1. Hormones and Feedback Mechanisms
Chapter16
How the endocrine system controls everything

2. The Endocrine System

3. ES and Homeostasis
Homeostasis

4. Feedback Mechanisms Stimulus Response
change in homeostatic environment
signal sent to CNS
Response
signal sent from CNS
produce effect
body returns to homeostasis

5. Basic ES cont. ES and NS = 2 main control systems of body
Endocrine organs located throughout body
Actions mediate all tissues
Control of ES through feedback mechanisms

6. II. ES anatomy basics Exocrine gland Ducts Lumen and surfaces
Ex: Sudoriferous, salivary
Endocrine gland
Chemical messengers
Blood stream
Ex: Testosterone, Estrogen, Thyroxin

7. C. Hormones Chemical messenger Secreted by endocrine gland
Specific to target
Activate cellular change

8. Hormone + Receptor

9. Where are Hormones Made ?

10. The H-P-A Hypothalamic-Pituitary Axis
Most feedback loops run through this axis
HPA mediates growth, metabolism, stress response, reproduction.
is secondarily in charge of almost everything else.

11. Why is the Hypothalamus so Important?
Secretes regulatory hormones
RH (releasing)
RIH (inhibiting)
"Directs" pituitary

12. (Release-Inhibiting Hormone)
STIMULUS
Hypothalamus
Releasing Hormone
(Release-Inhibiting Hormone)
Pituitary
Stimulating Hormone
Gland
Hormone
Target

14. E. Pituitary gland MASTER GLAND Anterior and posterior portions
Posterior connected to hypothalamus by infundibulum
Anterior connected via blood stream

15. 2. Anterior Pituitary Hormones
TARGET
FUNCTION
Thyroid (TSH) Stimulating
Thyroid gland
TH synthesis &
release
Growth (GH)
Many tissues
growth
Adrenocortico-
Tropin (ACTH)
Adrenal cortex
Cortisol release
(androgens)
Prolactin (Prl)
Breast
Milk production
Follicle (FSH)
Gonads
Egg/sperm prod.
Luteinizing (LH)
Sex hormones

16. III.Control of Endocrine Function
Positive
or Negative Feedback mechanisms
Self-regulating system

17. A. Positive Feedback Not common Classic example:
Action of OXYTOCIN on uterine muscle during birth.

18. B. Negative Feedback Most common control mechanism
Level of hormone in blood or body’s return to homeostasis shuts off loop at hypothalamus and pituitary
Ex: Thermostat controls and thyroxin (thyroid hormone)

19. Thyroid Problems
What would happen if the thyroid could no longer produce T3 and T4?
No negative feedback to hypothalamus and anterior pituitary

20. Goiter

21. Hyper-secretion of TSH or TH

22. B. Growth Hormone Stimulus = Tissue growth/ repair
Seen during infancy, toddler, adolescent stages.

23. What happens with too much GH?

24. GH = pituitary dwarfism

26. Too many steroids

27. Adrenal glands responsible for Hormone Adrenaline, which gives you the rush when presented with a fight or flight situation. The pancreas is responsible for producing insulin. Regulation determines if person is classified as diabetic or not.

28. Developmental Aspects
Levels of hormones decrease as the individual ages.
Gonads undergo significant changes especially in females. The ability to bear children decrease along with egg production.
In males, testosterone decreases in testes, but the effect is not seen until very old age.