![]() These independent endocrine glands have been described only in arthropods (where neurohormones are still the dominant type of endocrine messenger) and in vertebrates (where they are best developed). Some of the cells of these endocrine glands are derived from nerve cells that migrated during the process of evolution from the nervous system to various locations in the body. True endocrine glands probably evolved later in the evolutionary history of the animal kingdom as separate, hormone-secreting structures. The most primitive endocrine systems seem to be those of the neurosecretory type, in which the nervous system either secretes neurohormones (hormones that act on, or are secreted by, nervous tissue) directly into the circulation or stores them in neurohemal organs (neurons whose endings directly contact blood vessels, allowing neurohormones to be secreted into the circulation), from which they are released in large amounts as needed. If mating occurs, other hormones stimulate the release of ova from the ovary of the female and a range of different hormones maintains pregnancy, delivery of the kittens and lactation. Fear and stress then activates the adrenal glands to secrete the hormone adrenaline which increases the heart and respiratory rates. The initial response of both cats may include spitting, fighting and spine tingling yowling - all brought about by the nervous system. In general Endocrine system is represented by a set of heterogeneous structure and origin of formations capable of internal secretion, ie the release of biologically active substances (hormones) that flow directly into the bloodstream.įor example, think about what happens when a male and female cat meet under your bedroom window at night. In general the nervous system responds rapidly to short-term changes by sending electrical impulses along nerves and the endocrine system brings about longer-term adaptations by sending out chemical messengers called hormones into the blood stream. The nervous and endocrine systems both work together to bring about this adaptation. In order to survive, animals must constantly adapt to changes in the environment. The homeostatic mechanisms that allow an animal to control its body temperature, water balance, blood volume and acid/base balance.What is meant by homeostasis and feedback control.The main hormones produced by the pineal, thyroid, parathyroid and adrenal glands, the pancreas, ovary and testicle in regard to their effects on the body.The main hormones produced by the two parts of the pituitary gland and their effects on the body.The relationship between the pituitary gland and the hypothalamus.The position of the main endocrine glands in the body.The characteristics of endocrine glands and hormones.Maintenance of blood volume after moderate blood lossĪfter completing this section, you should know:
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