Chapter 10 Muscular Tissue

4 functions of muscular tissue

1) Producing body movement 2) Stabilizing body positions 3) Storing and moving substances within the body 4) Generating heat

M line;

A region in the center of the H zone that contains proteins that hold the thick filaments together at the center of the sacromere.

, triad,

A transverse tubule and the 2 terminal cisterns on either side of it form a ____.

A band,

The darker middle part of the sarcomere. Extends the entire length of the thick filaments.

, actin;

____ molecules join together to form an ____ filament, twisted into a helix. On each ____ molecule is a myosin binding site for the myosin head.

, troponin

______ holds tropomyosin in place.

; twitch contraction,

a brief contraction of all the muscle fibers in a motor unit in response to a single action potential in its motor unit.

tendon,

a cord of dense regular C.T. composed of parallel bundles of collagen fibers that attach a muscle to the periosteum of a bone. Ex; the calcaneal ______ of the gastrocnemius muscle, which attaches the muscle to the calcaneus.

dystrophin

a cytoskeletal protein that links thin filaments of the sarcomere to integral membrane proteins of the sarcolemma, which are attached in turn to proteins in the connective tissue extracellular matrix

deep fascia

a dense sheet or broad band of irregular connective tissue that lines the body wall and limbs and supports and surrounds muscles and other organs of the body. Holds muscles w/ similar functions together. Allows free movement of muscles, carries nerves, blood vessels, and lymphatic vessels, and fills spaces between muscles.

, satellite cells

a few myoblasts do persist in mature skeletal muscle as ______. These cells retain the capacity to fuse with one another or with damaged muscle fibers to regenerate functional muscle fibers. The # of new skeletal muscle fibers formed is not enough to compensate for significant skeletal muscle damage or degeneration.

sarcoplasmic reticulum

a fluid-filled system of membranous sacs. Encircles each myofibril. In relaxed muscle fiber, stores calcium ions. Release of CA2+ from the terminal cisterns of the _____ triggers muscle contraction.

, I band,

a lighter, less dense area that contains the rest of the thin filaments but no thick filaments. A z disc passes through the center of each ____.

, synapse,

a region where communication occurs between two neurons or between a neuron and a target cell.

muscle tone,

a small amount of tautness or tension in the muscle due to weak involuntary contractions of its motor units.

synaptic cleft,

a small gap at a synapse.

flaccid,

a state of limpness in which muscle tone is lost.

, hyperplasia

an increase in the number of fibers.

, fast oxidative-glycolytic fibers

are intermediate in diameter between the other two types of fibers. Dark red appearance. Can generate considearable ATP by aerobic cellular respiration, which gives them a moderately high resistance to fatigue.

, fast glycolytic fibers

are largest in diameter and contain the most myofibrils. They can generate the most powerful contractions. Have low myoglobin content.

thermogenesis

as muscular tissue contracts, it produces heat, a process known as ______.

smooth muscle tissue

located in the walls of hollow internal structures, such as blood vessels, airways, and most organs in the abdominopelvic cavity. Also found in the skin, attached to hair follicles. Lacks striations. It looks nonstriated, which is why it is refered to as smooth. The action of smooth muscle is usually involuntary, and some smooth muscle tissue such as the muscles that propel food through your gastrointestinal tract, has autohythmicity. Regulated by neurons that are part of the autonomic (involuntary) division of the nervous system and by hormones released by endocrine glands.

synaptic vesicles,

membrane-enclosed sacs located in synaptic end bulbs containing neurotransmitters

Skeletal muscle tissue

most ______ move bones of the skeleton. ( a few ______ attach to and move the skin or other _____) ______ is striated. Its activity can be consciously controlled by neurons that are part of the somatic (voluntary) division of the nervous system.

; the sliding filament mechanism;

muscle contraction occurs because myosin heads attach to and "walk along" the thin filaments at both ends of the sarcomere, pulling the thin filaments toward the M line and may even overlap. As a result the Z discs move closer together.

z-disc,

narrow, plate-shaped regions of dense protein material. Separate one sarcomere from the next.

endomysium,

penetrating the interior of each fascicle and separating individual muscle fibers from one another. A thin sheath of areolar C.T.

creatine phosphate,

produced when muscle fibers are relaxed and more ATP is available than needed for resting muscle metabolism.

; oxygen debt

refers to the added oxygen, over and above the resting oxygen consumption, that is taken into the body after exercise.

, red muscle fibers

skeletal muscle fibers that have a high myoglobin content, more mitochrondia and more capillaries

, white muscle fibers,

skeletal muscle fibers that have a low myoglobin content

myofibrils,

small structures. The contractile organelles of skeletal muscle. "Little threads"

extensibility,

the ability of muscular tissue to stretch without being damaged. Allows a muscle to contract forcefully even if it is already stretched. Smooth muscle subject to the greatest amount of stretching.

latent period

the delay (2 milliseconds) between the application of the stimulus and the beginning of contraction.

, epimysium,

the outermost layer of skeletal muscle encircling the entire muscle. Dense irregular C.T.

sarcolemma,

the plasma membrane of a muscle cell.

motor unit recruitment,

the process in which the number of active motor units increases.

motor end plate,

the region of the sarcolemma opposite the synaptic end bulb.

, fibrosis;

the replacement of muscle fibers by fibrous scar tissue.

, tintin,

(gigantic) Each _____ molecule connects a Z disc to the M line of the sarcomere and helps to stabilize the position of the thick filament.

refractory period;

The period of lost excitability where the muscle fiber cannot respond.

; excitation contraction coupling

The events that connect excitation (action potential) to contraction (sliding filaments).

; the neuromuscular junction

A synapse between the axon terminals of a somatic motor neuron and the sarcolemma of a muscle fiber.

isotonic contraction

the tension (force of contraction) developed by the muscle remains almost constant while the muscle changes its length.

, frequency of stimulation,

# of impulses per second.

thick filament,

16 nm in diameter and 1-2 um long.

thin filament,

8 nm in diameter and 1-2um long.

H zone,

A narrow _____ in the center of each A band contains thick but no thin filaments.

electrical excitability

A property of both muscle and nerve cells. The ability to respond to certain stimuli by producing electrical signals called action potentials. 2 types of stimuli trigger action potentials for muscle cells. Autorhythmic electrical signals arising in the muscular tissue itself, as in the heart's pacemaker. Chemical stimuli such as neurotransmitters released by neurons, hormones distributed by the blood, or even local changes in pH.

, contraction period,

Ca++ binds to troponin, myosin-binding sites are revealed, crossbridges formed and peak tension develops in the muscle fiber. 10-100msec

relaxation period,

Ca++ is actively transported back into the SR, myosin binding sites are covered and tension in the muscle fiber decreases, 10-100msec

junctional folds;

Deep grooves in the motor end plate that increase the surface area for neurotransmitters

, terminal cisterns

Dilated end sacs of the Sarcoplasmic reticulum called ____ butt against the T tubule from both sides.

cardiac muscle tissue

Involuntary. Forms most of the heart wall. Striated. The heart beats because it has a pacemaker that initiates each contraction. This built-in rhythm is termed autorhythmicity.

muscle metabolism,

Muscle fibers have three ways to produce ATP

zone of overlap

Toward each end of the A band is a ____, where the thick and thin filaments lie side by side.

unfused tetanus,

When a skeletal muscle fiber is stimulated at a rate of 20 to 30 times per second, it can only partially relax between stimuli.

fused tetanus;

When a skeletal muscle fibers is stimulated at a higher rate of 80 to 100 times per second, it does not relax at all.

motor unit

a somatic motor neuron and all the skeletal muscle fibers it stimulates

, tendon sheaths,

certain tendons, especially those of the wrist and ankle, are enclosed by tubes of fibrous C.T. called _______, which are similar in structure to bursae. The inner layer of a _____, the visceral layer, is attached to the surface of the tendon. The outer layer, known as the parietal layer, is attached to bone. Reduce friction as tendons slide back and forth.

multiunit smooth muscle tissue;

consists of individual fibers, few gap junctions. Stimulation of one multiunit fiber causes contraction of only that fiber

tropomyosin

covers the myosin binding sites on actin when the muscle is relaxed.

hypertrophy

dramatic muscle growth that occurs after birth. An enlargement of existing muscle fibers.

muscle fibers,

each of your skeletal muscles is a separate organ composed of hundreds to thousands of cells, which are called muscle fibers because of their elongated shapes. Thus, muscle cell and muscle fiber are 2 terms for the same structure.

myotome,

forms the skeletal muscles of the head, neck, and limbs

myosin

functions as a motor protein in all three types of muscle tissue. Motor proteins push or pull various cellular structures to achieve movement by converting the chemical energy in ATP to the mechanical energy of motion or the production of force. 300 molecules of this form a single thick filament. Shaped like two golf clubs twisted together.

contractile proteins,

generate force during contraction.

sclerotome

gives rise to vertebrae.

the contraction cycle

he Sarcoplasmic reticulum releases calcium ions. Once the myoin binding sites are free the _______ begins. It has four steps: · ________: the repeating sequence of events that causes the filaments to slide 1. ATP hydrolysis 2. Attachment of myosin to actin to form crossbridges 3. Power Stroke 4. Detachment of myosin from actin As long as ATP is available and the level of Calcium is high the _______ repeats itself, some heads attaching and others detaching.

regulatory proteins,

help switch the contraction process on and off

concentric isotonic contraction

if the tension generated is great enough to overcome the resistance of the object to be moved

; structural proteins

keep the thick and thin filaments in the proper alignment, give the myofibril elasticity and extensibility, and link the myofibrils to the sacrolemma and extracellular matrix.

; visceral smooth muscle tissue,

most common type. Fibers connect to one another via gap junctions. It is autorhythmic.

wave summation,

phenomenon in which stimuli arriving at different times cause larger contractions.

myogram,

record of a muscle contraction.

; slow oxidative fibers

smallest in diameter and thus are the least powerful type of muscle fibers. Appear dark red because they contain large amounts of myoglobin and many blood capillaries. Generate ATP mainly by aerobic cellular respiration.

fast/slow fiber

speed at which the ATPase in the myosin heads hydrolyzes ATP

perimysium,

surrounds groups of 10-100 or more muscle fibers, separating them into bundles called fascicles. Dense Irregular C.T.

contractility,

the ability of muscular tissue to contract forcefully when stimulated by an action potential.

elasticity;

the ability of muscular tissue to return to its original length and shape after contraction or extension.

sarcomere;

the basic functional units of a myofibril

neurotransmitter,

the chemical communication between the first cell and the second

; myoglobin

the red-colored protein that binds oxygen in muscle fibers

, isomentric contraction

the tension generated is not enough to exceed the resistance of the object to be moved and the muscle does not change its length.

transverse tubules,

thousands of tiny invaginations of the sarcolemma called _____, tunnel in from the surface toward the center of each muscle fiber. Open to the outside of the fiber and are filled with interstitial fluid. Muscle action potentials travel along the sarcolemma and through these, and quickly spreads throughout the muscle fiber.

aponeurosis

when the C.T. elements extend as a broad, flat layer, the tendon is called an _____. An example is the epicranial _____ on top of the skull between the frontal and occipital bellies of the occipitofrontalis muscle.

, eccentric isotonic contraction

when the length of a muscle increases during a contraction.

dermatome,

which forms the connective tissues, including the dermis of the skin

anerobic cellular respiration

ATP producing reactions that do not require oxygen.

, aerobic cellular respiration

Muscular activity that lasts longer than a half a minute depends increasingly on ACR, oxygen-requiring reactions