Importance of the Endocrine System

Chemical Controls The endocrine system consists of a number of glands and their respective hormones.The endocrine system consists of a number of glands and their respective hormones. The endocrine hormones are chemicals secreted by endocrine glands directly into the blood which affect cells in other areas of the body.The endocrine hormones are chemicals secreted by endocrine glands directly into the blood which affect cells in other areas of the body. Hormones may affect a specific target within the body or have a broad-spectrum effect on body function where several organs are affected at the same time by the hormone’s release.Hormones may affect a specific target within the body or have a broad-spectrum effect on body function where several organs are affected at the same time by the hormone’s release.

Endocrine Glands PituitaryPituitary PinealPineal ThyroidThyroid ParathyroidParathyroid ThymusThymus AdrenalAdrenal PancreasPancreas Ovary/TestesOvary/Testes

Steroid vs. Protein Hormones Steroid Hormones Lipids – made from cholesterol.Lipids – made from cholesterol. They diffuse from blood into the cell and attach to a receptor molecule.They diffuse from blood into the cell and attach to a receptor molecule. Taken into nucleus and attaches to chromatin at specific gene location.Taken into nucleus and attaches to chromatin at specific gene location. Hormone activates gene and required protein is made.Hormone activates gene and required protein is made. Protein Hormones Proteins – made of amino acid chains.Proteins – made of amino acid chains. The attach to receptor proteins in cell membrane.The attach to receptor proteins in cell membrane. The hormone-receptor complex produces a molecule that acts as a messenger and activates enzymes within the cell.The hormone-receptor complex produces a molecule that acts as a messenger and activates enzymes within the cell.

The All-Powerful Pituitary Gland Referred to as the “master gland” because it exercises control over the other glands.Referred to as the “master gland” because it exercises control over the other glands. Connected to the hypothalamus.Connected to the hypothalamus. The pituitary makes and stores hormones and the hypothalamus tells it when to release them using nerve impulses.The pituitary makes and stores hormones and the hypothalamus tells it when to release them using nerve impulses. The pituitary has two lobes – anterior and posterior.The pituitary has two lobes – anterior and posterior. The posterior lobe stores and releases hormones made by the hypothalamus.The posterior lobe stores and releases hormones made by the hypothalamus. The anterior lobe produces and releases its own hormones.The anterior lobe produces and releases its own hormones. See figure 6 on page 376 for examples of the hormones stored and/or produced by each lobe of the pituitary gland.See figure 6 on page 376 for examples of the hormones stored and/or produced by each lobe of the pituitary gland.

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Hormones That Affect Blood Sugar

Blood Sugar Hormones  The pancreas has cells that produce digestive enzymes and those that produce hormones – we will discuss the hormones.  Cells in the Islets of Langerhans (special pancreatic cells) produce insulin and glucagon.  Insulin is a hormone that allows for the uptake of glucose by body cells.  Glucagon is a hormone that promotes the conversion of glycogen to glucose. (A la Unit 1)

Blood Sugar Too High?  Pancreas secretes insulin – cells take in excess glucose from blood.  Liver also converts excess glucose into glycogen.  Glucose levels in the blood drop back to normal because excess glucose has gone from blood into cells or has been stored in the liver as glycogen.

Blood Sugar Too Low?  Pancreas releases glucagon into the blood which goes to the liver.  The liver starts to convert (breakdown) the glycogen it stores into glucose molecules which are then released into the blood.  Insulin and glucagon have opposing actions in terms of blood sugar management.

Diabetes  Diabetes is a chronic disease that occurs when the body cannot produce any insulin, or enough of it, or is unable to use the insulin in makes properly.  What could happen??? –After meals, blood sugar spikes (hyperglycemia), excess glucose exits body in urine and the threat of dehydration exists. –After time goes by, cells become starved for glucose and have to rely on other fuels. This can result in problems as harmful byproducts of the alternate fuel pathways. –If energy levels get too low, organs will be shut down and failure occurs.

Adrenal Glands  “Adrenal” = At the kidneys.  The adrenal gland has an inner core called the adrenal medulla which is surrounded by the adrenal cortex.  The adrenal medulla produces two hormones: epinephrine and norepinephrine.  Epinephrine is also known as adrenaline.  Norepinephrine is also known as noradrenaline.  Both of these hormones are released by the adrenal medulla in times of stress.

Short Term Stress Response  Both norepinephrine and epinephrine are released during times of stress. They help initiate the fight or flight response. (Hypothalamus  Spine  Adrenals) –They increase blood sugar levels by converting glycogen into glucose. –They increase heart rate and breathing rate for faster delivery of oxygen and glucose to the cells. –This results in faster energy production and higher metabolic rate within the cell. –Blood vessels dilate (widen) to deliver more blood. –Pupils dilate to allow more light into eye to gather as much information from surroundings as possible.

Long Term Stress Response  “Long term stress” means the threat is not incredibly urgent or threatening – though it is constant and ever present.  Hypothalamus  Spine  Adrenal  Adrenals secrete glucocorticoids & mineralocorticoids – they help with stress.  Glucocorticoid, called cortisol, promotes conversion of fat and protein into glucose – blood sugar level goes up overall.  Mineralocorticoids increase water retention by kidneys and this results in higher blood pressure and blood volume – greater delivery of blood to cells.

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