1 / 18

Homeostasis

Homeostasis. SBI4U Nov 7, 2012. Negative and positive feedback homeostatic mechanisms. Negative Feedback: Positive Feedback : change is encouraged or increased. Activity - Questions. Knowledge & Understanding

gyan
Download Presentation

Homeostasis

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Homeostasis SBI4U Nov 7, 2012

  2. Negative and positive feedback homeostatic mechanisms • Negative Feedback: • Positive Feedback : change is encouraged or increased.

  3. Activity - Questions Knowledge & Understanding Q1. Which of the following order is correct as it applies to negative feedback mechanism: • (a) effector, sensor, stimulus, integrator, response. • (b) stimulus, sensor, integrator, effector, response. • (c) sensor, stimulus, effector, integrator, response. • (d) none of the above

  4. Thinking & Inquiry • Q 2. For each of the following describe how homeostasis is achieved and indicate the type of homeostatic feedback mechanism: (a) A student is fasting and as a result his blood glucose level drops to 2.8 mmol/l or 50 mg/dl.

  5. Answer: • Negative Feedback. • After fasting the blood sugar level is low and alpha cells of islets of langerhans in the pancreas releases glucagon into blood. The liver than converts glycogen to glucose and releases it into blood.Bloodsugar level rises back to normal. • N.B: Glucagon is a hormone secreted by the pancreas. It does the opposite effect of insulin.

  6. (b) A mother giving birth starts experiencing increased uterine contractions.

  7. Answer: Positive feedback. • Labordecrease in progesterone uterine contractionsbaby creates pressure on cervixsignal sent to hypothalamusoxytocin released which stimulates the uterine contractions.

  8. (c) A patient diet lacks iodine and as a result she experiences low thyroid secretions

  9. Answer: • Negative feedback. • Low thyroid secretionnerve cells on hypothalamus secrete TRH (thyroid releasing hormone)pituitary releases thyroid stimulating hormone (TSH) travels in the bloodthyroxinerelease from the thyroid gland (also T3)  increase in thyroid secretion.

  10. (d) A marathon runner starts excessively sweating after 10 km.

  11. Answer: Negative Feeback. • Thermoreceptors signal an increase in temperature (sensor)hypothalamus turns on cooling system (integrator)skin blood vessels dilate causes increased blood flow to the skin and as a result there is a loss in thermal energy from skin and sweat glands initiate sweating in which evaporation of sweat causes cooling (effector). Body temperature decreases and hypothalamus turns off cooling system.

  12. Questions Continued... • Making connections • Q3. Methamphetamine such as ecstasy interfere with homeostatic feedback mechanism. Explain how these drugs are dangerous.

  13. Answer:Methamphetamine such as ecstasy interfere with the hypothalamus ability to regulate body temperature. A rapid increase in core body temperatures inactivates many enzymes which slows metabolic activityessential biochemical pathways that inactivate poisons and produced needed chemicals are impairedwhichmay lead to tissue damage and in extreme cases death.

  14. Methamphetamines such as ecstasy also increase production of antidiuretic hormone (ADH)this prevents the body from excreting urine and makes the mouth and throat feel dry .While ecstasy is making person thirsty the high level of ADH is preventing urination, water is not eliminated from the body and can cause the brain to swell which may lead to a coma or death.

  15. Q4. Boxers take laxatives when they need to meet the weight restrictions of lower fighting classes. How can this practice be dangerous and how do laxatives help them reduce weight?

  16. How do laxatives reduce weight? • Laxatives increase water loss , this loss is temporary once the body rehydrates the water weight lost comes back.

  17. Why is it dangerous? • It can be dangerous because there is a decrease in body fluids (dehydration) and a decrease in blood pressure. The decrease in blood pressure also upsets the balance of electrolytes in the body. The disturbance in electrolyte balance can damage the tissues and muscles of the body even those around the heart. Damage to muscles around the heart can lead to death.

More Related