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Learning Objectives
1.  Know the primary functions of the endocrine system. Compare and contrast the mechanisms of control of the endocrine versus nervous systems. (4,5) 2.  Differentiate between endocrine and exocrine glands. Be able to provide a brief description of each. (6)

3.  Name the two major structural classes of hormones. Describe the mechanism of action of water soluble hormones and the mechanism of action of lipid soluble hormones. (8-10) 4.  Describe the three types of control of hormone release (humoral, neural, hormonal). (11,12)

5.  List and describe three factors responsible for maintaining target cell specificity to a hormone. (13)
6.  Define the three types of interactions of hormones: permissive, synergistic, antagonistic. (14)
7.  Describe the location of the hypothalamus and pituitary gland and know that the infundibulum connects the two structures. Describe the structure of the posterior pituitary and anterior pituitary (size, tissue type, hormones released, hormones produced) and explain how each is connected to the hypothalamus (blood supply or neurons). (15-17) 8.  List the two hormones released from the posterior pituitary and describe their general functions. (18)

9.  List and describe the primary function of the hormones released by the anterior pituitary. (19,20)
10. Describe the stimulus, receptor/control center, effector and target organs/results of growth hormone release. Provide a brief description of how homeostatic imbalances in growth hormone can lead to pituitary dwarfism, acromegaly, and pituitary gigantism. (21-23)

Learning Objectives
11. For the thyroid gland describe its location, and list the two hormones released. Describe the stimulus, receptor/control center, effector and target organs/results of thyroid hormone release. Provide a brief description of how imbalances in thyroid hormone can lead to goiters and Grave’s Disease. (24-30)

12. Describe the stimulus, receptor/control center, effector and target organs/results of parathyroid hormone release. (31,32)
13. For the adrenal gland describe its location, general structure (adrenal cortex and adrenal medulla including the zones of the adrenal cortex), and hormones released. Describe the stimulus, receptor/control center, effector and target organs/results of cortisol hormone release, and know the general function of aldosterone. Provide a brief description of how imbalances in cortisol hormone can lead to Cushing’s Syndrome and Addison’s Disease. (33-39)

14. Describe the stimulus, receptor/control center, effector and target organs/results of norepinephrine and epinephrine hormone release. (40,41)
15. Describe the structure of the pancreas including the location and function of alpha and beta cells. Describe the stimulus, receptor/control center, effector and target organs/ results of insulin and also of glucagon hormone release. Provide a brief description of how imbalances in insulin and glucagon can lead to diabetes mellitus and hypoglycemia. (42-48)

Endocrine System: Overview
Acts with nervous system to coordinate and integrate activity of body cells 1. Hormones secreted into the blood
2. Binds to receptors on target
3. Response is slower
4. Response is longer lasting

Major processes that hormones control
and integrates are:
• Reproduction
• Growth and development
• Maintenance of electrolyte, water, and nutrient balance of blood • Regulation of cellular metabolism and energy balance
• Mobilization of body defenses



Compared to the Nervous System

Endocrine System: Overview
Glandular Epithelia (Glands):

Nervous System
•  Mediator molecules:
–  Neurotransmitters released
locally in response to nerve
•  Site of mediator action:
–  Close to site of release, at a
synapse; binds to receptors in
postsynaptic membrane.
•  Types of target cells:
–  Muscle (smooth, cardiac, and
skeletal) cells, gland cells, other
•  Time to onset of action:
–  Typically within milliseconds
(thousandths of a second).
•  Duration of action:
–  Generally briefer (milliseconds).

Endocrine System
•  Mediator molecules:
–  Hormones delivered to tissues
throughout the body by the
•  Site of mediator action:
–  Far from site of release
(usually); binds to receptors
on or in target cells.
•  Types of target cells:
–  Cells throughout the body.

•  Time to onset of action:
–  Seconds to hours or days.
•  Duration of action:
–  Generally longer (seconds to

Figure 16.1 Location of selected endocrine organs of the body.

Pineal gland
Pituitary gland
Thyroid gland
Parathyroid glands
(on dorsal aspect of thyroid gland)


Adrenal glands

i. Pituitary: master of
the endocrine system
ii. Pineal: monitors
sleep-wake patterns
iii. Thyroid: controls
protein production &
energy use
iv. Parathyroid:
controls calcium
levels in the
blood and bone


v. Adrenal: stress
induced hormones &
kidney function

• Ovary (female)
• Testis (male)

vi. Pancreas:
monitors blood
glucose levels
vii. Gonads:
estrogen &

–  One or more cells that makes and secretes an aqueous fluid called a secretion

1. Exocrine Glands
–  Secrete products into ducts
–  Secretions released onto body surfaces (skin) or into body cavities –  Examples include mucus, sweat, oil, saliva, digestive enzymes

3. Endocrine Glands
–  Secretions into the blood stream without flowing through a duct (ductless glands)
–  Secrete hormones that travel through blood to their specific target organs –  Target organs respond in some characteristic way

Endocrine glands in the human body:
• Pituitary, thyroid, parathyroid, adrenal, and pineal glands • Hypothalamus is Neuroendocrine organ
• Some have exocrine and endocrine functions:
–  Pancreas, gonads, placenta
• Other tissues and organs that produce hormones
–  Adipose cells, thymus, and cells in walls of small intestine, stomach, kidneys, and heart

Mechanisms of Hormone Action
Chemistry of Hormones (Two main classes):
1.  Amino acid-based hormones (most hormones in the body)
2.  Steroids
•  Synthesized from cholesterol (Gonadal and adrenocortical hormones)

Hormones act at receptors in one of two ways, depending on their chemical nature and receptor location
1. Water-soluble hormones (all amino acid–based hormones except thyroid hormone)
–  Act on plasma membrane receptors (cannot enter cell)
3. Lipid-soluble hormones (steroid and thyroid hormones)
–  Act on intracellular receptors that directly activate genes (can enter cell) • Though hormones circulate systemically only cells with receptors for that hormone affected • Target cells: Tissues with receptors for specific hormone • Hormones alter target cell activity:

–  Alter plasma membrane permeability and/or membrane potential ...

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