Chapter 21 The Endocrine System Regula on of Growth and Body Temperature How does the endocrine system regulate growth and temperature balance Insulin and glucagon are antagonists Insulin s ac9ons in the body are reinforced by opposing changes in glucagon a pep9de hormone secreted by alpha cells Glucagon secre9on decreases during the absorp9ve state and increase during the post absorp9ve state Body Growth Hormone ac9ons exert important in uences on energy metabolism as they promote growth During periods of growth there is an increase in both the size and number of cells in the body s soD 9ssues and length and thickness of bones Growth hormone secre9on is elevated in childhood E ects of Growth Hormone In children GH released by the anterior pituitary exerts several e ects on bones and soD 9ssues that results in body growth Growth Hormone Signaling Growth hormone directly promotes growth by S9mula9ng protein synthesis and cell size S9mula9ng cell division Growth hormone also indirectly promotes growth by Increasing plasma concentra9on of glucose faKy acids and glycerol Increasing the uptake of amino acids Journal of Cachexia Sarcopenia and Muscle Structure of a long bone S9mula9on of bone growth is an important part of growth hormone s ac9ons Under its in uence bone increases in circumference and length In the bones of growing children the epiphysis is separated from the shaD by a thin layer of 9ssue called epiphyseal plate which plays a key role in Elonga on of bones Osteoblasts or bone makers lay down osteoid which are organic components that consist of collagen bers embedded in a gel like substance followed by calcium phosphate which give bone a mineral component that helps the bone Osteoclasts secrete acid which dissolves calcium phosphate crystals and enzymes that breakdown osteoid This releases calcium and phosphate into the blood stream Bone growth Increases in length are brought about by addi9on of new bone 9ssue to either end of the shaD increase the size and number of chondrocytes produces car9age and resorb9on of bone by osetoclasts at the inner surface of the marrow cavity Excess growth hormone causes abnormal soD 9ssue growth 6 100 000 adults Caused by adenopituitary tumor The Thyroid Gland BuKer y shaped structure located on the ventral surface of the trachea Secretes two thyroid hormones tetraiodothyronine T4 and triiodothyronine T3 which regulate the body s metabolic rate and are necessary for normal growth and development Anatomy of the thyroid gland What happens during iodine de ciency Addi on of Iodide Goiter resul9ng from iodine de ciency Mental retarda9on from iodine de ciency Hashimoto s disease Autoimmune destruc9on of the thyroid Symptoms 9redness forge ulness depression coarse dry skin slow heartbeat weight gain cons9pa9on and intolerance to cold Glucocor9coids Their primary ac9ons are to maintain normal concentra9ons of enzyme necessary for the breakdown of protein fats and glycogen Are also required for growth hormone secre9on in synergism with thyroid hormones Secre9on of glucocor9coids by the adrenal cortex is s9mulated by Secre9on of glucocor9coids by the adrenal cortex is s9mulated by adrenocor9cotropic which in rst s9mulated hormone by the ACTH release from of cor9cotropin the anterior pituitary Surgery trauma burns infec9on shock pain anxiety etc Stress whether physical or emo9onal is an important s9mulus for ACTH and ul9mately cor9sol secre9on Cor9sol is considered a stress hormone and s9mulates energy mobiliza9on and lead to increased levels of glucose faKy acids and amino acids in the blood which is useful in 9ssue repair Thermoregula9on The body s e orts are to maintain a core temperature within internal structures including the central nervous system and abdominal and thoracic cavi9es This temperature is normally regulated at approximately 37 C Thermoregula9on Input about the core temperature is sensed by central thermo receptors that include temperature sensi9ve neurons in the brain and in other internal organs This informa9on is transmiKed to hypothalamus which contains heat losing and heat promo9ng centers Cutaneous Blood Flow The primary mechanism for regula9ng body temperature is to vary the amount of blood owing to the skin where thermal energy can be exchanged with the environment Heat Loss in a Warm Environment The average person has approximately 2 5 million sweat glands located in the skin Eccrine sweat glands produce a primary secre9on of water sodium chloride As the uid makes its way through the duct leading to the skin surface ions and water are ac9vely absorbed but as sweat produc9on increases more is secreted outside the body
View Full Document
Unlocking...