Animal Physiology (BIOB34) Term Test 2 Study

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University of Toronto Scarborough
Biological Sciences
Rosada Silva

Lecture 9: Endocrine System I Readings: pgs. 122-137 Key Thoughts Overview of endocrine system Evolution and diversity Mechanism of action Endocrine reflexes Pituitary glands Connection between Nervous System and Endocrine System The nervous system directs an immediate response to stimuli, usually by coordinating the activities of other organ systems Could lead to a long-term change directed by the endocrine system Both the endocrine and nervous system o Rely on chemicals that bind to receptors on target cells o Share many chemical messengers Norepinephrine and epinephrine can be neurotransmitters and hormones o Regulated primarily by negative feedback mechanisms o Share the common goal to preserve homeostasis By coordinating and regulating activities of other cells, tissues, organs and systems Vertebrate endocrine system o The endocrine system includes all the endocrine cells and tissues of an animal o Endocrine cells are glandular secretory cells that release their secretions into the blood Secretory Tissue Hormone Chemical Class Effects Pineal gland Melatonin Amine Circadian and seasonal rhythms Hypothalamus (clusters Trophic hormones Peptides Regulation of anterior pituitary of secretory neurons) Posterior pituitary Breast & uterus in mammals: also (extensions of Oxytocin Peptides hypothalamic neurons) involved in social bonding & behaviour Water reabsorption in excretory Vasopressin Peptides system Vasotocin (fish, Peptides Activates similar to both oxytocin and amphibians, birds) vasopressin Milk production in mammals, Anterior Pituitary gland Prolactin Peptides osmoregulation, growth, metabolism Growth Hormone (GH) Peptides Growth, metabolism Adrenocorticotropic Hormone (ACTH) Peptides Release of corticosteroids Thyroid stimulating Synthesis and release of thyroid Peptides hormone (TSH) hormones Follicle stimulating Egg or sperm production; sex hormone hormone (FSH) Peptides production Luteinizing hormone Sex hormone production; egg or sperm Peptides (LH) production o Endocrine system of vertebrates are all similar, same endocrine cells and tissues o Chemical messengers, receptor and cell signaling mechanisms of animals share many similarities (suggests common ancestor) Animals can use hormones for long-term effects o Substantial differences in endocrine system of different animals (ie. vertebrate vs. arthropods) o Invertebrates have few endocrine glands and most endocrine signaling utilizes neurohormones rather than hormones Evolution of endocrine system o Evolutionary changes in way the tissues respond to a hormone, rather than a change in hormone molecules o Some hormones have different effects in different animals o The endocrine system is quite diverse mostly because they are connected to the circulatory system and the circulatory system was thought to have arisen independently across different taxa (also substantial similarities) Examples of hormones having similar effects include: HGH in fish and humans, Estrogen from pregnant mares can be used in post-menopausal women. Examples of hormones having different effects include: Prolactin stimulates milk production in mammals, but inhibits metamorphosis and promotes growth in amphibians, and regulates water balance in fish Generally in the endocrine system o Hormones are released into the blood and transported by blood o Hormones are released at low amounts and circulate the blood in low concentrations o Hormones act on cells through interaction with specific receptors (act as first messengers in a series of messengers that lead to a specific response in target tissues.) Hydrophilic Hormones o Biological amines are derived from amino acids Catec
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