The Endocrine System
General Characteristics
Hormone Action
Control of Hormonal Secretions
Stress and Health
Introduction
• Endocrine system – includes cells, tissues and
organs collectively called endocrine glands.
• Secrete hormones – substances that diffuse from
the interstitial fluid into the blood stream and
eventually act on cells.
– Paracrine hormones = only affect neighboring cells.
– Autocrine hormones = affect only the secreting cell
itself.
General Characteristics
• Both the endocrine and nervous systems
communicate with cells using chemical
signals.
• Hormones are to the endocrine system as
neurotransmitters are to the nervous
system.
• Endocrine glands and their hormones help
regulate metabolic processes.
• They control
– Rates of certain chemical reactions
– Aid in transport of substances across
membranes
– Help regulate water and electrolyte balances.
– Play vital roles in reproduction, development,
and growth.
Glands we will look at:
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Pituitary
Thyroid
Parathyroid
Adrenal
Pancreas
Hormones
• Amines – norepinephrine, epinephrine
• Peptides – oxytocin, antidiuretic hormone,
• Proteins – growth hormone, parathyroid
hormone, prolactin
• Glycoproteins – FSH, LH, TSH
• *Steroids – Estrogen, testosterone,
aldosterone, cortisol
Steroid Hormones
events that occur when they enter a target cell
1. Diffuses through the cell membrane
2. Combines with a specific protein molecule
3. Resulting bound protein binds with a particular
region of the DNA of the nucleus and activates
transcription of specific genes into messenger
RNA molecules
4. mRNA molecules enter the cytoplasm
5. mRNA molecules associate with ribosomes to
direct the synthesis of specific proteins.
Analogy
• Lobbyists in Washington, D.C.(Mr. Pierson
story time)
Glands
Pituitary
Thyroid
Parathyroid
Adrenal
Pancreas
Pituitary Gland
• Located at the base of the brain.
• About 1 cm in diameter
• Consists of an anterior lobe and a posterior
lobe.
• ***THE BRAIN CONTROLS MOST OF
THE PITUITARY GLAND’S
ACTIVITIES.***
Anterior Pituitary Hormones
• Growth hormone(GH)- stimulates cell growth in
size and frequency.
• Prolactin(PRL)- stimulates a woman’s milk
production after the birth of an infant.
• Thyroid-stimulating hormone(TSH)- controls
thyroid gland secretion.
• Adrenocorticotropic hormone(ACTH)- controls
the manufacture and secretion of certain
hormones from the outer layer of the adrenal
gland.
• Follicle-stimulating hormone(FSH) and
Lutenizing hormone (LH)- also called
gonadotropins because they exert their actions on
the gonads (reproductive organs.)
Posterior Pituitary Hormones
• Antidiuretic hormone (ADH)- diuretics
are chemicals that increase urine
production, so antidiuretics decrease urine
production.
• Oxytosin (OT)- deals mostly with uterine
wall contractions for childbirth, but also
functions as an antidiuretic.
Thyroid Gland
• Vascular structure that consists of 2 large
lobes connected by a broad isthmus.
• Located below the larynx and anterior to the
trachea.
Thyroid Hormones
• Thyroxine (T4)
• Triiodothyronine (T3)
**These have primarily the same function,
except Triiodothyronine is 5 x’s more
potent. They help regulate the metabolism
of carbohydrates, lipids, and proteins.
• They are the major factors determining how
many calories the body must consume at
rest in order to maintain life. = Basal
Metabolic Rate (BMR)
Parathyroid Glands
• Located on the posterior surface of the
thyroid gland.
• 4 lobes: superior and inferior located on
each of the 2 lobes of the thyroid.
Parathyroid hormone
• Parathyroid hormone (PTH) – increases
blood calcium concentration and decreases
blood phosphate ion concentration.
• Affects the bones, kidneys and intestines.
Adrenal Glands
• Closely associated with the kidneys.
• A gland sits atop each kidney like a cap.
• Consists of 2 parts:
– Adrenal medulla = central portion
– Adrenal cortex = outer part
Adrenal Medulla Hormones
• Epinephrine – makes up 80% of adrenal
medullary secretion.
• Norepinephrine
**The effects of epinephrine and norepinephrine
include increased heart rate, force of cardiac
muscle contraction, increased breathing rate,
elevated blood pressure, increased blood
glucose, and decreased digestive activity.
Hormones of the Adrenal Cortex
• Aldosterone – helps regulate the concentration of
mineral electrolytes.
– Helps maintain blood volume and blood pressure.
• Cortisol – affects glucose metabolism. Also
influences protein and fat metabolism.
• Adrenal sex hormone = androgens and estrogens.
– Supplement the supply of sex hormones from the
gondads and stimulate early development of the
reproductive organs.
Pancreas
• Flattened, elongated organ posterior to the
stomach.
• Consists of 2 major types of secretory tissue
= endocrine and exocrine
• Endocrine = Islets of Langerhans
• Has a dual function:
– Secretes digestive enzymes
– Releases hormones
Hormones of the Islets of
Langerhans
• Glucagon – stimulates the liver to break
down glycogen into glucose.
• Insulin – stimulates the liver to form
glycogen from glucose.