CHEMICAL REGULATION (Endocrine System)
Chapter 39

Regulation- includes the processes by which organisms respond to stimuli within & around them. It results in the coordination and control of life processes. Regulation is achieved by the integration of the NERVOUS system & the ENDOCRINE system.

I. SIMILARITIES between Nervous & Endocrine Systems (Chemical vs. Nervous Regulation)

A. both maintain homeostasis
B. both secrete chemicals- such as:

II. DIFFERENCES between Nervous & Endocrine Systems

A. Endocrine System response last longer
B. Nervous System response is faster
C. Nervous System impulses travel via neurons
D. Endocrine System hormones travel via bloodstream

III. Endocrinology- is the study of the endocrine system. Two English physiologists, W.M. Baylis (1860-1924) & E.H. Starling (1866-1927), are founders of of endocrinology. In 1902, they demonstrated that a chemical messenger, which they called secretin, is carried by the bloodstream to the pancreas, causing it to secrete digestive juices.

A. Background Information on the Endocrine System-

1. associated with organs and tissues of the body that collectively release substances known as hormones.
2. known also as ductless glands because their secretions are released directly into the bloodstream.
3. in contrast exocrine glands, which discharge their secretions on such external or internal surface tissues as those of the skin, the lining of the stomach, or of the lining of the pancreatic ducts.

B. Glands- organs specialized for secretion

1. exocrine glands- discharge secretions into ducts such as digestive tract glands
ex.)liver, pancreas, salivary, sweat
2. endocrine glands- "ductless glands" discharge into bloodstream
ex.) pituitary, thyroid, thymus, pancreas, parathyroid, adrenal glands

C. Hormones- "chemical messengers" secretions produced by the endocrine system that
target specific tissue (2 types)

1. Protein-type hormones [ex. insulin, thyomisin]
2. Steroid-type hormones [produced by the adrenals]

a. Anabolic Steroids- synthetic version of male hormone testosterone which lead to increased muscle bulk & strength in both males and females. Side effects are: acne, head aches, sterility, stimulated growth, cancer & death.

D. The Mechanisms of Hormone Action

1. One Messenger Model- Steroid Hormone enters cell of target tissue & combines w/ a receptor inside; effect occurs
2. Two Messenger Model- Protein Hormone combines with receptor on cell
membrane (hormone doesn’t enter cell) of target tissue; this causes 2nd messenger
to enter cell & produce effect [ex. cAMP adenosine monophosphate, GMP]

E. REGULATION of HORMONE

1. POSITIVE FEEDBACK- reinforces original change [ex. poison ivy- first you get a rash, then you scratch...then you have a larger rash, then you scratch more....stop scratching]
2. NEGATIVE FEEDBACK "self-regulation"

1. mechanism by which hormone secretions are regulated (works like a thermostat)
2. one hormone in the blood stimulates or inhibits the production of another hormone
3. opposes original change
ex.)[Estrogen & FSH] + [Thyroid Stimulating Hormone(TSH) & thyroxin] + [Testosterone and Feedback Inhibition]

IV. The Human Endocrine System

A. Hypothalamus-controls body temperature, blood pressure, sleep & emotions

1. produces secretions that stimulates the pituitary

B. Pituitary Gland-"master gland" (hypophysis)

1. secretes hormones that control the activity of other endocrine glands and regulate
various biological processes. The pituitary gland is influenced both neurally
and hormonally by the hypothalamus.
2. secretions include:

1. growth hormone GH (stimulates cellular activity in bone, cartilage, and other structural tissue) disorders for GH include giantism (hypersecretion) & dwarfism (hyposecretion)
2. thyroid stimulating hormone TSH (causes the thyroid to release thyroxin)
3. follicle stimulating hormone FSH (stimulates activity in the ovaries & testes)
4. luteinizing hormone LH (causes the release of egg cells from ovaries & contols sex hormones in males + females)
5. prolactin (stimulates milk production and breast development in females)
6. adrenocorticotropic hormone ACTH (stimulates production & release from cortex layer of the adrenal glands; used in treatments of arthritis, asthma, + allergies)
7. oxytoxin hormone (stimulates contractions of smooth muscles of uterus during childbirth
8. antidiuretic hormone ADH vasopressin (which causes the nephrons of the kidney to excrete less water in the urine) ALCOHOL STOPS THE RELEASE OF ADH; therefore, IT CONTRIBUTES TO A HANGOVER

1-6 are found in the anterior lobe of the pituitary; 7-8 are found in the posterior lobe

C. Thyroid Gland- produces thyroxin which is made of iodine

1. located in the neck
2. thyroxin regulates the rate of metabolism

D. Parathyroid Glands- produces parathormone, located within the thyroid

1. parathormone controls metabolism of calcium which is necessary for growth, health of bones & teeth, *BLOOD CLOTTING*, nerve functions + muscle contraction

E. Adrenal Glands- secrete adrenaline causes "Flight or Fight" action

1. located on top of each kidney
2. adrenaline causes blood vessels to constrict, heartbeat, blood pressure, clotting
3. adrenaline also increases rate of metabolism and release of glucose by liver [example: slows flow of digestive juices]

F. Pancreas- ISLETS of LANGERHANS (cells found within pancreas)
-is both exocrine & endocrine gland

1. exocrine because the pancreas release digestive juices to complete the breakdown carbohydrates
2. endocrine because it has clusters of cell (islets of Langerhans) that
secrete hormones such as glucagon & insulin
Insulin- causes absorption of sugar into body cells which results in lowering blood sugar levels. The cells of the body need glucose as a source of energy. This sugar simply doesn't pass into the body cells. INSULIN MUST BE PRESENT. Also, insulin turns glucose into glycogen for storage of energy.
Glucagon- cause discharge of sugar from liver into blood which results in raising blood sugar levels glycogen into glucose. (opposite of insulin)

G. Gonads- sex glands (two each)

1. in females OVARIES secrete many hormones one is estrogen which causes development of female REPRODUCTIVE system & sex characteristics
2. in males TESTES secrete testosterone which causes development of male sex characteristics
Puberty, the time of sexual maturation, is marked by an increase in the secretion of pituitary gonad-stimulating hormones or gonadotropins, which cause maturation of the testes or ovaries and increased secretion of sex hormones. The sex hormones, in turn, affect the accessory sex organs and general somatic and psychic development.

Animation of ovulation, fertilization, & implantation

STRUCTURE of the HUMAN GONADS
Gonads—in the male, the testes (singular, testis), and in the female, the ovaries—are the organs that produce gametes and sex hormones. The male gamete is the spermatozoan, produced by cell division in the seminiferous tubules of the adult testes. Typically, several hundred million sperm reach maturity in the epididymis and are stored in the vas deferens each day. Whatever is not released in ejaculation is reabsorbed, part of a continuous cycle. In the female, the ovaries produce eggs, or ova. At birth, about 2 million oocytes, or immature eggs, are present in the ovaries. Once the female reaches puberty, one egg matures approximately every 28 days inside a saclike Graafian follicle. Ovulation occurs when the mature egg bursts from the follicle and the ovary, beginning its journey down the fallopian tube toward the uterus.

The Human Body. Hormones. Effects of 'Sex Hormones' on Body Function. Endrocrine System (Real - Microscopic Pictures)

H. Thymus- secretes thymosin which stimulates the production of T lymphocytes
-located in the center of the chest

I. Pineal Gland- secretes melatonin "biological clock"
-located in the brain

V. Disorders of the Endocrine System

A. Goiter- enlargement of the thyroid gland usually resulting from the gland’s inability to make thyroxin. It is associated with iodine deficiency in diet.

B. Diabetic Mellitus-(form of diabetic coma)disorder characterized by an INSULIN deficiency (hypoglycemia) which results in an elevated blood sugar level.

C. Diabetes Insipidus, rare disease caused by deficiency of vasopressin, one of the hormones of the posterior pituitary gland, which controls the amount of urine secreted by the kidneys. The symptoms of diabetes insipidus are marked thirst and the excretion of large quantities of urine, as much as 4 to 10 liters a day. This urine has a low specific gravity and contains no excess sugar. In many cases, injection or nasal inhalation of vasopressin controls the symptoms of the disease.

D. Diabetic Shock- hypersecretion of insulin. Glucose level in blood drops, leads to death, unconsciousness or convulsions.

E. Endocrine System Cancers

The Glossary is very useful for the explanation of medical and pharamcological
terminology, but it also includes links back to articles for further information.

Now that we've finished anatomy. Take a quiz on the entire body structure.

Play Jeopardy: topic REGULATION

Biology Trivia

1. What organ is both an exocrine & endocrine gland? answer

2. How does radioactive iodine help cure Graves' disease? answer

3. What condition do you have if you have an enlargement of the thyroid gland? answer

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