chapter 9:muscular system

a _______ _______ is an organ of the muscular system.

a skeletal muscle is composed of four things:

dense connective tissue that separates individual skeletal muscles

cordlike structure that consists of dense connective tissue

_______ connects a muscle to a bone

sheetlike structure composed of dense connective tissue

layer of connective tissue that closely surrounds a skeletal muscle

connective tissue that separates muscles into fascicles

a section of a muscle

connective tissue that surrounds individual muscle cells

fascia that surrounds or penetrates muscles

fascia just beneath the skin

connective tissue layer of the serous membrane covering organs in various body cavities and lining those cavities

a skeletal muscle fiber is a single muscle ____.

the plasma membrane of the cell

the cytoplasm of a muscle cell

the _________ contains many small nuclei, mitochondria, and myofibrils

threadlike structures that are located in the sarcoplasm

what fundamental role do myofibrils play in the muscle?

thick myofilaments are composed of ___________.

thin filaments are composed of ______.

the organization of __________ produces the alternating light and dark striation characteristic of skeletal muscles.

a repeating pattern of a myofibril

sarcomeres joined end to end are thought to be _______.

I bands are composed of _____ _______ ______

Z lines are structures that connect and anchor ____ ______

__ ______ are composed of thick myosin filaments overlapping thin actin filaments

the ___ ____ is a cenral region of an A band that only contains thick filaments

a region of an A band which consists of proteins that help hold the thick filaments in place

_____ connects proteins that connect myosin filaments to Z lines

a ______ extends from one Z line to another Z line

each ___ ______ consists of two twisted protein strands with globular parts called cross-bridges that project outward along their lengths

___ ______ consist of double strands of actin twisted into a helix

actin has a ___ _____ to which the cross-bridges of a myosin molecule can attach

_______ and _______ associate with actin filaments

endoplasic reticulum of a muscle fiber

membranous channels that extend into the sarcoplasm as invaginations continous with the sarcolemma and contains extracellular fluid

enlarged portions of sarcoplasmic reticulum

a ____ is formed by one transverse tubule and two cisternae

a motor neuron passes out from ___ or __ ___

normally, a skeletal muscle fiber contracts only upon what?

the site where the axon and muscle fiber meet

a specialized portion of the muscle cell membrane that is extensively folded

a motor neuron and the muscle fibers it controls

separates the membranes of the neuron and the membrane of the muscle fiber

synaptic vesicles store ______________.

the neurotransmitter that motor neurons use to control skeletal muscle

_____ is synthesized in the cytoplasm of the motor neuron and is stored in synaptic vesicles in axons.

when a nerve impulse reaches the end of an axon, __________ is released into the synaptic cleft.

___ combines with ACh receptors on the motor end plate, and stimulates the muscle fiber

an electrical signal that is like a nerve impulse

a ____ _____ changes the muscle cell membrane in a way that transmits the impulse in all directions along and around the muscle cell

where does the muscle impulse ultimately reach?

the __________ ___________ has a high concentration of calcium

in response to a muscle impulse, the membranes become more ______ to calcium, and the calcium ______ out of the cisternae into the cytosol of the muscle fiber.

when a muscle fiber is at rest, the _____-_______ complexes block the binding sites on the actin molecules

calcium ions bind to ______, changing its shape and altering the position of the tropomyosin

the movement of the tropomyosin molecule ________________________________, allowing linkages to form between myosin cross-bridges and actin.

the functional unit of skeletal muscles

according to the sliding filament theory, when sarcomeres shorten, the thick and thin filaments ______________________.

as contraction occurs, the H zones and I bands get ________, and the Z lines move ___________.

the force that shortens the sarcomeres comes from ___________________________.

a _______________ attaches to actin in order to pull on the actin filament.

myosin cross-bridges contain the enzyme ________.

ATPase catalyzes the breakdown of ____ to ____.

the force of muscle contraction is provided by the ____________________.

breaking down of ATP puts the myosin cross-bridge into a "______" position

when a muscle is stimulated to _______, a cocked cross-bridge attaches to actin and pulls the actin filament toward the center of the sarcomere, shortening the muscle.

when another ATP binds, the _________ is released, and then breaks down the ATP to return to the cocked position.

in order for a muscle fiber to relax, acetylcholine must be decomposed by an enzyme called ________.

the action of acetylcholinesterase prevents a single nerve impulse from continuously __________________.

moves calcium back into the sarcoplasmic reticulum

when calcium is removed from the cytoplasm, the cross-bridge linkages break and tropomyosin rolls back into its groove, preventing any _______________________.

_____ is necessary for both muscle contraction and relaxation

the _____________________ is the increase in cytosolic calcium in response to stimulation by ACh from a motor neuron.

energy source available to generate ATP from ADP.

contains a high energy phosphate bond

after creatine phosphate is used, a muscle cell must depend on _________________________ as a source of energy for synthesizing ATP.

typically, a muscle stores glucose in the form of ________.

occurs in the cytoplasm and is anaerobic

the complete breakdown of glucose occurs in __________ and requires __________.

the citric acid cycle and electron transport chain produce _______, ____________, and a large amount of _______.

_______ is carried in the blood stream bound to hemoglobin.

_________- stores oxygen in muscle tissue

rapid increase in blood levels of lactic acid

under _________conditions, glycolysis breaks down glucose into pyruvic acid and converts it to lactic acid.

carried by the blood to the liver

____________ can convert lactic acid to glucose.

condition in which a muscle fiber cannot contract.

__________--- may result from decreased blood flow, ion imbalances across the sarcolemma, and the psychological loss of the desire to exercise

a painful condition in which a muscle undergoes a sustained, involuntary contraction.

_____ is a by-product of cellular respiration

_____ transports heat throughout the body, which helps to maintain body temperature.

the minimal stimulus needed to start a muscle contraction

the response of a single muscle fiber to the ACh released by a single action potential

a recording of the events of a muscle twitch

three periods of a muscle fiber contraction are

during a period of contraction, a muscle fiber is generating force or ___________.

the period before contraction

the period in which a muscle fiber is decreasing tension

the period in which a muscle fiber is unresponsive to stimulation

a response in which a muscle fiber contracts completely or not at all

if a muscle is stretched well beyond its normal resting length, the force will ________.

the combination of the force of individual twitches

contractions that lack relaxation

the ______ ____ ___ in the motor units, the more precise the movements can be produced in a particular muscle.

all muscle fibers in a motor unit are stimulated at _______.

multiple motor unit summation is _____________.

an increase in the number of activated motor units

an increase in the number of activated motor units

_______ motor units respond later and more forcefully

muscle movements are smooth because_____________________________________________________________________.

the amount of sustained contractions in a muscle

muscle tone is important for maintaining __________.

a type of contraction that produces movement of a body part.

an isotonic contraction in which shortening of the muscle occurs.

an isotonic contraction in which lengthening of the muscle occurs

a contraction in which muscle tension increases but no movements of body parts are produced.

an example of an isometric contraction

an example of an isotonic contraction

type I fibers are _________ fibers

type I fibers are resistant to ________.

type IIa fibers are fast twitch _____ fibers.

type IIb fibers are fast twitch ______ fibers

two major types of smooth muscle

where is multiunit smooth muscle found?

where is visceral smooth muscle located?

fibers of viscera; smooth muscle are connected by ________.

a pattern of spontaneous repeated contractions

wavelike motion produced by smooth muscle contraction

what does peristalsis do?

two neurotransmitters that affect smooth muscle

hormones effect smooth muscle in two ways

stretching of smooth muscle can trigger ______.

smooth muscle is _____ to contract and to relax then skeletal muscle

unlike skeletal muscle, smooth muscle fibers can change ___ without changing _____.