of the myosin head

A power stroke involves:

a myosin head pulling a thin filament toward the center of the sarcomere.

A drug that inhibited acetylcholinesterase would result in:

enhanced stimulation of the muscle due to decreased Ach breakdown.

For relaxation to occur:

Ach receptors close and Ca++ channels on the sarcoplasmic reticulum close.

For relaxation to occur:

sarcoplasm calcium levels fall, calcium is removed from troponin, and tropomyosin blocks binding sites on actin.

When a muscle relaxes:

crossbridges stop forming and muscle elasticity returns the muscle to rest length.

The phosphagen system is used for:

immediate ATP needs and is not dependent on oxygen.

Glycolysis is an:

anaerobic process that occurs in the cytosol.

The net energy yield from one glucose molecule through the process of glycolysis is:

2 ATP.

For a sprint lasting 60 seconds, ATP is supplied initially by:

the phosphagen system but primarily by glycolysis.

Oxidative fibers are:

red and fatigue-resistant.

The type of fibers specialized to continue contracting for extended periods of time, as would be required in running a marathon, for example, are _____ fibers.

slow

The vascular supply to slow muscle fibers is ______ the network of capillaries around fast muscle fibers.

more extensive than

"Intermediate fibers" is another name for:

fast, oxidative fibers.

Which fibers dominate many of the back and calf muscles that contract almost continually to maintain posture?

Slow

Muscles of the eye and hand have a high percentage of _______ fibers.

fast

Events of excitation contraction coupling, such as the release of calcium from intracellular stores, occur during the ________ period of a muscle twitch.

latent

Release of crossbridges and a decline in muscle tension characterize the _______ period of a twitch.

relaxation

The increase in muscle tension that occurs with an increase in the intensity (voltage) of a stimulus is called:

recruitment.

Consider the difference between lifting a light pad of paper versus a heavy text book. The primary way the level of force of muscle contraction is controlled is by:

recruiting a different number of motor units.

"Staircase" and "warm up" are alternative names for ___________, an increased muscle response to a constant stimulus.

treppe

In a lab, wave summation is demonstrated by increasing the _________ of the stimulus.

frequency

Muscle tone is a result of _________ nervous system activity, and it acts to _________ joint position.

involuntary, stabilize

Which contraction occurs when you try (unsuccessfully) to move a wall?

Isometric

When a muscle is isometrically contracted, its length _______ change.

does not

The top long distance runners probably have _______ proportion of slow muscle fibers in their leg muscles.

a higher

The most prevalent of skeletal muscle fibers in the body are _____ fibers.

fast

One of the reasons you might struggle to lift a heavy object if you tried to lift it with your arm at a fully extended posture is that:

full extension results in decreased overlap between thick and thin filaments in the muscle.

Increased phosphate ion concentration is believed to contribute to fatigue by interfering with:

phosphate release by myosin heads during crossbridge cycling.

Which may occur as a result of muscle atrophy?

Reduction in muscle size incorrect Fibers become weaker Muscle loses tone Fibers waste away and die

With increased age, skeletal muscles show:

a decrease in the number of myofibrils.

The main way a body builder’s muscles become larger is:

by an increase in the size of muscle cells.

A term that describes the change in muscle following a lack of exercise is:

atrophy.

The type of muscle fibers that have only a single nucleus, both thick and thin filaments, but no Z discs, are:

smooth.

Growth of the uterus during pregnancy is accomplished by _________ of its smooth muscle.

both hypertrophy and hyperplasia

The latchbridge mechanism of myosin heads is a property of ________ muscle.

smooth

To initiate a smooth muscle cell contraction, calcium enters the cell and binds to:

calmodulin, which then binds to and activates myosin light chain kinase.

The branch of the nervous system that helps govern smooth muscle contraction is the _______ nervous system.

autonomic

When smooth muscle is stretched for a prolonged period of time, it responds by:

relaxing.

Smooth muscle tissue in which cells are individually sent signals to contract (rather than contracting in unison) is referred to as:

multiunit.

The iris of the eye contains:

multiunit smooth muscle.

The most abundant form of smooth muscle is:

single-unit, which is also known as visceral smooth muscle.

Rather than tightly coupled synapses between neurons and muscle cells, single-unit smooth muscle contains:

diffuse junctions where neuron varicosities are responsible for neurotransmitter release.

This sarcomere depicts relaxed muscle. Number 1 denotes the

A band

This sarcomere depicts relaxed muscle. The M line is noted by number

4

The type of muscle fibers that are striated, form Y-shaped branches, and have junctions called intercalated discs are:

cardiac.