Chapter 8 Exercise Physiology

The most obvious function of skeletal muscle is to _____

enable an individual to move freely and breathe

The innermost layer of connective tissue that surrounds individual muscle fibers is called

endomysium

Identify a true statement about the sarcolemma.

It surrounds the muscle fiber cell.

In response to resistance exercise training, _____ become activated and divide; this increases the number of nuclei in the muscle fiber

satellite cells

In order to maintain a constant myonuclear domain within skeletal muscle fibers, new nuclei are obtained and incorporated from ___

satellite cells

Identify the functions performed by skeletal muscles. (Select all that apply.)

Heat production during cold stress
Force generation for locomotion and breathing
Force generation for postural support

Within the sarcoplasm, there are numerous threadlike structures that contain contractile proteins. These are called ___

myofibrils

Match the layers of connective tissue (in the left column) with their locations in the skeletal muscle (in the right column).

Epimysium: It surrounds the entire muscle.
Perimysium: It surrounds individual bundles of muscle fibers.
Endomysium: It surrounds each muscle fiber within the fasciculus.

The cell membrane surrounding a muscle fiber cell is called the

sarcolemma

The two proteins located on the actin molecule that play an important role in the regulation of muscular contraction are ___

troponin and tropomyosin

Satellite cells play a key role in muscle growth and repair, because they are _____ cells

undifferentiated

The volume of cytoplasm surrounding an individual nucleus is termed the

myonuclear domain

The site where a motor neuron and a muscle cell meet is called the

neuromuscular junction

Myofibrils are composed of a thick protein filament and a thin protein filament called

myosin and actin

The sliding filament model of muscle contraction is also called the _____ of muscle contraction.

swinging lever-arm model

True or false: The majority of a muscle is made up of the proteins troponin and tropomyosin.

False. These proteins make up only a small portion of the muscle, but they play an important role in the regulation of the contractile process.

The energy for muscular contraction comes from the breakdown of adenosine triphosphate (ATP) by the enzyme

myosin ATPase

The pocket formed by the sarcolemma at the neuromuscular junction is called the

synaptic cleft

During the excitation process, depolarization of the muscle results in the

release of calcium from the sarcoplasmic reticulum

The process of muscular contraction is explained by the _____ model of contraction

sliding filament

is defined as a reduction in muscle power output that can result from a decrease in both muscle force generation and shortening velocity

Muscle fatigue

The breakdown of adenosine triphosphate and the release of energy serves to energize the

myosin cross-bridges

True or false: A potential cause of increased motor neuron excitability includes high levels of excitatory input to the motor neurons

True

Muscle fibers classified as type I and type II are also known as _____ fibers

slow twitch and fast twitch

In the excitation process, the binding of the neurotransmitter to receptors on the motor end plate leads to the

depolarization of the muscle cell

Identify factors that determine the oxidative capacity of a muscle fiber. (Select all that apply.)

The number of capillaries surrounding the fiber
The amount of myoglobin within the fiber
The number of mitochondria

Muscle fibers that have a high aerobic capacity will be fatigue resistant during

prolonged bouts of submaximal exercise

High-intensity exercise or prolonged, submaximal exercise results in a decline in the muscle's ability to generate power. This decrease is called

fatigue

Myosin isoforms influence muscle performance because they differ in

their myosin ATPase activity

Which of the following statements are true of exercise-induced muscle cramps

Experimental evidence suggests that exercise-induced muscle cramps can occur due to changes in the central nervous system.
Experimental evidence does not support the notion that dehydration is the most common cause of muscle cramps.

Human skeletal muscle can be divided into major classes based on the histochemical and biochemical characteristics of the individual fibers. These two general categories are _____ fibers.

type I and type II

Fibers that contain large amounts of actin and myosin

generate more force

The amount of myoglobin within a fiber influences its oxidative capacity because myoglobin

is similar to hemoglobin in that it binds oxygen

The contraction speed of muscle fibers is compared by measuring the maximal shortening velocity (called V max). V max is determined by the rate of

cross-bridge cycling

A muscle fiber with a high concentration of myoglobin, along with a high number of mitochondria and capillaries, will have a high _____ capacity

aerobic

Which of the following is true of muscle fibers with a high force generating capacity and a fast shortening velocity

They produce a high power output.

Muscle fibers that contain ATPase isoforms with high ATPase activity will degrade ATP rapidly and result in a high speed of

muscle shortening

The efficiency of a fiber is calculated by dividing the amount of energy used by the

amount of force produced

Identify the true statements about the difference between slow (type I) muscle fibers and fast (type II) muscle fibers. (Check all that apply.)

Slow (type I) muscle fibers have a higher resistance to fatigue than fast (type II) muscle fibers.
Slow (type I) muscle fibers have a larger capacity for aerobic metabolism than fast (type II) muscle fibers.

The contractile properties of muscle fibers are influenced by the

abundance of contractile proteins

Type II fibers have a limited capacity for aerobic metabolism because they

have a relatively smaller number of mitochondria

The key biochemical factor that regulates fiber V max is the

myosin ATPase activity

The maximal power output of a muscle fiber is defined as the product of force generation multiplied by the

shortening velocity

The fastest muscle fiber in human skeletal muscle is the _____ fiber.

type IIx

An efficient fiber would require _____ to perform a certain amount of work

less ATP

When compared to fast type II muscle fibers, slow type I muscle fibers, also known called slow-oxidative or slow-twitch fibers have

higher efficiency

Type II muscle fibers, also known as fast-twitch fibers are

rich in glycolytic enzymes

True or false: The term "muscle action" is now used to describe only shortening muscular contractions.

false

There is a quicker release of energy in fast fibers because of higher

ATPase activity

The myosin ATPase activity in type IIx fibers is higher than other fiber types, resulting in the highest _____ of all fiber types

V max

As the frequency of neural stimulation to a muscle is increased, the muscle does not have time to relax between stimuli, and the force produced is additive. This response of addition of successive twitches is called

Summation

The average sedentary man or woman possesses approximately _____ slow fibers

50%

At any absolute force the speed of movement is greater in muscles with a high percentage of _____ fibers

fast twitch

The term that has been proposed to describe the process of muscle force development is known as

muscle action

The speed of shortening is greater in fast fibers than in slow fibers, because the sarcoplasmic reticulum in fast fibers releases _____ at a faster rate

calcium ions

If the frequency of stimuli is increased past summation, individual contractions are blended in a single, sustained contraction called

tetanus

Match the type of athletes (in the left column) with their typical fiber make up (in the right column).

Power athletes: Large percentage of fast fibers
Endurance athletes: Large percentage of slow fibers

For both fast and slow fibers, the maximum velocity of shortening is greatest at the

lowest

True or false: The term "muscle action" is now used to describe only shortening muscular contractions

false