Transcript Endocrine System

Endocrine System
Anatomy and Physiology
What is the Endocrine
System?
A communication and control
system
Organs of the endocrine
system are called glands
Are all glands part of the
endocrine system?
NO! Exocrine glands are
not. These include sweat
glands and salivary glands.
What is a hormone?
A chemical secreted by an
endocrine gland
Hormones are the main
regulators of metabolism,
growth and development,
reproduction, and many
other activities
There are two major
classes of hormones
These are:
Steroid hormones
Non-steroid hormones
The difference is the
mechanism by which they
influence target organ cells.
Regulation of Hormone Secretion
• Hormone secretion is controlled by
homeostatic feedback
• Negative Feedback- mechanisms that
reverse the direction of a change in a
physiological system
• Positive Feedback-(uncommon) mechanisms
that amplify physiological changes
An example of how negative
feedback works
Look in your textbook on page 350 for diagram
• The intestines absorb glucose after a meal.
• Blood glucose level increases.
• Pancreas responds to the high glucose level by
secreting insulin.
• Insulin causes the liver to take up more glucose.
• Homeostasis is restored for awhile.
• Eventually blood glucose drops because you
haven’t eaten in awhile, so you feel hungry, so you
eat. So…the cycle begins again.
Mechanisms of Endocrine Disease
• Hypersecretion-secretion of an
excess of hormones
• Hyposecretion-insufficient hormone
secretion
• Target Cell insensitivity produces
results similar to hyposecretion
Prostaglandins (PGs)
• Tissue hormones
• Influence respiration, blood pressure,
gastrointestinal secretions, inflammation,
and the reproductive system
• Important in treatment of ulcers, high
blood pressure, and asthma
• Aspirin and other common treatments
create their effects by altering the
functions of PGs.
Pituitary Gland
• Located in the
brain’s diencephalon
• Though it is the size
of a pea, it is really
two endocrine glands
– the anterior
pituitary and the
posterior pituitary
Anterior Pituitary Gland Hormones
• Thyroid-stimulating hormone (TSH) – stimulates
thyroid gland
• Adrenocorticotropic hormone (ACTH) – stimulates
adrenal cortex
• Follicle-stimulating hormone (FSH) – stimulates
reproductive organs to mature
• Luteinizing hormone (LH) – works with FSH. In
females, it causes ovulation. In males, it stimulates
production of testosterone
• Prolactin – during pregnancy, prepares the breasts
for lactation
• Growth hormone (GH) – see next slide…
Anterior Pituitary Gland Hormones
• More about Growth Hormone (GH) –
– moves amino acids out of the blood and into the
cells, accelerating the building of proteins
– also affects the fat and carbohydrate
metabolism and thus affects blood glucose levels
– increases blood glucose where insulin decreases
blood glucose
– Hypersecretion of GH during the early years of
life results in GIGANTISM.
– Hypersecretion of GH after normal growth years
results in ACROMEGALY.
– Hyposecretion of GH during the growth years
causes pituitary dwarfism.
Posterior Pituitary Gland
• Secretes two hormones:
– Antidiuretic hormone (ADH)
• Decreases urine volume
• Hyposecretion of this hormone causes
diabetes insipidus, treated by replacement
doses of ADH
– Oxytocin
• Produced during pregnancy
– Stimulates contraction of the pregnant uterus
when it is time for labor
– Causes breasts to release milk
A little trivia about the
Posterior Pituitary Gland
• Doesn’t actually produce these two
hormones…do you want to guess which
part of the brain does this?
• The hypothalamus
Thyroid Gland
• Located in the
neck anterior to
trachea
• Takes up iodine
from the diet
• Hormones
– Thyroxine
– Triiodothyronine
– Calcitonin
Thyroid Gland Disease
• Hyperthyroidismdramatically increases
the metabolic rate. Can
cause brittle hair, dry
skin, unintended weight
loss, enlarged thyroid
• Graves diseaseHyperthyroidism with
exopthalmos
Thyroid Imaging
• Ultrasound
• Nuclear Medicine
Thyroid Gland Disease
• Hypothyroidism-under secretion of
thyroid hormone.
• Creatinism-hyposecretion of thyroid
hormones in formative years
–
–
–
–
low metabolic rate
retarded growth
retarded sex organ development
metal retardation
Thyroid Gland Disease
• Myxedema-late life hyposecretion of
thyroid hormones
–
–
–
–
lessens mental and physical vigor
weight gain
loss of hair
accumulation of mucous fluid in tissue
most often around eyes
Parathyroid Glands
• Four small glands located on the back of
the thyroid gland.
• Secretes Parathyroid Hormone
• Increases the concentration of calcium in
the blood-opposite of calcitonin
• Stimulates bone-resorbing cells or
osteoclasts, to increase their breakdown of
bone’s hard matrix thus weakening the
bone
Adrenal Gland
• Sits on top of each kidney
• Contains
– Adrenal cortex which secretes
mineralocorticoids hormones
– Adrenal medulla – the inner portion of the
adrenal gland, which produces
• Epinephrine also called adrenaline
• Norepinephrine
– They help the body to resist stress and are often called the
‘fight or flight” hormones
Mineralocorticoids hormones
• Aldosterone– to increase the amount of sodium and decrease the
amount of potassium in the blood.
– To speed up kidney reabsorption of water
• Glucocorticoids
– help maintain normal blood glucose concentration
– increases gluconeogenesis- a process that converts amino
acids or fatty acids to glucose
• Androgens
– Females stimulate the female sexual drive
– Males- they are similar to testosterone and since so
much testosterone is secreted adrenal androgens are
physiologically insignificant
Pancreatic Islets
• Also called islets of Langerhans-cells
scattered throughout the pancreas
• Types of cells in pancreatic islets
– Alpha secretes glucagon
– Beta secretes insulin
• Glucagon and Insulin are antagonist
Diabetes Mellitus
• A normal blood glucose is 80-120 mg
• Pancreatic islets secrete a normal amount
of insulin, a normal amount of glucose
enters the cells and a normal amount of
glucose stays behind in the blood
• If too much insulin is secreted
hypoglycemia occurs
• If too little insulin is secreted DM occurs
(also called hyperglycemia)
Other Glands
• Female sex glands-ovaries
• Males-sperm
• Thymus-larger in children, produces
thymosin which assists in the development
and function of the body’s immune system
• Placenta-chorionic gonadotropins, estrogen
and progesterone
• Pineal Gland-melatonin-inhibits the tropic
hormones that affect the ovaries