Homeostasis & Hormones Past Paper PDF

What is homeostasis? Homeostatis is the maintenance of a constant internal environment Why is homeostasis important? Homeostasis ensures a relatively stable internal environment, which allows an organism to be independent of the changes in the external environment State and describe...

What is homeostasis? Homeostatis is the maintenance of a constant internal environment Why is homeostasis important? Homeostasis ensures a relatively stable internal environment, which allows an organism to be independent of the changes in the external environment State and describe the 5 processes of the negative feedback process? set point - normal level to be maintained Stimulus - change in internal environment Receptor - detect the stimulus and send signals to the control centre control centre corrective mechanism - brings the reverse effect of the stimulus What are 3 eg of homeostasis in humans? 1. Regulating body temperature 2. Regulating water potential of blood and tissue fluid 3. Regulating blood glucose concentration Describe the negative feedback process of the regulation of blood glucose contraction. When the blood glucose concentration rises above normal (stimulus), the islets of langerhans are stimulated secrete more insulin into the blood stream and gets transported to the liver and muscles(receptor). Insulin causes the Permeabilty of the cell membrane to glucose increases, hence more glucose is absorbed by the cells. The respiration rate of the cells increases as well. Liver and muscles absorbs more glucose in the same way and converts excess glucose to glycogen for storage. Glucose concentration of blood decreases. when the blood glucose concentration decreases below normal, the islets of langerhans are stimulated and secrete more glucagon into the bloodstream and gets transported to the liver and muscles. Glucagon causes the conversion of stored glycogen, fats and amino acids back to glucose in the liver cells and enter the blood stream. Blood glucose concentration increases. What is the receptor and corrective mechanism for the regulation of the water potential of blood and tissue fluids? hypothalamus; less/more antidiuretic hormone (ADH) is released from the pituitary gland ◦ What will happen if the water potential is higher/lower than normal? if higher, cells will swell and bust. If lower, cells will crenate. What is a hormone? A hormone is a chemical messenger produced in minute quantities by an endocrine gland Function? Hormones control and coordinate body activities, affecting processes such as growth, development and activity of an organism ◦ What happens to hormones after performing their function? ‣ They are destroyed in the liver and excreted by the kidneys What are the 2 types of glands? Endocrine Glands - ductless glands that transported their secretions through the bloodstream Exocrine Glands - ducts present to transport secretions to target organs 5 endocrine glands and state the function of the first 3. Hypothalamus - regulates the secretion of some hormones Pituatary Gland - secretes a number of hormones, which control the secretion of hormones of several other endocrine glands; secrete ADH, this decreases the amount of urine produced Pancreas - islets of langerhans in the pancreas secrete insulin and glucagon Ovary - Secretes oestrogen and progesterone Testis - Secretes testosterone What is diabetes? Diabetes a disease in which the body is unable to control its blood glucose concentration in order for it to remain within the normal limit ◦ Type 1 vs type 2 diabetes type 1 - the islets of langerhans are unable to produce sufficient insulin type 2 - target cells do not respond well to insulin Symptoms of diabetes persistent high blood glucose level, presence of glucose in urination, healing of wounds is slow or difficult, frequent urination, weight loss, thirst Treatment? measure blood glucose concentration and test urine regularly watch diet and make sure they’re not taking too much carbs type 1 diabetics have to inject insulin regularly into fat tissue under the skin Risk Factors? Obesity, age, family history, blood lipid levels, sedentary lifestyle Suggest reasons for the increase in diabetes across the world? Increase in percentage of overweight adults, lack of physical exercise in the population, increase in excessive food intake for many individuals ◦ How can one reduce the risk of diabetes? eat healthily, engage in physical activities, avoid being inactive for long period of time Describe the negative feedback process on the regulation of body temp. When the body temp rises above normal, thermoreceptors in the skin and hypothalamus are stimulated. The arterioles in the skin dilate so that more blood can flow through the blood capillaries in the skin, hence more heat will be lost through the skin. The sweat glands also become more active and produce more sweat, thus more water in the swear evaporates off the skin and more heat is lost from the body. Their metabolic rate also decreases, reducing the amount of heat released within the body. As a result, the body temperature decreases. When the body temp falls below normal, thermoreceptors in the skin and hypothalamus are stimulated. The arterioles in the skin constrict so less blood will flow through the blood capillaries in the skin, hence less heat is lost through the skin. The sweat glands also become less active and produce less sweat, thus less water in the sweat evaporates off the skin and less heat is lost from the body. When these reponses are not sufficient, shivering occurs. The rapid contractions and relaxation of the sketletal muscles increases the amount of heat released. Hence, the body temperature increases. What’s the function of the skin? the skin forms a protective covering over the body and also helps regulates our body temperature and excretion State the 3 main features of the skin. Blood Vessels (capillaries & arterioles) under the skin surface, sweat glands, sensory receptors Explain what vasodilation and vasoconstriction is and what happens? Vasodilation - the dilation (opening up) of the arteriole. When the arteriole dilates, more blood is sent to blood capillaries in the skin Vasoconstriction - the constriction (closing up) of the arteriole. When the arteriole constricts, less blood glows through the capillaries in the skin, causing the skin to turn pale What is sweat made up of? Water, dissolved salts (sodium chloride), small amounts of urea ◦ Why is the skin considered a excretory organ? Since sweat contains small amount of metabolic waste products, the skin is considered to be an excretory organ What do the sensory receptors in the skin sense? pain, pressure and temperature changes in the external environment ◦ Where are the sensory receptors in the skin? The nerve endings in the skin. How does the body gain heat? Metabolic activities such as cellular respiration, vigorous muscular exercise, consumption of hot food, being in a warm environment How does the body lose heat? through the skin, evaporation of water in sweat off the body, faeces and urine, exhaled air