Endocrine System in Animals

• The endocrine system helps in maintaining homeostasis by producing hormones that are sent to different glands and organs of the body, keeping the body healthy and in equilibrium
• Cells throughout our body sense the condition of our inner properties and send chemical signals to the nervous system or hormonal glands, which secrete hormones to control homeostasis
• Vertebrates and invertebrates possess an endocrine system but have a unique distinction between the two based on structures and functions
• In vertebrate organisms, the endocrine system comprises several glands such as the pituitary, thyroid, adrenal, and pancreas which secrete hormones that travel through tissues and organs
• Invertebrate organisms lack distinct endocrine glands but possess neurosecretory cells that perform similar functions as in vertebrates
• Hormonal signalling involves the release of hormones or chemical messengers secreted by endocrine glands and transferred through the bloodstream to target tissues and organs
• Regulation of hormone signalling involves both negative and positive feedback mechanisms to maintain hormone levels at equilibrium
• Major endocrine glands in vertebrates include the hypothalamus, pituitary (anterior and posterior), thyroid, parathyroid, adrenal (cortex and medulla), pancreas, pineal gland, testes, and ovaries
• Key hormones in vertebrates include:

  • Thyroid hormones (triiodothyronine and thyroxine) boost metabolism, protein production, and enzyme activity
  • Growth hormones (GH) promote cell division, growth, and regeneration, especially in cartilage and bones
  • Gonadal hormones regulate the reproductive system, with androgens like testosterone from testes and estrogens like progesterone and estradiol from ovaries
  • Adrenal hormones like cortisol and aldosterone respond to stress, control blood sugar, reduce inflammation, and regulate blood pressure
• Thyroid hormones, triiodothyronine and thyroxine, are peptide hormones that boost metabolism, protein production, and enzyme activity
• Growth hormones, such as somatotropin (GH), promote cell division, growth, and regeneration, especially in cartilage and bones
• Gonadal hormones, like testosterone from testes and progesterone and estradiol from ovaries, regulate the reproductive system and development of primary and secondary sexual characteristics
• Adrenal hormones, including cortisol and aldosterone, respond to stress, control blood sugar, reduce inflammation, and regulate blood pressure
• Aldosterone aids in controlling electrolyte levels and blood pressure
• "Fight or flight" hormones are norepinephrine (noradrenaline) and epinephrine (adrenaline), which are neurotransmitters that force the heart to beat faster and pump more blood to the brain and muscles
• Insects:

  • The endocrine system of insects consists of specialized glands known as corpora allata, which generate juvenile hormones
  • Juvenile hormones govern growth and development, while ecdysteroids control molting and metamorphosis
• Crustaceans:

  • Molting hormones are produced by Y-organs found in crustaceans, which include crabs and lobsters
  • Crustaceans also have hormones that prevent molting
• Annelids:

  • Hormones for development and reproduction are produced by segmental ganglia in annelids, which include leeches and earthworms
  • Annelids generate peptide hormones essential for sexual development, maturation, and regeneration
• Mollusks:

  • The ganglia of mollusks, such as snails and clams, contain neurosecretory cells that generate hormones
  • Peptides play a critical function in reproduction and neurotransmission in mollusks
• Echinoderms:

  • Specialized cells called neurons are found in echinoderms, which include sea urchins and starfish, and these cells secrete hormones
  • Echinoderms create peptide hormones that control development and growth
• Cnidarians:

  • Nerve cells of cnidarians, which include jellyfish and corals, provide hormones necessary for development and reproduction
  • The main neuropeptides produced by cnidarians control feeding behavior, muscle contraction, and metamorphosis
• Vertebrates and invertebrates both have an endocrine system that controls physiological functions like growth, metabolism, reproduction, and stress reactions
• Both vertebrates and invertebrates use hormone levels as feedback systems to sense changes in order to maintain homeostasis
• Vertebrates have more sophisticated endocrine systems with specialized glands that generate distinct hormones, while invertebrates have more scattered endocrine cells
• Invertebrates undergo hormone-regulated metamorphosis, while vertebrates use specialized glands and hormone regulation for growth and development
• Endocrine disruptors are chemicals that can impede the proper operation of the body's endocrine system, potentially causing cancer, metabolic diseases, and reproductive problems
• Endocrine disruptors can affect conservation efforts by hampering the reproduction of vulnerable animals and reducing genetic variety in populations