Chapter 6: The Muscular System
What creates the alternating light and dark bands that provides the striation pattern on skeletal muscle tissue?
A & I bands
(T/F) The striations seen in skeletal muscle are actually alternating dark A and light I bands
True
(T/F) When a muscle fiber contracts, the I bands nearly disappear, and the A bands move closed together but do not change the length
True
(T/F) Cardiac and skeletal muscle both possess striations
True
(T/F) Cardiac muscle fibers are joined by special gap junctions called intercalated discs; these discs allow heart activity to be closely coordinated
True
(T/F) The neurotransmitter used by the nervous system to activate skeletal muscle cells is acetylcholine
True
(T/F) The sarcoplasmic reticulum wraps like a sleeve around the myofibril and stores and releases calcium
True
What is acetylcholine?
a neurotransmitter that stimulates skeletal muscles to contract
The mechanical force of contraction is generated by
a sliding of thin filaments past thick filaments
What must occur first to trigger the skeletal muscle to generate an action potential and contract?
acetylcholine binds to receptors on the sarcolemma and allows pass of sodium ions into the cell
What enzyme breaks down acetylcholine into acetic acid and choline to prevent continued contraction of the muscle fiber?
acetylcholinesterase
Enzyme that breaks down acetylcholine (ACh)
acetylcholinesterase (AChE)
During skeletal muscle contraction, to what do myosin heads bind?
actin filaments
Electrical current that travels the length of the sarcolemma that results in the contraction of the muscle fiber
action potential
What is the unstoppable electrical current that travels down the length of the entire surface of sarcolemma?
action potential
What is covered by the endomysium
an individual muscle fiber
Muscles that perform opposite actions to one another are termed
antagonists
Neurotransmitters are release upon stimulation from a nerve impulse from the
axon terminals of the motor neuron
The sarcoplasmic reticulum stores this chemical
calcium ions
Why are calcium ions necessary for skeletal muscle contraction?
calcium ions trigger the binding of myosin heads to actin filaments
Muscle tissue composed of branching cells and intercalated discs
cardiac
Muscle tissue found only in the heart
cardiac
Striated involuntary muscle tissue found in the heart is
cardiac
Striated involuntary muscle tissue is classified as ______ muscle
cardiac
The arrangement of fascicles in orbicularis oris is
circular
Muscle tissue has the ability to shorten when adequately stimulated, a characteristic known as:
contractability
The heads of the myosin myofilaments are called when they link the thick and thin filaments together during skeletal muscle contraction
cross bridges
According to the sliding filament theory, how does muscle contraction occur?
myosin heads form cross bridges and pull thin filaments, causing them to slide
The point of muscle attachment to an immovable or less movable bone is knows as the:
origin
Which of the following is an example of an isometric contraction?
pushing against an immovable wall
What organelle wraps and surrounds the myofibril and stores calcium?
sarcoplasmic reticulum (SR)
Muscle tissue that is multinucleate
skeletal
Muscle tissue that maintains posture, body position, and stabilizes joints
skeletal
Voluntary muscle tissue
skeletal
Which type of muscle tissue contracts most quickly upon stimulation?
skeletal
Muscle tissue that activates arrector pili muscles to stand hairs on end
smooth
Muscle tissue that dilates and constricts the pupils of our eyes
smooth
Performs very slow, sometimes rhythmic, contractions
smooth
Chemical that enters a muscle cell upon excitation
sodium ions
What must rush into a muscle cell to promote its depolarization?
sodium ions
Creatine phosphate functions within the muscle cells by
storing energy that will be transferred to ADP to resynthesize ATP as needed
Gap between the axon terminals and the plasma membrane of ta neighboring muscle cell
synaptic cleft
The gap between the axon terminal of a motor neuron and the sarcolemma of a skeletal muscle cell is called the
synaptic cleft
The condition of skeletal muscle fatigue can be best explained by
the inability of the muscle to contract even if it is being stimulated
A skeletal muscle twitch differs form a tetanic contraction in that
the muscle twitch is a brief and jerky movement, while the tetanic contraction is prolonged and continuous
Which of the following is composed mostly of the protein myosin?
thick filaments
(T/F) Depolarization of a skeletal muscle cell leads to the opening of more channels that only allow potassium entry
False
(T/F) Smooth muscles stabilize joints of the skeleton
False
Specific neurotransmitters that stimulate skeletal muscles cells
acetylcholine
A smooth, sustained contraction, with no evidence of relaxation, is called
fused, or complete, tetanus
What does anaerobic glycolysis require to make ATP?
glucose ONLY
Skeletal muscle, as a whole, can generate different amounts of force, and different degrees of shortening, in response to stimuli. What is this concept called?
graded response
What are the 3ish functions of the muscular system?
is responsible for body movements, maintains posture, stabilizes joints, and generates heat
Contractions in which muscles shorten and produce movement are known as
isotonic contractions
A motor neuron and all of the skeletal muscle fibers it stimulates are termed a
motor unit
One neuron and all the skeletal muscles it stimulates is known as a:
motor unit
An inherited disease that causes muscles to degenerate and atrophy is known as
muscular dystrophy
