Biology Questions

Among the given options, the correct statement about immunodeficiency is "The causative agent in acquired immune deficiency syndrome (AIDS) is a virus that recognizes CD4 proteins".

The three types of muscle fibers are slow oxidative (SO), fast oxidative (FO) and fast glycolytic (FG). Slow oxidative fibers use aerobic metabolism to produce low power contractions over long periods and are slow to fatigue.

The mammalian heartis called myogenic (myo = muscle, genie = originating from). It means the heart beat or the activities of the heart are auto regulated which originates from a muscle called nodal tissue.In the human heart,heartbeat originates and contraction is initiated by a special modified heart muscle known as sinoatrial node. It is located in the right atrium; while the QRS waves are the depolarisation of the ventricles, which initiates the ventricular contraction.The T-wave represents the repolarisation,that is, the return of the ventricles from excited tonormal state.Hepatic portal system is the unique vascular connection that exists between the digestive tract and liver. This vein carries blood from intestine to the liver.