1. Chapter 45: Hormones & The Endocrine System
Steph Jones
AP Biology
Ms. Loughnane

2. Basics
Hormone: a chemical signal that is secreted into the circulatory system (usually the blood) and communicates regulatory messages within a body
Target cells are the cells that contain the specific receptor that only activates when that specific hormone is secreted
Two main systems involved are:
Nervous System & Endocrine System

3. Control Pathways Three major hormonal control pathways:
Endocrine, Neurohormone, Neuroendocrine.
Regulation by hormones:
Receptor detects stimulus and sends info to control center
After comparing the desired set point, the control center sends signal to an effector
The effector responds and sends a changing signal into the control pathways

4. Feedback
After the effector sends out a changing signal into the pathways, it becomes either:
Negative feedback, where the effector response reduces the initial stimulus, and eventually the response stops OR
Positive Feedback, which reinforces the stimulus and leads to a greater response
Feedback regulates hormonal pathways used to maintain homeostasis

5. Classes of Hormones
Proteins and Peptides - small polypeptide containing up to 30 amino acids (both are water-soluble)
Amines that come from Amino Acids (water-soluble)
Steroids (lipid-soluble)

6. Signaling Three Key Events:
Reception – occurs when the signal molecule binds to a specific receptor protein in or on target cell
Signal Transduction – events within target cell
Response – a change in cell behavior as a response to the stimulus and to maintain homeostasis

7. Cell-Surface Receptors for Water-Soluble Hormones
Most peptide/protein hormones that come from amino acids bind to receptors that are located inside the plasma membrane
Signal Transduction Pathway: a series of changes in cellular proteins that converts an extracellular chemical signal to specific intracellular response

8. Cell-Surface Receptors for Water-Soluble Hormones (cont’d)
Binding causes a signal transduction pathway that leads to a response in cytoplasm or changes in gene expression
* Remember: the same hormone can have different effects on target cells that have:
Different receptors
Different signal transduction pathways
Different effector proteins

9. Intracellular Receptors for Lipid-Soluble Hormones
Intracellular receptors of steroid hormones transduce a signal within a target cell
The chemical signal activates the receptor which leads to the cell’s response

10. Paracrine Signaling
Paracrine Signaling: local regulators convey messages between neighboring cells
Faster than the long-distance endocrine signaling

11. Paracrine Signaling (cont’d)
Local regulators greatly help maintain homeostasis
ex: nitric oxide (NO) is released by by blood vessels when blood oxygen level falls. NO activates an enzyme that relaxes smooth muscle cells, which dilates vessels and improves blood flow to tissues

12. Hypothalamus
Hypothalamus: a region of the lower brain that contains different sets of nuerosecretory cells

13. Pituitary Gland Pituitary Gland: At the base of
the Hypothalamus; has two parts:
- Posterior Pituitary: stores and secretes 2 hormones that are made by neurosecretory cells located in the hypothalamus
- Anterior Pituitary: make and secrete at least 6 hormones into the blood

14. Tropic Hormones
Regulate the function of endocrine organs, and coordinate endocrine signaling throughout the body

15. Posterior Pituitary Hormones
Releases 2 hormones:
ADH (antidiuretic hormone): kidney tubules
Oxytocin: mammary glands, uterine muscles

16. Anterior Pituitary Hormones: Tropic Effects Only
thyroid-stimulating hormone (TSH): Thyroid
follicle-stimulating hormone (FSH): testes & ovaries
luteinizing hormone (LH): testes & ovaries
adrenocorticotropic hormone (ACTH): Adrenal cortex

17. Anterior Pituitary Hormones: Nontropic Effects Only
Prolactin: mammary glands
Endorphin: pain receptors in brain
Melanocyte-stimulating hormone (MSH): melanocytes

18. Anterior Pituitary Hormones: Nontropic & Tropic Effects
Growth hormone: Liver & bones

19. Nonpituitary Hormones
Help regulate metabolism, homeostasis, development, and behavior
There are 6 types: Thyroid, Parathyroid & Calcitonin, Insulin & Glucagon, Adrenal, Gonadal, Melatonin & Biorhythms

20. Thyroid Hormones
Thyroid Gland: two lobes on the ventral surface of the trachea, produce 2 hormones produced by the amino acid tyrosine: Triiodothyronine (T3) and Thyroxine (T4).
They stimulate metabolism, influence development and maturation

21. Parathyroid Hormone (PTH) & Calcitonin
Play the major role in calcium (Ca2+) homeostasis, control blood calcium levels
PTH raises blood Ca2+ levels when they drop and Calcitonin lowers Ca2+ levels when they rise

22. Insulin & Glucagon
Help maintain glucose homeostasis, the pancreas synthesizes them
Insulin lowers blood glucose levels and glucagon raises them

23. Adrenal Hormones: Adrenal Medulla
Secreted by the Adrenal glands, two glands, adrenal cortex, outer portion and adrenal medulla, central portion
Epinephrine and norepinephrine are releasedby nuerosecretory cells in the adrenal medulla in response to stress or danger.
Adrenal Medulla

24. Adrenal Hormones: Adrenal Cortex
The adrenal cortex releases glucocorticoids (influence glucose metabolism & immune system), mineralocorticoids (salt and water balance), and small amounts of sex hormones
Adrenal Cortex

25. Gonadal Sex Hormones
There are three sex hormones: androgens (ex. Testosterone), estrogens, and progestins
-Androgens stimulate development/maintenance of male reproductive system
- Estrogen maintain female reproductive system and female secondary sex characteristics
- Progestins prepare/maintain uterus
Produced by the gonads, or testes and ovaries
Produced in both males and females, just in different amounts

26. Melatonin and Biorhythms
Pineal gland in the brain secretes melatonin
The secretion of Melatonin is regulated by light/dark cycles and is related to biological rhythms with reproduction

27. Invertebrates
They also contain endocrine system and nervous system interactions
Varied hormones regulate many different aspects of homeostasis
Molting in insects includes 3 different hormones
Brain hormone
Ecdysone
Juvenile Hormone

28. Picture Citations (respectively)