Toohat 13: muscle tissue
An activity that would require primarily anaerobic metabolism would be which of the following? A.Low intensity like washing dishes B.High intensity intermittent bouts like jumping rope C.Moderate intensity like going on a walk D.Running a 100m dash
B.High intensity intermittent bouts like jumping rope Explanation: In order to perform forceful movements, the skeletal muscle needs more ATP than can be produced with aerobic metabolism alone. Therefore, pyruvic acid is also broken down without oxygen though glycolysis to supply the remainder of ATP needed.
To allow for cross-bridge interactions during muscular contraction, Ca2+ must bind with which of the following? A.Troponin B.Tropomyosin C.Actin D.Myosin
A. Troponin Explanation: A cross-bridge between actin and myosin is formed when Ca^{2+}2+ is released from the sarcoplasmic reticulum and binds to troponin. This binding causes troponin to change its shape and rotate in such a way that it allows the myosin head to attach on the binding site of actin to form a cross-bridge
Once an action potential excites the sarcolemma, a series of actions take place in order to produce a muscle contraction. This process primarily includes which of the following ions? A.Ca2+ B.ATP C.Potassium D.Sodium
A.Ca2+ Explanation: Ca2+ is responsible for the coupling of excitation of the fiber membrane to the muscle contraction.
Smooth muscles are responsible for which of the following functions? A.Involuntary movements like regulation of blood flow through vital organs. B.Voluntarily contracting to digest food. C.Coordinating actions and transmitting signals to and from different parts of its body. D.Permitting blood to circulate and transport nutrients
A.Involuntary movements like regulation of blood flow through vital organs.
Delayed-onset muscle soreness is due to which of the following mechanisms? A.Microtears to the muscle fiber B.Inury to the connective tissue C.Lactic acid build up
A.Microtears to the muscle fiber B.Inury to the connective tissue Explanation: Lactic acid is not likely the cause of muscle soreness because it is reused in the muscle to produce energy and is generally gone from the muscle one hour post-exercise. Instead, research has shown that microtrauma to the muscle fiber and connective tissue during eccentric muscle actions are most likely the cause of DOMS.
What forms of energy reserves do resting skeletal muscle fibers contain?
ATP creatine phosphate glycogen Explanation: At rest, a muscle fiber has time to replenish each type of energy reserve. At high intensities that are ongoing, energy stores may become depleted, which requires a person to slow down their force output due to the lack of available energy.
Which of the following is not an effect of aging on the muscular system? A. Atrophy of type II fibers B. Sarcopenia C. Strength and power decline D. Muscle fibers become shorter
D. Muscle fibers become shorter
Skeletal muscle maintains heat in the body by doing which of the following?
Releasing heat with muscle contractions
What is the neuromuscular junction?
Where the axons of motor nerves meet the muscle A chemical synapse formed between a motor neuron and a muscle fiber
What is the principle that describes how the strength by which a nerve or muscle fiber responds to a stimulus is independent of the strength of the stimulus?
all-or-nothing principle
The disassociation of the myosin cross-bridge is directly activated by which of the following?
attachment of ATP to myosin heads
Which of the following is NOT a function of skeletal muscle? a Maintains posture b Regulates temperature c Circulates blood through the body d Creates bodily movement
c. circulates blood throughout body
Smooth muscle can maintain optimal force at a range of lengths due to which of the following characteristics?
plasticity Explanation: Plasticity is the ability to maintain contractibility over a wide range of lengths. As a result, smooth muscle can contract over a range of lengths four times greater than skeletal muscle.
If a motor unit contained 1500 muscle fibers, what type of movements would this muscle likely be responsible for?
powerful movements Explanation: higher number of fibers for powerful movements and lower number for fine movements
When an action potential moves down an excitable membrane, this process is called ______________.
propagation
In order to create movement (and according to the sliding filament theory), muscles:
pull Explanation: Muscles create movement by pulling toward the center of the sarcomere
Which of the following cells are spindle-shaped and have a single, centrally located nucleus? a. Skeletal muscle cells b. Cardiac muscle cells c. Smooth muscle cells d. Brain cells
smooth muscle cells
Muscle tone increases as ____________ increases
strength
Action potential propagation of an excitable membrane involves:
the same events taking place over and over Explanation: During excitation, action potential sends a message across the sarcolemma and affects the entire excitable membrane.
Most smooth muscles are single-unit functioning, meaning that either the whole muscle ______________ or the whole muscle ______________.
contracts, relaxes
Which of the following is not true regarding differences in smooth and skeletal muscle? a. There are more cross-bridges in smooth muscle cells than skeletal muscle cells. b. Smooth muscle can produce more force and achieve a greater change in size than skeletal muscle. c. Smooth muscle cells are involuntary, slower, and able to endure longer than skeletal muscle. d. Smooth muscle cells are under more conscious control than skeletal muscles.
d. Smooth muscle cells are under more conscious control than skeletal muscles. Explanation: Smooth muscle cells are responsible for involuntary movements like regulation of blood flow through vital organs and movement of materials along digestive and urinary passageways.
What is the sequence of events that converts action potentials in a muscle fiber to a contraction?
excitation-contraction coupling
Muscle fibers in a skeletal muscle form bundles called ______________.
fascicles Explanation: Fascicles are several muscle fibers (10-100) bundled together by a sheath called perimysium
When muscle contraction occurs, which of the following is true?
z-disks move closer together Explanation: The Z-disks, located on each end of the sarcomere, move closer together, which shortens the length of the muscle.
What molecule is responsible for the coupling of excitation of the fiber membrane to the muscle contraction?
CA2+
Sort the steps in the sliding filament theory in order of occurrence.
1. cross-bridge 2. power-stroke 3.dissociate 4. reactivate
An activity that would require anaerobic activity would be which of the following?
100-meter dash
When a person dies and rigor mortis occurs, which molecule causes the maintenance of a constant muscle contraction?
CA2+
Smooth muscle can hold an involuntary contraction for long periods of time; some smooth muscles are in nearly a constant state of contraction. Which of the following is an example of an involuntary smooth muscle contraction that humans are consciously aware of? A.Bladder collecting urine before disposal via urination B.Heart contracting to pump blood to the extremities C.Uterus contractions during child birth D.Biceps contracting to pick up a pencil
C. Uterus contractions during child birth
Match the following structural and functional differences to the respective muscle type: Contractions are involuntary¸ slower¸ and are able to endure When it contracts¸ the muscle cell twists in a spiral-like fashion Pull on the tendons which are inserted into the bones to create movement Made of hundreds or even thousands of fibers that are bundled together and wrapped by a connective tissue covering Has the ability to maintain contractibility over a wide range of lengths
Contractions are involuntary¸ slower¸ and are able to endure= SMOOTH MUSCLE When it contracts¸ the muscle cell twists in a spiral-like fashion= SMOOTH MUSCLE Pull on the tendons which are inserted into the bones to create movement= SKELETAL MUSCLE Made of hundreds or even thousands of fibers that are bundled together and wrapped by a connective tissue covering= SKELETAL MUSCLE Has the ability to maintain contractibility over a wide range of lengths= SMOOTH MUSCLE
The primary functions of skeletal muscle include which of the following?
Create movement by contracting and pulling on tendons Communicate by speaking¸writing¸ and making facial expressions Support organs and shield tissue from injury
Sort the following sequence of events: What happens in the skeletal muscle when lactic acid is produced during high intensity activity?
Lactic acid causes an increase in acidity. Muscular fatigue ensues. When exertion levels are still high¸lactic acid is converted to pyruvic acid in the liver. Eventually muscular activity decreases as a result of fatigue. When more oxygen is available¸lactic acid is reused in the muscle as energy.
Match the following skeletal muscle functions with their definitions:
Movement= created by contracting and pulling on tendons Supporting Structure= support visceral organs and shield tissue from injury Posture= contract to hold the body still Communication= speak, type, write, facial expressions, and gestures
Do muscles only push, only pull, or do they push and pull?
Muscles only pull. Yes, we can push things away from our bodies with our arms or legs (e.g. a push up). However, a pushing movement is a function of the muscles pulling toward their center.
Match the following structural and functional differences to the respective muscle type. Non-striated¸ sheets of tissue that line hollow organs Striated tissue under voluntary control of the nervous system wherein cells are lined up in sarcomeres and bundled together by connective tissue Made up of muscle tissue¸ connective tissue¸ blood vessels¸ and nerves Has more cross-bridges and is therefore able to produce more force with slower and enduring contractions Cells are scattered¸ have greater plasticity¸ and are able to contract at a range of lengths
Non-striated¸ sheets of tissue that line hollow organs= SMOOTH MUSCLE Striated tissue under voluntary control of the nervous system wherein cells are lined up in sarcomeres and bundled together by connective tissue= SKELETAL MUSCLE Made up of muscle tissue¸ connective tissue¸ blood vessels¸ and nerves= SKELETAL MUSCLE Has more cross-bridges and is therefore able to produce more force with slower and enduring contractions= SMOOTH MUSCLE Cells are scattered¸ have greater plasticity¸ and are able to contract at a range of lengths= SMOOTH MUSCLE
A cross-bridge forms when which of the following occurs?
The myosin heads bind to the attachment sites on the actin myofilament. Actin and myosin bind to form a physical link.
All innervated muscle fibers of a motor unit fully contract when stimulated beyond threshold due to which of the following explanations:
When a motor neuron is stimulated, all of the fibers it innervates are activated Explanation: The motor unit recruits all of the muscle fibers that the motor neuron innervates.
The contraction of a skeletal muscle exerts a pull on a bone because...
muscles are attached to bones by tendons Explanation: Muscles are attached to bones by tendons, which are inserted into the bone. When the muscle contracts, it shortens and pulls on the tendon, which in turn pulls on the bone to create movement.