Endocrine System Notes

[Types of Glands]

1. exocrine glands: duct glands

ex. tear glands, sweat glands

2. endocrine glands: ductless glands

3. dual glands: function as both an endocrine & an exocrine gland ex. pancreas

Hormones -- chemicals secreted in one area of the body which affect responses in other areas

** The circulatory system aids in the distribution of these hormones since the endocrine glands are ductless.

target organ -- the organ influenced by the action of a hormone

Hormones have specific shapes that fit with receptors on the surface of the target organ or structure they are going to influence.

** Hormones interact and exert control on metabolic activities such as reproduction and development, including metamorphosis.

metamorphosis -- a change in form in development found in many insects and amphibians

ecdysone -- hormone causing the shedding of an insect's exoskeleton

The nervous and endocrine systems interact to control and coordinate the body's responses to changes in the environment.

Homeostasis in an organism is constantly threatened. Failure to respond effectively can result in disease or death.

** Hypothalamus: a small region of the brain that produces hormones influencing the pituitary gland

Some specific Functions:

1. Regulates posterior pituitary through direct sensory-nervous control.

(ex. water balance, body temperature, hunger)

2. Regulates the pituitary indirectly through releasing factors.(chemicals)

ENDOCRINE SYSTEM

1. Pituitary gland: nicknamed the "Master gland"

-- secretes numerous hormones

Some Hormones Produced:

(a.) growth stimulating hormone

-- stimulates the elongation of long bones

(b.) follicle stimulating hormone (FSH)

-- stimulates activity in the ovaries and testes

(c.) thyroid stimulating hormone (TSH)

-- stimulates the thyroid gland to secrete thyroxin

(d.) LH (luteinizing hormone)

--brings about the change of the follicle to the corpus luteum (yellow body)

-- this corpus luteum thus secretes the hormone progesterone -- preparing the embryo for implantation in the uterus and thus pregnancy

2. Thyroid gland: large gland near the lower part of the larynx where it joins the trachea

--functions to maintain body metabolism

--produces the hormone THYROXIN which is mostly iodine based (controls the rate of metabolism and is responsible for normal physical and mental development)

3. Parathyroid glands: patches of pea shaped tissue embedded in the thyroid gland

--produces the hormone PARATHORMONE (controls the metabolism of calcium -- needed for nervous function, strong bones and teeth, and blood clotting)

4. Adrenal Glands: two small glands located at the top of each kidney

-- produce adrenalin

adrenalin -- "Fight or flight hormone" -- secreted during times of emergency

-- increases the blood sugar level and accelerates heart and breathing rates

cortisol -- promotes proper cartilage composition --- stimulates carbohydrate, protein, and lipid metabolism (cortisone is a man-made cortisol used in the treatment of joint disorders)

6. Islets of Langerhans (pancreas)

-- small groups of cells located in the pancreas

glucagon: stimulates the release of stored animal starch in the liver (glycogen) into the

blood as glucose when needed

insulin: has 2 basic roles:

(a.) facilitates the entrance of glucose into the cells

(b.) lowers blood sugar levels by promoting the movement of glucose

from the blood into the muscles and liver (for conversion into glycogen)

7. Testes -- male sex glands -- secrete testosterone

testosterone: influences the development of male secondary sex characteristics

8. Ovaries -- female sex glands --secrete estrogen

estrogen: influences the development of female secondary sex characteristics

Graphic of the Major Glands of the Human Endocrine System

(Some Endocrine Malfunctions)

(a.) goiter: enlargement of the thyroid gland usually resulting from the gland's inability to manufacture thyroxin

--often associated with an iodine deficiency in the diet

(b.) diabetes: a disorder characterized by an insulin deficiency which results in an elevated blood sugar level

(7 Diabetes Symptoms)

1. craving for water

2. craving for sweets

3. frequent urination

4. heart and circulation

5. sudden changes in vision problems

6. sudden changes in weight

7. frequent shifts in body energy (intense fatigue)

[Negative Feedback]

-- also called biofeedback

-- a type of organism self regulation

-- operates on the principle that the level of one hormone in the blood inhibits or stimulates the production of another hormone (or substance)

ex. (The relationship between TRF, TSH, and thyroxin)

ex. (relationship between insulin, glucagon, and glucose homeostasis)

(Comparison of Nervous and Endocrine Systems)

Nervous system:

1. Nerves secrete chemicals called neurotransmitters.

2. Help maintain homeostasis.

3. Nerve responses are rapid and of short duration.

4. Nerve impulses are transmitted via neurons.

Endocrine system:

1. Secrete chemicals called hormones.

2. Help maintain homeostasis.

3. Endocrine responses are slow but of long duration.

4. Hormones are carried by the blood plasma.