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Muscle Tissue

Anatomy and Physiology Chapter 10
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Muscle tissue, one of the four basic tissue groups, consists chiefly of cells that are highly specialized for
contraction
The dense layer of connective tissue that surrounds an entire skeletal muscle is the
epimysium.
The delicate connective tissue that surrounds the skeletal muscle fibers and ties adjacent muscle fibers together is the
endomysium
An ________ can be described as a broad tendinous sheet.
aponeurosis
The repeating unit of a skeletal muscle fiber is the
sarcomere
The region of the sarcomere containing the thick filaments is the
A band
At rest, the tropomyosin molecule is held in place by
troponin molecules
The area in the center of the A band that contains no thin filaments is the
H band
Each thin filament consists of
two actin protein strands coiled helically around each other
At rest, active sites on the actin are blocked by
tropomyosin molecules
The thin filaments of striated muscle are made primarily of which protein(s)?
tropomyosin, actin, troponin, nebulin
The protein that regulates muscle contraction by controlling the availability of active sites on actin is called ________.
tropomyosin
The protein that is found in the Z line of a sarcomere is called ________.
actinin
Thin filaments are mostly made of the protein ______.
actin
Thick filaments are made of the protein ________.
myosin
In a neuromuscular junction, synaptic vesicles in the motor neuron contain which neurotransmitter?
acetylcholine (ACh)
When an action potential arrives at the axon terminal of a motor neuron, which ion channels open?
voltage-gated calcium channels
What means of membrane transport is used to release the neurotransmitter into the synaptic cleft?
exocytosis
The binding of the neurotransmitter to receptors on the motor end plate causes which of the following to occur?
Binding of the neurotransmitter causes chemically gated sodium channels to open in the motor end plate.
How is acetylcholine (ACh) removed from the synaptic cleft?
acetylcholinesterase (AChE; an enzyme)
The action potential on the muscle cell leads to contraction due to the release of calcium ions. Where are calcium ions stored in the muscle cell?
terminal cisternae of the sarcoplasmic reticulum
Each skeletal muscle fiber is controlled by a motor neuron at a single
neuromuscular junction
Receptors for acetylcholine are located on the
motor end plate
The action potential is conducted into a skeletal muscle fiber by
transverse tubules
When calcium ion binds to troponin,
tropomyosin moves into the groove between the helical actin strands
After death, muscle fibers run out of ATP and calcium begins to leak from the sarcoplasmic reticulum into the sarcoplasm. This results in a condition known as
rigor mortis
The cytoplasm of the neuromuscular terminal contains vesicles filled with molecules of the neurotransmitter
acetylcholine
Which statement about excitation-contraction coupling is incorrect?
Calcium ion is released from the transverse tubule
A single motor neuron together with all the muscle fibers it innervates is called
motor unit
The type of contraction in which the muscle fibers do not shorten is called
isometric
Suppose that you try to pick up an object and discover that it is much heavier than you expected. Which process must occur in the muscle to increase tension so you can pick up the object?
recruitment
A muscle produces its highest tension when in complete ________.
tetanus
A single contraction-relaxation cycle in a muscle fiber produces a ________.
twitch
During the Cori cycle, in the liver
glucose is produced from lactic acid.
During the recovery period the body's need for oxygen is increased because
additional oxygen is required to restore energy reserves consumed during exercise.
A resting muscle generates most of its ATP by
aerobic metabolism of fatty acids
Creatine phosphate
acts as an energy reserve in muscle tissue
During anaerobic glycolysis
ATP is produced, carbohydrate is metabolized, oxygen is not consumed, pyruvic acid is produced.
Aerobic metabolism normally provides ________ percent of the ATP demands of a resting muscle cell.
95
Which of these would lead to increased oxygen consumption?
increased muscle activity, increased conversion of lactic acid to glucose, increased heat production, increased aerobic respiration by muscle cells.
During activities requiring aerobic endurance
most of the muscle's energy is produced in mitochondria
Fast muscle fibers can adapt to aerobic metabolism by generating more mitochondria in response to
repeated, exhaustive stimulation
Which of the following statements is (are) true regarding human muscles?
most have slow and fast fibers, eye muscles are composed entirely of fast fibers, slow fibers are abundant in the calf muscles, slow fibers are abundant in the back muscles.
The ability of smooth muscle to function over a wide range of lengths is called
plasticity
Which of the following is not a function of smooth muscle tissue?
forcing blood from the heart into the major arteries
Inside a muscle, bundles of single muscle fibers form __________.
fascicles
The muscle action potentials that initiate contraction are transmitted from the sarcolemma into the interior of the muscle fiber by __________.
T tubules
T tubules and the terminal cisternae are clustered into structures called __________.
triads
The sarcoplasmic reticulum contains __________.
calcium
Which organelle completely surrounds each myofibril inside a muscle fiber?
sarcoplasmic reticulum
To what regulatory protein does calcium bind during the initiation of the contraction cycle in skeletal muscle fibers?
troponin
Which of the following causes the active site on actin to be exposed or uncovered?
tropomyosin shifting position
Which of the following most correctly describes excitation in the context of excitation-contraction coupling in skeletal muscle?
the generation of an action potential in the sarcolemma
Which of the following phrases best describes how excitation is coupled to contraction in skeletal muscle fibers?
through calcium release from the sarcoplasmic reticulum
Malignant hyperthermia (MH) is a rare genetic disease in which the sarcoplasmic reticulum leaks calcium when the patient is put under general anesthesia. Which of the following best describes how anesthesia would affect the skeletal muscles of a patient with MH?
The muscles would contract because of calcium binding to troponin.
What causes the release of calcium from the terminal cisternae of the sarcoplasmic reticulum within a muscle cell?
arrival of an action potential
The binding of calcium to which molecule causes the myosin binding sites to be exposed?
troponin
A myosin head binds to which molecule to form a cross bridge?
actin
What causes the myosin head to disconnect from actin?
binding of ATP
What energizes the power stroke?
hydrolysis of ATP