Stabilization of the deltoid muscles helps prevent subluxation of the humeral head from the glenoid foss a.True or False
FALSEWhy?The rotator-cuff muscles surround the head of the humerus, with the primary stabilizing function of holding the humeral head in the glenoid fossa. The lack of bone supporting the shoulder joint requires that these muscles and their associated tendons work as stabilizers to prevent subluxation or dislocation of the humeral head from the glenoid fossa.
You are watching: The quadriceps femoris is the prime mover of knee extension.
FALSEWhy?The quadriceps femoris is the prime mover for knee extension when acting concentrically. The hamstrings are the primary knee flexors.
TRUEWhy?The sartorius is the longest muscle in the body, originating from the anterior superior iliac spine (ASIS) and inserting onto the medial tibia, just below the knee. This multijoint muscle flexes, abducts, and externally rotates the hip while flexing and internally rotating the knee.
TRUEWhy?The hamstrings are referred to as a biarticular group of muscles, producing knee flexion as well as hip extension when acting concentrically. Additionally, the lateral hamstring, the biceps femoris, is an external rotator of the knee.
FALSEWhy?Although they originate from different areas, all four quadriceps muscles converge and share one tendon of insertion, the patellar tendon.
RelaxWhy?One of the Golgi tendon organ”s functions when it senses muscle contraction is to cause inhibition of the contraction (or relaxation). It has been theorized that this function adjusts muscle output in response to fatigue.
Muscle spindles respond to muscle fibers being overstretched by causing a _______________, known as the _______________.
Muscular contraction; stretch reflexWhy?The muscle spindle stretches when the muscle itself experiences a stretch force, thereby exciting the muscle spindle and causing a reflexive contraction in the muscle, known as the stretch reflex.
When the muscle spindle”s reflex contraction occurs, it causes the antagonist muscle group to relax. This is known as _______________.
Reciprocal inhibitionWhy?The muscle spindle”s reflex contraction of its associated muscle simultaneously causes the antagonist muscle group to relax. This is called reciprocal inhibition. For example, if the gastrocnemius is stretched rapidly, the muscle spindles within the muscle belly cause it to contract. At the same time, if the anterior tibialis (opposing muscle group) is contracting, the muscle spindle reflex causes it to relax.
TRUEWhy?Type IIx muscle fibers fatigue more easily than type I muscle fibers. In fact, these fibers cannot sustain their effort for more than a few seconds.
TRUEWhy?Type IIx fibers are the largest and fastest, and are capable of producing the most force of all the skeletal muscle fibers, but are notably less efficient than type I muscle fibers.