1. 6.6 Hormones and homeostasis

2. understandings
U1. Insulin and Glucagon are secreted by alpha and beta cells in the pancreas to control blood glucose concentrations.
U2. Thyroxin is secreted by the thyroid gland to regulate the metabolic rate and help control body temperature.
U3. Leptin is secreted by cells in adipose tissue and acts on the hypothalamus of the brain to inhibit appetite.
U4. Melatonin is secreted by the pineal gland to control circadian rhythms.
U8. Feedback control.
A1.Causes and treatment of Type 1 and Type 2 Diabetes.
A2. Testing of leptin on patients with clinical obesity and reasons for the failure to control the disease.
A3. Causes of jet lag and use of melatonin to alleviate it.

3. Endocrine Control of Homeostasis The release of hormones into the blood.

4. Endocrine System
1. System of ductless glands which secrete hormones directly into the blood.
2. Hormones travel to target tissues or glands.
3. Hormones are used to maintain HOMEOSTASIS.

5. U8. Feedback control to maintain homeostasis
Homeostasis: is the control process that maintains the body’s internal environment at a relatively constant level or within very narrow limits. (Usually uses negative feedback loops to maintain.)
Negative Feedback: (stabilizing) Equal but opposite response. A rise in level feeds back to decrease production and reduce levels. A decrease in levels feds back to increase production and rise levels.
*Positive Feedback: (amplifies)tends to lead to sudden rises or falls, because a rise causes further rises and falls cause further falls.

6. Negative feedback loop

8. Control of Blood Glucose

10. Low Blood Glucose Levels
High Blood Glucose Levels
BETA cells of the PANCREAS as stimulated to release INSULIN into the blood.
Body cells take in glucose AND the liver and muscle cells store glucose as GLYCOGEN
Blood glucose levels decline to a set point. Stimulus for INSULIN release diminishes.
Low Blood Glucose Levels
ALPHA cells of the PANCREAS are stimulated to release GLUCAGON into the blood.
The liver and muscle cells break down GLYCOGEN and releases glucose into the blood.
Blood glucose levels RISE to set point. Stimulus for GLUCAGON release diminishes.

11. A1.Causes and Treatment of Type1 and Type 2 Diabetes
Diabetes Mellitus: Condition where a person has a constant elevated blood glucose level. ( Glucose detected in urine.) (Symptoms: frequent urination, excessive thirst, and lethargy)
Type 1 Diabetes: “early onset”
Cause: The destruction of BETA cells by the body’s own immune system. (AUTOIMMUNE).
Effect: Inability to produce sufficient amounts of INSULIN.
Treatment: Regular testing of blood glucose levels and insulin injections when blood sugar is too high or likely to become too high.
Type 2 Diabetes: “late onset”
Cause: Inability to respond to insulin due to a deficiency of the insulin receptors or glucose transporters on target cells. (INSULIN RESISTANCY)
Risk factors: sugary, fatty diets ,obesity due to over eating, lack of exercise genetic predisposition.
Treatment: Adjustment of the diet to reduce fluctuations in blood sugar. Frequent small meals lower in sugar and fat content.
Exercise and Weight Loss.

13. U2.Thyroxin is secreted by the thyroid gland to regulate the metabolic rate and help control body temperature.
THYROXINE:
-Protein hormone that contains 4 atoms of IODINE. A deficiency of IODINE in diet prevents the synthesis of Thyroxine.
- Almost all cells in body are target cells.
-Regulates cell metabolism.
(METABOLISM: any/all chemical reaction in the body)

14. U2.Thyroxin is secreted by the thyroid gland to regulate the metabolic rate and help control body temperature.
Regulation of Body Temperature:
STIMULUS: Drop in body temperature detected by the HYPOTHALAMUS.
Response: PITUITARY GLAND stimulates the THYROID GLAND to secrete THYROXINE.
Effect: Increase metabolic rate of cellular respiration in brown adipose tissue creating heat by shivering.
May also cause VASOCONSTICTION reducing heat loss though the skin.
Normal body temperature reached. (37 °C ± .5 °C )

15. Vasoconstriction Vasodialation

16. U3. Leptin is secreted by cells in adipose tissue and acts on the hypothalamus of the brain to inhibit appetite.
LEPETIN: “satiety hormone” protein hormone secreted by ADIPOSE (fat storing cells) tissue.
-Acts upon the hypothalamus to control appetite.
LOW ADIPOSE TISSUE and LOW FOOD INTAKE
Leads to: LEPTIN not being released there is an INCREASE in appetite and INCREASE food intake.
HIGH ADIPOSE TISSUE and HIGH FOOD INTAKE
Leads to: Release of LEPTIN allowing for long-term APPITITE INHIBITION and REDUCED food intake.

17. A2. Testing of leptin on patients with clinical obesity and reasons for the failure to control the disease
-In the 1950’s Obese mice were found to have a recessive gene mutation ob/ob.
-It was determined in the early 1990’s that these mice were UNABLE to produce the newly discovered “satiety” hormone LEPTIN due to their mutation.
-When the ob/ob mice were INJECTED with LEPTIN
their appetite decline, energy increased, and body mass dropped by 30%.
POSSIBLE TREATMENT FOR OBESITY FOR HUMANS…………………………………………...

18. Large clinical trials were carried out of a double blind study
Large clinical trials were carried out of a double blind study. Neither the researchers or the subjects knew if they were getting LEPTIN or a PLACEBO.
FINDINGS:
-LEPTIN did NOT have the same effect on humans as it did in mice.
- Obese humans already had high levels of LEPTIN in their blood.
- Target cells on the hypothalamus may have become RESISTANT to LEPTIN.
Appetite was not inhibited and food intake was excessive.
- Was also found that very few obese humans had the gene mutation for not producing LEPTIN. ( The shots did work for them but had to be given too frequently so they opted out.)

19. U4. Melatonin is secreted by the pineal gland to control circadian rhythms

20. Circadian rhythms: are the 24 hour behavioral cycle that humans are adapted to.

21. MELATONIN: Hormone that affects the sleep- wake cycle.
INCREASING Melatonin cause feelings of drowsiness and promotes sleep.
FALLING melatonin levels encourages waking at the end of night.
PRODUCTION OF MELATONIN:
Light or dark is detected by ganglia in the retina of the eye.
This information is taken to the SUPERCHIASMATIC NUCLEUS (SCN) in the hypothalamus.
Neurons here control the release of MELATONIN by the PINEAL GLAND.
LIGHT- INHIBITS MELATONIN SECRETION.
Low during the day.
DARK- STIMULATES MELATONIN SECRETION.
Higher at night.

22. A3. Causes of jet lag and use of melatonin to alleviate it.
JET LAG occurs when someone crosses 3 or more time zones.
SYMPTOMS: Difficulty in staying awake during daylight hours and difficulty sleeping through the night.
Fatigue, irritability, headaches, and indigestion.
CAUSE: Your body is still set in the circadian rhythm from which you left not for where you are.
EFFECT OF MELATONIN ON JET LAG:
While the ganglia of the retina is sending new information to the SCN when light is detected which allows for a reset of the circadian clock.
Melatonin can be take at the time when sleep “should” occur to reduce the effects. or
Taken before travel to prevent jet lag.