Muscular System Questions

Describe two types of recommended exercise.

According to the National Institue on Aging, exercise should include strength training and aerobics.

What is the relationship between cellular respiration and heat production?

All active cells generate heat, which is a by-product of cellular respiration.

What is the function of an antagonist? A synergist?

An antagonist works against the action. Synergists contribute to an action by helping the agonist.

Describe how connective tissue is associated with a skeletal muscle.

An individual skeletal muscle is separated from adjacent muscles and held in position by layers of dense connective tissue called fascia. Layers of connective tissue, therefore, enclose and separate all parts of a skeletal muscle.

Which muscles move the thigh?

Anterior group: psoas major, iliacus Posterior group: gluteus maximus, gluteus medius, gluteus minimus, piriformis, tensor fasciae latae

What changes are associated with an aging muscular system?

At a microscopic level, supplies of the molecules that enable muscles to function-myoglobin, ATP, and creatine phosphate- decline. Gradually, the muscles become smaller, drier, and capable of less forceful contraction. Connective tissue and adipose cells begin to replace some muscle tissue. By age eighty, nearly half the muscle mass has atrophied, due to a decline in motor neuron activity. Diminishing muscular strength slows reflexes.

Define agonist

Causes an action

What special characteristics of visceral smooth muscle make peristalsis possible?

Conduction of impulses from cell to cell and rhythmicity are largely responsible for the wavelike motion called peristalsis of certain tubular organs. Peristalsis consists of alternate contractions and relaxations of the longitudinal and circular muscles.

Muscles that move the foot?

Dorsal flexors: tibialis anterior, fibularis tertius, extensor digitorum longus, extensor hallucis longus invertor: tibialis posterior

Describe the general structure of a skeletal muscle fiber.

Each fiber forms from many undifferentiated cells that fuse during development. The resulting multinucleated muscle fiber is a thin, elongated cylinder with rounded ends that attach to the connective tissues associated with a muscle. Just beneath the muscle cell membrane (sarcolemma), the cytoplasm (sarcoplasm) of the fiber contains many small, oval nuclei and mitochondria. The sarcoplasm also has abundant long, parallel structures called myofibrils.

Explain the physical relationship between the sarcoplasmic reticulum and the transverse tubules

Each transverse tubule lies between two enlarged portions of the sarcoplasmic reticulum called cisternae.

Which muscles provide facial expression?

Epicranius, orbicularis oculi, orbicularis oris, buccinator, zygomaticus major, zygomaticus minor, platysma

Define muscle tone

Even when a muscle appears to be at rest, its fibers undergo a certain degree of sustained contraction. This continuous state of partial contraction is called muscle tone (tonus), and it is a response to impulses originating repeatedly in the spinal cord and conducted along axons to a few muscle fibers.

Muscles that move the leg?

Flexors: Beiceps femoris, semitendinosus, semimembranosus, sartorius Extensors: quadriceps femoris group

Muscles that move the forearm?

Flexors: Biceps brachii, brachialis, brachioradialis Extensor: Triceps brachii Rotators: Supinator, pronator teres, pronator quadratus

Which muscles move the arm

Flexors: Coracobrachialis, Pectoralis major Extensors: Teres major, Latissimus dorsi Abductors: supraspinatus, deltoid Rotators: subscapularis, infraspinatus, teres minor

Muscles that move the hand?

Flexors: flexor carpi radialis, flexor carpi ulnaris, palmaris longus, flexor digitorum profundus, flexor digitorum superficialis Extensors: Extensor carpi radialis longus, extensor carpi radialis brevis, Extensor carpi ulnaris, Extensor digitorum pectineus, adductor brevis, adductor longus, adductor magnus, gracilis.

What is the function of inercalated discs?

Intercalated discs help join cells and transmit the force of contraction from cell to cell, and also allow ions to diffuse between the cells.

How is cardiac muscle similar to skeletal muscle?

It is composed of striated cells joined end to end, forming interconnected, branching, three-dimensional networks. Each cell contains a single nucleus and many filaments of actin and myosin similar to those in skeletal muscle.

Which muscles provide the ability to chew?

Masseter, Temporalis, medial pterygoid, lateral pterygoid

Distinguish between fast-twitch and slow-twitch muscle fibers.

Slow-twitch fibers (type 1) are always oxidative and are therefore resistant to fatigue. Fast-twitch fibers (type 2) may be primarily glycolytic (fatigable) or primarily oxidative (fatigue resistant). Slow-twitch (type 1) fibers, such as those in the long muscles of the back, are also called red fibers, because they contain the red, oxygen-storing pigment myoglobin. Fast-twitch glycolytic (type 2B) are also called white fibers, because they have less myoglobin and have a poorer blood supply than red fibers.

How is smooth muscle contraction similar to skeletal muscle contraction?

Smooth muscle contractions resemble skeletal muscle contraction in a number of ways. Both mechanisms reflect reactions of actin and myosin. Both are triggered by membrane impulses and release of calcium ions. Finally, both use energy from ATP molecules. However, smooth muscle and skeletal muscle also differ in their actions. Smooth muscle cells do not have troponin, the protein that binds to calcium ions in skeletal muscle. Instead, smooth muscle uses a protein called calmodulin, which binds to the calcium ions released when its cells are stimulated, activating contraction. In addition, much of the calcium necessary for smooth muscle contraction diffuses into the cell from the extracellular fluid.

How do the contraction mechanisms of smooth and skeletal muscles differ?

Smooth muscle is slower to contract and relax than skeletal muscle, yet smooth muscle can forcefully contract longer with the same amount of ATP.

Which muscles provide the ability for head movements?

Sternocleidomastoid, splenius capitis, semispinalis capitis, scalenes, quadratus lumborum, erector spinae

What are the sources of oxygen required for the aerobic reactions of cellular respiration?

The complete breakdown of glucose occurs in the mitochondria and is aerobic, requiring oxygen. Blood carries the oxygen necessary to support the aerobic reactions of cellular respiration from the lungs to body cells. In regions of the body where the oxygen concentration is low, oxygen is released from hemoglobin and becomes available for the aerobic reactions of cellular respiration.

Distinguish between a twitch and a sustained contraction.

The contractile response of a single muscle fiber to a single impulse is called a twitch. A twitch consists of a period of contraction, during which the fiber pulls at its attachments, followed by a period of relaxation, during which the pulling force declines. During sustained muscle contractions smaller motor units, whose neurons have smaller-diameter axons, are more easily stimulated and are recruited first. Larger motor units, whose neurons have larger diameter axons, respond later and with greater force. Summation and recruitment together can produce a sustained contraction of increasing strength.

What are the sources of energy used to regenerate ATP?

The initial source of energy available to regenerate ATP from ADP and phosphate is creatine phosphate.

What characteristic of cardiac muscles cause the heart to contract as a unit?

The ion movement from intercalated discs allows action potentials to travel from cell to cell. In this way, impulse passes rapidly to other cells of the network, and the whole structure contracts as a unit or syncytium; that is, the network responds to stimulation in an all-or-nothing manner.

Distinguish between the origin and the insertion of a muscle.

The less movable end is called the origin of the muscle, and the more movable end is called its insertion.

Describe a neuromuscular junction.

The synapse where a motor neuron axon and a skeletal muscle fiber meet.

How does cardiac muscle differ from skeletal muscle?

The transverse tubules of cardiac muscle cells are larger than those in skeletal muscle cells, and they release many calcium ions into the sarcoplasm in response to a single impulse.

Describe two major types of smooth muscle

The two major types of smooth muscle are multiunit and visceral. In multiunit smooth muscle, the muscle cells are less well organized and function as separate units, independent of neighboring cells. Smooth muscle of this type is found in the irises of the eyes and in the walls of large blood vessels. Typically, multiunit smooth muscle contracts only after stimulation by neurons or certain hormones. Visceral smooth muscle (single-unit smooth muscle) is composed of sheets of spindle-shaped cells held in close contact by gap junctions.

Explain why skeletal muscle fibers appear straited

They consist of two types of protein filaments: thick filaments composed of the protein myosin, and thin filaments composed primarily of the protein actin. (Two other thin filament proteins, troponin and tropomyosin, will be discussed later.) The organization of these filaments produces the alternating light and dark striations characteristic of skeletal muscle (and cardiac muscle) fibers. The striations form a repeating pattern of units called sarcomeres along each muscle fiber.

Which muscles move the pectoral girdle?

Trapezius, rhomboid major, rhomboid minor, levator scapulae, serratus anterior, pectoralis minor

Explain how a motor neuron action potential can trigger a skeletal muscle fiber contraction.

When a motor neuron stimulates a muscle cell, the situation changes. The result of this second set of channels opening is an impulse, an action potential. In much the same way that an impulse is conducted along the axon of a neuron, an impulse now spreads throughout the muscle cell. This electrical impulse is what triggers the release of calcium ions from the sarcoplasmic reticulum, leading to muscle contraction.

Define threshold stimulus

When an isolated muscle fiber is exposed to a series of electrical stimuli of increasing strength, the fiber remains unresponsive until a certain strength of stimulation called a threshold stimulus is applied.

How do lactic acid and oxygen debt relate to muscle fatigue?

When the oxygen supply is low, however, the pyruvic acid reacts to produce lactic acid, which enters the bloodstream and eventually reaches the liver. Consequently, as lactic acid accumulates, a person develops an oxygen debt or excess postexercise oxygen consumptions (EPOC) that must be repaid at a later time. The degree of oxygen debt includes the amount of oxygen that liver cells require to convert the accumulated lactic acid into glucose, as well as the amount that the muscle cells require to resynthesize sufficient ATP and creatine phosphate to restore their original concentrations. The degree of oxygen debt also reflects the oxygen required to restore blood and tissue oxygen levels to preexercise levels. As muscle metabolism shifts from aerobic to anaerobic ATP production, lactic acid begins to accumulate in muscles and to appear in the bloodstream (lactic acid threshold). In the body, lactic acid dissociates rapidly into lactate ion (lactate) and hydrogen ion. Recent studies on the effect of both hydrogen ion and lactate suggest that the relationship between lactic acid and muscle fatigue may not be as clear-cut as once thought.

Explain how parts of the upper limb form a first-class lever and a third-class lever.

When the upper limb bends, the forearm bones represent the rigid bar, the elbow joint is the fulcrum, the hand is moved against the resistance provided by the weight, and the force is supplied by muscles on the anterior side of the arm. One of these muscles, the biceps brachii, is attached by a tendon to a projection (radial tuberosity) on the radius bone in the forearm, a short distance below the elbow. Because the parts of this lever are arranged in the sequence resistance-force-fulcrum, it is a third-class lever. When the upper limb straightens at the elbow, the forearm bones again serve as the rigid bar, the hand moves against the resistance by pulling on the rope to raise the weight, and the elbow joint serves as the fulcrum. However, in this case, the triceps brachii, a tendon of this muscle attaches to a projection (olecranon process) of the ulna bone at the point of the elbow. Because the parts of the lever are arranged resistance-fulcrum-force, it is a first-class lever.

Explain the differences between isometric and isotonic contractions.

if a person lifts an object, the muscles remain taut, their attached ends pull closer together, and the object is moved. This type of contraction is termed isotonic (equal force- change in length), and because shortening occurs, it is called concentric. Tension within the muscles increases, but the wall does not move, and the muscles remain the same length. Contractions of this type are called isometric (equal length- change in force). Isometric contractions occur continuously in postural muscles that stabilize skeletal parts and hold the body upright.