1. Cells communicate with each other through direct contact with other cells or from a distance via chemical signaling
Endocrine signals are produced by endocrine cells that release signaling molecules, which are specific and can travel long distances through the blood to reach all parts of the body

2. Endocrine Communication
Animal hormones are chemical signals that are secreted into the circulatory system and communicate regulatory messages within the body
Hormones reach all parts of the body, but only target cells are equipped to respond

3. Two systems coordinate communication throughout the body: the endocrine system and the nervous system
The endocrine system secretes hormones that coordinate slower but longer-acting responses including reproduction, development, energy metabolism, growth, and behavior
The nervous system conveys high-speed electrical signals along specialized cells called neurons; these signals regulate other cells

4. Endocrine signals (hormones) are secreted into extracellular fluids and travel via the bloodstream
Endocrine Signaling

5. Paracrine and Autocrine Signaling
Local regulators are chemical signals that travel over short distances by diffusion
Local regulators help regulate blood pressure, nervous system function, and reproduction
Two types
Paracrine signals act on cells near the secreting cell
Autocrine signals act on the secreting cell itself
Paracrine and Autocrine Signaling

6. Synaptic Signaling and Neuroendocrine Signaling
At synapses, neurons often secrete chemical signals called neurotransmitters that diffuse a short distance to bind to receptors on the target cell
Neurohormones are a class of hormones that originate from neurons in the brain (i.e. hypothalamus) and diffuse through the bloodstream to act on target cells (possibly an endocrine gland to produce a 2nd hormone).
Synaptic Signaling and Neuroendocrine Signaling

7. Receptor Location Varies with Hormone
Signaling by any of these hormones involves three key events:
Reception
Signal transduction
Response
Receptor Location Varies with Hormone

8. One Hormone – Different Effects
The same hormone may have different effects on target cells that have
Different receptors for the hormone
Different signal transduction pathways
Different proteins for carrying out the response
A hormone can also have different effects in different species
One Hormone – Different Effects

9. Major endocrine glands:
Fig
Major endocrine glands:
Hypothalamus
Pineal gland
Pituitary gland
Organs containing
endocrine cells:
Thyroid gland
Thymus
Parathyroid glands
Heart
Liver
Adrenal
glands
Stomach
Figure Major human endocrine glands
Pancreas
Testes
Kidney
Kidney
Small
intestine
Ovaries

10. A negative feedback loop inhibits a response by reducing the initial stimulus
Negative feedback regulates many hormonal pathways involved in homeostasis

11. Insulin & Glucagon: control blood glucose
Pancreas contains clusters of endocrine cells known as Islets of Langerhans
Islets of Langerhans contain alpha and beta cells
Beta cells secrete insulin which triggers uptake of glucose from the blood
Alpha cells secrete glucagon which promotes the release of glucose into the blood
Hormones secreted into the interstitial fluid and enter circulatory system

12. Insulin & Glucagon
Insulin – stimulates nearly all body cells to take up glucose;
Insulin – slows glycogen breakdown in liver and glucose production
Glucagon –targets cells in liver to increase glycogen hydrolysis – release glucose into the bloodstream
Negative Feedback – stimulus leads to release of hormone which works on target cell to bring about response; response shuts off hormone

13. Diabetes Melitus Causes: Deficiency of insulin
Decreased response to insulin
Results in increased blood glucose levels
Body forced to use fat as main fuel – can result in acidic metabolite build up lowering pH
Kidney can’t handle high level of glucose in blood = sugar in urine leading to frequent urination and extreme thirst
Diabetes Melitus

14. Insulin-dependent diabetes is an autoimmune disorder in which the immune system destroys the beta cells of the pancreas
Often thought of as childhood diabetes
Destroys a person’s ability to produce insulin
Treatment = insulin injections
Type I Diabetes

15. Target cells fail to respond to insulin – blood glucose levels remain high
Develops with age – usually around 40
Excess weight and lack of exercise can contribute to type 2 diabetes
Most common form of diabetes
Type 2 Diabetes

16. Human Growth Hormone
Releasing hormones from hypothalamus trigger anterior pituitary to secrete growth hormone
Growth Hormone has Tropic effects (regulates other endocrine cells) and Nontropic effects (targets nonendocrine cells)
Major target of GH is the liver which secretes IGF’s (insulin-like growth factors) which stimulate bone and cartilage growth

17. Gigantism Hypersecretion of GH during childhood can lead to gigantism
Person grows unusually tall
Results in overgrowth of extremities in adults (acromegaly)

18. Dwarfism
Hyposecretion of GH in childhood retards long-bon growth and can pituitary dwarfism
If diagnosed before puberty, can be treated with HGH

19. Thyroid Hormones
The thyroid gland consists of two lobes on the ventral surface of the trachea
It produces two iodine- containing hormones: triiodothyronine (T3) and thyroxine (T4)
The thyroid is regulate by Thyroid Stimulating Hormone (TSH) from the antior pituitary

20. Thyroid Gland
Triiodothyroxine (T3) called T3 because it has three iodine atoms
thyroxine (T4) called T4 because it has four iodine atoms
Both have basically the same effect:
Bone and nerve cell development
Help maintain normal blood pressure, heart rate, muscle tone, digestion & reproductive function

21. Hyperthyroidism
Hyperthyroidism, excessive secretion of thyroid hormones, causes high body temperature, weight loss, irritability, and high blood pressure
Graves’ disease is a form of hyperthyroidism in humans
In Grave’s disease, the body's natural defense (immune) system attacks the thyroid gland. The thyroid fights back by making too much thyroid hormone

22. Hypothyroidism
Hypothyroidism, low secretion of thyroid hormones, causes weight gain, lethargy, and intolerance to cold

23. Goiter – Excess TSH enlarge the thyroid gland results in a large swelling just above the breast bone. Rarely, it may constrict the trachea (windpipe) or esophagus and cause difficulty breathing or swallowing. The rest of the symptoms come from thyroxin or the lack of it.
Iodine Deficiency
Severe iodine deficiency causes problems because the thyroid can never produce enough T3 and T4 but is still continually stimulated by TSH resulting in elargement
childhood can cause cretinism
Adulthood can cause goiter
Cretinism – congenital condition due to thyroid hormone deficiency during fetal development and marked in childhood by dwarfed structure, mental retardation dystrophy of the bones, and low basal metabolism

24. Antidiuretic Hormone
Neurosecretory cells extend from the hypothalamus into the posterior pituitary where ADH is released into the blood stream
Antidiuretic hormone (ADH) enhances water reabsorption in the kidneys

26. Luteinizing Hormone and Follicle Stimulating Hormone
Male
Females

27. Estrogen
Estrogens, most importantly estradiol, are responsible for maintenance of the female reproductive system and the development of female secondary sex characteristics

28. Testosterone
The testes primarily synthesize androgens, mainly testosterone, which stimulate development and maintenance of the male reproductive system
Testosterone causes an increase in muscle and bone mass and is often taken as a supplement to cause muscle growth, which carries health risks

29. Hypothalamus/ posterior pituitary
Fig
Pathway
Example
Stimulus
Suckling +
Sensory neuron
Hypothalamus/ posterior pituitary
Neurosecretory cell
Posterior pituitary secretes oxytocin ( )
Positive feedback
Blood vessel
Figure A simple neurohormone pathway
Target cells
Smooth muscle in breasts
Response
Milk release

30. Positive Feedback Hormones
Oxytocin induces uterine contractions and the release of milk
Suckling sends a message to the hypothalamus via the nervous system to release oxytocin, which further stimulates the milk glands