Endocrine System By Dr. Shamanthakamani Narendran
Endocrine System The endocrine system is made up of the cells, tissues, and organs that secrete hormones into body fluids
OBJECTIVES The Endocrine System consists of glands that transmit chemical messengers throughout the body. These chemical messengers, called hormones circulate in the bloodstream and affect many types of body cells. Compare exocrine glands with endocrine glands. Contrast amino acid-based hormones with steroid hormones. Affect the target cells in two ways. These are different from prostaglandins.
HORMONES: Chemical Signals 1. A GLAND is an Organ that consists of Cells that Secrete materials into other regions of the Body. 2. The body contains TWO TYPES of GLANDS A. EXOCRINE GLANDS : Secrete NONHORMONAL Chemicals into DUCTS, which transport the Chemicals to a Specific Location inside and outside the Body. Eg., Sweat Glands, Mucous Glands, Salivary Glands, and other Digestive Glands. B. ENDOCRINE GLANDS - are DUCTLESS Glands that are located throughout the body. Secrete Hormones into the Bloodstream through the fluid that surrounds their Cells.
3. A HORMONE is a Chemical Signal, made in one place and delivered to another, that regulates the body's activities. They are secreted in small amounts into the bloodstream and that influence the activity of distant cells. 4. Some other Organs NOT considered glands produce Hormones. Eg., Brain and Kidney 5. The Hormones travel to a specific tissue or organ called TARGET CELLS, to elicit a specific response.
6. Hormones are essential for maintaining Homeostasis (nutrition, metabolism, excretion, water and salt balances). a. React to stimuli from outside the body. b. Regulate growth, development and reproduction. c. Produce, use and store energy 7. The Endocrine and Nervous Systems are so closely linked that they are often considered a single system – The Neuroendocrine System .
8. Both Nerve Impulses and Hormones elicit a response BUT: A. Nerve Impulses prompt a nearly instantaneous response to a change in the environment. B. Hormones on the other hand are released more slowly than nerve impulses, but their effects usually last longer. Effects of some hormones can last 10 to 20 minutes. Some can last for several hours.
HOW HORMONES WORK 1. A Hormone DOES NOT seek out a particular organ which is AWAITING the arrival. 2. Cells that can react to a hormone have specific receptor proteins on their plasma membrane or in their cytoplasm that combine with the hormone In a " LOCK-AND-KEY " manner.
3. RECEPTORS are proteins that are located both Inside the cytoplasm and on the surface of a target cell. 4. Therefore, certain cells respond to one hormone and not another, depending on their receptor proteins. 5. Fitting the hormone molecule into the receptor CHANGES the receptor's shape. 6. The MAIN effect of a hormone on a cell is to change the activity or amounts of enzymes.
TWO TYPES OF HORMONES A. STEROID HORMONES – Secreted from lipid (cholesterol). B. AMINO ACID-BASED HORMONES (PEPTIDE HORMONES)
STEROID HORMONES A. Steroid Hormones are produced by the Adrenal Cortex , the Ovaries , and the Testes . B. They DO NOT bind with plasma membrane. They can ENTER the Cell and the Nucleus FREELY. C. Within the cytoplasm, it binds with a receptor protein and enters the DNA, and triggers changes in the chromosomes. D. DNA attachment activates certain genes in that cell to produce particular proteins, and enzymes.
E. The Male Sex Hormone TESTOSTERONE and the Female Sex Hormones ESTROGEN and PROGESTERONE are examples of Steroid Hormones.
AMINO ACID-BASED HORMONES Peptide Hormones: A. Hormones made from Amino Acids.
B. Peptide hormones are polar molecules (posses both positive and negative ends) they CANNOT PASS ( DIFFUSE ) through the plasma membrane of their target cells. C. Peptide hormones must send their message from OUTSIDE the target cell, a TWO-Messenger system is commonly required for the action of most of these hormones. D. Peptide hormones attaches to receptors on the plasma membrane, THE FIRST MESSENGER , carrying the message from the endocrine gland to the cell surface, and pass the message to another molecule inside the cytoplasm – THE SECOND MESSENGER .
PROSTAGLANDINS 1. PROSTAGLANDINS are a group of hormone-like lipids, that also regulate cell activities. 2. Unlike hormones, prostaglandins are NOT produced by specific endocrine glands. 3. They are produced in small quantities by many cells throughout the body. They ACT LOCALLY .
4. Relaxation of Smooth Muscles that line the air passages and blood vessels, regulation of blood pressure, contraction of the intestinal walls and the uterus, and stimulation of the body's inflammatory response to infection.
FEEDBACK MECHANISMS The endocrine system uses feedback mechanisms to respond and adjust to changes that occur in and outside the body. In a Feedback Mechanism , the last step in a series of events controls the first step.
HOMEOSTASIS 1. HOMEOSTASIS is defined as a STABLE internal environment. 2. ANTAGONISTIC HORMONES have opposite effect on the body. 3. To maintain homeostasis, hormone secretions must be tightly regulated. 4. Most hormones are controlled by a FEEDBACK MECHANISM .
5. NEGATIVE FEEDBACK INHIBITS further release of the initial hormone. 6. POSITIVE FEEDBACK STIMULATES further release of the initial hormone. Glycogen secretion Insulin secretion Blood glucose level decreases Blood glucose level Increases
NEGATIVE FEEDBACK MECHANISMS Regulating Hormone Release 1. Regulates the release of 30 Hormones . 2. Involves interactions of nervous, endocrine, and circulatory systems. 3. Involves hypothalamus and anterior pituitary
RELATIONSHIP B/W HYPOTHALAMUS & PITUITARY GLAND 1. The HYPOTHALAMUS regulates body temperature, breathing, hunger, thirst, and internal environment. 2. It is the master switchboard for the endocrine system. It REGULATES the two lobes of pituitary gland. 3. It LINKS the nervous system to the endocrine system.
PITUITARY GLAND has two lobes – POSTERIOR & ANTERIOR 1. A small gland about 1 cm in diameter is connected to the Hypothalamus by a Stalk-like Structure. 2. The Posterior pituitary Stores Two Hormones, Vasopressin or ADH and Oxytocin.
A. ANTIDIURETIC HORMONE - (ADH ) causes the kidneys to form more concentrated urine, conserving water. Thus, the kidneys produce urine with a High Solute Concentration. B. OXYTOCIN – Stimulates Contractions of the uterus during labor and helps in secreting milk.
ANTERIOR PITUITARY GLAND A. GROWTH HORMONE ( GH ) ( SOMATOTROPIN ) – Promotes cell division, protein synthesis, and Bone and Muscle Growth. B. Prolactin ( PRL ) – Helps mammary gland development and secretion of milk. It plays a role in carbohydrate and fat metabolism. C. Melanocyte-stimulating hormone - stimulates Melanocytes of the Skin.
Hormones Secreted by the Pituitary Gland Jump to 54 Slide
THE PINEAL GLAND Located near the base of the brain . Secretes Melatonin . Melatonin increases at night and decreases in the day. This cyclic release helps regulate sleep.
THYROID GLAND 1. Located at the base of the neck just below the larynx. 2. Thyroid-stimulating hormone ( TSH ) regulates the thyroid gland. 3. Produces thyroxin, triiodothyronine, and calcitonin a. THYROXIN and TRIIODOTHYRONINE stimulates and maintains metabolic activities, normal heart rate, blood pressure, and body temperature. they also promote carbohydrate usage over fat usage for energy. b. CALCITONIN (c cells) inhibits release of calcium from bones. or regulates the level of calcium in the blood.
4. In order to produce thyroxin and triiodothyronine, the thyroid gland requires IODINE . iodized salt. 5. GOITER the swelling of the thyroid gland is a result of iodine deficiency.
6. Decreased levels of thyroxin causes a decrease in the cellular respiration rate. cells produce less energy and become less active.
HYPERTHYROIDISM HYPOTHYROIDISM too much thyroxin results in nervousness, elevated body temperature, increased heart and metabolic rates, increased blood pressure, and weight loss. Treatment : Medication or surgical not enough thyroxin results in lower metabolic rates (lethargy) and body temperature, lack of energy, and weight gain. Goiter , or enlargement of the thyroid gland. Treatment : Supplementary thyroxin. hypothyroidism in infants affects normal development of the skeleton, muscular, and nervous systems and results in a condition called cretinism . Cretinism is characterized by dwarfism and mental retardation.
PARATHYROID GLANDS <ul><li>Attached to or embedded in the back surface of the thyroid gland, two in each lobe. </li></ul><ul><li>Produces parathyroid hormone ( PTH ) regulates the calcium levels in the blood by increasing the reabsorption of calcium in the kidneys and by increasing the uptake of calcium from the digestive system. </li></ul>
3. Parathyroid hormone is important in promoting proper nerve and muscle function as well as maintaining bone structure . 4. Loss of parathyroids causes a drop in the level of calcium in the blood , which may result in violent muscular spasms known as TETANY . 5. Can be relieved by the administration of large amounts of PTH and injections of calcium.
ADRENAL GLANDS (CORTEX & MEDULLA) 1. One gland is located on top of each kidney. 2. Composed of two very different types of tissue a. Outer - The adrenal cortex b. Inner - The adrenal medulla
ADRENAL CORTEX <ul><li>The outer portion, makes up 80 percent of the mass of the gland. </li></ul><ul><li>The adrenal cortex responds to adrenocorticotropic hormone ( ACTH ), which is secreted by the anterior pituitary gland. </li></ul><ul><li>Produces more than two dozen hormones called corticosteroids , which are steroid hormones and essential for normal body function. </li></ul>
4. Aldosterone regulates the reabsorption of sodium and the excretion of potassium by the kidneys. this affects water and salt balance in the body. 5. Cortisol affects carbohydrate, protein and fat metabolism. it also helps people cope with stress. 6. Decrease activity of the adrenal cortex can result in Addison's Disease - weight loss, low blood pressure, and general weakness, death may occur because of heart failure.
7. People with Addisons Disease receive regular doses of adrenal cortical hormones. 8. Increase activity of the adrenal cortex can result in Cushing Syndrome - obesity, increase blood sugar levels, high blood pressure, and weakening of bones. 9. Treatment involves decreasing the secretion of hyperactive hormone, if possible.
ADRENAL MEDULLA <ul><li>The inner portion, is a specialized part of the sympathetic nervous system. </li></ul><ul><li>Secrets two amino acid based hormones called Neurohormones - Adrenaline (epinephrine) and Noradrenaline (norepinephrine) . </li></ul><ul><li>Adrenaline is more powerful in its actions and makes up 80 percent of the total secretions. </li></ul>
4. " Fight or flight " hormones - nerve impulses from the sympathetic nervous system results in the secretion of adrenaline and noradrenaline . 5. Adrenaline increases heart rate, blood pressure, and blood supply to skeleton muscles, increases the conversion of glycogen to glucose and stimulates the rate of metabolism. 6. Noradrenaline stimulates the heart muscle - increases rate and strength of heartbeat.
REPRODUCTIVE GLANDS - GONADS <ul><li>GONADS - The ovaries in females and the testes in males - are gamete-producing organs that also produce a group of steroid sex hormones. </li></ul><ul><li>SEX HORMONES - regulate body changes that begin with puberty. </li></ul><ul><li>PUBERTY is the adolescent stage during which the sex organs mature and secondary sex characteristics, such as facial hair, appear. </li></ul>
4. When secreted by the anterior pituitary gland, luteinizing hormone ( LH ) and follicle-stimulating hormone ( FSH ) stimulate secretion of sex hormones from the gonads. 5. The female gonads, or ovaries produce eggs ( ova ) and also produce sex hormones that affect cells throughout the body. 6. The ovaries produce the female sex hormones, the estrogens and progesterone .
7. Estrogens are required for the development of ova and for the formation of the physical characteristics (secondary sex characteristics). 8. These characteristics include the development of the female reproductive system, the menstrual cycle begins, widening of the hips, and development of the breast. Puberty. 9. Progesterone prepares the uterus for the arrival of a developing embryo - or controls the menstrual cycle.
10. Male gonads or testes produce sperm, and sex hormones that affect cells throughout the body. Testes produce Androgens or the male sex hormone. It regulates male secondary sex characteristics. 11. Androgens: the development of physical (secondary sex) characteristics associated. Puberty. These characteristics include the growth of facial hair, increase in body size, and deepening of the voice.
PANCREAS <ul><li>Located just behind the stomach. </li></ul><ul><li>Pancreas is both an exocrine (ducts) and endocrine gland. </li></ul><ul><li>The hormone producing portion of the pancreas consists of clusters of cells that resemble islands, called islets of langerhans . </li></ul><ul><li>4. Each islet is composed of beta cells which secretes insulin, and alpha cells which secretes glucagon . </li></ul>
5. These two hormones, insulin and glucagon regulate the metabolism of blood glucose (sugar) and the hormones have opposite effects. ( Antagonistic hormones ) 6. Insulin stimulates its target cells to take up and use glucose. This action lowers blood glucose levels. " Use or store "
7. Glucagon stimulates its cells to breakdown stored glycogen and increase glucose levels in the blood. 8. When there is an under secretion of insulin, a condition called Diabetes Mellitus ( DM ) occurs.
DIABETES MELLITUS TYPE I OR JUVENILE ONSET Before age 25, little or no insulin production, requires a strict diet and daily injections of insulin. TYPE II OR ADULT ONSET After age 40, produce normal amounts of insulin, but cells are unable to respond properly because of lack of insulin receptors, can be controlled by diet.
11. HYPOGLYCEMIA CAUSED BY EXCESS (HIGH) INSULIN OR LOW BLOOD SUGAR, A Disorder in which Glucose is Stored rather than being properly delivered to the cells of the body – causing cells to starve to death. This leads to a lower blood glucose concentration and subsequent release of Glucagon and Epinephrine ( Adrenaline ).
Symptoms of hypoglycemia include Lethargy, Dizziness, Nervousness, Overactivity, and in extreme cases, Unconsciousness ( Ketoacidosis or Diabetic Coma ) and DEATH. 12. HYPERGLYCEMIA CAUSED BY LOW INSULIN OR HIGH BLOOD SUGAR. Can cause Nausea and Rapid Breathing, possibly leading to Oxygen Deficiency, Circulatory and Nervous System Failure, Diabetic Coma, or even Death.
THE THYMUS GLAND <ul><li>The thymus gland is located beneath the sternum ( breastbone ) and between the lungs. </li></ul><ul><li>The thymus consists mostly of T-cells and plays a role in the development of the immune system. </li></ul><ul><li>The thymus gland secretes Thymosin , an amino acid based hormone that stimulates the formation of t-cells, which help defend the from pathogens. </li></ul>
See previous chart: Hormones Secreted by the Pituitary Gland Summary of Endocrine Glands and their Functions
DIGESTIVE ORGANS <ul><li>Endocrine cells within the walls of some digestive organs also secrete a variety of hormones that help digest food. </li></ul><ul><li>When food is eaten, endocrine cells in the stomach lining secrete gastrin , a hormone that stimulates other stomach cells to release digestive enzymes and hydrochloric acid (HCL). </li></ul><ul><li>Endocrine cells of the small intestine release secretin , a hormone that stimulates the release of various digestive fluids from the pancreas and bile from the liver. </li></ul>
STRESS & HEALTH A. Factors that serve as stressors to the body produce stress and threaten homeostasis. B. Types of Stress Stress may be physical, psychological, or some combination of the two. 1. Physical stress threatens the survival of tissues, such as extreme cold, prolonged exercise, or infections.
<ul><li>2. Psychological stress results from real or perceived dangers, and includes feelings of anger, depression, fear, and grief; sometimes pleasant stimuli cause stress. </li></ul><ul><li>C. Response to Stress </li></ul><ul><li>Responses to stress are designed to maintain homeostasis. </li></ul><ul><li>The hypothalamus controls the general stress syndrome, which involves increased sympathetic activity and increased secretion of cortisol, glucagon, growth hormone, and antidiuretic hormone. </li></ul>