Quick Quiz - hormones How do hormones move around the body? What is the meaning of “target organ”? List 3 endocrine glands. Where is urine produced? What is the chemical name and symbol for common salt? Why are marathon runners in danger of loosing too much salt?

The role of hormones in our body Objectives: To be able to explain: the source, role and regulation of thyroxine The source, role and regulation of ADH The source, role and regulation of aldosterone How the blood works as an electrolyte Homeostasis of sodium chloride Problems associated with too much salt / not enough salt

The role of hormones in our body Hormones are released in endocrine glands into the blood stream. They then travel around the body in the blood to the target organ. You already know about the actions of insulin and glucagon.

The role of hormones in our body The thyroid gland in our neck makes a hormone called thyroxine.

The role of hormones in our body The mineral iodine is needed to make thyroxine. Deficiency of iodine causes the thyroid gland to swell – this disease is called goitre.

The role of hormones in our body Effects of thyroxine: Increases and regulates basal metabolic rate Improves oxygen uptake Increases heart rate Regulates growth and development Regulates body temperature

The role of hormones in our body Hypothyroidism means a reduced level of thyroid hormone (thyroxine) causing things to “slow down”. This can cause various symptoms, the most common being: tiredness, weight gain, constipation, aches, dry skin and lifeless hair feeling cold. Treatment is usually easy by taking a tablet each day to replace the missing thyroxine. Treatment usually works well and symptoms usually go.

The role of hormones in our body Antidiuretic hormone - ADH

The role of hormones in our body Antidiuretic hormone - ADH Roughly 60% of our body mass is water, and despite wide variation in the amount of water taken in each day, body water content remains incredibly stable. This is a good example of HOMEOSTASIS. Such precise control of body water and solute concentrations is a function of several hormones acting on both the kidneys and vascular system. The main hormone involved in this is ADH.

The role of hormones in our body Antidiuretic hormone - ADH

The role of hormones in our body Antidiuretic hormone - ADH 1. Effects on the Kidney The single most important effect of antidiuretic hormone is to conserve body water by reducing the loss of water in urine. Antidiuretic hormone binds to receptors on cells in the collecting ducts of the kidney and promotes reabsorption of water back into the blood. In the absence of antidiuretic hormone, the collecting ducts are virtually impermeable to water, and it flows out as urine.

The role of hormones in our body Antidiuretic hormone - ADH 1. Effects on the Kidney

The role of hormones in our body Antidiuretic hormone - ADH 2. Effects on the Vascular (Blood) System High concentrations of antidiuretic hormone also cause constriction of arterioles (vasoconstriction), which leads to increased arterial pressure. A negative feedback loop exists so that increased blood pressure blocks the secretion of more ADH.

The role of hormones in our body Antidiuretic hormone - ADH Some facts: ADH is made in the hypothalamus (in the brain) It is transported from here to the pituitary gland (another part of the brain) via the nerves. It is then released into the blood Release of ADH is controlled by the hypothalamus The hypothalamus can detect changes in the water potential of the blood and also changes in pressure of the blood vessels The receptors in the hypothalamus that detect the changes in water potential are called osmoreceptors.

The role of hormones in our body Antidiuretic hormone - ADH

The role of hormones in our body Aldosterone This hormone is made in the adrenal cortex of the adrenal glands, near the kidneys

The role of hormones in our body Aldosterone Aldosterone helps to control blood pressure and concentrations of salt in the blood. It is made in the adrenal cortex and is carried in the blood to the kidneys where it acts on the tubules and collecting ducts.

The role of hormones in our body Aldosterone A quick chemistry lesson! Na+ = sodium ion Cl- = chloride ion NaCl = sodium chloride (salt) K+ = potassium ion These are all examples of electrolytes.

The role of hormones in our body Aldosterone Aldosterone has 4 main effects on the kidneys: causes the conservation of sodium ions, secretion of potassium ions, increased water retention (because chloride ions come with the sodium), increased blood pressure (due to water). The overall effect of aldosterone is to increase reabsorption of ions and water in the kidney.

The role of hormones in our body Aldosterone The blood is a mixture of aqueous electrolytes which includes sodium and chloride ions. These ions are important for normal body function but if too much salt is in the diet it can cause problems.

The role of hormones in our body Importance of salt "Salt" is sodium chloride. By weight, it is 40% sodium and 60% chloride. Sodium is an essential nutrient, a mineral that the body cannot manufacture itself but which is required for life itself and good health. Sodium is the major electrolyte responsible  for regulating water balance, pH, and osmotic pressure.   It is also important in nerve conduction.   

The role of hormones in our body Importance of salt Chloride too, is essential to good health. It preserves acid-base balance in the body, aids potassium absorption, supplies the essence of digestive stomach acid, and enhances the ability of the blood to carry carbon dioxide from respiring tissues to the lungs.

The role of hormones in our body Sources of salt Food is the main source of salt in the diet. The recommended daily intake for adults is 6g per day – equivalent to 2.5g of sodium

The role of hormones in our body How salt is lost from the body

The role of hormones in our body Consequences of salt deficiency Severe and prolonged diarrhea can also cause salt deficiency. Severe diarrhea results in the loss of large amounts of water, sodium, and various nutrients. Excessive drinking of beer, which is mainly water and low in sodium, can also produce salt deficiency when combined with a poor diet. Marathon running, under certain conditions can lead to loss of too much salt. Races can result in the loss of great quantities (8 to 10 liters) of sweat, which contains both sodium and water.

The role of hormones in our body Consequences of salt deficiency

The role of hormones in our body Problems of excess salt in the diet Too much salt in the blood Lowers the water potential of the blood Water moves out of the body cells into the blood by OSMOSIS More water in the blood Increased blood pressure

The role of hormones in our body Endocrine gland Target Organ Effect Insulin Glucagon Thyroxine ADH Aldosterone