Endocrine System PDF

1/30/2024 Endocrine System & Reproduction Endocrine System How does the endocrine system regular body processes? What are the endocrine glands? How does negative feedback regular hormone levels? 1 Importance of a Signal Signals instruct changes within the human body Two systems regulate the human bo...

1/30/2024 Endocrine System & Reproduction Endocrine System How does the endocrine system regular body processes? What are the endocrine glands? How does negative feedback regular hormone levels? 1 Importance of a Signal Signals instruct changes within the human body Two systems regulate the human body 1. Nervous system 2. Endocrine system Nervous system  sends nerve impulses around the body Endocrine system produce chemicals (hormones) that control the body’s activities. Also regulates changes like growth and development 2 1 1/30/2024 What is the Endocrine System? Endocrine system is made up of glands that produces and releases chemicals. Two main types of glands within the body - Exocrine gland  secrete chemicals through a duct e.g. sweat glands, salivary glands - Endocrine glands  secrete chemicals directly into the bloodstream e.g. adrenal glands, thyroid 3 Endocrine Glands Produce hormones which are chemicals that cause changes the activity within the body’s organs or tissues. Turn on Turn off Speed up Slow down specific activities occurring within the body  chemical messenger Affects organs that can be far away from the gland producing it 4 2 1/30/2024 Production of Hormones Hormone production is triggered by three pathways: Neural stimuli  due to nervous system Humoral stimuli  due to changes in fluid and chemical levels in body Hormonal stimuli  due to levels of other hormones that were released by the body 5 Example of Neural Stimuli 1. 2. 3. 4. Person sees a large bear about 1 yard away Nervous impulses travel from eyes to the brain Brain interprets signal and sends signals to adrenal gland Adrenal gland releases the hormone adrenaline into the body’s bloodstream 5. Adrenaline causes the heart to pump faster  lungs breathe more effectively  blood sent effectively to brain  person more alert  raise blood sugar level to provide energy. Person feels less pain to allow person to keep running or fighting for a longer duration Prepares body for a fight or flight situation 6 3 1/30/2024 Example of Humoral Stimuli 1. Person has a large meal and body digested and absorbed nutrients e.g. sugar from the food 2. Blood sugar level rises 3. Rise of blood sugar triggers the production of insulin (hormone) from the pancreas (gland) 4. Insulin triggers the absorption of sugar from the bloodstream by muscles, fat and liver to return blood sugar levels to normal. Sugar from the blood may be used as energy or converted into fat. 7 Example of Hormonal Stimuli Hypothalamus (gland found in the brain), produces hormones that will circulate within the blood stream to trigger other glands in other organs to produce hormones. Example: GnRH produced by the hypothalamus triggers production of sex hormones by the gonads within the person’s body. e.g. estrogen from the ovaries or testosterone from the testes 8 4 1/30/2024 9 Hormone Action Hormone effects  slower but longer, more lasting response. e.g. Adrenaline released from the adrenal gland which causes heart to beat faster  heart continues to beat fast even for some time even when the adrenaline levels have returned to normal. 10 5 1/30/2024 Target Cells Hormones affect only certain organs – not all organs. This is due to the chemical structure of the hormone. Interacts with only specific cells  target cells Target cells recognize the chemical structure and fit the hormone like a “lock and key”. Hormone travels in the bloodstream until it finds the cell that it can “fit” which will be the target cells. 11 Hypothalamus – links the nervous & endocrine systems. Also controls the pituitary gland Pituitary gland – controls other endocrine glands and regulates growth, blood pressure and water balance Endocrine Glands Thyroid gland – Controls release of energy from food molecules inside the cells Parathyroid glands – Regulate the amount of calcium in the blood Thymus gland – Help develop the immune system during childhood Pancreas – Produces insulin and glucagon which regulate blood sugar levels Adrenal glands – Releases several hormones like adrenaline which triggers fight or flight response. Also produces other hormones regulating salt and water balance in kidneys and sugar in blood Testes – release testosterone which control male body changes and regulates sperm production Ovaries – release estrogen and progesterone which controls female body development and trigger egg development respectively. 12 6 1/30/2024 Hypothalamus and Pituitary Glands These two glands produce hormones that in turn control other glands to produce other hormones. Hypothalamus Located in the middle of the brain Links nervous system and endocrine system Sends nerve messages regulating basic processes like sleep and hunger Produces hormones that controls other glands and organs Sends hormones to other glands like the pituitary gland Critical in maintaining homeostasis within the body 13 Pituitary Gland Located just below hypothalamus Receives hormones or nerve signals from hypothalamus to control many body activities Releases hormones to serve as a “switch” for other endocrine glands e.g. Pituitary gland  hormones (TSH)  control thyroid gland to produce hormone (T3 & T4)  regulate metabolism, energy levels, internal body temperature 14 7 1/30/2024 Negative Feedback Loop – Daily Lives Thermostat of home set at 25 C Temperature falls below 25 C  thermostat senses lower temperature  signals furnace to turn on Temperature rises to 25 C  thermostat receives “feedback” that right temperature is achieved  thermostat sends signal to furnace to turn off Negative feedback  system is turned off by the condition that produces it 15 Negative Feedback in the Endocrine System When the amount of hormone reaches a certain level, the endocrine system sends signal to stop the release of the hormone. 16 8