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Unit 7 Lecture Notes
CHAPTER 15
ENDOCRINE SYSTEM
Endocrinology is the study of hormones, their receptor cells, and the results of hormone action.
Hormones are chemicals that regulate processes throughout the body; they are produced by the glands
of the endocrine system. Some hormones have direct effects on a target tissue or chemical, whereas
others stimulate the production of additional hormones from another gland. Hormones control growth,
mood, system functions, metabolism, sexual maturity, and reproduction. Each hormone that is released
into the bloodstream has particular target cells for action.
Glands are categorized as either endocrine or exocrine. Exocrine glands secrete through a duct directly
onto the skin, or into the mouth such as the salivary or sweat glands. An endocrine gland such as the
thyroid gland or gonads secretes its hormones directly into the bloodstream. Some glands are both
endocrine and exocrine glands, such as the pancreas, which secretes insulin as an endocrine gland and
gastric secretions as an exocrine gland.
The major glands of the endocrine system are the pituitary, hypothalamus, pineal body, thyroid,
parathyroids, adrenals, and the reproductive organs (ovaries and testes). The pancreas is also a part of
the endocrine system; it has a role in hormone production as well as in digestion.
The pituitary gland is sometimes called the master gland because it helps to regulate hormones in the
other glands, namely the thyroid, adrenal, ovaries and testes. The hypothalamus helps to stimulate or
inhibit hormone production. The body’s natural balance, homeostasis, is controlled by the hypothalamus.
Much of the function of the pineal gland is unknown. However, the purpose of the pineal gland is to
produce and regulate melatonin. Melatonin has two primary functions in humans, to help control your
circadian (or biological) rhythm, and to regulate certain reproductive hormones. Circadian rhythms
involve the cycles of activity, sleep, etc. which occur daily. Circadian comes from the Latin words for
“about a day.” These cycles are regulated in part by internal signals such as hormones, but are also
influenced by external cues such as periods of daylight.
The thyroid gland regulates the body’s metabolism. Metabolism is the chemical process of the body,
where the body breaks down food and converts it to energy. The parathyroids regulate the body’s
calcium levels. Adrenal glands are made up of two parts—the adrenal cortex produces cortisol which
helps to regulate the body’s metabolism and helps to control stress, and the adrenal medulla produces
adrenaline which helps your body to adjust to stress.
Ovaries are the egg-producing organs located in females. Ovaries secrete the hormones estrogen and
progesterone. Testes are sperm-producing organs located in males. Testes produce the hormone
testosterone. Both the female ovaries and the male testes are known as gonads, meaning they are
primary reproductive organs.
The pancreas maintains energy and helps to regulate homeostasis throughout the body. The pancreas
secretes the hormones glucagon and insulin. In the pancreas, hormones are produced by specialized
groups of cells known as Islets of Langerhans, or islets. Within the islets, specific cell types produce
insulin (beta cells) and glucagon (alpha cells), as well as somatostatin (delta cells). Glucagon is secreted
in response to low blood glucose in the body. Insulin is released when the blood glucose is too high.
One of the most common conditions that affect the pancreas is known as diabetes. There are two
categories of diabetes that are a direct result of how the pancreas and its hormones function. Type I
diabetes (diabetes mellitus) is also known as insulin dependent diabetes; Type II diabetes is known as
non-insulin dependent diabetes.
Diabetes mellitus affects patients from an early age; patients are insulin-dependent for their entire life.
The person who has been diagnosed with diabetes mellitus must be able to tell the difference between
hyperglycemia and hypoglycemia. The signs of hypoglycemia usually have a slow onset and include
shakiness, palpitations, vertigo, diaphoresis, hunger, pallor, fatigue, confusion, irritable behavior, and
visual disturbances. If the patient does not receive glucose, he or she may become comatose. The
condition can be a medical emergency if the person is not given glucose while still alert.
Type II diabetes or non-insulin dependent patients are diagnosed in later life. Treatment is usually oral
medications, or the patient must commit to a lifestyle change. Recent studies have shown that many
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Unit 7 Lecture Notes
people with slightly elevated blood sugar levels (called prediabetes) can prevent the onset of non-insulin
dependent diabetes through moderate exercise and weight loss.
Another common type of diabetes is known as gestational diabetes which occurs in women during
pregnancy. Blood glucose levels usually return to normal after delivery. Up to 10% of pregnant women
develop gestational diabetes (GD). This condition is caused by insulin resistance, which occurs to some
extent in all pregnant women, but which progresses to unhealthy levels in some. The main risk of
uncontrolled GD is a large baby, caused by the high levels of sugar in the bloodstream. If blood sugar
levels are controlled, the risks to both mother and baby are minimal. Most women with GD can control
their blood sugar levels through monitoring and diet alone. When these measures are not effective,
insulin injections can be used.
Review Table 15-6 on textbook page 489 to learn more about the most commonly prescribed insulins for
insulin-dependent diabetes mellitus. Then review Table 15-7 on textbook page 490 for the most common
anti-diabetic agents for type II diabetes. Finally, review Table 15-8 on textbook page 491 for the
combination oral agents prescribed for type II diabetes.
CHAPTER 22
URINARY SYSTEM
As previously specified in the textbook readings, a human is described as being in a state of homeostasis
when the body is in balance. The term homeostasis is derived from the Greek word homeo- or “same”,
and stasis meaning “standing still.” Therefore, human homeostasis means the body is the same state of
standing still, or in a steady-state of equilibrium. Human homeostasis is accomplished through a process
known as negative feedback. Negative feedback occurs because the body’s receptors (special structures
located in different parts of the body that are capable of recognizing and receiving messages), are notified
when the body is out of balance. The receptors signal the body’s effectors (cells which produce a
response after receiving a signal or stimulus from the receptor), and signal that specific changes must be
made in order for the body to remain in balance.
The urinary system, also known as the excretory system, is responsible for maintaining correct levels of
water and dissolved substances in the body. The body remains in homeostasis because the liver filters
blood, removing toxins from the blood and converts them into chemicals that can be removed from the
body by the kidneys. Blood byproducts are filtered by the kidneys and leave the body as urine.
Essentially, the main function of the urinary system is to filter and remove metabolic waste products and
toxins from the bloodstream and excrete waste from the body as urine.
Urine is the waste product produced by the kidneys. Urine contains mostly water, as well as salts and
nitrogen compounds. Urine is stored in the bladder which empties urine from the body in a process
known as urination. An adult bladder holds approximately 1000 mL of urine. During urination, the
sphincter muscles relax to open the bladder while the bladder (which is also a muscle) contracts to
squeeze out the urine. Urine contains urea, which is produced by liver; urea is a byproduct of protein
metabolism in the liver.
The structure and function of the urinary system include all of the following: two kidneys which produce
urine and help regulate body fluids; two ureters that transport urine to the bladder; a urinary bladder,
serving as a reservoir for urine; and one urethra that conveys urine to the outside of the body.
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Kidneys are bean-shaped organs located at the posterior region of the abdominal cavity between the 12
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thoracic and 3 lumbar vertebrae. Each kidney is encased in three capsules for protection, known as the
true capsule, perirenal capsule, and renal fascia. Besides filtering waste, the kidneys produce
erythropoietin, a stimulator of red blood cell formation; renin, a blood pressure regulator; and the active
form of vitamin D. Within each kidney are approximately 1,000,000 nephrons. The nephrons are the
functional units of the kidneys and filter blood to help remove bodily waste. The glomerulus, Bowman’s
capsule, and loop of Henle are integral components of the nephron.
Click here to view a brief video of the urinary system.
Having less than 25% of normal kidney function will cause health problems. A patient with less than
about 15% of normal kidney function requires either dialysis or a transplant for survival. When both
kidneys are working normally, kidney function is 100%. Drinking plenty of water will cleanse the body of
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Unit 7 Lecture Notes
toxins and other unwanted chemicals. A normal adult is usually advised to drink 8 to 10 glasses of water
each day. However, it is possible to drink too much water, although it is not common. Hyponatremia is
the resulting condition (sometimes called “water intoxication”), and comes from the lack of sufficient
electrolytes being taken in along with the water. Excess water dilutes the sodium levels in the blood and
causes cells to swell. In practice, hyponatremia is seen most often in athletes who drink large quantities
of water without electrolytes, and in babies who drink several bottles of water each day or whose formula
is too diluted. Hyponatremia is also a rare side effect of MDMA (Ecstasy) use, where the drug stimulates
an antidiuretic hormone.
CHAPTER 24
REPRODUCTIVE SYSTEM
The major function of the reproductive system is to produce offspring for the survival of the species. The
reproductive system operates interdependently along with the endocrine system. As previously specified,
hormones are chemicals that regulate processes throughout the body and are produced by the glands of
the endocrine system. Ovaries are the “egg-producing” organs located in females which secrete the
hormones estrogen and progesterone. Testes are the “sperm-producing” organs located in males which
produce the hormone testosterone. In both males and females, the reproductive organs are divided
between the primary, secondary, and accessory organs. Both the female ovaries and the male testes are
known as “gonads” and are primary reproductive organs, necessary for producing gametes, or sex cells.
In females, the secondary reproductive organs are the fallopian tubes. The fallopian tubes transport the
female egg (gamete) from the ovary into the tube for reproduction. During sexual intercourse, the male
sperm are deposited from the penis, the male secondary sex organ, into the female vagina, another
female secondary organ. The sperm will swim rapidly into the fallopian tubes where fertilization will occur.
Sperm remain viable in the female reproductive tract for about 72 hours. If the female is within a few
days of ovulation, or is ovulating, the egg may be fertilized by the male sperm. The egg is then slowly
transported through the fallopian tube and into the uterus for fetal development; the female is now
considered to be pregnant and the full cycle of reproduction has occurred.
When a female patient considers oral contraceptives to prevent pregnancy, there are a number of patient
characteristics the provider must consider. Oral contraception is not an appropriate choice for all
patients. For example, a patient who cannot (or is unwilling to) correctly take the pills is not a good
candidate, and a patient who engages in high-risk sexual behavior should always use condoms even if
oral contraceptives are being used. Women who use oral contraceptives and smoke (especially women
older than age 35) or who have a history of cardiovascular problems are at increased risk of serious
complications including heart attack, stroke, and blood clots.
Aside from abstinence and barrier devices such as condoms, there are no male options for birth control.
However, the creation of an effective and reversible male contraceptive pill is a current hot topic.
According to new research, a hormone-free drug tested in male mice might someday prove viable for
men who want their own birth control pill. The compound stifles sperm production but not sexual activity,
fertility returns once treatment stops, and males can go on to father healthy offspring. Strictly speaking,
however, the new drug is not yet a male “pill.”
Click here to learn more about the possibility of a male birth control drug.
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