Leaving Certificate Agricultural Science The Endocrine System Introduction

Leaving Certificate Agricultural Science The Endocrine System

Introduction � The Endocrine System is the set of hormone secreting glands within the body. � An Endocrine gland is a ductless organ and makes and secretes specific chemical messengers into the blood. � An Exocrine gland secretes directly or by a duct to the outside of the body e. g. sweat gland, salivary gland � The pancreas is both an endocrine and exocrine gland (Islets of Langerhans secrete insulin) � A Hormone is a chemical messenger, secreted by a endocrine gland into the blood which alters the effect of a specific tissue.

Main Hormones and Their Functions Hormone Gland Function ADH / Growth Hormone Pituitary Increases water re-absorption by the kidney / bone elongation Thyroxine Thyroid Regulates Metabolism, growth and development Adrenalin Adrenals Raises heart rate, breathing rate, blood pressure and blood glucose levels Insulin Pancreas Uptake of glucose from blood. Oestrogen Ovaries Endometrium Formation, female secondary sexual characteristics Testosterone Testes Sperm Production, male secondary sexual characteristics Melatonin Pineal Sleep Pattern, Ovulation, Sexual Maturity

Endocrine VS. Nervous System � NS is fast acting, ES is slower (growth) � NS is electrical, ES is chemical. � NS has fast transmission, ES is slow (blood) � NS is short lived response, ES is long lasting. � NS affects local, ES has widespread affect.

The Pituitary Gland The Pituitary gland is located in the hypothalamus (front of the brain) and is the most important part of the endocrine system. � The Pituitary gland has two parts, the anterior and posterior. � The Anterior part produces two hormones, ADH and Oxytocin. � ADH is involved in water level control in the blood. � Oxytocin controls lactation (milk let down) and is released from the pituitary when an animal is suckled. � The Posterior part of the Pituitary produces a number of important hormones. � These include FSH (Follicle Stimulating Hormone), LH (Luteinizing Hormone), Prolactin and Growth Hormones. � The Pituitary also releases hormones which control the Adrenal and Thyroid glands. �

The Thyroid Gland � The thyroid glands are found on the trachea. � The main hormone produced is called thyroxine. � This hormone controls the growth and development of animals. � Iodine is required for its production. � Lack of thyroxine causes deformation and retardation. � The glands swell if not enough hormone is produced – this is called goitre in humans.

Parathyroid & Thymus � These are located on either side of the thyroid. � They produce two hormones: Parathormone and Calcitonin. � These hormones control the level of calcium, magnesium and phosphate in the body. � The Thymus A very small gland located on the neck. � Has some involvement in the production of lymphocytes (white blood cells), which are involved in immune response.

The Pancreas � The Pancreas produces insulin. � It is produced in the pancreas in the Islets of Langerhans. � Insulin is required for the intake of glucose in cells and prevents the excess breakdown of glycogen. � If insulin is lacking, one outcome is the passing of glucose in the urine. � This is called diabetes mellitus. � This can cause coma because the brain needs glucose. � Synthetic Insulin is now available for diabetics. � It must be injected because if it was eaten it would be digested.

The Adrenal Glands � The adrenal glands are found near the kidney. � They produce over fifty different hormones which are vital for life. � Hydrocortisone is produced in the adrenal glands and is required to control blood pressure and controls the loss of blood. � Adrenalin is secreted from the adrenal glands during stress. � It redirects blood to the head and increases the heartbeat. � It makes the individual more acute to their surroundings. � It is usually secreted when frightened. � Another hormone called non-adrenalin, turns off the effects of adrenalin.

The Gonads �The gonads are the sex glands - the testes and ovaries. �The hormones produced are involved in the reproductive systems of the animal. �These include testosterone, oestrogen and progesterone. �These hormones will be looked at in more detail in Animal Reproduction.