A&P chapter 9
During muscle contraction, ATP supplies energy for
Myofilament movement
Name the connective tissue that separates a skeletal muscle into fascicles
Perimysium
An electrical impulse traveling along the sarcolemma and into the transverse tubules causes calcium ions to diffuse from the ______into the_______
Sarcoplasmic reticulum; sarcoplasm
What happens to the A band in a contracted muscle
The A bands do not change length
What is the I band?
The area with thin filaments only; no thick filaments
The functional unit of muscle contraction is
The sarcomere
People with myasthenia gravis have a deficiency of
acetylcholine receptors
A gluteal gait, in which a person walks with a waddling limp, is usually caused by a disorder of the
gluteus medius, gluteus minimus
Both acetylcholine and norepinephrine can affect
smooth muscle contraction
transverse tubules
transmit muscle impulses into the cell interior.
The striations seen in skeletal muscles consist of alternating dark bands called the _________bands , and light bands called the _______bands.
A; I
As strenuous activity begins, muscle cells first use the ______molecules present in their cytoplasm as their source of energy. The supply of this molecule, however, is limited. It must be produced by other means in order for exercise to continue.
ATP
Tawanda finishes a sprint and suffers great pain in her calf muscles. Her muscle cramps are most likely due to a temporary deficit of
ATP
Myosin heads directly use __________ to transition to their __________ conformation, which enables them ready to bind to actin.
ATP; energized
The chemical used at the junction with a skeletal muscle cell is
Acetylcholine
What is the first event in muscle fiber contraction
Acetylcholine is released from the end of the motor neuron
Neurotransmitters
Acetylcholine molecule
Location of binding sites for myosin
Actin
How does an electrical impulse travel into the interior of a muscle fiber
By way of transverse tubules
1. The layer of connective tissue that closely surrounds a skeletal muscle is called the
Epimysium
which muscle group is composed of mainly slow twitch (typeI) fibers
Erector spinae muscles of the back
cardiac muscle
Excites itself
The presence of calcium in the sarcoplasm is directly responsible for______
Exposing the binding sites on actin
As exercise continues, the cells now begin to use______ as a fuel to produce ATP. Initially, the anaerobic pathway called______ uses this fuel to produce 2 ATP and 2 molecules of pyruvic acid.
Glucose; glycolysis
In a recording of a muscle twitch, the delay between the time a stimulus is applied and the time the muscle responds is called the
Latent period
Site of ATP production
Mitochondrion
Location of receptors for neurotransmitters
Motor end plate
A weightlifter uses muscles so the muscles exert more than 75% of their maximum tension, this stimulates
Muscle fibers developing new filaments of actin and myosin.
An example of a partial but sustained contraction would be
Muscle tone
The electrical impulse that moves over the surface of a muscle fiber and into the T-tubules results from increased membrane permeability to what ion?
Sodium
The point of communication between a motor neuron and a muscle fiber is called a
Synapse
Define muscle tone
The state of partial contraction of resting muscles
What is the name of the neurotransmitter used at a skeletal neuromuscular junction
acetylcholine
Myofibrils are composed of
actin and myosin
myasthenia gravis is
an autoimmune disorder
The muscle that opposes a particular action is called
antagonist
A muscle fiber exposed to a series of stimuli of increasing frequency combines individual twitches (summation) which results in
complete sustained contraction.
If there was a high concentration of acetylcholine within the synaptic cleft, but little to no response at the motor end-plate, you would expect ________________ to be the responsible neuromuscular-blocking agent.
curare
What is the A band?
length of the myosin filament
Site of ATP production
mitochondria
The antidote that holds the most promise to counteract the effects of tubocurarine is one that _________________________.
modifies acetylcholine receptors so that they bind acetylcholine stronger than tubocurarine
At a neuromuscular junction, the muscle fiber membrane folds, forming a
motor end plate
Place in order, from largest to smallest, the components of a skeletal muscle
muscle, fascicle, muscle fiber, myofibril, myofilaments
The characteristic reddish brown color of skeletal muscle comes from which substance
myoglobin
Forms cross bridges
myosin
Botulinum toxin causes muscle paralysis because
no acetylcholine enters the synaptic cleft
Facial wrinkles, such as glabellar or "frown" lines, appear with aging as a result of natural, repetitive muscle contractions. Botox® helps alleviate the appearance of these wrinkles by _________________.
relaxing the facial muscles that cause the wrinkles
Plasma membrane of muscle fiber
sarcolemma
The striated appearance of skeletal muscle results from the
sarcomere organization
creatine phosphate
supplies energy for the synthesis of ATP
Acetylcholine (ACh) is released from motor neurons and enters the
synaptic cleft
Space between axon and muscle fiber
synaptic cleft
A muscle that assists the agonist is a(n)
synergist
Blocks myosin binding sites
tropomyosin
Calcium ions bind to _____ in order to initiate a muscle contraction
troponin
In what type of muscles does some of the calcium needed for contraction come from the extra cellular fluid?
Cardiac muscle and visceral smooth muscle
The structures that connect cardiac muscle cells are
Intercalated discs
Which of the following best describes the role of calcium in muscle contraction
It binds to troponin, moving tropomyosin, so that myosin heads can bind to actin.
Describe the role of acetylcholinesterase in stimulation of a muscle fiber
It is the enzyme that breaks down acetylcholine in the synaptic cleft, ending stimulation of the muscle fiber
The binding of the chemicals to the muscle cell causes a electrical impulse to travel across the sarcolemma and down the _____tubules
Transverse
The triangle of auscultation, commonly used to hear sounds of respiratory organs, is located near the border of the
Trapezius and latissimus dorsi
In order for a skeletal muscle fiber to contract, calcium must bind to_____
Troponin
If little or no oxygen is available, pyruvic acid is converted to_______. If, however oxygen is available the pyruvic acid molecules enter the aerobic respiration pathways
Lactic acid
The chemicals then bind to receptors located on the _______, a specialized area of the sarcolemma
Motor end plate
At this neuromuscular junction, a ________releases a type of chemical called a neurotransmitter.
Motor neuron
Provides stimulation to the muscle fiber
Motor neuron axon
In order for muscle contraction to occur, cross- bridges for between
Myosin and actin
During the contraction cycle, what is the result of ATP binding to myosin
Myosin heads release from the binding sites on actin
Acetylcholine causes an end plate potential by triggering the
Opening of sodium channels
At what level of organization is a skeletal muscle such as the biceps brachii
Organ
2.Another layer of connective tissue, called the_______, extends inward from the epimysium and separates the muscle tissue into groups of muscle fibers. These groups are called ________.
Perimysium; fascicles
Functions of the muscles include
Pumping blood
At neuromuscular junctions, acetylcholine binds to
Receptors in the muscle fiber membrane
Which of the following is not true
Red fibers have fewer mitochondria than white.
The discoloration and swelling that occurs with a muscle strain is due to
Ruptured blood vessels
Muscle fibers are basically a collection of
Sarcomeres
Compared to skeletal muscle, smooth muscle is ______ to contract and _______to relax
Slower; slower
These chemicals diffuse across a small gap between the neuron and muscle fiber called the
Synaptic cleft
What is the name of the space between a motor neuron and a muscle fiber at the neuromuscular junction
Synaptic cleft
Storage of neurotransmitters
Synaptic vesicles
What happens to the H zone in a contracted muscle
The H zones shorten
What happens to the I bands in a contracted muscle
The I bands shorten
What is the H zone?
The area with thick filaments only; no thin filaments
Location of binding sites for calcium
Troponin
The amount of oxygen needed to repay the oxygen debt includes the amount of oxygen that muscle cells need to resynthesize ATP.
True
Transverse tubules (T-tubules) are invaginations of the sarcolemma of a muscle cell
True
Thin filaments connect and extend from either side of a _______. These thin filaments are composed largely of the myofilament ________.
Z disc; actin
As long as oxygen is available, the oxidation of each glucose molecule using ______ metabolism will produce, in total,______ATP molecules
aerobic; 30
The muscle that causes an action is the
agonist
An action, such as flexing the knee, is caused by the contraction of a muscle acting as an ______ and is opposed by a muscle acting as an ______.
agonist and antagonist
If it were possible to move the terminal cisternae further away from the T-tubules. It would
interfere with the signal required for the release of calcium from the sarcoplasmic reticulum
Fibers of muscles whose motor neurons are severed
may be replaced by fat or fibrous connective tissue
A threshold stimulus is the
minimum strength of stimulation required to contract a muscle fiber
Threadlike bundles of thick and thin filaments
myofibril
Functional unit of contraction within muscle fiber
sarcomere
cytoplasm of a muscle fiber
sarcoplasm
Site for storage of calcium
sarcoplasmic reticulum
Regina began an exercise program six months ago, and the muscles of her upper limbs and lower limbs are more prominent. Exercise can lead to formation of new muscle by
stimulating skeletal muscle cells to release IL-6, which stimulates satellite cells to divide, producing more muscle cells.
Which of the following describes smooth muscle contraction but not skeletal muscle contraction
Hormones can inhibit muscle contraction
Hundreds of mutations have been identified in RyR1 that contribute to multiple muscular diseases. Assume that a new mutation was discovered that causes this receptor to continually remain open. Based on what you know about the function of this receptor, how would you expect this new mutation to impact contraction?
this mutation will increase levels of calcium in the sarcoplasm, which will induce continued muscle contraction
Channel formed by invagination of plasma membrane
transverse (T) tubule
When myosin heads form cross bridges during muscle contractions, they bind to binding sites found on _______, a component of thin filaments.
Actin
Choose the correct statement about muscle contraction
Actin filaments slide along side myosin filaments
The two types of myofilaments are thin filaments, composed primarily of the protein _______. And thick filaments composed of ________.
Actin; myosin
Describe how action potentials travel from the sarcolemma into the interior of the muscle fibers, resulting I. The release of calcium ions into the sarcoplasm.
Action potentials travel along T tubles
What are intercalated discs that are found in cardiac muscle
Complex membrane junctions that include desomones and gap junctions
Which of the following statements describes myofibrils
Comprised of thick and thin filaments
4. Therefore, as described, layers of _________ enclose and separate the various parts of a skeletal muscle.
Connective tissue
The muscle that adducts and flexes the arm is the
Coracobrachilias
In order to produce ATP, the muscle cells next start to use__________, also present in the cytoplasm, to form new ATP. This is done by moving a phosphate and it's energy from this molecule to ADP, forming new ATP.
Creatine phosphate
What happens to each sarcomere during contraction
Each sarcomere shortens
3. Each muscle fiber within a fascicle is surrounded by a thin covering called a
Endomysium
Rigor mortis occurs after death because
detachment of crossbridges does not occur due to the lack of ATP
