Download Endocrine system

• The Endocrine System
I. Hormones:
A. Endocrine system produces hormones that
are important in maintaining homeostasis &
regulating reproduction & development.
B. A Hormone is a chemical messenger
produced by a cell that effects specific change
in the cellular activity of other cells (target
cells).
C. Unlike exocrine glands that release their
products at the body’s surface or into body
cavities through ducts, the endocrine glands
do not secrete substances into ducts instead
their hormones are secreted directly into the
surrounding extracellular space & then diffuse
into nearby capillaries & are transported
throughout the body in the blood.
• D. The endocrine & nervous systems often
work together to maintain homeostasis.
• E. The nervous system uses neurotransmitters
to act on cells (which is usually short-lived) to
maintain homeostasis
• F. The endocrine system uses hormones
(which effects last longer) to produce
homeostasis.
• G. Hormones are classified into 2 basic
categories: peptides (including amino acids,
polypeptides, & proteins) & steroids (complex
rings of carbon & hydrogen atoms)
• synthesized by cholesterol. Ex. Gonadal
hormones adrenocortical hormones
Now we are going to look at each
gland individually:
• These next few slides will be copied onto your
paper but do not have blanks to fill in
• H. Pituitary – found in sella turcia pea-size,
master gland. The Anterior pituitary has
hormone production glandular portion. The
Posterior pituitary neural portion & extension
of hypothalamus. Ex. GH (bone & muscle) &
TSH (growth of thyroid)
• I. Thyroid-Found in anterior throat overlying
inferior border of larynx. One of the largest
endocrine glands & has a heavy blood supply. Ex.
Thyroid hormone T3 & T4 contain iodine.
• J. T3-T4 Function to 1) accelerate cellular
metabolism, 2) tissue growth, 3) skeletal
reproductive & nervous system development.
• K. Thyroid gland unique because it can store &
slowly release its hormones (up to 3 months
worth)
• L. Over active & uner active thyroid can cause severe
disturbances. Ex. Hypothroid syndrome – goiter; Severe
hypothyroidism – cretinism; Graves disease-most
common.
• M. Parathyroid – 4 to 8 embedded in posterior aspect
of thyroid gland. Ex. PTH important in controlling level
of calcium in blood.
• N. Hyperparathyroidism- rare result of PTH deficiency
untreated death may occur. Kidney stones, reflexes &
skeletal muscle weakness.
• O. Adrenal glands almond size atop the
kidneys.
1. Adrenal Medulla- epinephrine &
norepinephrine
2. Adrenal cortex- corticosteroids
• P. Pancreas- located partially behind the
stomach. Endocrine & exocrine – Islets of
Langerhans-minute clusters of cells that produce
pancreatic hormones. Ex. Insulin-lowers blood
sugar levels: hypoglycemic; Glucagon-causes
release of glucose into blood-major target cell are
liver cells: hyperglycemic
• Q. Pineal located in brain secretes melatonin its
fuction is unclear.
• The information on the next slides will be
found on your notes papers
II. Hormone Action
• C. Hormones activate target cells by 1 of 2
methods, depending upon the chemical
nature of the hormone:
•
1) peptide hormones {water soluble} that
bind to a receptor protein on the plasma
membrane of the cell. The receptor protein,
then stimulates the production of a second
messenger (either cAMP or calcium.)
II. Hormone Action
• 2) steroid hormones {lipid soluble} that
diffuse through the plasma membrane of the
target cell & bind to receptor protein present
in the cytoplasm that activates a DNA
segment that turns on specific genes
III. Control of Hormone Production
• A. Endocrine glands release hormones in
response to 1 or more of the following stimuli:
•
1. Hormones form other endocrine glands
•
2. Chemical characteristics of the blood
•
3. Neural stimulation
III. Control of Hormone Production
• 4. most hormone production is regulated by
negative feedback system.
•
a. negative feedback: hormones
secretion is triggered by some internal or
external stimulus, then rising hormones levels
inhibit further hormone release resulting in
blood levels of many hormones varying only
within a very narrow margin.
IV. Communication b/w the
Hypothalamus & Pituitary Glands
• A. Communication b/w the hypothalamus &
the Anterior Pituitary Gland occurs through
chemicals that are produced by the
hypothalamus & delivered to the ant. pituitary
through blood vessels.
IV. Communication b/w the
Hypothalamus & Pituitary Glands
• B. Communication b/w the hypothalamus &
the Posterior Pituitary Gland occurs through
neurosecretory cells that connect the 2
glands.
V. Antagonistic Hormones
• A. When the body hormone levels drop below normal
homeostasis levels the antagonistic hormones are
secreted to bring the body back to homeostasis.
• B. Ex. Bundles of cells in the pancreas called the islets
of Langerhans contain 2 kinds of cells alpha (secrete
glucagons) & beta (secrete insulin) cells, that control
blood glucose concentrations by producing the
antagonistic hormones insulin & glucagon
•
VI. Major Endocrine Organs
Gland
Pineal
Hypothalamus
Anterior
Pituitary
Posterior
Pituitary
Thyroid
Hormone Released
Target Tissue/Organ
Chief Function of
Hormone
VI. Major Endocrine Organs
Gland
Parathryroid
Thymus
Adrenal Gland
Adrenal Medulla
Adrenal Cortex
Hormone Released
Target Tissue/
Organ
Chief Function of
Hormone
VI. Major Endocrine Organs
Gland
Pancreas
Gonads
Ovaries
Testes
Hormone Released
Target Tissue/
Organ
Chief Function of
Hormone
• THE END!!!!