3.4 Homeostasis in Humans

explain the necessity of maintaining optional physical and chemical conditions in the internal environment

State the meaning of homeostasis

Relate changes in blood osmotic pressure to urine output

Describe the formation of urine and relate the formation of urine

Describe briefly the mechanism of osmoregulation

Predict the consequences of impaired kidney functionDescribe the regulation of blood sugar level.

Describe the regulation of body temperature

Conceptualise the homeostasis

to ensure the physiology processes in the body can proceed at optimum rates in order to promote harmonious growth and development Homeostasis : process of maintaining the internal environment of the body at constant level.Internal environment : i. Physical Factor: body temperature ; blood pressure ii. Chemical Factor : partial pressure of oxygen and carbon dioxideThe organs involved in maintaining the internal environment: i. kidney (blood osmotic pressure) ii. Skin (temperature) iii. Pancreas (blood sugar level)

water content of the blood determines the blood osmotic pressure.osmotic pressure of blood increases; Sweating (body losses water) More water is reabsorbed into the blood by the kidney decreasing the amount of urine eliminated.Osmotic pressure is low : less water reabsorb into the blood stream-increase the volume of urine output

Kidneys is are organs that filter wastes from the blood and excrete them along with water, as urine. has two distinct regions namely the outer renal cortex and the inner renal medullaRenal artery : supplies oxygenated blood and nutrients to the kidneysRenal veins: carries filtered blood from the kidneys to the body.Function : a. filter blood and form urine b. carry out osmoregulation

Nephrons is the fucntional unit of the kidneysEach kidney consists of about one million nephronsNephron consist of : 1. Glomerus 2. Bowmans Capsule 3. renal convulated tubuleRenal tubule is made up of the : 1. proximal convulated tubule 2. loop of Henle 3. distal convulated tubuleFormation of urine involved three process namely: 1. Ultrafiltration 2. Reabsortion 3. Secretion

1. UltrafiltrationTake place in Bowmans capsuleBlood entering the glomerulus under high pressure because the afferent arteriole has large diameter than efferent arteriole.The high pressure forces fluid through the epithelial cells of the blood capillaries and the cell of the Bowmans capsular space.Only molecules of a certain size can pass throughThe fluid enters the capsular space is known as Glomerular filtrate

1. reabsorption

Part of nephronSubstance reabsorbedProcess involvedProximal convoluted tubuleGlucose and amino acidActive transportwaterOsmosisSodium ionsActive transportChloride ionsPassive transportLoop of HenleSodium and chloride ionsActive TransportwaterOsmosisDistal concoluted tubulewaterOsmosisSodium chlorideActive transportCollecting ductWaterOsmosis

Secretion is a process in which waste and excess substances are secreted into the renal tubuleTakes place in the distal convoluted tubule and collecting ducts by passive diffusion and active transportSubstance that are secreted into the renal tubule are hydrogen ions, potassium ions, ammonia, urea, creatinine, toxins and certain drugs.Secretions help to : i. increase the rate of waste removal from the body ii. Regulate blood levels of a certain ions such as hydrogen and potassium ions

Process of regulating the salt and water balance in the body to maintain blood osmotic pressureBlood osmotic pressure is high when there is excess salt and less water in the blood.Blood osmotic pressure is low whenthere is more water and less salt in the blood.Osmoregulation control by two hormones (ADH and aldosterone) that work through the negative feedback mechanismADH : control the reabsoption of waterAldosterone : control the absorption of the salt.