1. The Endocrine System

2. The Endocrine System
collection of glands that produce hormones that regulate metabolism, growth and development, tissue function, sexual function, reproduction, sleep, and mood and other functions
secrete hormones (chemical messages) directly into the circulatory system to be carried towards distant target organs
coordinates whole body to maintain homeostasis
accessory organs:
(secondary endocrine functions)
kidney, liver, heart and gonads

3. Regulation and Communication
Animals rely on two systems for regulation
endocrine system
system of ductless glands
secrete chemical signals directly into blood
chemical travels to target tissue
target cells have receptor proteins
slow, long-lasting response
nervous system
system of neurons
transmits “electrical” signal & release neurotransmitters to target tissue
widely dispersed
fast, short-lasting response

4. Regulation by Chemical Messengers
Neurotransmitters released by neurons Hormones release by endocrine glands
hormone carrier
By blood
neurotransmitter
Target
cell
Pheromones
Hormones
Local Regulators
Chemical signal from 1 individual to another individual
Chemical signal from endocrine gland through blood to target cell
Chemical signal from one cell to an adjacent cell
Eg. ant trail; sex phermones
Eg. peptide, steroid hormones
Eg. cytokines, growth factors, nitric oxide (NO)

5. Classes of Hormones Protein-based hormones polypeptides
small proteins: insulin, ADH
glycoproteins
large proteins + carbohydrate: FSH, LH
amines
modified amino acids: epinephrine, melatonin
Lipid-based hormones
steroids
modified cholesterol: sex hormones, aldosterone

6. Hormones Action on Target Cells
Protein-based hormones (Peptide)
Water-soluble
Bind to receptors on plasma membrane & triggers signal transduction pathway
Affects protein activity already present in cell
Rapid response
Short-lived
Eg. oxytocin, insulin, epinephrine
Lipid-based hormones (steroid)
Lipid-soluble
Enters cell & binds to intracellular receptors
Causes change in gene expression (protein synthesis)
Slower response
Longer life
Eg. androgens (testosterone), estrogen, progesterone, cortisol
animation

7. Action of Lipid (Steroid) Hormones

8. Action of Protein Hormones
Uses Signal
Transduction Pathway o
Secondary
Messenger
System

9. Action of Epinephrine (adrenaline)
Liver cells break down glycogen and release glucose
Blood vessels to skeletal muscles dilate
Blood vessels to intestines constrict

10. Benefits of a Secondary Messenger

11. Hormones and Homeostasis
Negative feedback
“more gets you less”
stimulus triggers control mechanism that inhibits further change
body temperature
sugar metabolism
Positive feedback
“more gets you more”
stimulus triggers control mechanism that amplifies effect
lactation
labor contractions

12. Negative Feedback Stimulus & Response in opposite directions
Thyroid hormones
Blood Ca2+ levels
Blood glucose levels

13. Positive Feedback
Stimulus and response in same direction Pressure on uterus  oxytocin released causing more pressure

14. Nervous System Control of Body Temperature

15. Endocrine Control Regulation of Blood Sugar (Insulin and Blucagon)

16. Diabetes Mellitus
Type I diabetes (10%):deficiency of insulin Insulin-dependent Autoimmune disorder  beta cells of pancreas destroyed Type II diabetes (90%): failure of target cells to respond to insulin Non-insulin dependent Insulin produced  cells don’t respond (defect in insulin receptor or response pathway) Risk factors: obesity, lack of exercise

17. Endocrine Control of Blood Osmolarity
Maintaining Water Balance
Low blood osmolarity level/low BP
Juxtaglomerular apparatus (JGA)
releases renin in kidney
Renin converts angiotnesinogen to angiotensin
Angiotensin causes arterioles to constrict
increases blood pressure
Angiotensin triggers release of aldosterone from adrenal gland
Increases reabsorption of NACl
and H2O in kidneys
puts more water and salts back in blood

18. Regulating Blood Osmolarity
If amount of dissolved material in blood is too high, body needs to dilute blood

19. Endocrine Control Regulation of Blood Calcium

20. Female Reproductive Cycle
hormones from the hypothalamus and anterior pituitary control the ovarian cycle
ovarian cycle is hormonally regulated in two phases
estrogen secreted before ovulation;
progesterone secreted after ovulation.

21. Nervous and Endocrine Systems Linked
Hypothalamus “master nerve control center”
nervous system
Receives info from nerves and brain
Regulates release of hormones from pituitary
Pituitary gland
“master gland”
endocrine system
secretes broad range of “tropic” hormones regulating other glands in body

22. Endocrine Glands Pituitary Growth hormone Stimulates growth Oxytocin
Childbirth; lactation
attachment
Tropic hormones
Travel to other glands
(ex: TSH, ACTH, FSH)
ADH (Anti-Diuretic Hormone)
Retain water

23. Endocrine Glands Thyroid Thyroxine Regulates metabolism Calcitonin
Uptake of Ca in blood
animation

24. Thyroid Disorders Goiter due to iodine deficiency
Thyroid enlarges as it tries to produce thyroxine
Graves’ Disease:
autoimmune disorder
antibodies bind to TSH receptor
hyperthyroidism
high temp, sweating, weight loss, high BP

25. Endocrine Glands Adrenal Epinephrine Fight-or-flight response
Release of glucose
for more ATP
animation
Parathyroid
Parathyroid hormone
Regulates calcium
levels
(adds Ca to blood)

26. Adrenal Gland: Effect of Stress

27. Endocrine Organs Pancreas (Pancreatic islets) Insulin
Removes glucose from
blood
Glucagon
Release glucose from
glycogen (add to blood)
Testes
Testosterone
Stimulated sperm production
Maintains male sex characteristics

28. Tropins (tropic hormones)
stimulate growth in target organs/cells (tropic means nourishment)
when the target organ is another gland, tropic hormones cause them to produce & release their own hormones

29. Regulating Metabolism
Hypothalamus
TRH = TSH-releasing hormone
Anterior Pituitary
TSH = thyroid stimulating hormone
Thyroid
produces thyroxine hormones
metabolism & development
bone growth
mental development
metabolic use of energy
blood pressure & heart rate
muscle tone
digestion
reproduction
Hypothalamus
TRH
Anterior
pituitary
TSH
Thyroid T3 T4

30. Homology in Hormones
This list suggests that prolactin is an ancient hormone whose functions have diversified during the evolution of the various vertebrate groups.
Growth hormone (GH) is so similar structurally to prolactin that scientists hypothesize that the genes directing their production evolved from the same ancestral gene. Gene duplication.

31. Homology in Hormones

32. Hormonal Regulation in Insect Development