71) Unlike inspiration, expiration is a passive act because no muscular contract

Question

71) Unlike inspiration, expiration is a passive act because no muscular contractions are involved. Expiration, however, depends on two factors. Which of the choices below lists those two factors? A) the expansion of respiratory muscles that were contracted during inspiration and the lack of surface tension on the alveolar wall B) combined amount of CO2 in the blood and air in the alveoli C) the recoil of elastic fibers that were stretched during inspiration and the inward pull of surface tension due to the film of alveolar fluid D) the negative feedback of expansion fibers used during inspiration and the outward pull of surface tension due to surfactant 72) Which of the following is true regarding the generation of a membrane potential? A) In the polarized state, sodium and potassium ion concentrations are in static equilibrium. B) When the sodium-potassium pump is activate d, potassium is pumped into the cell twice as fast as the sodium is pumped out, thus causing the membrane potential. C) The maintenance of the potential is based exclusively on diffusion processes. D) Both potassium and sodium ions can "leak" through the cell membrane due to diffusion. 73) Which of the following statements is false or incorrect? A) Cardiac muscle contracts when stimulated by its own autorhythmic muscle cells. B) Cardiac muscle fibers can use lactic acid to make ATF C) Cardiac muscle fibers depend mostly on anaerobic cellular respiration to generate ATP. D) Under normal resting conditions, cardiac muscle tissue contracts and relaxes about 75 times per minute. 74) If the ventral root of a spinal nerve were cut, what would be the result in the tissue or region that nerve supplies? A) a complete loss of voluntary movement B) loss of neither sensation nor movement but only of autonomic control C) a complete loss of sensation and movement D) complete loss of sensation

Explanation / Answer

71) Inspiration is a active process, due to the contraction of the inspiratory muscles. But expiration is a passive process. Following inspiration, the expiration occurs due to the recoil of elastic fibers that were stretched during inspiration and the inward pull of surface tension due to the film of the alveolar fluid. The elastic recoil of the lungs depend two factors,

1- elasticity of the collagen fires: Elastic fibers are present plentifully in the lungs, around the alveolar and bronchial tree. During inspiration, due to stretching, the lungs expand but as soon as the inspiration ends, the elastic fibers recoil and the expansion occurs.

2)Surface tension: The inner side of the alveolus, normally, is lined by a thin, monomolecular layer of fluid. Molecules of this layer of fluid exert van der walls force (inter molecular force that attract each other). As a result of this, molecules of fluid cling to each other and resist separation. The resultant of all such forces, is the surface tension and if not opposed causes collapse of the lungs.

72) The generation of membrane potential: When the sodium potassium pump is activated potassium is pumped in to the cell twice as fast as the sodium is pumped out, which causes membrane potential. The factors include the genesis of membrane potential includes the selective permeability of the cell membrane.

74) The ventral root of the spina nerve also called as motor nerve and is responsible for voluntary motor activity of the muscle. The dorsal root of the nerve is called sensory nerve and is responsible for carrying sensation. The mixed nerve consists of both the motor and sensory fires. So when there I a cut in ventral nerve root, which result in complete loss of voluntary movement.

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