Chapter 9 - Muscles and Muscle Tissue

Skeletal muscle is made up of several kinds of tissues. Skeletal fibers mainly but also what three other things?

1. Blood vessels 2. Nerve fibers 3. and Connective tissue.

Their diameter ranges from ______ times that of an average body cell and their length is phenomenal.

10

How many hours after death does rigor mortis usually begin?

3-4 hours post mortem

Smooth muscle takes ____x longer to contract and relax than skeletal.

30

How much ATP is stored in the body?

4-6 seconds worth

Only about ___% of the energy released during muscle contraction is converted to useful work.

40

Skeletal muscle accounts for about what percent of body mass?

40%

Myofibrils account for how much of cellular volume?

80%

What is a recording of contractile activity of a muscle?

A myogram

Chemical transmitter substance released by some nerve endings.

ACh or Acetylcholine

Junctional folds provide a large surface area for the millions of _____ ______ located there and includes the axon terminals, the synaptic cleft, and the junctional folds of the sarcolemma.

ACh receptors

Enzyme present at the neuromuscular junction and synapses that degrades acetylcholine and terminates its action.

AChE or Acetylcholinesterase

There are slow and fast fiber types and this is based directly on how fast their myosin ATPases split ____.

ATP.

Thin filaments are composed mainly of the protein ______.

Actin

The _____ ________ is automatically propagated along the sarcolemma. Then, intracellular calcium ion levels must rise briefly providing the final trigger for contraction.

Action potential

To induce contraction the fiber must be stimulated by a nerve ending so that a change in membrane potential occurs. Next it must generate an electrical current called ______ ________ in its sarcolemma.

Action potential

The length of time a muscle can continue to contract using aerobic pathways is called _______ _______ .

Aerobic endurance.

The point at which muscle metabolism converts to anaerobic glycolysis is called _____ ______.

Anaerobic threshold

Peak rigidity occurs when after death?

At 12 hours

What is the word for "degeneration and loss of mass"?

Atrophy

In smooth muscle, there's an intermediate filament-dense _______ network.

Body

Skeletal muscles span joints and attach to _________ in at least how many places?

Bones, at least two.

Somatic Motor Neurons reside in the _______ or _______ _______.

Brain or Spinal Cord.

In smooth muscle, calcium activates myosin by interacting with a regulatory molecule called _______, which is a cytoplasmic calcium-binding protein.

Calmodulin.

Which kind of muscle occurs only in the heart?

Cardiac

What muscles helps maintain blood pressure?

Cardiac and smooth

Key words to remember when it comes to cardiac muscle are:

Cardiac, striated, involuntary.

In smooth muscle, T tubules are absent, but sarcolemma has multiple _______, pouchlike infoldings that sequester bits of extracellular fluid containing a high concentration of Ca close to the membrane.

Caveolae

Somatic Motor Neurons reside in the brain or spinal cord but their axons travel to ________.

Cells

Where is their nucleus located?

Centrally

In the _______ layer, the fibers run around the circumference of the organ. Contraction of this layer constricts the lumen of the organ and elongates the organ.

Circular

When maximal tension is reached and the contractions fuse into a smooth, sustained contraction plateau this is called _______ ______.

Complete tetanus.

________ contractions are those in which the muscle shortens and does work. (Picking up a book, kicking a ball.)

Concentric

What are the two different "flavors" of Isotonic contractions?

Concentric and Eccentric

The response that generates an electrical impulse that travels along the plasma membrane of the muscle cell and causes the cell to contract is known as:

Conductivity

The ability to shorten forcibly when adequately stimulated (which sets muscle apart from other tissue types) is known as:

Contractility

Both tropomyosin and troponin help control the myosin-actin interations involved in __________.

Contractions.

_________ phosphate a unique high energy molecule stored in muscles, is tapped to regenerate ATP while the metabolic patheways adjust to the suddenly higher demand for ATP. (When you start working out)

Creatine

Muscle cells store 2-3x more CP than aTP. The CP-ADP reaction catalyzed by the _______ _______ kinase, is so efficient that the amount of ATP in muscle cells changes very little during the initial period of contraction.

Creatine kinase

Coupling CP with ADP transfers energy and a phosphate group from CP to ADP to form ATP almost instantly.

Creatine phosphate + ADP ---->creatine +ATP

These _______ ________ attachments form and break several times during a contraction, acting like tiny ratchets to generate tension and propel the thin filaments toward the center of the sarcomere.

Cross Bridge

The globular heads link the think and thin filaments together forming _____ _______, which swivel around the point of attachment.

Cross bridges.

The dark ____ bands and light ____ bands are nearly perfectly aligned, giving the cell its striated appearance.

Dark - A bands, light I bands.

In smooth muscle, thick and thin filaments arranged _________.

Diagonally.

The varicosities release neurotransmitter into a wide synaptic cleft in the general area of the smooth muscle cells. Such junctions are called _____ ______.

Diffuse junctions

In ________ or _______ ___________, the epimysium of the muscle is fused to the periosteum of a bone or perichondrium of a cartilage.

Direct, fleshy attachments

Most common and serious form of muscular dystrophy which is inherited as a sex-linked recessive disease. Almost exclusively in males.

Duchenne muscular dystrophy

Why does rigor mortis occur?

Dying cells are unable to get rid of calcium. Actin and myosin become cross-linked which produce the stiffness which eventually fades as the proteins break it down after death.

Links the thin filaments to the integral proteins of the sarcolemma (which in turn are anchored to the extracellular matrix.

Dystrophin

In _________ contractions the muscle generates force as it lengthens, and are equally important for coordination and purposeful movements.

Eccentric

The ability of a muscle cell to recoil and resume its resting length after stretching is called:

Elasticity.

"Within the muscle"

Endomysium

A wispy sheath of connective tissue that surrounds each individual muscle fiber. It consists of fine areolar connective tissue.

Endomysium

"Outside the muscle"

Epimysium

An "overcoat" of dense irregular connective tissue that surrounds the whole muscle. Sometimes blends with deep fascia that lies between neighboring muscles or the superficial fascia deep to the skin. Meaning "outside the muscle"

Epimysium

What are the four special characteristics of muscle tissues?

Excitability or responsiveness, contractility, extensibility, and elasticity.

The ability to receive and respond to a stimulus or chance in internal or external environment is known as:

Excitability.

Why does muscle fatigue happen? Most experimental evidence indicates that fatigue is due to a problem in _____-_______ ________ or in rare cases problems at the neuromuscular junction.

Excitation-contraction coupling

______-_______ ______ is the sequence of events by which transmission of an action potential along the sarcolemma leads to the sliding of myofilaments.

Excitation-contraction coupling

Contraction of smooth muscle in the rectum, urinary bladder, and uterus helps those organs to ______ their contents.

Expel

The ability to extend or stretch is known as:

Extensibility

These in turn become taut and transfer their tension, called the _____ _____ to the load (muscle insertion).

External tension

T/F Cardiac muscles are not striated.

False. Cardiac muscle cells are striated.

"Bundles"

Fascicles

What is the role of smooth muscle tissue?

Force fluids and other substances through internal body channels.

How many distinct special characteristics does muscle tissue have?

Four

When does rigor mortis start dissipating?

From 48-60 hours after death.

Produces movement, maintains posture, stabilizes joints, generates heat.

Functions of muscles and muscle tissues.

Each myosin molecule consists of two heavy and four light polypeptide chains and has a rodlike tail attached by a flexible hinge to two _______ ______.

Globular heads.

Initial phase of glucose breakdown is called ______.

Glycolysis.

Those that rely more on anaerobic glycolysis are ________ fibers.

Glycolytic

What are granules of stored glycogen that provide glucose during muscle cell activity?

Glycosomes

Healthy muscle contractions are relatively smooth and vary in strength. They are referred to as ______ _____ _______.

Graded muscle responses.

Each dark A band has a lighter region in its midsection called the ________ zone.

H zone.

What do muscles generate as they contract?

Heat

All muscle cells can hypertrophy (increase in cell size), but certain smooth muscle fibers can also undergo ______ that is, they divide to increase their numbers.

Hyperplasia

Smooth muscle tissue is usually found where in the body?

In the walls of hollow visceral organs, such as stomach, urinary bladder, and respiratory passages.

If the degree of wave summation becomes greater and greater, progressing to a sustained but quivering contraction referred to as unfused or _____ ______.

Incomplete tetanus.

Aerobic, or endurance exercise causes changes in skeletal muscles. The number of capillaries in the muscle fibers _______. The number of mitochondria ________. And fibers synthsize more ______.

Increases. Increases. Myoglobin.

In ____________ _____________ the muscle's connective tissue wrappings extend beyond the muscle either as a ropelike tendon or as sheetlike aponeurosis.

Indirect attachments

Which kind of attachments are more common and why?

Indirect attachments are more common because of their durability and size.

When a muscle contracts, the movable bone, or the muscle's __________ moves toward the immovable, or less movable bone, the muscle's origin.

Insertion, origin.

Skeletal muscles also protect what by enclosing them?

Internal organs (the viscera)

As a muscle begins to contract, the force generated by the cross-bridges-the ____ _____- stretches the connective tissue sheaths. (Noncontractile components)

Internal tension

Is cardiac muscle voluntary or involuntary?

Involuntary. It contracts without being stimulated by the nervous system. We have no control over how fast our heart beats.

Is smooth muscle voluntary or involuntary?

Involuntary. It's contractions are slow and sustained.

If muscle tension develops but the load is not moved, the contraction is called _________.

Isometric

In _________ contractions tension may build to the muscles peak tension-producing capacity, but the muscle neither shortens nor lengthens. They occur when a muscle attempts to move a load greater than the force the muscle is able to develop.

Isometric

If muscle tension developed overcomes the load and muscle shortening occurs, the contraction is called ________.

Isotonic

What kind of contraction occurs when muscle length changes and moves a load?

Isotonic

When muscles contract vigorously and compress the blood vessels within them, which impairs blood flow and oxygen delivery, under anerobic conditions, most of the pyruvic acid is converted into ____ ____ and the overall process is referred to as anerobic glycolysis.

Lactic acid

The _____ _____ is the first few milliseconds following stimulation when excitation-contraction coupling is occurring. Cross bridges begin to cycle but muscle tension not yet measurable and myogram shows no response.

Latent period.

The opposing force exerted on the muscle by the weight of the object to be moved is called the _____.

Load.

In the ___________ layer, the muscle fibers run parallel to the long axis of the organ. When these fibers contract, the organ dilates and shortens.

Longitudinal

Each H zone is bisected vertically by a dark line called the

M Line

The _______ ________ is the strongest stimulus that increases contractile force. It represents the point at which all the muscles motor units are recruited.

Maximal stimulus

Aerobic respiration occurs in the ________, requires oxygen, and involves a sequence of chemical reactions that break the bonds of fuel molecules and release energy to make ATP.

Mitochondria

A _______ ______ consists of one motor neuron and all the muscle fibers it innervates, or supplies. When it transmits an action potential, all the muscle fibers it innervates contract.

Motor unit

What is sarcoplasm?

Muscle cell cytoplasm.

___ _____ is a state of physiological inability to contract even though the muscle still may be receiving stimuli.

Muscle fatigue.

If muscle cells are elongated, they can also be called what?

Muscle fibers.

When ________ __________ contract, they pull on these sheaths, which transmit the pulling force to the bone to be moved. The sheaths contribute somewhat to the natural elasticity of musle tissue, and also provide entry and exit routes for the blood vessels and nerve fibers that serve the muscles.

Muscle fibers.

The force exerted by a contracting muscle on an object is called ______ _______.

Muscle tension

Phenomenon that keeps the muscles somewhat firm, tightened, and always slightly contracted due to activated stretch receptors.

Muscle tone

A motor unit's response to a single action potential of its motor neuron is called what? Where the muscle fibers contract quickly and then relax?

Muscle twitch

Whenever you see the prefixes "myo" and "mys" both are root words meaning what?

Muscle.

A group of inherited muscle-destroying diseases that generally appear during childhood. Affected muscles generally enlarge due to deposits of fat and connective tissue, but muscle fibers atrophy and degenerate.

Muscular Dystrophy

All three types of muscle tissue develop from embryonic cells called _______.

Myoblasts

A single muscle fiber contains hundreds to thousands of rod like ____________ that run parallel to its length.

Myofibrils

The ___________ are so densely packed in the fiber that mitochondria and other organelles appear to be squeezed between them.

Myofibrils

In addition to the usual organelles, a muscle cell also contains:

Myofibrils, sarcoplasmic reticulum, and T tubules.

Filament that constitutes myofibrils. Of two types: actin and myosin.

Myofilament.

What is a red pigment that stores oxygen?

Myoglobin

Proteins actin and _______ play a role in motility and shape change in virtually every cell in the body.

Myosin

Muscle contraction depends on the ______ and ________ containing myofilaments.

Myosin and Actin

Calmodulin, in turn, interacts with a kinase enzyme called _______ kinase.

Myosin.

In smooth muscle the thick filaments are fewer but have _______ heads along their entire length.

Myosin.

Thick filaments are composed primarily of the protein _________.

Myosin.

Which system stimulates muscle fibers, the myosin heads on the thick filaments latch onto myosin-binding sites on actin in the thin filaments, and the sliding begins.

Nervous

The axon of each motor neuron divides as it enters each muscle and each ending gives off short branches that form elliptical ___________ _______ or ______ ________ with a single muscle fiber.

Neuromuscular junction or end plate.

Are there striations in smooth muscle? Sarcomeres?

No. No.

This heat is vitally important in maintaining what?

Normal body temperature.

Skeletal muscle has a rich blood supply and uses huge amounts of energy and require almost continuous delivery of oxygen and nutrients. How is it delivered to skeletal muscle? And how are wastes removed?

Nutrients delivered through arteries. Wastes removed through veins.

In general, what makes up each muscle?

One nerve, one artery, and one more veins serve each muscle.

Usually, each muscle fiber has how many neuromuscular junctions? Where is it typically located?

One, Midway along it's length.

What within our body controls how fast our heart beats?

Our body's natural pacemaker. But neural controls allow the heart to speed up for brief periods.

Skeletal muscle is responsible for:

Overall body mobility.

Cells that rely mostly on oxygen-using aerobic pathways for ATP generation are ________ fibers.

Oxidative

"Around the muscles"

Perimysium

Within each skeletal muscle, the muscle fibers are grouped into fascicles that resemble bundles of sticks. Surrounding each fascicle is a layer of fibrous connective tissue called perimysium meaning "around the muscle".

Perimysium and fascicles.

During the _____ ___ _____ cross bridges are active, from onset to peak of tension development, the myogram tracing rises to peak. Lasts 10-100ms. If tension becomes great enough to overcome the resistance of the load, the muscle shortens.

Period of contraction

_____ ____ _______ During this phase lasting 10-100ms is initiated by reentry of Ca into the SR. Because contractile force is declining, muscle tension decreases to zero the tracing returns to the baseline. If muscle shortened during contraction, it returns to original length.

Period of relaxation.

The alternating contraction and relaxation of these layers mixes substances in the lumen and squeezes them through the organs internal pathway. This propulsive action is called ______.

Peristalsis.

During glycolysis, glucose is broken down to two ________ acid molecules releasing enough energy to form small amounts of ATP.

Pyruvic acid

This controls the force of contraction more precisely. In the lab it is achieved by delivering shocks of increasing voltage to muscle, calling more and more muscle fibers into play.

Recruitment or multiple motor unit summation.

_____ ______ is when muscles stiffen after death.

Rigor mortis

"Muscle segment"

Sarcomere

The region of a myofibril between two successive Z discs is called a __________.

Sarcomere.

The smallest contractile unit of a muscle fiber-the functional unit of skeletal muscle.

Sarcomere.

What is the cytoplasm of a muscle cell called which contains unusually large amounts of glycosomes and myoglobin.

Sarcoplasm

________ cells, myoblast-like cells help repair injured fibers and allow limited regeneration of dead skeletal muscle, a capability that declines with age.

Satellite

Smooth muscle lacks the coarse connective tissue _______ like in skeletal tissue.

Sheaths

As this event occurs simultaneously in sarcomeres throughout the cell, the muscle cell ________.

Shortens

What kind of muscle generates the most heat?

Skeletal

Of the three types of muscle tissue, which two are elongated?

Skeletal and smooth muscle cells.

Each ________ ________ fiber is a long cylindrical cell with multiple oval nuclei just beneath its sarcolemma or plasma membrane.

Skeletal muscle

Which muscle cells are the longest and have striations?

Skeletal muscle.

_________ _________ fibers are huge cells.

Skeletal muscle.

What muscles are responsible for locomotion and manipulation?

Skeletal muscles.

What muscles are we rarely aware of, yet function almost continuously to help maintain body posture and counteract the downward pull of gravity?

Skeletal muscles.

What are the three types of muscle tissue?

Skeletal, cardiac, and smooth.

Contraction in smooth muscle cells are similar to skeletal in the following ways: Actin and myosin interact by the ______ filament mechanism. The final trigger for contraction is a rise in the intracellular _____ ____ level. ____ evergiezes the sliding process.

Sliding, calcium ion, ATP

Apart from the heart, all of the muscles in the body's hollow organs is entirely what kind of muscle?

Smooth

What kind of muscle forms valves that regulates the passage of substances through internal body openings, dilates and constricts the pupils of your eyes, and forms the arrector pili muscles attached to hair follicles?

Smooth

What muscles propel substances through the organs and along the tract?

Smooth muscle tissue.

The nerve cells that activate skeletal muscle fibers are called _______ ______ ________.

Somatic Motor Neurons

Smooth muscle fibers are what kind of shape?

Spindle

Is smooth muscle striated? Cells elongated or no?

Striated and elongated.

Repeating series of dark and light bands, are evident along the length of each myofibril.

Striations

A stimuli that produces no observable contractions are _________ ________.

Subthreshold stimuli

What space separates the axon terminal and the muscle fiber?

Synaptic cleft

Within the moundlike axon terminal are _____ ______, small membranous sacs containing the neurotransmitter __________. or ACh.

Synaptic vesicles, tylcholine

Smooth muscle fibers exhibit slow, _________, contractions, the whole sheet responding to a stimulus in unison. Reflecting electrical coupling of smooth muscle cells by _____ junctions.

Synchronized, gap.

At each A band-I band junction, the sarcolemma of the muscle cell protrudes deep into the cell interior, forming an elongated tube called the __ _______.

T tubules

If two stimuli are delivered to muscle in rapid succession, the second twitch will be stronger than the first. This phenomenon called _____ ________ occurs because the second contraction occurs before the muscle has completely relaxed yet.

Temporal summation.

The ________ or _________ anchors the muscle to the connective tissue covering of a skeletal element (Bone or cartilage) or to the fascia of other muscles.

Tendon or aponeurosis

What are made of mostly tough collagen fibers that can withstand the abrasion of rough bony projections that would tear apart the more delicate muscle tissues.

Tendons

The _____ _____ ____ __ ________ states that during contraction the thin filaments slide past the thick ones so that the actin and myosin filaments overlap to a greater degree.

The Sliding Filament Model of Contraction

What is a sarcolemma?

The plasma membrane of a muscle cell.

An elaborate smooth endoplasmic reticulum.

The sarcoplasmic reticulum.

What are capillaries?

The smallest of the body's blood vessels and are long and winding. The have numerous cross-links.

The central portion of a _____ _______ is smooth but its ends are studded with a staggered array of myosin heads.

Thick filament

Each ______ _______ contains about 300 myosin molecules bundled togetherd, with their tails forming the central part of the " " and their heads facing outward at the end of each " ".

Thick filament.

The central ______ _______ containing myosin (red) extend the entire length of the A band. They are connected in the middle of the sarcomere at the M line.

Thick filaments.

In smooth muscle, no troponin complex in _______ filaments.

Thin

As the ____ _________ slide centrally, the Z discs pulled toward the M line. Overall, as a muscle cell shortens the I bands shorten, the distance between Z discs shortens, the H zones disappear and the contiguous A bands move closer together but their length does not change.

Thin Filaments

The more lateral ________ _________ containing actin (blue) extend across the I band and partway into the A band.

Thin Filaments.

How many phases are there to a twitch myogram?

Three

The stimulus at which the first observable contraction occurs is called the _______ ______. At this point the muscle contracts more and more vigorously as the stimulus strength increases.

Threshold stimuli

The elastic filament is composed of the giant protein ______.

Titin.

On a myogram, the line recording the activity is called a what?

Tracing

Thin filaments also contain polypeptide strands of _____________ and ________.

Tropomyosin, and Troponin.

T/F Just about all movements result from muscle contraction.

True

T/F Skeletal muscle can contract rapidly, tires easily, must rest after short periods of activity, and can exert tremendous amounts of power.

True.

In most cases there are ______ sheets of smooth muscle with their fibers oriented at right angles to each other.

Two

The innervating nerve fibers, which are part of the autonomic (involuntary) nervous system, have numerous bulbous swellings, called ________.

Varicosities

Unitary smooth muscle is also called _______ muscle and lines the walls of all hollow organs except the heart. Most common.

Visceral.

Is skeletal muscle voluntary or involuntary?

Voluntary. It is the only type within conscious control.

Does smooth muscle contain thick and thin filaments?

Yes

Which striation is coin shaped?

Z line

Each light I band also has a midline interruption, a darker area called the _ _____.

Z line.

Smooth muscle contraction also accounts for the constricted breathing of _______ and for stomach ______.

asthma, cramps.

In excitability, the stimulus is generally a:

chemical

Within a sarcomere, the ideal ____-_____ relationship occurs when a muscle is slightly stretched and the thin and thick filaments overlap optimally, because this relationship permits sliding along nearly the entire length of the thin filaments.

length-tension

Smooth muscles in the airways of the lungs, large arteries, arrector pili muscles attached to hair follicles, and the internal eye muscles that adjust pupil size and allow the eye to focus visually are all examples of ____ ____ smooth muscle.

multi unit

The extra amount of oxygen that the body must take in for these restorative processes is called the excess postexercise _______ ________.

oxygen consumption

Smooth muscle fibers in the stomach are ______ cells that act as "drummers" and set the pace of contraction for an entire muscle sheet. They have fluctuating membrane potentials and are self-excitatory, that is, they depolarize spontaneously in the absence of ______ stimuli.

pacemaker, external

Most smooth muscle is organized into ______. These sheets occur in the walls of all but the smallest blood vessels and in the walls of hollow organs of the respiratory, digestive, urinary, and ______ tracts.

sheets, reproductive.

The three things to think of when you think skeletal muscle is:

skeletal, striated, voluntary.

This ____-_____ response allows a hollow organ to fill or expand slowly to accommodate a greater volume without causing strong contractions that would expel its contents.

stress-relaxation

When we think of smooth muscle we must think of three words:

visceral, nonstriated, and involuntary.