Chapter 10 Study Guide The Endocrine System By: Sarah Genet

Chapter 10 Study Guide
The Endocrine System
By: Sarah Genet
Endocrine System
• Controls body functions via hormones.
So let’s say there’s too much glucose in your blood. Your pancreatic
islets cells send insulin into the blood which tells your cells to start
absorbing all the glucose, thereby decreasing the concentration of
glucose in your blood. The hormone in this situation is insulin, and
you can deduce how it is affecting bodily functions.
Pretty big deal, no? If a patient’s pancreatic islet cells stop making insulin, or if they can
no longer act on their target cells, that patient has diabetes mellitus. Do you know
someone with diabetes?
Two types of Glands
• The endocrine system secretes hormones
using endocrine glands (kind of makes
sense, no?) These are glands which lack
ducts. Ducts are like tubes which carry
hormones into the blood so they can be
circulated around the body and distributed.
• So what is the other possible type of gland?
Not endocrine, but exocrine.
Hormone Types
1. Nonsteroid Hormones – Proteins, short chain
amino acids or single amino acids
1. Proteins are water soluble and therefore cannot pass
through the cell membrane. Therefore nonsteroid
hormones affect the activity of the cell via a secondary
messenger system (see: lock and key model and cyclic
AMP)
2. Steroid Hormone – Lipid soluble steroid
hormone
1. Can pass through a cell’s cell membrane, travel through
the cytoplasm, enter the nucleus and act on DNA (see:
hormone receptor complex)
Prostaglandins
•
Not actually hormones….hormones are
produced in one location (for example,
insulin is made only in the pancreas) but
prostaglandins are produced in many
places, throughout the body
•
Prostaglandins are frequently produced in
tissues and act locally. In other words, they are
produced in a tissue and diffuse a short distance
to act on cells within that tissue
Regulation of Hormone Secretion
• Negative feedback: the output of a system acts
to oppose changes to the input of the system
– Ex) During periods of high blood sugar pancreatic
islet cells secrete insulin in order to decrease blood
sugar levels and bring them back to normal.
• Positive feedback: amplify changes to the
system
– Ex) Oxytocin increases the force of contractions
during labor
Endocrine Glands
•
•
•
•
•
•
•
•
•
Hypothalamus
Pituitary
Pineal
Thyroid
Parathyroid
Thymus
Adrenal
Pancreas
Ovaries (female), Testes (male)
Pituitary Gland
• Located in sella turcica of the Sphenoid bone
• Two parts
– Anterior pituitary,aka adenohypophysis
– Posterior pituitary, aka neurohypophysis
Pituitary Hormones
Anterior Pituitary
FLAT (all tropic hormones)
1. FSH
2. LH
3. ACTH
4. TSH
PG
5. Prolactin
6. GH
Posterior Pituitary
1. ADH
2. Oxytocin
Pituitary Disorders
• Hyperglycemia: too much sugar in blood.
One cause is too much GH
• Diabetes Insipidus: dehydration and
electrolyte imbalance due to hyposecretion
of ADH
Hypothalamus
• Nervous and endocrine function
• Nervous – Specialized neurons produce
ADH and oxytocin (to posterior pit.)
• Endocrine - Releases releasing and
inhibiting hormones. These travel to the
anterior pituitary and cause the ant. Pit. to
release or inhibit the production/release of
hormones.
Thyroid Gland
• Located in neck below the larynx
• Secretes T3 (triiodothyronine) and T4
(thyroxine). T3 has 3 molecules of iodine and
T4 has 4 molecules of iodine.
– Stores T3 and T4 in the follicle. Most endocrine
organs do not store hormones, so this function is
unique!
• Secretes calcitonin – decreases concentration of
calcium in the body. This hormone is used to
prevent an excess of calcium in the blood, a
condition known as hypercalcemia.
Example of negative feedback
• In this diagram T3 and T4
perform negative
feedback on the anterior
pituitary and the
hypothalamus, causing
them to decrease their
release of TSH and TRH.
Thyroid Hormone Abnormalities
• Hyperthyroidism – over secretion of
thyroid hormone
• Hypothyroidism – under secretion of
thyroid hormone
– Simple Goiter – enlargement of thyroid gland
caused by low dietary intake of iodine
– Cretinism – hyposecretion of thyroid hormone
during formative years
– Myxedema – hyposecretion of thyroid
hormone later in life.
Parathyroid Gland
• Located on the back of the thyroid
• Secretes parathyroid hormone (PTH) –
increases blood calcium levels.
• What hormone decreases blood calcium
levels?
Adrenal Gland
• Composed of two endocrine glands: the
adrenal cortex and the adrenal medulla
Adrenal Gland
• Adrenal Cortex secretes corticoids:
– mineralocorticoids
(MC). ex) aldosterone
– Glucocorticoids (GC)
ex) cortisol aka
hydrocortisone
– Sex hormones
ex)androgens
• Adrenal Medulla
– Epinephrine and
norepinephrine
Adrenal Medulla Abnormalities
• Cushing’s Syndrome – overproduction of adrenal cortex
hormones. Symptoms include moon-face, buffalo hump
on upper back, elevated blood sugar and frequent
infections (Seen in photo below)
• Addison’s Disease – hyposecretion of adrenal cortex
hormones. Results in muscle weakness, reduced blood
sugar, nausea, loss of appetite and weight loss
Pancreatic Islet
• Located in exocrine pancreas.
• Two types – alpha and beta cells. Alpha
release glucagon and beta release insulin.
– Glucagon  increased blood glucose
concentration via liver glycogenolysis
– Insulin  decreased blood glucose
concentration
• Secrete pancreatic enzyme juice.
Diabetes Mellitus
• Type I diabetes – increase in blood glucose
levels due to hyposecretion of insulin
• Type II diabetes – increase in blood glucose due
to an abnormality of insulin receptors.
Sometimes accompanied by hyposecretion of
insulin.
• Diabetes Mellitus results in glycosuria - glucose
in the urine. Doctors can diagnose diabetes by
checking the blood or urine.
Sex Glands - Female
•
Female Sex Glands – two ovaries
– Composed of two parts:
1. the follicle – secretes estrogen and the egg or
ova developes here
1. Estrogen – involved in development and maturation of
breast and external genitalia, development of adult
female contours (hips, curves) and initiation of the
menstrual cycle
2. Corpus Luteum – secretes
progesterone and some estrogen.
Sex Glands - Male
• The testes are made of many cell types. One
cell type, the interstitial cell, makes testosterone
which is the male sex hormone.
• Testosterone – “masculinizing hormone” –
maturation of external genitalia, beard growth,
changes in voice at puberty, muscular
development and male contour.
Thymus
• Located in the mediastinum (adults) or may
extend up into the neck as far as the bottom of
the thyroid gland (infants)
• Composed of a cortex and medulla. What other
organ contains a cortex and medulla?
• Both parts are composed of lymphocytes; the
thymus plays a critical role in defense against
infections
• Produces thymosin
Placenta
• Temporary endocrine
structure present during pregnancy
• Produces chorionic gonadotropins
(tropic hormones produce by the chorion),
estrogen and progesterone
• During the earlier weeks of pregnancy the
placenta excretes large amounts of chorionic
gonadotropins into the blood. So, when a
woman takes a pregnancy test, it is looking for
the presence of this hormone because some of
the hormone is secreted in the urine 
Pineal Gland
• Located near the roof of the third ventricle in the brain.
• Easily located in a child but not in an adult. This is
because the gland becomes encrusted with calcium
deposits as a person ages.
• Makes many hormones, the most important one being
melatonin.
• Melatonin – inhibits the tropic hormones which affect the
ovaries and is throught to be involved in regulating the
onset of puberty and the menstruation in women. The
release of melatonin is increased during the night and
decreased during the day.
Additional Endocrine Structures
• Atrial Natriuretic Hormone – secreted by cells in
the hearts’ atria (upper chambers of the heart).
Regulates fluid and electrolytes in the body and
is an antagonist to aldoesterone. (Aldosterone
causes the body to hold on to sodium and water
while ANH stimulates the loss of sodium and
water.
• Leptin – secreted by fat storing cells. Regulates
how hungry/full we feel and how fat is
metabolized by the body.