1. Hormones and the Endocrine system chapter 45
By: Allysa Yi,
Gunjan Nachane,
Michael Wormley,
and Vickie Eickelberg

2. Hormones & Local Regulators (#1)
Hormones: a molecule that’s secreted into the extracellular fluid, circulates in blood or hemolymph, and communicates regulatory messages throughout the body.
Local Regulators: secreted molecules that act over short distances and reach their target cells by diffusion.
Basic path of a hormone. Hormones travel through the bloodstream. In contrast, a local regulator would diffuse from its origin to its target cell through diffusion.

3. Paracrine vs Autocrine (#2&3)
Paracrine signaling: target cells lie near the secreting cell.
Autocrine signaling: secreted molecules act on the secreting cell itself.
Neurohormone: A specific class of hormones secreted by neurosecretory cells that secrete the neurohormones and once secreted they travel from nerve cell endings into the bloodstream.
Ex: Vasopressin which is critical to kidney function and water balance.
Secreted to the bloodstream and a target cell
Diffused locally to trigger response in cells that secrete them
Diffused locally to trigger response in neighbor cells
Diffused into the bloodstream to trigger a response in a target cell

4. 3 Major Classes of Molecules (#4)
Polypeptides (proteins and peptides): water soluble, made of polypeptide chains or from cleavage of longer protein chains. Ex: Insulin
Amines: water soluble, made from single amino acid. Ex: Epinephrine
Steroids: Lipid soluble and pass through cell membranes readily, made from four fused carbon rings. Ex: Cortisol
Major Classes of hormones summarized into peptides, steroids, and amino acid derivative (Amines)

5. Intracellular Receptors in Steroid Hormones (#5)
The hormone estradiol, a form of estrogen was studied.
Experimented on rats by treating them with radioactive forms of estradiol.
Results: Hormone accumulated in the nuclei.
Showed that the receptors for steroid hormones are indeed inside the cell.
The path of a steroid hormone. Important to notice how it diffuses through the plasma membrane.

6. Water-Soluble Hormones (#6)
Binding of a hormone to its receptor initiates a signal transduction pathway, a series of changes in cellular proteins that converts an extracellular chemical signal to a specific intracellular response.
Receptors for most water–soluble hormones are embedded in the plasma membrane. They are secreted by exocytosis, travel freely in bloodstream, and bind to cell-surface receptors
Depending on the hormone and target cell, the response may be:
Activation of an enzyme
A change in the uptake or secretion of specific molecules
Rearrangement of the cytoskeleton.
Signal transduction from some cell–surface receptors activates proteins in the cytoplasm that then move into the nucleus and directly or indirectly regulate transcription of specific genes. OR
Pathway of water-soluble hormones.

7. Lipid-Soluble Hormones (#8)
Intracellular receptors are found either in the cytoplasm or in the nucleus of the target cell.
Lipid-soluble hormones (steroid hormones) pass easily through cell membranes, while water-soluble hormones (polypeptides and amines) do not.
Lipid-soluble hormones diffuse across cell membranes, travel in the bloodstream bound to transport proteins, and diffuse through the membrane of target cells.
Lipid-soluble hormones are different than signal-transduction pathway/water-soluble because lipid-soluble hormones activate the receptor which directly triggers the cell’s response.

8. Diverse Response (#7)
Target cells with the same receptor exhibit different responses if they have different signal transduction pathways and/or effector proteins. Responses of target cells may also differ if they have different receptors for the hormone.
The effects brought about by a particular hormone can vary if target cells differ in the molecules that receive or produce the response to that hormone.

9. Local Regulators in Paracrine Signaling (#9)
Paracrine Signaling: Local regulators convey messages
between neighboring cells.
Cytokines: plays a role in immune responses.
Growth factors: stimulate cell proliferation and differentiation.
Nitric oxide (NO):
Serves in the body as both a neurotransmitter and a local regulator.
NO activates an enzyme that relaxes neighboring smooth muscle cells, dilating the walls of blood vessels and improving blood flow to tissues.
Highly reactive NO usually triggers changes in the target cell within a few seconds of contact and then breaks down.
When secreted by white blood cells, it kills bacteria and cancer cells.
Prostaglandins (PG):
In the immune system, prostaglandins promote fever and inflammation and intensify the sensation of pain which contribute to the body’s defense.
They help regulate aggregation of platelets, an early step in formation of blood clots.
They regulate nearby cells in various ways, depending on the tissue.
In semen that reaches the female reproductive tract, prostaglandins trigger the contraction of the smooth muscles of the uterine wall, helping sperm to reach the egg.
PGs secreted by the placenta cause the uterine muscles to become more excitable, helping to induce uterine contractions during childbirth.
Prostaglandin E signals the muscle cells to relax, dilating the blood vessels and promoting oxygenation of the blood.
Prostaglandin F signals the muscle cells to contract, constricting the vessels and reducing blood flow through the lungs.

10. Simple Hormone Pathway with Negative Feedback #10
Negative feedback: a loop in which the response reduces the initial stimulus.
An example is insulin. Insulin is released when there are high levels of glucose and insulin decreases it by taking it in and reaches homeostasis.
Simple hormone pathway: Hormones are released from an endocrine cell, travel through the bloodstream, and interact with specific receptors within a target cell to cause a physiological response.
Example is secretin signaling in the endocrine system. (Picture to the right).
Pathway
Example
Low pH in duodenum
Stimulus
S cells of duodenum secrete the hormone secretin ( ).
Endocrine cell
Hormone
Blood vessel
Pancreas
Target cells
Bicarbonate release
Response
Example of a Simple Pathway

11. Comprehension Checks
Steroid Hormones are also called _____________ and their receptors are located inside or outside the cell?
Where can you find most of the receptors for water-soluble hormones? Why?

12. Answer is…
Steroid Hormones are also called lipid-soluble hormones and their receptors are located inside or outside the cell?
Where can you find most of the receptors for water-soluble hormones? Why?
Embedded in the plasma membrane and because they cannot pass easily through cells.

13. Comprehension Checks
1. Growth factors are local regulators that A. Are modified fatty acids that stimulate bone and cartilage growth B. Are found on the surface of cancer cells and stimulate abnormal cell division C. Are proteins that bind to cell-surface receptors and stimulate growth and development of target cells D. Convey messages between nerve cells

14. Answer is… C

15. Insulin vs. Glucagon (#11) Antagonistic Hormones
Body cells take up more glucose
Insulin
Antagonistic Hormones
2 hormones that regulate a function
Their effects are opposite on the body
Insulin: Secreted by the beta cells of the pancreas and decreases blood glucose level.
Glucagon: Secreted by the alpha cells of the pancreas and increases blood glucose level.
Beta cells of pancreas release insulin into the blood.
Liver takes up glucose and stores it as glycogen.
Stimulus: blood glucose level rises
Blood glucose level decreases
Homeostatis:
Blood glucose level
Blood glucose level rises
Stimulus: blood glucose level falls
Liver breaks down glycogen and releases glucose into the blood
Alpha cells of pancreas release glucagon into the blood.
Glucagon

16. Type 1 and 2 Diabetes ( #12) Type 1 Diabetes: Type 2 Diabetes:
-Immune system destroys beta cells of pancreas, which leads to insulin deficiency.
-Appears during childhood
Type 2 Diabetes:
-Failure of target cells to respond normally to insulin
-Individual still makes insulin, but blood glucose levels are high
-Correlated with obesity

17. Invertebrate Hormones (#13)
Secreted by
Action
Growth hormone
Anterior pituitary gland
Stimulates bone growth
FSH, LH
Stimulates ovaries and testes
TRH
Hypothalamus
Indirectly causes release of TSH
Prolactin
Stimulates milk production and secretion
Calcitonin
Thyroid
Lowers blood calcium level
PTH
Parathyroid
Raises blood calcium level
Glucagon
Pancreas
Raises blood glucose level
Insulin
Lowers blood glucose level
Testosterone
Testes
Supports sperm formation and secondary sex characteristics
Estradiol
Ovaries
Stimulates uterine lining growth and secondary sex characteristics.
Invertebrate Hormones (#13)

18. Hypothalamus and Pituitary Glands(#14 & 15)
Hormones produced by posterior pituitary
-ADH
Goes to kidney tubules
-Oxytocin
Goes to mammary glands, uterine muscles
Posterior
pituitary
Anterior
pituitary GH
FSH
TSH LH
ACTH
Hormone
Prolactin
Ova and
sperm
Increases
iodine
Function
Milk
production
Ovaries/testes
Growth
Stimulates adrenal cortex

19. Comprehension Check
Type 1 diabetes mellitus is caused by a deficiency of ________
A. exercise
B. glucagon
C. glucose
D. glycogen
E. insulin

20. Answer is… E

21. Positive Feedback by Oxytocin Signaling (#16)
Suckling stimulates sensory nerve cells in the nipples, which send nervous signals that reach the hypothalamus, the control center. The hypothalamus triggers the release of the neurohormone oxytocin from the posterior pituitary gland. Oxytocin causes the mammary glands to secrete milk. The release of milk in turn leads to more suckling and stimulation of the pathway, until the baby is full.

22. Tropic Hormones (#17)
All four anterior pituitary tropic hormones participate in complex neuroendocrine pathways.
In each pathway, signals to the brain stimulate release of an anterior pituitary tropic hormone.
The tropic hormone then acts on its target endocrine tissue, stimulating secretion of a hormone that exerts systemic metabolic or developmental effects.

23. Thyroid Gland and Parathyroid Glands (#18 & 19)
The thyroid gland produces two very similar hormones derived from the amino acid tyrosine: triiodothyronine (T3), which contains three iodine atoms, and thyroxin (T4), which contains four iodine atoms. Throughout the body, T3 and T4 are important in bioenergetics, increasing the rate of oxygen consumption and cellular metabolism. In addition to cells that produce T3 and T4, the mammalian thyroid gland produces calcitonin. Rigorous homeostatic control of blood calcium level is critical to cell function. When blood Ca2+ falls below the set point, parathyroid hormone (PTH) is released from four small structures, the parathyroid glands, embedded on the surface of the thyroid.

24. Hormones of Adrenal Medulla (#20)
In mammals, each adrenal gland is actually made up of two glands with different cell types, functions, and embryonic origins.
The adrenal cortex is the outer portion, and the adrenal medulla is the central portion.
The adrenal medulla produces two hormones, epinephrine (adrenaline) and norepinephrine (noradrenaline).
Either positive or negative stress stimulates secretion of epinephrine and norepinephrine from the adrenal medulla.

25. Comp Check (Check yo Comp)
Question 1:
The hypothalamus triggers the release of the neurohormone _____________
Question 2:
The thyroid gland produces two very similar hormones ____ and T4.
Question 3:
In mammals, each adrenal gland is actually made up of ___ glands.

26. Hormones of the Adrenal Cortex (#21)
Glucocorticoids: Steroid and raises blood glucose level.
Mineralocorticoids: Steroid and promotes re-absorption of sodium and excretion of potassium in the Kidneys.
Where the adrenal cortex is located in the adrenal gland. Within the adrenal cortex the hormones are glucocorticoid and mineralcorticoid.
Adrenal gland

27. Steroid Hormones produced by gonads
The gonads, testes and ovaries, produce most of the sex hormones: androgens, estrogens, and progestins.
The testes primarily synthesize androgens, mainly testosterone, which stimulate development and maintenance of the male reproductive system
Androgens produced early in development determine whether a fetus develops as a male or a female.
At puberty, high levels of androgens are responsible for the development of male secondary sex characteristics, including male patterns of hair growth, a low voice, and increased muscle mass and bone mass typical of males.
Ovaries produce estrogens, most importantly estradiol, which are responsible for maintenance of the female reproductive system and the development of female secondary sex characteristics.
In mammals, progestins, which include progesterone, are primarily involved in promoting uterine lining growth to support the growth and development of an embryo.
Steroid Hormones produced by gonads
(#22)
Male vs. Female

28. Pineal Gland and Melatonin (#23)
Side of brain
Melatonin
Communicates info about light to different parts of the body
Regulates a human’s circadian sleep-wake cycle
-Has sleep promoting effects  decreases motor activity and increases fatigue
Thought to have a role in reproductive cycles
-Allows certain animals to sense a change in season, which indicates that a breeding season has begun