1. Chapter 10 Study Guide The Endocrine System
By: Sarah Genet

2. Endocrine System Controls body functions via hormones.
So let’s say there’s too much glucose in your blood. Your pancreatic islets cells send insulin into the blood which tells your cells to start absorbing all the glucose, thereby decreasing the concentration of glucose in your blood. The hormone in this situation is insulin, and you can deduce how it is affecting bodily functions.
Pretty big deal, no? If a patient’s pancreatic islet cells stop making insulin, or if they can no longer act on their target cells, that patient has diabetes mellitus. Do you know someone with diabetes?

3. Two types of Glands
The endocrine system secretes hormones using endocrine glands (kind of makes sense, no?) These are glands which lack ducts. Ducts are like tubes which carry hormones into the blood so they can be circulated around the body and distributed.
So what is the other possible type of gland?
Not endocrine, but exocrine.

4. Hormone Types
Nonsteroid Hormones – Proteins, short chain amino acids or single amino acids
Proteins are water soluble and therefore cannot pass through the cell membrane. Therefore nonsteroid hormones affect the activity of the cell via a secondary messenger system (see: lock and key model and cyclic AMP)
Steroid Hormone – Lipid soluble steroid hormone
Can pass through a cell’s cell membrane, travel through the cytoplasm, enter the nucleus and act on DNA (see: hormone receptor complex)

5. Prostaglandins
Not actually hormones….hormones are produced in one location (for example, insulin is made only in the pancreas) but prostaglandins are produced in many places, throughout the body
Prostaglandins are frequently produced in tissues and act locally. In other words, they are produced in a tissue and diffuse a short distance to act on cells within that tissue

6. Regulation of Hormone Secretion
Negative feedback: the output of a system acts to oppose changes to the input of the system
Ex) During periods of high blood sugar pancreatic islet cells secrete insulin in order to decrease blood sugar levels and bring them back to normal.
Positive feedback: amplify changes to the system
Ex) Oxytocin increases the force of contractions during labor

7. Endocrine Glands Hypothalamus Pituitary Pineal Thyroid Parathyroid
Thymus
Adrenal
Pancreas
Ovaries (female), Testes (male)

8. Pituitary Gland Located in sella turcica of the Sphenoid bone
Two parts
Anterior pituitary,aka adenohypophysis
Posterior pituitary, aka neurohypophysis

9. Pituitary Hormones Anterior Pituitary FLAT (all tropic hormones) FSHLH
ACTH
TSH PG
Prolactin GH
Posterior Pituitary
ADH
Oxytocin

10. Pituitary Disorders
Hyperglycemia: too much sugar in blood. One cause is too much GH
Diabetes Insipidus: dehydration and electrolyte imbalance due to hyposecretion of ADH

11. Hypothalamus Nervous and endocrine function
Nervous – Specialized neurons produce ADH and oxytocin (to posterior pit.)
Endocrine - Releases releasing and inhibiting hormones. These travel to the anterior pituitary and cause the ant. Pit. to release or inhibit the production/release of hormones.

12. Thyroid Gland Located in neck below the larynx
Secretes T3 (triiodothyronine) and T4 (thyroxine). T3 has 3 molecules of iodine and T4 has 4 molecules of iodine.
Stores T3 and T4 in the follicle. Most endocrine organs do not store hormones, so this function is unique!
Secretes calcitonin – decreases concentration of calcium in the body. This hormone is used to prevent an excess of calcium in the blood, a condition known as hypercalcemia.

13. Example of negative feedback
In this diagram T3 and T4 perform negative feedback on the anterior pituitary and the hypothalamus, causing them to decrease their release of TSH and TRH.

14. Thyroid Hormone Abnormalities
Hyperthyroidism – over secretion of thyroid hormone
Hypothyroidism – under secretion of thyroid hormone
Simple Goiter – enlargement of thyroid gland caused by low dietary intake of iodine
Cretinism – hyposecretion of thyroid hormone during formative years
Myxedema – hyposecretion of thyroid hormone later in life.

15. Parathyroid Gland Located on the back of the thyroid
Secretes parathyroid hormone (PTH) – increases blood calcium levels.
What hormone decreases blood calcium levels?

16. Adrenal Gland
Composed of two endocrine glands: the adrenal cortex and the adrenal medulla

17. Adrenal Gland Adrenal Cortex - secretes corticoids: Adrenal Medulla
mineralocorticoids (MC). ex) aldosterone
Glucocorticoids (GC) ex) cortisol aka hydrocortisone
Sex hormones ex)androgens
Adrenal Medulla
Epinephrine and norepinephrine

18. Adrenal Medulla Abnormalities
Cushing’s Syndrome – overproduction of adrenal cortex hormones. Symptoms include moon-face, buffalo hump on upper back, elevated blood sugar and frequent infections (Seen in photo below)
Addison’s Disease – hyposecretion of adrenal cortex hormones. Results in muscle weakness, reduced blood sugar, nausea, loss of appetite and weight loss

19. Pancreatic Islet Located in exocrine pancreas.
Two types – alpha and beta cells. Alpha release glucagon and beta release insulin.
Glucagon  increased blood glucose concentration via liver glycogenolysis
Insulin  decreased blood glucose concentration
Secrete pancreatic enzyme juice.

20. Diabetes Mellitus
Type I diabetes – increase in blood glucose levels due to hyposecretion of insulin
Type II diabetes – increase in blood glucose due to an abnormality of insulin receptors. Sometimes accompanied by hyposecretion of insulin.
Diabetes Mellitus results in glycosuria - glucose in the urine. Doctors can diagnose diabetes by checking the blood or urine.

21. Sex Glands - Female Female Sex Glands – two ovaries
Composed of two parts:
the follicle – secretes estrogen and the egg or ova developes here
Estrogen – involved in development and maturation of breast and external genitalia, development of adult female contours (hips, curves) and initiation of the menstrual cycle
Corpus Luteum – secretes
progesterone and some estrogen.

22. Sex Glands - Male
The testes are made of many cell types. One cell type, the interstitial cell, makes testosterone which is the male sex hormone.
Testosterone – “masculinizing hormone” – maturation of external genitalia, beard growth, changes in voice at puberty, muscular development and male contour.

23. Thymus
Located in the mediastinum (adults) or may extend up into the neck as far as the bottom of the thyroid gland (infants)
Composed of a cortex and medulla. What other organ contains a cortex and medulla?
Both parts are composed of lymphocytes; the thymus plays a critical role in defense against infections
Produces thymosin

24. Placenta Temporary endocrine structure present during pregnancy
Produces chorionic gonadotropins
(tropic hormones produce by the chorion), estrogen and progesterone
During the earlier weeks of pregnancy the placenta excretes large amounts of chorionic gonadotropins into the blood. So, when a woman takes a pregnancy test, it is looking for the presence of this hormone because some of the hormone is secreted in the urine 

25. Pineal Gland
Located near the roof of the third ventricle in the brain.
Easily located in a child but not in an adult. This is because the gland becomes encrusted with calcium deposits as a person ages.
Makes many hormones, the most important one being melatonin.
Melatonin – inhibits the tropic hormones which affect the ovaries and is throught to be involved in regulating the onset of puberty and the menstruation in women. The release of melatonin is increased during the night and decreased during the day.

26. Additional Endocrine Structures
Atrial Natriuretic Hormone – secreted by cells in the hearts’ atria (upper chambers of the heart). Regulates fluid and electrolytes in the body and is an antagonist to aldoesterone. (Aldosterone causes the body to hold on to sodium and water while ANH stimulates the loss of sodium and water.
Leptin – secreted by fat storing cells. Regulates how hungry/full we feel and how fat is metabolized by the body.