Download The Endocrine System

5/9/2014
The Endocrine System
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The Endocrine System
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Second messenger system of the body
Uses chemical messages (hormones) that are
released into the blood
Hormones control several major processes
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Reproduction
Growth and development
Mobilization of body defenses
Maintenance of much of homeostasis
Regulation of metabolism
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Hormone Overview
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The Chemistry of Hormones
Hormones are produced by specialized cells
Cells secrete hormones into extracellular
fluids
Blood transfers hormones to target sites
These hormones regulate the activity of other
cells
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Amino acid-based hormones
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Steroids hormones - made from cholesterol
Ex: Proteins
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Mechanisms of Hormone Action
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Effects Caused by Hormones
Hormones affect only certain tissues or
organs (target cells or organs)
Target cells must have specific protein
receptors
Hormone binding influences the working of
the cells
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Changes in plasma membrane permeability
or electrical state
Synthesis of proteins, such as enzymes
Activation or inactivation of enzymes
Stimulation of mitosis
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Steroid Hormone Action
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Steroid Hormone Action
Diffuse through the plasma membrane of
target cells
Enter the nucleus
Bind to a specific protein within the nucleus
Bind to specific sites on the cell’s DNA
Activate genes that result in synthesis of new
proteins
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STEROID HORMONE ANIMATION
Figure 9.1a
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Nonsteroid Hormone Action
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Nonsteroid Hormone Action
Hormone binds to a membrane receptor
Hormone does not enter the cell
Sets off a series of reactions that activates an
enzyme
Catalyzes a reaction that produces a second
messenger molecule
Oversees additional intracellular changes to
promote a specific response
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Figure 10
9.1b
Endocrine Glands – may be activated
by other hormones
Control of Hormone Release
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NONSTEROID HORMONE ANIMATION
Hormone levels in the blood are maintained
by negative feedback
A stimulus or low hormone levels in the blood
triggers the release of more hormone
Hormone release stops once an appropriate
level in the blood is reached
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Figure 12
9.2a
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Endocrine Glands - may be activated
by the nervous system
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Location of Major Endrocrine Organs
Nerve impulses
stimulate hormone
release
Most are under control
of the sympathetic
nervous system
Figure 13
9.2c
Figure 14
9.3
Hormones of the Pituitary –
Growth Hormone (GH)
Hormones of the Pituitary
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General metabolic hormone
Major effects are directed to growth of
skeletal muscles and long bones
Causes amino acids to be built into proteins
Causes fats to be broken down for a source
of energy
Figure 15
9.4
Functions of Pituitary Hormones
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Stimulates follicle development in ovaries
Stimulates sperm development in testes
Luteinizing hormone (LH)
Triggers ovulation
Causes ruptured follicle to become the
corpus luteum
 Stimulates testosterone production in
males
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Regulates endocrine activity of the adrenal cortex
Thyroid-stimulating hormone (TSH)
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Follicle-stimulating hormone (FSH)
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Stimulates and maintains milk production
following childbirth
Adrenocorticotropic hormone (ACTH)
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Functions of Pituitary Hormones
Prolactin
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Influences growth and activity of the thyroid
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Functions of the Pituitary Hormones
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Oxytocin
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Thyroid Gland
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Stimulates contractions of the uterus during labor
Causes milk ejection
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Antidiuretic hormone (ADH)
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Can decrease urine production (less water in
urine)
In large amounts, causes increased blood
pressure
Found at the base of the throat
Consists of two lobes and a connecting
isthmus
Produces two hormones
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Thyroid hormone
Calcitonin
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Thyroid Hormone
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Thyroid hormone - Calcitonin
Thyroxin - major metabolic hormone
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Decreases blood
calcium levels by
depositing Ca in
bone
Opposite of
parathyroid hormone
Figure 22
9.9
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Parathyroid Glands
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Adrenal Glands
Tiny masses on the posterior of the thyroid
Secrete parathyroid hormone
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Two glands
At the top of the kidneys
Stimulate bone cells to remove calcium from bone
Stimulate the kidneys and intestine to absorb
more calcium
Raise calcium levels in the blood
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Hormones of the Adrenal Glands
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Pancreatic Islets
Produce sex hormones
The pancreas produces:
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Produce cortisone and cortisol
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Promote normal cell metabolism
Help resist long-term stressors
Insulin – allows glucose to pass through cell
membranes into cells
Glucagon – allows glucose to enter the blood from
cells
Insulin and glucagon hormones maintain blood
sugar homeostasis
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Pancreatic Hormones and Blood
Sugar
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Pineal Gland
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Secretes melatonin
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Helps establish the body’s wake and sleep cycles
Figure 27
9.14
Thymus
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Hormones of the Ovaries
Located posterior to the sternum
Largest in infants and children
Produces thymosin
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Estrogens
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Matures some types of white blood cells
Important in developing the immune system
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Stimulates the development of secondary female
characteristics
Matures female reproductive organs
Helps prepare the uterus to receive a fertilized egg
Helps maintain pregnancy
Prepares the breasts to produce milk
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Hormones of the Ovaries
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Hormones of the Testes
Progesterone
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Produced by the corpus luteum
Acts with estrogen to bring about the menstrual
cycle
Helps in the implantation of an embryo in the
uterus
Testosterone
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Responsible for adult male secondary sex
characteristics
Promotes growth and maturation of male
reproductive system
Required for sperm cell production
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The Endocrine System and Aging
The Placenta
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Produces hormones that maintain the
pregnancy
Some hormones play a part in the delivery of
the baby
Produces HCG in addition to estrogen,
progesterone, and other hormones
Most endocrine organs operate smoothly until
old age
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Menopause is brought about by lack of efficiency
of the ovaries
Problems associated with reduced estrogen are
common
Growth hormone production declines with age
Many endocrine glands decrease output with age
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Effect of growth hormone
Endocrine
organs
(review)
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Greatest production occurs during childhood
Lack of GH- pituitary dwarfism
Excess - giantism
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Abnormalities of the thyroid
Cretinism- abnormal thyroid development; short, stocky
body type. Severe hypothyroidism causes mental
retardation
Myxedema - Hypothyroidism in adults-lethargy, weight
gain, loss of hair. Grave’s disease- hyperthyroidism;
causes exophthalmic goiter-edema behind eyes
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causes bulging; hyperactivity, arrythmias.
Addison’s disease
ACTH accumulates causing stimulation of
melanocytes (bronze skin color). Without cortisol,
there is no mobilization of glucose under stress; can
be life-threatening. Hyposecretion of aldosterone-most
serious, causes hyperkalemia (low blood potassium)
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leading to cardiac arrest
Acromegaly
Excess production of GH; the growth plates of
bone have closed so no increased growth in
height. Feet, hands, and face become “heavy”
in appearance
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Cushing’s syndrome
Hypersecretion of the adrenal cortex hormone,
cortisol is primary problem. Results in Diabetes
mellitus from increased blood glucose;
Subcutaneous fat deposited in midsection; High
blood pressure
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