Homeostasis and the Endocrine System PDF

 describes the process living organisms use to maintain consistent internal conditions is involved in every organ system of the body requires constant monitoring & adjusting permits normal functioning of the body can be maintained by separate organs or the entire body Homeostasis is a...

 describes the process living organisms use to maintain consistent internal conditions is involved in every organ system of the body requires constant monitoring & adjusting permits normal functioning of the body can be maintained by separate organs or the entire body Homeostasis is a dynamic equilibrium, where continuous changes occur to maintain steady conditions. In order to balance any variable, homeostatic mechanisms employ four units: Stimulus Effector Sensor Control Unit  Stimulus ( trigger ) something that results in changes, this variable has moved away from its normal range, initiating the process of homeostasis. example: increased body temperature above 37°C  Sensor ( detector ) the sensing unit of homeostasis, where it monitors and responds to triggers the sensor then sends information to the control unit. example: nerve cells such as thermoreceptors  Control Unit compares the changed value to its normal value. If the value is significantly different the control center activates the effectors against the stimulus. example: thermoregulatory unit in the brain that controls the temperature of the body is activated  Effector (responder) can be muscles, organs, glands, etc. that are activated by the control unit. acts bring the value of variable back to normal. counteracts the stimulus to oppose its effect. example: sweat glands are effectors that act to lower body temperature back to its normal value.  Feedback A feedback loop is a biological system Loop that helps to maintain homeostasis. It is activated when a stimulus is detected, and the control unit responds. There are two types of feedback loops involved in the process of homeostasis: negative & positive Negative Feedback loop: Most homeostatic processes are maintained by negative feedback loops. result in an output that opposes the stimulus (counteract the stimulus) are activated if a variable is either too high or too low example: increased production of erythrocytes when a low level of oxygen is detected in the body. Positive Feedback Loop: seen in processes that need to happen quickly to move the process towards completion rather than towards equilibrium. The output amplifies the stimulus example: childbirth As the baby’s head pushes the cervix, the neurons in that region are activated, causing the brain to send signals to produce oxytocin which further increases the uterine contractions putting more pressure on the cervix, facilitating childbirth.  Thermoregulation is the process responsible for maintaining body temperature works by the negative feedback loop - when body temperature is either increased or decreased beyond its normal temperature, it is brought back to normal. includes sweating, dilation or contraction of blood vessels, shivering and breakdown of fat to produce heat. maintained by organs like skin and adipose (fat) tissue and the brain.  Osmoregulation is the process of maintaining a constant osmotic pressure in the body by balancing the concentration of fluids and salts. excess water, ions, & other molecules are removed from the body to maintain the osmotic balance. example: Osmoregulation the removal of excess water and ions out of the blood in the form of urine this maintains the osmotic pressure of the blood. Hormones like antidiuretic hormone act as messengers in this system  Osmoregulation example: blood pressure when high, stretch receptors in the blood vessels trigger the nervous system to decrease cardiac output and blood vessels to dilate, resulting in falling of blood pressure Chemoregulation is the process of balancing the concentration of chemicals (glucose, CO2 ) by producing hormones. example: the concentration of insulin increases when the blood sugar level increases in order to bring the level back to normal. Chemoregulation example: in the respiratory system, the rate of breathing increases as the concentration of carbon dioxide increases. Chemoregulation example: acid-base balance in blood plasma: excessive carbonic acid is broken down into hydrogen ion and bicarbonate ions. If the pH of the blood is low, the hydrogen ions are released into urine causing the pH to rise if the pH of the blood is high, the bicarbonate ions are released into urine causing the pH to drop.  is a complex network composed of glands and hormones influences all metabolic processes, such as ⚬ growth ⚬ energy levels & stress ⚬ reproduction ⚬ development ⚬ immune defence & injury response ⚬ mood & behaviour  hormao (greek) = to excite or arouse are chemical messengers. may be derived from steroids, peptides, or modified amino acids are produced by a gland or organ & secreted into the bloodstream may act locally (act near to where they are secreted) or generally (transported to remote areas)  There are two major types of glands - endocrine & exocrine endo = inner, within exo = outer, outside crine = to separate or secrete Endocrine glands secrete products directly into the bloodstream ex. pituitary, ovaries, adrenal glands Exocrine glands secrete substances into a duct system ex. gall bladder, salivary gland, sweat gland The pancreas acts as both an endocrine & exocrine gland. exocrine: digestive enzymes (chymotrypsin, trypsin, amylase, lipase) are secreted into the small intestine through the pancreatic duct endocrine: hormones such as insulin & glucagon are released into the bloodstream to regulate blood sugar, by instructing the liver to either release or store glucose.  hypothalamus pineal gland pituitary gland thyroid thymus gland testes pancreas ovaries adrenal glands Pituitary Gland: located at the base of the brain pituitary gland consists of 2 parts - anterior lobe & posterior lobe Anterior lobe secretes several hormones: human growth hormone GH, (somatotropin) promotes growth by accelerating protein synthesis prolactin promotes breast development & milk secretion in females thyroid-stimulating hormone TSH regulates thyroid gland secretions adrenocorticotropic hormone ACTH regulates adrenal gland secretions melanocyte stimulating hormone MSH triggers production of skin pigments follicle stimulating hormone FSH & luteinizing hormone LH play different roles in males & females  pineal hypothalamus gland pituitary gland Posterior lobe: releases 2 hormones that are produced in the hypothalamus of the brain antidiuretic hormone ADH triggers water reabsorption in the kidneys oxytocin stimulates uterine contractions Pineal gland: associated with regulating circadian cycle (day & night) Thyroid gland: thyroxine regulates the rate of metabolism in the body. thyroid calcitonin regulates the level of calcium in the blood. Parathyroids: parathyroid hormone regulated calcium metabolism Thymus gland: thymosins influence the growth of lymphocytes in thymus gland the immune system Adrenal glands: pyramid shape glands sitting atop the kidneys secrete corticosteroids such as cortisol, which controls glucose metabolism & protein synthesis epinephrine (adrenalin) increases heart rate, blood pressure, & blood flow to skeletal muscles as part of the fight or flight response norepinephrine (noradrenalin) magnifies the effects of epinephrine Testes: Ovaries: secrete androgens, which secrete estrogens, which promote secondary male encourage the characteristics. development of secondary Testosterone is an female characteristics. important androgen. testes ovaries Prostaglandins: Erythropoietin: Gastrin and secretin: are hormones is a hormone hormones secreted by produced by the produced by various tissue kidney cells. digestive glands to cells. functions in the influence digestive cause different production of processes. effects on smooth red blood cells. muscles, glands, and in reproductive physiology.