Download Answers to WHAT DID YOU LEARN questions

McKinley/O’Loughlin
Human Anatomy, 2nd Edition
CHAPTER 20
Answers to “What Did You Learn?”
1.
Cells that respond to a specific hormone are called target cells.
2.
In a negative feedback loop, the result of a process acts back at an earlier step in
the process to slow down or turn off the process.
3.
The hypothalamus secretes regulatory hormones that are releasing hormones (RH)
and inhibiting hormones (IH) to control the function of the anterior pituitary
gland.
4.
The pituitary gland lies inferior to the hypothalamus within the sella turcica of the
sphenoid bone. It is connected to the hypothalamus by a thin stalk, the
infundibulum.
5.
The anterior pituitary secretes adrenocorticotropic hormone (ACTH),
gonadotropins (FSH and LH), thyroid-stimulating hormone (TSH), growth
hormone (GH), prolactin (PRL), and melanocyte-stimulating hormone (MSH).
ACTH stimulates the adrenal cortex to produce and secrete some corticosteroid
hormones. FSH and LH influence reproductive system activities by regulating
hormone synthesis and secretion in both female and male gonads and the
production and maturation of gametes in both sexes. TSH regulates the release of
thyroid hormone from the thyroid gland. GH affects cellular activities in most
body cells, especially growth in the skeletal and muscular systems, and it causes
the liver to produce somatomedins, which stimulate growth at the epiphyseal plate
of long bones. Although GH affects activities in almost every cell in the body, its
strongest effects are upon the growth and development of the skeletal and
McKinley/O’Loughlin
Human Anatomy, 2nd Edition
muscular systems. In females, PRL regulates mammary gland growth and the
production of breast milk, and in males, prolactin may play a role in the
sensitivity of the interstitial Leydig cells to LH. MSH stimulates both the rate of
melanin synthesis by melanocytes in the integument and their distribution through
the skin.
6.
The anterior pituitary is controlled by regulatory hormones (releasing and
inhibiting hormones) released from the hypothalamus. These hormones enter the
hypothalamo-hypophyseal portal system and stimulate cells in the anterior
pituitary. In contrast, the posterior pituitary is under neural control from the
hypothalamus. Axons from neurons in the paraventricular nucleus and supraoptic
nucleus terminate in the posterior pituitary. These axons transport the hormones
to the posterior pituitary for eventual release. Stimulation of these neurons causes
release of hormones from their axon terminals.
7.
Colloid is a viscous, protein-rich fluid housed within the lumen of the thyroid
follicle.
8.
Thyroid hormone stimulates its target cells (many of the cells in the body), so
cellular metabolism increases in these cells. Basal body temperature rises as a
result of this stimulation.
9.
Parathyroid hormone increases calcium levels in body by (1) stimulating
osteoclasts to resorb bone, (2) stimulating calcitriol synthesis to increase calcium
absorption in the small intestine, and (3) preventing calcium loss during the
formation of urine.
McKinley/O’Loughlin
10.
Human Anatomy, 2nd Edition
Aldosterone regulates the sodium (Na+) and potassium (K+) ion ratio by
promoting sodium ion retention with the concomitant reabsorption of water and
the excretion of potassium from tubular fluid through kidney tubule cells.
11.
Stimulation by the sympathetic division of the ANS causes chromaffin cells to
secrete epinephrine.
12.
The hormones produced by the endocrine cells of the pancreas are glucagon,
insulin, somatostatin, and pancreatic polypeptide.
13.
The pineal gland is located in the posterior region of the epithalamus.
14.
Modified cardiac muscle cells in the wall of the right atrium secrete the hormone
atriopeptin.
Answers to “Content Review”
1.
Hormones are molecules released by endocrine glands into the bloodstream. Only
cells with specific receptors for the hormone (so the hormone can bind or attach to
the cell or a molecule within the cell) will respond to that hormone. These cells
are called target cells and the organs that contain these target cells are called
target organs. In contrast, organs, tissues or cells that do not have the specific
"receptor" for a hormone do not bind or attach the hormone and do not respond to
its stimulating effects.
2.
Peptide hormones are formed from chains of amino acids. An example would be
growth hormone. Biogenic amines are small molecules produced by altering the
structure of an amino acid. An example would be thyroid hormone.
Steroid
McKinley/O’Loughlin
Human Anatomy, 2nd Edition
hormones are a type of lipid derived from cholesterol. An example would be
testosterone.
3.
The hypothalamus has special neurosecretory cells that secrete hormones to
influence the secretory activity of the anterior pituitary gland. These hormones
are called regulatory hormones because they are molecules secreted into the blood
to regulate secretion of most anterior pituitary hormones.
Regulatory hormones
fall into one of two groups: Releasing hormones [RH] stimulate the production
and secretion of specific anterior pituitary hormones, and Inhibiting hormones
[IH] deter the production and secretion of specific anterior pituitary hormones.
Additionally, the hypothalamus produces two hormones that are transported
through axons to the posterior pituitary and stored there until needed. These two
hormones are oxytocin and antidiuretic hormone (ADH).
4.
The anterior pituitary gland is controlled by regulatory hormones secreted by the
hypothalamus. These regulatory hormones reach the anterior pituitary by traveling
through a blood vessel network called the hypothalamo-hypophyseal portal
system. A portal system is composed of two capillary plexuses interconnected by
a portal vein. The hypothalamo-hypophyseal portal system is essentially a venous
"shunt" that takes venous blood (carrying regulatory hormones) from the
hypothalamus directly to the anterior pituitary first, before the blood returns to the
heart. Thus, it provides a pathway for hypothalamic hormones to immediately
reach the anterior pituitary. In addition, the veins that drain this portal system
also provide a pathway by which the anterior pituitary hormones may be released
into the general bloodstream.
McKinley/O’Loughlin
5.
Human Anatomy, 2nd Edition
The anterior pituitary secretes (1) adrenocoticotropic hormone [ACTH] to
stimulate the adrenal cortex to produce and secrete some corticosteroid hormones,
(2 and 3) gonadotropins (FSH and LH) to stimulate the gonads in males and
females both for regulation of reproductive system activities through hormone
synthesis and secretion, and the production and maturation of gametes, (4)
thyroid-stimulating hormone (TSH) to stimulate the thyroid gland to release
thyroid hormones, (5) growth hormone (GH) affects cellular activities in most
body cells, especially growth activities in the skeletal and muscular system, and it
causes the liver to produce somatomedin, which stimulates growth activities at the
epiphyseal plate of long bones, (6) prolactin (PRL) regulates mammary gland
growth and the production of breast milk in females, and in males, prolactin may
play a role in the sensitivity of the interstitial cells in the testes to LH, and (7)
melanocyte-stimulating hormone (MSH), which stimulates both the rate of
melanin synthesis by melanocytes in the integument and their distribution through
the skin.
6.
Parafollicular cells secrete the hormone calcitonin in response to elevated blood
calcium levels. Calcitonin acts to reduce blood calcium levels by stimulating
osteoblast activity and inhibiting osteoclast activity. New bone matrix formation
with the simultaneous deposition of calcium salts onto this matrix, and a decrease
in bone matrix resorption.
7.
PTH secretion occurs when there is a decrease in calcium ion concentration in the
body. Calcium ions are needed for many body activities, such as activity at nerve
synapses, muscle contraction, etc. Insufficient PTH secretion may result in
McKinley/O’Loughlin
Human Anatomy, 2nd Edition
adequate levels of calcium in the blood, and consequently some body functions
would be interrupted. Symptoms are mostly neuromuscular in nature and range
from mild tingling of the fingers and extremities, to marked muscle cramps and
contractions (tetany), and in severe cases there may even be convulsions.
8.
The adrenal cortex is partitioned into three separate regions or zones. Different
functional categories of steroid hormones are synthesized and secreted in the
separate zones; the zona glomerulosa (produces mineralocorticoids) , the zona
fasciculata (produces glucocorticoids), and the zona reticularis (produces
androgens).
9.
Four endocrine cell types form the islets: alpha cells secrete glucagon to raise
blood glucose levels; beta cells produce insulin causing blood glucose levels to
decline; delta cells produce somatostatin to slow down or inhibit digestive
activities in the digestive tract; and F cells secrete pancreatic polypeptide to
suppress and regulate somatostatin secretion from delta cells.
10.
Some of the organs of the GI tract, heart, kidneys, and gonads contain their
endocrine cells which secrete their own hormones. These hormones help regulate
digestive system activities, blood volume, electrolyte levels in the blood, red
blood cell production, blood pressure, and sexual maturation and activity,
respectively.