Abstract
The endocrine system comprised of ductless glands that secrete hormones. Along with the nervous system, it regulates various homeostatic mechanisms in an animal’s body and serves as a communication channel between various organ systems.
Based on their chemical nature, hormones can be classified as polypeptides, proteins, amines, or derivatives of fatty acids. They bind to specific receptors and elicit biological effects in the target organs. Cranial endocrine glands such as the hypothalamus, pituitary, and pineal gland secrete neurohormones that are synthesised by distinct neuroendocrine cells. Hypothalamic releasing and inhibitory hormones carried by the hypophyseal portal system serve to regulate different endocrine activities of the pituitary gland. The pituitary gland in turn controls various endocrine glands, forming a functional hierarchy in the endocrine system. The hypothalamus and pituitary hormones are responsible for maintaining normal growth, metabolism, reproduction, and animal behavioural patterns. The pattern of their secretion will be regulated chiefly by negative feedback mechanisms based on the changes in the concentration of a specific target hormone or a metabolite in circulation. Apart from the hypothalamus and the pituitary gland, melatonin secreted from the pineal gland regulates circadian rhythm, sleep, seasonal breeding and ensures optimum fertility in farm animals.S. K. B. A. A ( )
Department of Veterinary Physiology, Rajiv Gandhi Institute of Veterinary Education and Research, Kurumbapet, Puducherry, India
Sai Mounica P
Division of Veterinary Microbiology, ICAR-Indian Veterinary Research Institute, Bareilly, Uttar Pradesh, India
© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023
P. K. Das et al. (eds.), Textbook of Veterinary Physiology, https://doi.org/10.1007/978-981-19-9410-4_15
Graphical Abstract
Description of the graphic: Functional hierarchy of the endocrine system.
The releasing and inhibitory hormones secreted from the hypothalamus will act on the anterior pituitary lobe to affect its hormone secretion. The pituitary hormones further affect the secretory activities of different endocrine glands situated in the body. TRH thyrotropin-releasing hormone; CRH corticotropin-releasing hormone; GnRH gonadotropin-releasing hormone; GHRH growth hormone-releasing hormone; GnIH gonadotropin-inhibiting hormone; GHIH growth hormone inhibitory hormone; GH growth hormone; LH luteinising hormone; FSH follicle-stimulating hormone; ACTH adreno-corticotrophin hormone; PRL prolactin; ADH antidiuretic hormone; (+) stimulate; (-) inhibitKeywords
Hormone ∙ Hypothalamus ∙ Hypophyseal portal system ∙ Pituitary gland ∙ Pineal gland
Learning Objectives
• General properties of hormones
• Classification of different types of hormones
• General mechanism of action of peptide and steroid hormones
• Hypothalamus and its hormones
• Pituitary gland, its cell types and hormones
• Pineal gland
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