stylopharyngeus muscle

Examples of stylopharyngeus muscle in the following topics:

• Glossopharyngeal (IX) Nerve

  • It controls muscles in the oral cavity and upper throat, as well as part of the sense of taste and the production of saliva.

• How Skeletal Muscles Are Named

  • Parallel muscles are characterized by fascicles that run parallel to one another, and contraction of these muscle groups acts as an extension of the contraction of a single muscle fiber.
  • Convergent muscles have a common point of attachment, from which the muscle fascicles extend outward, not necessarily in a specific spatial pattern, allowing the muscle to cover a broad surface.
  • In Pennate muscles, the tendon runs through the length of the muscle.
  • However, these muscles tend to have relatively more muscle fibers than similarly sized parallel muscles, and thus carry more tension.
  • If the central tendon branches within a pennate muscle, the muscle is called multipennate.

• Impacts of Exercise on Muscles

  • Sustained, repeated overload of a muscle group leads to hypertrophy and strengthening of those muscles.
  • In the short term muscle can become fatigued and sore for reasons like impaired blood flow, ion imbalance within the muscle, nervous fatigue, loss of desire to continue exercising, and most importantly, the accumulation of lactic acid in the muscle.
  • Muscle hypertrophy, or the increase in muscle mass due to exercise , particularly weight training, is a noticeable long-term effect of exercise.
  • Exercise of specific muscles can often result in hypertrophy in the opposite muscles as well, a phenomenon known as cross education.
  • With sufficient training the metabolic capacity of a muscle can change, delaying the onset of muscle fatigue.

• Types of Muscle Tissue

  • The function of muscles is movement, but the types of movement elicited differ between skeletal, cardiac, and smooth muscle.
  • Skeletal muscle fibers are the longest muscle fibers and have stripes on their surface.
  • Cardiac muscle is found in the walls of the heart.
  • Although cardiac muscle is involuntary in nature, it is structurally different from smooth muscle.
  • Cardiac muscle is striated, similar to skeletal muscle, but beats involuntarily.

• Arrangement of Fascicles

  • Skeletal muscles are grouped into fascicles, which are bunches of muscle fibers surrounded by a perimysium.
  • Skeletal muscle tissue is composed of numerous muscle fibers which are separated from adjacent muscles and other tissues by a layer of dense, elastic connective tissue termed the fascia.
  • This fascia can project beyond the end of the muscle and attach to bones, other muscles, and other tissues.
  • The fascia surrounding a muscle or muscle group does not contain many blood vessels, but is rich with sensory receptors.
  • It extends inwards and becomes the perimysium, then into the muscle separating muscle fibers into small bundles termed fascicles.

• Types of Muscle Contractions: Isotonic and Isometric

  • Muscle contractions are defined by changes in the length of the muscle during contraction.
  • Isotonic contractions maintain constant tension in the muscle as the muscle changes length.
  • Cross-bridge cycling occurs, shortening the sarcomere, muscle fiber, and muscle.
  • Cross-bridge cycling occurs even though the sarcomere, muscle fiber, and muscle are lengthening, controlling the extension of the muscle.
  • In both instances, cross-bridge cycling is maintaining tension in the muscle; the sarcomere, muscle fibers, and muscle are not changing length.

• Abnormal Contractions of Skeletal Muscle

  • Involuntary muscle contractions are referred to as spasms, and can be due to abnormal activity of the nerve or the muscle.
  • In medicine, a spasm is a sudden, involuntary contraction of a muscle, a group of muscles, or a hollow organ, or a similarly sudden contraction of an orifice .
  • Examples of spasms include muscle contractions due to abnormal nerve stimulation, or abnormal activity of the muscle itself.
  • In this case, the hypertonic muscle tone is excessive and the muscles are unable to relax.
  • Hypertonic muscle spasms is the state of chronic, excessive muscle tone, or tension in a resting muscle – the amount of contraction that remains when a muscle is not actively working.

• How Skeletal Muscles Produce Movements

  • Muscles exist in groupings that work to produce movements by muscle contraction.
  • For muscle pairings referred to as antagonistic pairs, one muscle is designated as the extensor muscle, which contracts to open the joint, and the flexor muscle, which acts opposite to the extensor muscle.
  • The majority of muscles are grouped in pairs, with an antagonist to each agonist muscle.
  • Exceptions include those muscles such as sphincter muscles that act to contract in a way that is opposite to the resting state of the muscle.
  • Synergist muscles act around a moveable joint to produce motion similar to or in concert with agonist muscles.

• Hypotonia and Hypertonia

  • Hypertonia is the reduced ability of muscles to stretch due to increased muscle tension; hypotonia, due to chronic reduced muscle tension.
  • Hypertonia is a reduction in the ability of a muscle to stretch due to increased muscle tension; it is caused by lesions to upper motor neurons.
  • Effects of hypertonia include spasticity dystonia (a state of prolonged muscle contractions) and rigidity (a state of muscle stiffness and decreased flexibility).
  • Hypotonia is the state of reduced muscle tone and tension, resulting in lessened ability to generate force from muscle contractions.
  • A muscle spindle, with γ motor neurons, sensory fibers and proprioceptor that detect the amount and rate of change of length in a muscle.

• Muscle Fatigue

  • Muscle fatigue refers to the decline in muscle force generated over sustained periods of activity or due to pathological issues.
  • Muscle fatigue has a number of possible causes including impaired blood flow, ion imbalance within the muscle, nervous fatigue, loss of desire to continue, and most importantly, the accumulation of lactic acid in the muscle.
  • Long-term muscle use requires the delivery of oxygen and glucose to the muscle fiber to allow aerobic respiration to occur, producing the ATP required for muscle contraction.
  • With sufficient training, the metabolic capacity of a muscle can change, delaying the onset of muscle fatigue.
  • Muscle fibers shrink or are lost and surrounding connective tissue hardens, making muscle contraction slower and more difficult.