Chapter 15 Hormones

Objectives n Students should be able to: –Define a hormone as a chemical substance, produced by a gland, carried by the blood, which alters the activity of one or more specific target organs and is then destroyed by the liver –Explain what is meant by a endocrine gland, with reference to the islets of Langerhans in the pancreas

n State the role of the hormone adrenaline in boosting blood glucose levels and give examples of situations in which this may occur n Explain how the glucose concentration is regulated by insulin and glucagon as a homeostatic mechanism n Describe the signs such as an increased blood glucose level and glucose in urine, and the treatment of diabetes mellitus using insulin

Living with stress n Butterflies in your stomach? n Increase in pulse rate? n Sweaty hands which feel cold and clammy? –Why? –Because we are nervous and our body is preparing for action

n Such symptoms are induced by the hormone ADRENALINE n Adrenaline: –Increases the heart rate –Increases the rate of breathing –Causes vasoconstriction of the blood vessels around the intestine (why?) –Raises the metabolic rate? –Dilates the pupils

15.1 Hormones n A hormone is a chemical substance produced in minute quantities by an endocrine gland. It is transported in the bloodstream to target organ(s) where it exerts its effects n Hormones influence the growth, development and activity of an organism n Some hormones also exercise control over other glands or muscles

Where are hormones produced? n Hormones are produced by glands n Hormones are produced by ductless glands. This means that the hormones which the glands produce passes directly into the bloodstream which then distributes the hormones round the body

n Some glands are purely endocrine glands producing only hormones (e.g. adrenal gland produces only adrenaline) n There are glands that produce both hormones and other secretions. Can you think of one? n

n Hormones production must be balanced to ensure that body functions normally n After hormones have performed their functions, they are eventually destroyed by the liver and excreted by the kidneys

Chapter 15 Hormones Glands and Their Hormonal Secretions 17 October 2015

Glands and Their Hormonal Secretions Hypothalamus An endocrine gland that regulates the secretion of some pituitary hormones.

Pituitary gland Plays an important role as a ‘controller’. It secretes a number of hormones, which control the functions of several other endocrine glands. This is why the pituitary gland is often referred to as the ‘master gland’. The pituitary gland also secretes antidiuretic hormone (ADH). Glands and Their Hormonal Secretions Hypothalamus An endocrine gland that regulates the secretion of some pituitary hormones.

Pituitary gland Plays an important role as a ‘controller’. It secretes a number of hormones, which control the functions of several other endocrine glands. This is why the pituitary gland is often referred to as the ‘master gland’. The pituitary gland also secretes antidiuretic hormone (ADH). Glands and Their Hormonal Secretions Thyroid gland Secretes thyroxine. Thyroxine controls the rate of metabolism and influences physical development. Hypothalamus An endocrine gland that regulates the secretion of some pituitary hormones.

Pituitary gland Plays an important role as a ‘controller’. It secretes a number of hormones, which control the functions of several other endocrine glands. This is why the pituitary gland is often referred to as the ‘master gland’. The pituitary gland also secretes antidiuretic hormone (ADH). Glands and Their Hormonal Secretions Thyroid gland Secretes thyroxine. Thyroxine controls the rate of metabolism and influences physical development. Adrenal gland (medulla) Secretes adrenaline. Adrenaline has wide- ranging effects that prepare the body for ‘fight or flight’ situations. kidney Hypothalamus An endocrine gland that regulates the secretion of some pituitary hormones.

Pituitary gland Plays an important role as a ‘controller’. It secretes a number of hormones, which control the functions of several other endocrine glands. This is why the pituitary gland is often referred to as the ‘master gland’. The pituitary gland also secretes antidiuretic hormone (ADH). Glands and Their Hormonal Secretions Thyroid gland Secretes thyroxine. Thyroxine controls the rate of metabolism and influences physical development. Adrenal gland (medulla) Secretes adrenaline. Adrenaline has wide-ranging effects that prepare the body for ‘fight or flight’ situations. Pancreas Islets of Langerhans in the pancreas secrete insulin and glucagon that regulate the blood glucose concentration. kidney Hypothalamus An endocrine gland that regulates the secretion of some pituitary hormones.

Pituitary gland Plays an important role as a ‘controller’. It secretes a number of hormones, which control the functions of several other endocrine glands. This is why the pituitary gland is often referred to as the ‘master gland’. The pituitary gland also secretes antidiuretic hormone (ADH). Glands and Their Hormonal Secretions Thyroid gland Secretes thyroxine. Thyroxine controls the rate of metabolism and influences physical development. Adrenal gland (medulla) Secretes adrenaline. Adrenaline has wide-ranging effects that prepare the body for ‘fight or flight’ situations. Pancreas Islets of Langerhans in the pancreas secrete insulin and glucagon that regulate the blood glucose concentration. kidney Hypothalamus An endocrine gland that regulates the secretion of some pituitary hormones. Ovaries (in females) Secretes oestrogen and progesterone.

Pituitary gland Plays an important role as a ‘controller’. It secretes a number of hormones, which control the functions of several other endocrine glands. This is why the pituitary gland is often referred to as the ‘master gland’. The pituitary gland also secretes antidiuretic hormone (ADH). Glands and Their Hormonal Secretions Thyroid gland Secretes thyroxine. Thyroxine controls the rate of metabolism and influences physical development. Adrenal gland (medulla) Secretes adrenaline. Adrenaline has wide-ranging effects that prepare the body for ‘fight or flight’ situations. Pancreas Islets of Langerhans in the pancreas secrete insulin and glucagon that regulate the blood glucose concentration. kidney Hypothalamus An endocrine gland that regulates the secretion of some pituitary hormones. Ovaries (in females) Secretes oestrogen and progesterone. Testes (in males) Secretes testosterone.

Chapter 15 Hormones How Adrenal Medulla Responds to Stimuli 17 October 2015

Copyright © Marshall Cavendish International (Singapore) Pte. Ltd. 20 Stimuli Fear, anger, anxiety, stress, etc 1 How Adrenal Medulla Responds to Stimuli

17 October 2015 Copyright © Marshall Cavendish International (Singapore) Pte. Ltd. 21 Stimuli Fear, anger, anxiety, stress, etc 1 Receptor Hypothalamus stimulated 2 How Adrenal Medulla Responds to Stimuli

17 October 2015 Copyright © Marshall Cavendish International (Singapore) Pte. Ltd. 22 Stimuli Fear, anger, anxiety, stress, etc 1 2 How Adrenal Medulla Responds to Stimuli Receptor Hypothalamus stimulated 3 sensory neurone Certain sensory neurones in the hypothalamus are activated

17 October 2015 Copyright © Marshall Cavendish International (Singapore) Pte. Ltd. 23 Stimuli Fear, anger, anxiety, stress, etc 1 2 How Adrenal Medulla Responds to Stimuli Receptor Hypothalamus stimulated 3 sensory neurone spinal cord Nerve impulses are transmitted to the spinal cord 4

17 October 2015 Copyright © Marshall Cavendish International (Singapore) Pte. Ltd. 24 Stimuli Fear, anger, anxiety, stress, etc 1 2 How Adrenal Medulla Responds to Stimuli Receptor Hypothalamus stimulated 5 3 adrenal medulla sensory neurone spinal cord Nerve impulses leave the spinal cord to adrenal medulla 4

17 October 2015 Copyright © Marshall Cavendish International (Singapore) Pte. Ltd. 25 Stimuli Fear, anger, anxiety, stress, etc 1 2 How Adrenal Medulla Responds to Stimuli Receptor Hypothalamus stimulated adrenal medulla sensory neurone spinal cord Adrenal medulla is stimulate, producing adrenaline. 4

17 October 2015 Copyright © Marshall Cavendish International (Singapore) Pte. Ltd. 26 Stimuli Fear, anger, anxiety, stress, etc 1 2 How Adrenal Medulla Responds to Stimuli Receptor Hypothalamus stimulated adrenal medulla sensory neurone Adrenaline is carried in blood 7 spinal cord 4

17 October 2015 Copyright © Marshall Cavendish International (Singapore) Pte. Ltd. 27 Stimuli Fear, anger, anxiety, stress, etc 1 2 How Adrenal Medulla Responds to Stimuli Receptor Hypothalamus stimulated adrenal medulla sensory neurone Adrenaline is carried in blood 7 spinal cord Adrenaline reaches target organs in various parts of the body. It brings about short-term responses that prepare the body for ‘fight or flight’. 8 4

Effects of adrenaline secretion n Increases blood glucose levels by speeding up the breakdown of glycogen to glucose in the liver and muscles n Increases metabolic rate (more energy released) n Increases rate of heartbeat n Constricts arteries in skin n Causes pupils to dilate to enhance vision n Contracts hair muscles producing ‘goose pimples’

Effects of Insulin n Secreted by Islets of Langerhans in pancreas n Secretion caused by an increase in concentration of blood glucose above the normal level

n Effect(s): –Decrease in blood glucose concentration by: n Increasing the permeability of cell membranes to glucose thereby increasing the rate of glucose uptake by cells n Causing the conversion of glucose to glycogen for storage in liver and muscles n Causing an increased oxidation of glucose during tissue respiration –This leads to an overall increase in the utilization of glucose by cells

n Lack of secretion: –Glucose cannot be utilized by cells, some lost in urine => diabetes mellitus –Muscle cells no reserves of glycogen, body weakness flows and then loss of weight –Body oxidizes fats instead of glucose to produce energy resulting in poisonous substances formed

n Effects of Oversecretion –Abnormal decrease in blood sugar concentration –Shock HAPPENS –Coma and death may follow

Diabetes mellitus n A disease where the body is unable to control its blood glucose concentration so that it remains within normal limits. n Kidneys unable to reabsorb all the glucose, hence some gets excreted in the urine

2 Types of diabetes: n Type 1: –Juvenile diabetes. Inability of the pancreas to produce insulin n Type 2: –Occurs later in life. Overweight people seem more prone to it. May be due to a decrease in the production of insulin by the pancreas or a failure of the target cells to respond well to it.

n Signs –Persistently high blood glucose level –Glucose in urine after a meal –Healing of wounds is slow or difficult n Treatment –Measure blood glucose concentrations and test urine regularly –Watch their diet, take less carbohydrates –Inject insulin into veins (Type 1) –Control intake of carbohydrate (Type 2)

Glucagon n Produced by islets of Langerhans when the concentration of blood glucose decreases below the normal levels n Target organ of glucagon is Liver n Glucagon increases the blood glucose concentration by stimulating: –The conversion of glycogen into glucose –The conversion of fats and amino acids into glucose –The conversion of lactic acid into glucose

Hormonal & Nervous Control n Both serve as a means of co-ordination within the body n There are differences between the 2 systems though: