Introduction To Biology ch 45
Which type of hormone is lipid soluble? steroids Steroid hormones are lipid soluble.
Which molecules determine the tissue specificity of hormones? receptors Hormones bind to receptors on target cells and trigger a cellular response.
True or false? Lipid-insoluble hormones affect their target cells by binding to receptors inside the cell. False
Lipid-insoluble hormones cannot cross the plasma membrane and get into
the cell, so they must bind to receptors on the cell surface and
transduce their signals through signal transduction pathways.
Which of the following statements about lipid-soluble hormones is true? They act by affecting the transcription of genes.
Lipid-soluble hormones act by affecting the transcription of genes.
Which of the following is a structure that allows hormone-receptor complexes to bind to specific DNA sequences? zinc
finger A zinc finger is a distinctive DNA-binding domain on some
hormone receptors that is exposed when hormone-receptor complexes are
What is the role of cAMP in the signal transduction pathway activated by epinephrine? It
binds to and activates protein kinase A, which then phosphorylates
other enzymes. cAMP binds to and activates protein
kinase A, which then phosphorylates other enzymes in the signal
or false? For a signal transduction pathway to be activated, hormones
must be present in the bloodstream at very high concentrations. False Only low
concentrations of hormones are needed in the bloodstream to activate a
signal transduction pathway, which works by producing second messengers
inside the cell that amplify the hormonal signal.
Receptors for nonsteroid hormones are located in _____. association with a cell's plasma membrane
Since nonsteroid hormones do not cross a
cell's plasma membrane, their receptors are located in association with
the plasma membrane.
Which of these is a nonsteroid hormone? epinephrine and oxytocin
How do nonsteroid hormones differ from steroid hormones? nonsteroid hormones act via signal transduction pathways; steroid hormones do not act via signal transduction pathways
Since they do not enter the
cell, nonsteroid hormones act via signal transduction pathways.
Which of these extracellular signal molecules could diffuse through a
plasma membrane and bind to an intracellular receptor? estrogen
Steroid hormones such as estrogen can diffuse
through the plasma membrane and bind to intracellular receptors.
The primary reason steroid hormones usually act slowly is that _____. they turn genes on or off and it takes time for gene products to build up or become depleted
Steroid hormone-receptor complexes act in _____. the nucleus Steroid
hormone-receptor complexes bind to DNA, where they affect transcription.
The hormone epinephrine causes opposite effects in two populations of target cells because _____. each set of target cells has different receptor-transduction mechanisms
Look at the epinephrine
example in your text. That hormone can trigger different responses in
different target cells. Epinephrine can trigger vasodilation responses
(blood vessels in skeletal muscles used for fight-or-flight) and
vasoconstriction responses (gut vasculature) in an emergency that evokes
In their mechanism of action, a difference between lipid-soluble and water-soluble hormones is that _____. lipid-soluble hormones bind to an intracellular receptor and this hormone-receptor complex binds to DNA
Most water-soluble signals
bind to plasma membrane proteins, initiating signal-transduction
pathways. In contrast, the lipid-soluble hormones enter target cells and
bind with intracellular receptors; the hormone-receptor complexes act
as transcription factors, thus altering gene expression.
Oxytocin secretion and milk release from the mammary glands of lactating female mammals are initiated by _____.
the physical sensation of the baby sucking at the nipple
The milk-release response
system was given as an example of a neuroendocrine pathway with positive
feedback leading to milk release from the nursing mother to the sucking
baby. The "neuro" part includes the baby's activation of the mother's
mechanoreceptor neurons in the breast
The counter-regulatory functions of the pancreas refer to the fact that it _____.
releases one hormone that reduces glucose levels in the blood and another that increases them
hormones and their actions are insulin, which decreases glucose levels
in the blood, and glucagon, which increases glucose levels in the blood.
This disorder typically arises prior to puberty and is generally
treated by injections of the hormone missing from the affected
individual's bloodstream. Type I diabetes mellitus
Type I diabetes mellitus is
also known as childhood-onset diabetes. Hypoactivity of the pancreas'
secretion of insulin disturbs the homeostasis of glucose levels in the
blood, and these are corrected by administering injections of insulin.
Homeostasis (video) The
body's tendency to maintain relatively constant internal conditions.
ex: The sugary snack you devour enters your digestive system & is
broken down to simple sugars like glucose. Glucose enters the
bloodstream, causing an increase in blood glucose levels. But various
mechanisms bring blood glucose back down to its normal level, the set
insulin(video) negative feedback maintaining homeostasis key: B-blood G-glucose Ins-insulin BG-blood glucose Hormones
produced by the pancreas regulate BG levels. When BG levels are high, G
molecules leave the B & enter the beta cells in the pancreas. The
beta cells respond by releasing Ins, which enters the bloodstream &
is transported to cells all over the body. In the liver; Ins binds to
receptors on liver cells, causing the cells to take in more G. In liver
cells, G is converted to glycogen, & BG levels decrease as G is
taken up by liver cells & other body cells resulting in less Ins
release by the pancreas.
Glucagon-what happens if you skip lunch and BG levels are low? key; BG- blood glucose G- glucose When
BG levels are low, alpha cells in the pancreas release
glucagon(hormone), which enters the bloodstream & acts on target
cells in the liver. Glucagon binds to receptors on the liver cells,
signaling the liver cells to break glycogen down to G. G is released
& BG levels increase, resulting in less glucagon release by the
pancreas, & BG levels stabilize at their set point. 2 hormone w/
opposing effects allow the body to maintain homeostasis of BG levels
Diabetes(video)key; BG- blood glucose the
body is unable to maintain homeostasis of BG levels. Type I, the beta
cells of the pancreas are destroyed by the immune system, & so no
insulin is produced. Type II, the pancreas produces insulin but target
cells do not take up glucose. In both types, when BG levels rise, cells
do not take up the additional glucose, & so BG remains high.
Maintaining homeostasis-animals body maintains in a similar way as a thermostat This heating system maintains room temperature at or near a particular value, known as the set point. You open the window, a blast of icy air enters the room. The temp drops to 17 degrees Celsius, which acts as a stimulus to the heating system. The thermostat is a sensor that detects the stimulus & triggers a response The heater turns on, and the temp in the room increases until it returns to the original setting. The response of the heating system reduces the stimulus. This is an example of negative feedback. The maintenance of a relatively constant internal environment is known as homeostasis.
Insulin and glucose act together to maintain homeostasis of blood glucose levels When
blood glucose levels rise, insulin is released. Insulin causes the
liver to take up glucose and convert it to glycogen. Insulin also causes
most cells in the body to take up glucose. As a result, blood glucose
returns to its normal range. When blood glucose levels fall,
glucagon is released. Glucagon causes the liver to break down glycogen
and release glucose into the blood. As a result, blood glucose returns
to its normal range.
In people with Diabetes mellitus, the body is unable to maintain homeostasis of blood glucose In
type 1 diabetes, the immune system destroys most of the beta cells of
the pancreas. Little or no insulin is produced. As a result, blood
glucose levels remain elevated for a longer period than in healthy
individuals. In type 2 diabetes, the pancreas produces
sufficient insulin. However, the body's target cells do not respond to
insulin effectively. As a result, blood glucose levels remain elevated
for a longer period than in healthy individuals. Because glucose levels
remain high, the pancreas continues to release insulin -- this is why
insulin levels are also higher than in healthy individuals. Chronic
disruption of glucose homeostasis has serious effects, particularly for
the heart, blood vessels, kidneys, and eyes. In the U.S., diabetes is a
major cause of blindness and the seventh most common cause of death.
Which of these glands secretes releasing hormones? hypothalamus The hypothalamus secretes both releasing and inhibiting hormones.
Which of these hormones are responsible for the "fight or flight" response to danger? epinephrine and norepinephrine These hormones, secreted by the adrenal medulla,
are responsible for the "fight or flight" response.
Adrenocorticotropic hormone (ACTH) triggers the release of _____ in response to stress. glucocorticoids
In response to stress, ACTH stimulates the adrenal
cortex to secrete glucocorticoids.
_____ are the main male hormones. Androgens Androgens, such as testosterone, are the main male hormones.
What hormone promotes water retention by the kidneys? antidiuretic hormone (ADH) A diuretic promotes water loss; thus it makes sense
that ADH (secreted by the anterior pituitary) promotes water
Which hormone opposes the action of parathyroid hormone? calcitonin
Parathyroid hormone increases blood calcium levels;
calcitonin lowers blood calcium levels.
Which hormone stimulates hormone production by the ovaries and testes? luteinizing hormone (LH) LH stimulates hormone production by both the ovaries and testes.
Which hormone stimulates milk production? prolactin
Prolactin, secreted by the
anterior pituitary, stimulates milk production by the mammary glands.
True or false? The homeostatic system for blood calcium concentration
is maintained by the hormones calcitonin and parathyroid hormone.True
Which of the following statements about the pituitary gland is false? Neurosecretory cells produce
hormones that are stored in the anterior pituitary.This statement is false; neurosecretory cells produce hormones that are stored in the posterior pituitary.
True statements about the pituitary gland It
produces hormones that control the menstrual cycle. The anterior
pituitary is connected to the hypothalamus by blood vessels The
posterior portion is an extension of the hypothalamus.
True or false? The pancreas is responsible for producing hormones that
maintain the homeostatic levels of glucose in the blood. True
The pancreas produces two hormones, insulin and
glucagon, which work together to maintain the homeostatic levels of
glucose in the blood.
How is the production of hormones such as thyroxine and estrogen regulated? The
hypothalamus directs the anterior pituitary to produce hormones that
then stimulate or inhibit the production of these hormones.
The hypothalamus directs the anterior pituitary to produce
hormones that regulate other hormones in a variety of endocrine organs,
including the thyroid gland and ovaries.
Which of the following statements about endocrine glands and the hormones they produce is true? Aldosterone produced by the adrenal glands controls the reabsorption of sodium ions by the kidneys. The adrenal glands sit atop the kidneys and
secrete a variety of hormones, including aldosterone, which controls the
reabsorption of sodium ions by the kidneys.
Gigantism, a condition characterized by exceptionally rapid growth, is
sometimes caused by a tumor that induces the gland in which it develops
to overproduce a certain hormone. Where would such a tumor be expected
to grow? Pituitary
gland Since the anterior
pituitary produces growth hormone (GH), which has growth-stimulating
effects throughout the body, a tumor of the anterior pituitary could
is an extension of the hypothalamus posterior pituitary
synthesizes oxytocin and ADH hypothalamus
(PRL) is an anterior pituitary hormone; as one of its many functions,
PRL stimulates milk production in mammals. PRL is unusual in that it is
generally under negative control by the hypothalamus, with hypothalamic
dopamine inhibiting the release of PRL when there are no suckling young.
lactating mammals (those with nursing young),suckling (the stimulus)
initiates nerves impulses that travel to the hypothalamus;the
hypothalamus releases releasing hormones, including TRH;TRH, in addition
to other functions, stimulates the anterior pituitary to release
PRL;PRL travels in blood vessels to receptors in the mammary glands and
triggers milk production (the response).
Jet lag occurs when a person moves rapidly from one time zone to
another, causing conflict between the body's biological rhythm and the
new cycle of light and dark. Some scientists suspect that jet lag may
result from disruption of the daily cycle of secretion of the hormone
known as _____. melatonin
Melatonin is produced by
the pineal gland, but only at night; its production is regulated to some
extent by day length.
How does the adrenal gland respond to stress? The adrenal medulla secretes epinephrine and norepinephrine in response to short-term stress.
A major activity of these
catecholamines secreted by the adrenal medulla is to increase the amount
of chemical energy available for immediate use.