7.20.F - QUIZ: THE ENDOCRINE
SYSTEM EXAM QUESTIONS WITH
CORRECT ANSWERS
Circadian Rhythms
Circadian rhythms are physical, mental, and behavioral changes that follow a 24-
hour cycle and can influence our bodies' important functions, such as hormone
release, eating habits, body temperature, and digestion. Most people notice the
effect of circadian rhythms on their sleep patterns. These rhythms respond primarily
to the amount of light you are exposed to, which is why your circadian rhythm
typically coincides with the sun's cycle. Darkness stimulates the pineal gland to start
producing melatonin, while light causes that production to stop. - ANSWER-The
thymus gland is a small gland comprised of two identically sized lobes, located
behind the sternum but in front of the heart. It plays an important function both in the
immune system and endocrine system. Relatively large in infants, it grows until
puberty. In adulthood, it starts to shrink and become slowly replaced by fat. The
shrinking is due to the reduced immune system role of the thymus in adulthood. The
immune system produces most of its T cells during childhood and requires very few
new T cells after puberty.
Thymosin
The thymus produces and secretes thymosin, a hormone necessary for T-cell, a.k.a.
T-lymphocyte development and production. T-cells, a type of white blood cell,
originate in the bone marrow and migrate to the thymus gland to mature.
The Thyroid Gland
One of the largest endocrine glands is the thyroid. It is located on the neck's anterior
aspect, below the thyroid cartilage that forms the laryngeal prominence, or Adam's
apple. The thyroid gland is constructed of two lobes connected by the isthmus, giving
the thyroid a butterfly-like shape. - ANSWER-Thyroid Hormone: T3 and T4
The thyroid hormone, often referred to as the body's major metabolic hormone, is
actually two active iodine-containing hormones. The thyroid gland takes iodine,
found in many foods, and converts it into thyroid hormones: thyroxine (T4) and
triiodothyronine (T3). Thyroid cells are the only cells in the body that can absorb
iodine. This means that a deficiency of iodine in the diet will cause the thyroid to be
incapable of making thyroid hormones.
Triiodothyronine (T3) is the active form of thyroid hormone that can readily go into
the human body's cells. This means that every cell of the human body has thyroid
receptors. Most T3 is formed at the target tissues by the conversion of T4 to T3. The
normal thyroid gland produces about 80% T4 and about 20% T3.
The Parathyroid Glands
Tiny masses of glandular tissue, the parathyroid glands, are located on the thyroid
gland's posterior surface. Typically, there are two glands located within each thyroid
lobe, but the exact location and number may vary.
,The four green shaded areas represent the most common position of the parathyroid
glands, which are generally four in number and situated behind the lateral lobes of
the thyroid gland (shaded orange). - ANSWER-Actions of the Thyroid Hormone
Every cell in the body is a target since the thyroid hormone controls the rate at which
glucose is converted to chemical energy. The calorgenic, or heat-producing, effect of
this hormone results from the increased oxidation of glucose, thus increasing the
body's metabolic rate and body heat production.
TH is also critical for regulating tissue growth and development, especially in the
reproductive and nervous systems. The body's metabolism, the rate of the body's
use of energy, synthesis of proteins, and sensitivity to other hormones are all
affected by the thyroid hormone.
The hormonal output from the thyroid is regulated by thyroid-stimulating hormone
(TSH) produced by the anterior pituitary, which itself is regulated by thyrotropin-
releasing hormone (TRH) produced by the hypothalamus. The thyroid hormone also
provides negative feedback to the hypothalamus and anterior pituitary gland.
Elevated thyroid hormone in the blood leads to a reduction in TSH production and
TRH production, and vice versa.
Parathyroid Hormone
The parathyroid glands release parathyroid hormone (PTH). PTH is secreted directly
into the bloodstream. It travels to target cells in the bones, kidneys, and
gastrointestinal system resulting in the release of calcium from the bones and into
the extracellular fluid.
The parathyroid hormone acts to increase blood calcium levels through osteoclasts'
stimulation, which break down the bone, causing calcium release into the blood.
PTH and calcitonin (produced by the thyroid) work together to maintain calcium
homeostasis. - ANSWER-What Is Hypothyroidism?
Hypothyroidism is an abnormally low thyroid gland activity and means that the
damaged thyroid gland cannot make enough thyroid hormones to keep the body
running normally. The pituitary gland secretes increasing amounts of TSH in a futile
attempt to make more TH. This results in an enlarged, protruding yet nonfunctional
thyroid gland known as a goiter.
Hypothyroidism can result from an autoimmune disease such as Hashimoto's
thyroiditis, dietary iodine deficiency, surgical removal of the thyroid, or inadequate
TRH or TSH release. It occurs more frequently in women than men.
The most common cause of hypothyroidism is Hashimoto's thyroiditis. In this
condition, the body produces antibodies that damage the thyroid gland, causing it to
be unable to make enough thyroid hormone.
PTH and Calcitonin Interaction
Bone remodeling is a process that goes on throughout life wherein new bone tissue
is formed as mature bone. This is a lifelong process where mature bone tissue is
removed from the skeleton and new bone tissue is formed. Bone remodeling is also
impacted by the interaction of PTH and calcitonin with each other. - ANSWER-What
Is Hyperthyroidism?
Hyperthyroidism refers to any condition in which there is too much thyroid hormone
produced in the body.
The most common hyperthyroid pathology is Graves' disease. With Graves' disease,
a person's antibodies attack the thyroid and cause it to secrete too much thyroid
, hormone. This type of autoimmune hyperthyroidism tends to run in families and
occurs more often in young women.
Typical hyperthyroidism symptoms include an elevated metabolic rate, rapid,
irregular heart rate, nervousness, and sweating. Exophthalmos can result when the
tissue behind the eyes becomes edematous and fibrous, causing the eyeballs to
protrude.
Hyperthyroidism can be permanently cured by surgical removal of all or most of the
thyroid gland.
The reproductive glands and their hormones will be discussed in detail in the
Reproductive System Lessons. - ANSWER-Calcitonin
Calcitonin, a hormone that regulates blood calcium levels, is also produced by the
thyroid. PTH and calcitonin (produced by the thyroid) work together to maintain
calcium homeostasis.
The secretion of calcitonin is determined by the calcium level in the blood, as
indicated at the top of the graphic shown to the left. When levels of calcium in the
blood increase (hypercalcemia), calcitonin is secreted in higher quantities. When
calcium levels in the blood decrease (hypocalcemia), this causes the amount of
calcitonin secreted to decrease.
Calcitonin decreases blood calcium levels through the stimulation of osteoblasts,
which deposit bone, causing calcium removal from the blood.
Which two regions does the pituitary gland consist of? - ANSWER--Posterior lobe
AND -Anterior lobe
Which hormone increases the reabsorption of water and inhibits urine production? -
ANSWER-Antidiuretic hormone
Which organ stores hormones rather than producing them? - ANSWER-Posterior
pituitary gland
Which organ consists of hypothalamic tissue that grows downward? - ANSWER-
Neurohypophysis
A few hormones, such as those involved in the reproductive system and blood
clotting, use positive feedback mechanisms. In these cases, the body senses that a
substance has been secreted or a series of events has begun. This in turn increases
or magnifies the response to the event, causing the process to move forward. For
example, when a mother is in labor, stretching of the uterine walls will cause the
increased release of oxytocin. This hormone encourages uterine contractions and
speeds labor to its conclusion.
Type of Stimuli
Endocrine glands are regulated in three different ways: hormonal control, neural
control, and humoral control. These hormonal negative feedback mechanisms
prompt a gland to secrete or inhibit a hormone.
Hormonal control refers to the release of hormones in response to other hormones
released by the hypothalamus. This is the most common type of stimulus. For
example, when your metabolism needs a boost, the hypothalamus will release
thyrotropin-releasing hormone (TRH) to cause the anterior pituitary to release
SYSTEM EXAM QUESTIONS WITH
CORRECT ANSWERS
Circadian Rhythms
Circadian rhythms are physical, mental, and behavioral changes that follow a 24-
hour cycle and can influence our bodies' important functions, such as hormone
release, eating habits, body temperature, and digestion. Most people notice the
effect of circadian rhythms on their sleep patterns. These rhythms respond primarily
to the amount of light you are exposed to, which is why your circadian rhythm
typically coincides with the sun's cycle. Darkness stimulates the pineal gland to start
producing melatonin, while light causes that production to stop. - ANSWER-The
thymus gland is a small gland comprised of two identically sized lobes, located
behind the sternum but in front of the heart. It plays an important function both in the
immune system and endocrine system. Relatively large in infants, it grows until
puberty. In adulthood, it starts to shrink and become slowly replaced by fat. The
shrinking is due to the reduced immune system role of the thymus in adulthood. The
immune system produces most of its T cells during childhood and requires very few
new T cells after puberty.
Thymosin
The thymus produces and secretes thymosin, a hormone necessary for T-cell, a.k.a.
T-lymphocyte development and production. T-cells, a type of white blood cell,
originate in the bone marrow and migrate to the thymus gland to mature.
The Thyroid Gland
One of the largest endocrine glands is the thyroid. It is located on the neck's anterior
aspect, below the thyroid cartilage that forms the laryngeal prominence, or Adam's
apple. The thyroid gland is constructed of two lobes connected by the isthmus, giving
the thyroid a butterfly-like shape. - ANSWER-Thyroid Hormone: T3 and T4
The thyroid hormone, often referred to as the body's major metabolic hormone, is
actually two active iodine-containing hormones. The thyroid gland takes iodine,
found in many foods, and converts it into thyroid hormones: thyroxine (T4) and
triiodothyronine (T3). Thyroid cells are the only cells in the body that can absorb
iodine. This means that a deficiency of iodine in the diet will cause the thyroid to be
incapable of making thyroid hormones.
Triiodothyronine (T3) is the active form of thyroid hormone that can readily go into
the human body's cells. This means that every cell of the human body has thyroid
receptors. Most T3 is formed at the target tissues by the conversion of T4 to T3. The
normal thyroid gland produces about 80% T4 and about 20% T3.
The Parathyroid Glands
Tiny masses of glandular tissue, the parathyroid glands, are located on the thyroid
gland's posterior surface. Typically, there are two glands located within each thyroid
lobe, but the exact location and number may vary.
,The four green shaded areas represent the most common position of the parathyroid
glands, which are generally four in number and situated behind the lateral lobes of
the thyroid gland (shaded orange). - ANSWER-Actions of the Thyroid Hormone
Every cell in the body is a target since the thyroid hormone controls the rate at which
glucose is converted to chemical energy. The calorgenic, or heat-producing, effect of
this hormone results from the increased oxidation of glucose, thus increasing the
body's metabolic rate and body heat production.
TH is also critical for regulating tissue growth and development, especially in the
reproductive and nervous systems. The body's metabolism, the rate of the body's
use of energy, synthesis of proteins, and sensitivity to other hormones are all
affected by the thyroid hormone.
The hormonal output from the thyroid is regulated by thyroid-stimulating hormone
(TSH) produced by the anterior pituitary, which itself is regulated by thyrotropin-
releasing hormone (TRH) produced by the hypothalamus. The thyroid hormone also
provides negative feedback to the hypothalamus and anterior pituitary gland.
Elevated thyroid hormone in the blood leads to a reduction in TSH production and
TRH production, and vice versa.
Parathyroid Hormone
The parathyroid glands release parathyroid hormone (PTH). PTH is secreted directly
into the bloodstream. It travels to target cells in the bones, kidneys, and
gastrointestinal system resulting in the release of calcium from the bones and into
the extracellular fluid.
The parathyroid hormone acts to increase blood calcium levels through osteoclasts'
stimulation, which break down the bone, causing calcium release into the blood.
PTH and calcitonin (produced by the thyroid) work together to maintain calcium
homeostasis. - ANSWER-What Is Hypothyroidism?
Hypothyroidism is an abnormally low thyroid gland activity and means that the
damaged thyroid gland cannot make enough thyroid hormones to keep the body
running normally. The pituitary gland secretes increasing amounts of TSH in a futile
attempt to make more TH. This results in an enlarged, protruding yet nonfunctional
thyroid gland known as a goiter.
Hypothyroidism can result from an autoimmune disease such as Hashimoto's
thyroiditis, dietary iodine deficiency, surgical removal of the thyroid, or inadequate
TRH or TSH release. It occurs more frequently in women than men.
The most common cause of hypothyroidism is Hashimoto's thyroiditis. In this
condition, the body produces antibodies that damage the thyroid gland, causing it to
be unable to make enough thyroid hormone.
PTH and Calcitonin Interaction
Bone remodeling is a process that goes on throughout life wherein new bone tissue
is formed as mature bone. This is a lifelong process where mature bone tissue is
removed from the skeleton and new bone tissue is formed. Bone remodeling is also
impacted by the interaction of PTH and calcitonin with each other. - ANSWER-What
Is Hyperthyroidism?
Hyperthyroidism refers to any condition in which there is too much thyroid hormone
produced in the body.
The most common hyperthyroid pathology is Graves' disease. With Graves' disease,
a person's antibodies attack the thyroid and cause it to secrete too much thyroid
, hormone. This type of autoimmune hyperthyroidism tends to run in families and
occurs more often in young women.
Typical hyperthyroidism symptoms include an elevated metabolic rate, rapid,
irregular heart rate, nervousness, and sweating. Exophthalmos can result when the
tissue behind the eyes becomes edematous and fibrous, causing the eyeballs to
protrude.
Hyperthyroidism can be permanently cured by surgical removal of all or most of the
thyroid gland.
The reproductive glands and their hormones will be discussed in detail in the
Reproductive System Lessons. - ANSWER-Calcitonin
Calcitonin, a hormone that regulates blood calcium levels, is also produced by the
thyroid. PTH and calcitonin (produced by the thyroid) work together to maintain
calcium homeostasis.
The secretion of calcitonin is determined by the calcium level in the blood, as
indicated at the top of the graphic shown to the left. When levels of calcium in the
blood increase (hypercalcemia), calcitonin is secreted in higher quantities. When
calcium levels in the blood decrease (hypocalcemia), this causes the amount of
calcitonin secreted to decrease.
Calcitonin decreases blood calcium levels through the stimulation of osteoblasts,
which deposit bone, causing calcium removal from the blood.
Which two regions does the pituitary gland consist of? - ANSWER--Posterior lobe
AND -Anterior lobe
Which hormone increases the reabsorption of water and inhibits urine production? -
ANSWER-Antidiuretic hormone
Which organ stores hormones rather than producing them? - ANSWER-Posterior
pituitary gland
Which organ consists of hypothalamic tissue that grows downward? - ANSWER-
Neurohypophysis
A few hormones, such as those involved in the reproductive system and blood
clotting, use positive feedback mechanisms. In these cases, the body senses that a
substance has been secreted or a series of events has begun. This in turn increases
or magnifies the response to the event, causing the process to move forward. For
example, when a mother is in labor, stretching of the uterine walls will cause the
increased release of oxytocin. This hormone encourages uterine contractions and
speeds labor to its conclusion.
Type of Stimuli
Endocrine glands are regulated in three different ways: hormonal control, neural
control, and humoral control. These hormonal negative feedback mechanisms
prompt a gland to secrete or inhibit a hormone.
Hormonal control refers to the release of hormones in response to other hormones
released by the hypothalamus. This is the most common type of stimulus. For
example, when your metabolism needs a boost, the hypothalamus will release
thyrotropin-releasing hormone (TRH) to cause the anterior pituitary to release
