 Dear students, in this topic we shall discuss the dormant states sleep and tarpore. Dormancy is a state of slowed down physiological processes and is represented by reduced body activities and reduced metabolic rate. Dormancy has many types for example, sleep, tarpore, hibernation, winter sleep and activation. These are classified on the basis of duration of dormancy, ability for arousal during the dormant period and decrease in the body temperature during this state. Next we shall discuss sleep in detail. Sleep is a naturally recurring state of mind and body which is characterized by altered consciousness, decreased ability to react to stimuli, inhibition of most voluntary muscles and reduced interactions with the surroundings. It is the most thoroughly investigated form of dormancy. Dear students, various animals sleep for different times. The for example, seals which sleep on ice beds sleep only for few minutes at a time. Humans and many other mammals sleep hours at a time while big carnivores, for example lions and tigers sleep up to 20 hours a day especially after meals. Sleep is triggered by a variety of factors. The most common triggering factor in mammals is the build up of some sleep inducing substances in the extracellular fluids during the wakefulness timing. This accumulation happens in the central nervous system. The process of sleep is divided into two alternating phases. The first phase, the one phase is slow wave sleep which is called deep sleep. The second phase is the REM sleep or rapid eye movement sleep. Both these patterns of sleep alternate with each other many times during one sleeping shift. Dear students, the slow wave sleep is associated with a drop in body temperature, a drop in the hypothalamic temperature sensitivity and changes in respiratory and cardiovascular reflexes. The REM sleep is a small portion of the total sleep time. It is associated with the desynchronized and fast brain waves. Deep sleep eye movements also occur during this phase. This phase is also associated with loss of muscle tone. Suspension of homeostasis also occurs while the hypothalamic temperature control remains under suspension. Dear students, now we shall discuss another dormant state that is tarpore. You know that some small endothermic animals are continuous feeders. When they are inactive, they cannot feed during that period of inactivity because of non-feeding they cannot maintain high rates of metabolism without taking energy. To pass the periods of rest, they enter a state of dormancy which is called tarpore. During the tarpore, body temperature and metabolic rates are allowed to fall. Metabolic rate to maintain is very important when the energy is low or the animal cannot afford to fall, it will let its body temperature to fall. The basal metabolic rate is also lowered. This lowers the conversion of energy stores into body heat. Dear students, an animal immediately after coming out of tarpore has to do certain changes. It undergoes a burst of metabolic activity. Its body temperature rises through shivering or oxidation of brown fat and as a result animal becomes active. Dear students, we shall take few examples of tarpore. Daily tarpore is practiced by many terrestrial birds. A classic example of daily tarpore is found in the hummingbirds. Hummingbirds may body temperature, that is allowed to fall to about the level of 13 degree centigrade during tarpore. In addition to birds, some species of mammals also do daily tarpore, for example shiryus.