Physiology - Musculoskeletal
Which receptor protects the body by limiting structural damage to the muscle in situations of extreme tension? Golgi tendon organ Merkel's discs muscle spindles free nerve endings
Correct Answer: Golgi tendon organ Golgi tendon organs limit structural damage to the muscle by inhibiting the agonist and facilitating the antagonist.
Which of the following receptors senses compression of the joint capsule? Golgi-Mazzoni corpuscles free nerve endings Meissner's corpuscles Pacinian corpuscles
Correct Answer: Golgi-Mazzoni corpuscles Golgi-Mazzoni corpuscles sense compression of the joint capsule. They are located primarily in the joint capsule of the knee
The area of a sarcomere where only myosin filaments are present is known as the: A-band Z-line I-band H-zone
Correct Answer: H-zone The H-zone is located in the center of a sarcomere and decreases in size during a muscle contraction as the actin filaments slide over the myosin filaments toward the center of the sarcomere. Only myosin filaments are present in the H-zone.
Which type of sensory receptor is most susceptible to light touch? Golgi tendon organs Meissner's corpuscles Pacinian corpuscles Ruffini endings
Correct Answer: Meissner's corpuscles Meissner's corpuscles, located in the dermis, are a type of mechanoreceptor responsible for detecting light touch.
Which type of sensory receptor is located in the subcutaneous tissue? Merkel's discs Meissner's corpuscles Pacinian corpuscles Ruffini endings
Correct Answer: Pacinian corpuscles Pacinian corpuscles are located in the subcutaneous tissue of the skin and in deep tissues of the body. The remaining options are located in the epidermis or dermis.
What is the thin protein of the myofilament called? sarcomere sarcolemma myosin actin
Correct Answer: actin Actin and myosin are the proteins that compose myofilaments. These myofilaments form sarcomeres, which are the contractile units of the muscles. Actin is the thin filament composed of troponin and tropomyosin. Actin and myosin use cross-bridge cycling to contract the muscle fibers.
The energy required for actin and myosin cross-bridging inside a sarcomere is produced through the breakdown of which substance? calcium adenosine triphosphate glycogen acetylcholine
Correct Answer: adenosine triphosphate Energy for muscle activity comes from the hydrolysis, or breakdown, of adenosine triphosphate (ATP) into adenosine diphosphate (ADP) and phosphate. Another molecule of ATP must replace the ADP on the myosin cross-bridge head in order for the head to detach from the active actin site and return to the resting position.
In which of the following sports would it be most beneficial to have a high percentage of slow twitch muscle fibers? distance running weight lifting javelin alpine skiing
Correct Answer: distance running Characteristics of type I "slow twitch" muscle fibers include aerobic, red, tonic, slow twitch, and slow oxidative. Marathon runners and swimmers are two examples of athletes that would benefit from having a high percentage of slow twitch muscle fibers.
According to the stress-strain curve, which of the following phases occurs when tissues are stretched so that the collagen fibers align, but when tension is released the tissues return to their original size and shape? toe region elastic range plastic range failure
Correct Answer: elastic range The elastic range comes directly after the toe region and is characterized by the alignment of collagen fibers, strain between the bonds of fibers and matrix, and displaced water from the ground substance. This range of load and deformation does not exceed the elastic limit, therefore the effects are reversible once the load is removed from the tissues.
Which term best describes non-contractile tissue that envelops the entire muscle creating a fascial sheath? epimysium perimysium endomysium sarcomere
Correct Answer: epimysium The epimysium is the outermost layer of non-contractile tissue of a muscle. The epimysium envelops the muscle, the perimysium envelops the fiber bundles, and the endomysium separates individual myofibrils and muscle fibers. A sarcomere is the contractile component of a muscle.
What is the major limitation of type II B muscle fibers? slow acting limited force production low velocity high fatigability
Correct Answer: high fatigability Muscle fibers are defined as type I, type II A or type II B. Type II B has larger muscle fibers, less blood supply, and fewer mitochondria than the other fiber types. Use of the fast-glycolytic energy system allows the muscle fiber to produce a large total peak power, quickly, in about 25 milliseconds, however, fatigue occurs rapidly.
Of the three biological energy systems, which factor(s) determine which energy system is most active during a given activity? bodyweight and gender of the individual intensity and duration of the activity macronutrients consumed in the most recent meal previous training experience of the individual
Correct Answer: intensity and duration of the activity All three energy systems (phosphagen, glycolysis, and the oxidative system) are active at any given time. However, the magnitude of the contribution of each system is primarily dependent on the intensity of the activity and secondarily the duration of the performance of the activity in question
Which sensory receptor is responsible for responding to mechanical deformation of the receptor by touch, pressure, stretch or vibration? mechanoreceptors chemoreceptors thermoreceptors proprioceptors
Correct Answer: mechanoreceptors Sensory receptors are located at the distal ends of peripheral neurons. Each type of receptor is specialized, responding only to a specific type of stimulus. Examples of mechanoreceptors include free nerve endings, Merkel's disks, Ruffini endings, hair follicle endings, Meissner's corpuscles, and Pacinian corpuscles.
Which biological energy system is the primary source of adenosine triphosphate at rest? glycolysis oxidative system phosphagen system Krebs cycle
Correct Answer: oxidative system The oxidative system is the primary source of adenosine triphosphate (ATP) at rest and with low-intensity activity. The oxidative system uses primarily carbohydrates (approximately 70%) and fats (approximately 30%) as substrates. Protein is not normally metabolized to any meaningful extent except during long bouts of exercise and extreme conditions such as starvation.
Which type of receptor provides the brain with information about where the body is in space? nociceptors exteroceptors interoceptors proprioceptors
Correct Answer: proprioceptors In the limbs, the proprioceptors are sensors that provide information about joint angle, muscle length, and muscle tension, which is integrated to give information about the position of the limb in space. The muscle spindle is one type of proprioceptor that provides information about changes in muscle length.
Which of the following is the smallest element of muscular tissue? fascicle myofibrils motor unit sarcomere
Correct Answer: sarcomere A sarcomere is the basic unit of striated muscle tissue. The structure is made up of actin and myosin myofilaments that cause shortening of the muscle unit upon contraction.
The ability of the body to bypass slow-twitch motor units and recruit fast-twitch motor units when performing an explosive movement is referred to as: size principle cross-education specificity selective recruitment
Correct Answer: selective recruitment Normally, slow-twitch motor units are recruited initially with fast-twitch motor units being recruited only when needed. When powerful, explosive movements are performed, there is not enough time to go through the normal process since speed is a major factor. In this situation, the body bypasses recruitment of the slow-twitch motor units and instead almost immediately activates the fast-twitch motor units.
The designation of a muscle fiber as fast-twitch or slow-twitch is primarily determined by which factor? the amount of time it takes the fiber to develop force and relax the amount of time it takes the fiber to reach a full contraction the amount of time it takes the fiber to relax from a full contraction the speed of transmission of an action potential
Correct Answer: the amount of time it takes the fiber to develop force and relax The twitch classification of a muscle is determined by the time it takes for the fiber to develop force and then relax. A fast-twitch fiber develops force quickly and then quickly relaxes resulting in a short "twitch" time. A slow-twitch fiber develops force slowly and then takes longer to relax resulting in a long "twitch" time.
The amount of force produced by a muscle at any point in time is directly related to: the number of myosin cross-bridge heads bound to actin filaments the length of the muscle belly the gender of the individual producing the force the age of the individual producing the force
Correct Answer: the number of myosin cross-bridge heads bound to actin filaments The number of myosin cross-bridge heads that are attached to actin filaments at any point in time dictates the force production of that muscle. Actin and myosin cross-bridging occurs in the smallest contractile unit of a skeletal muscle known as a sarcomere.
