The hormone epinephrine causes opposite effects in two populations of target cells because _____.
A. epinephrine can only reach target cells in adipose tissue, as it is fat-solubleepinephrine activates biochemical pathways in one set of target cells but works only by changing gene expression in the other set of target cells
B. the chemical form of epinephrine released by neurons is different from the epinephrine released by endocrine cells
C. epinephrine crosses the membrane on one set of target cells but binds to membrane-bound receptors in the other set of target cells
D. each set of target cells has different receptor-transduction mechanisms
D. 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 its secretion.
Steroid and peptide hormones typically have in common _____.
A. their requirement for travel through the bloodstream
B. the building blocks from which they are synthesized
C. their reliance on signal transduction in the cell
D. their solubility in cell membranes
A. their requirement for travel through the bloodstream
Calculate the volume of blood moved per minute by a heart at rest.
A heart "at rest" beats at a rate of 72 beats per minute
and moves 70 milliliters (mL) of blood per beat.
When the heart is stimulated by epinephrine (the fight or flight
hormone), the heart rate doubles and the volume of blood moved per
beat triples.
The total volume of blood moved in one minute by a resting heart = the number of beats in a minute x the volume of blood moved per beat
72 beats/1 min X 70 beats/1 min = 5040 mL/min
Calculate the volume of blood moved per minute by a heart that has been stimulated by epinephrine.
The heart rate at rest is 72 beats per minute. Stimulation with
epinephrine doubles the heart rate to 144 beats per minute. The blood
volume moved per beat at rest is 70 mL. Stimulation with epinephrine
triples the volume moved per beat to 210 mL.
The total volume moved per minute when the heart is stimulated is:
144 beats/1 min X 210 mL/1 min = 30240 mL/min
How much more blood does the heart move in a minute when stimulated compared to at rest?
At rest, 5040 mL of blood is moved per minute. When the heart is stimulated, 30240 mL of blood is moved per minute. To calculate how much more blood is moved per minute during stimulation:
30240 - 5040 = 25200 mL
What is the percent increase in blood flow due to stimulation?
To find the percent increase, compare the increase to the value at rest:
25200/5040 = 5 = 5.00 = 500%
A 500% increase means that 5 times more blood is pumped when the heart is stimulated by epinephrine than when it is at rest.
Receptors for nonsteroid hormones are located in _____.
A. the extracellular fluid
B. the cytoplasmthe nucleus
C. the cytosol
D. association with a cell's plasma membrane
D. 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?
A. estrogen
B. testosterone
C. both estrogen and testosterone
D. oxytocin
E. epinephrine and oxytocin
E. epinephrine and oxytocin
Both epinephrine and oxytocin are nonsteroid hormones.
How do nonsteroid hormones differ from steroid hormones?
A. nonsteroid hormones bind to a cell's DNA; steroid hormones do not bind to a cell's DNA
B. nonsteroid hormones act via signal transduction pathways; steroid hormones do not act via signal transduction pathways
C. the action of nonsteroid hormones never affects gene expression; the action of steroid hormones always affects gene expression
D. nonsteroid hormones bind to cytoplasmic receptors; steroid hormones bind to plasma membrane receptors
E. nonsteroid hormones are fat-soluble; steroid hormones are water-soluble
B. 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?
A. estrogen
B. epinephrine
C. cellulose
D. oxytocin
E. starch
A. 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 _____.
A. they are produced at very low concentrations
B. acting via a signal transduction pathway makes for slower responses than does directly interacting with a cell's DNA
C. they are too large to enter a cell and therefore must first bind to a plasma membrane receptor before having an effect on a cell
D. target cells tend to ignore steroid hormones in favor of nonsteroid hormones
E. they turn genes on or off and it takes time for gene products to build up or become depleted
E. they turn genes on or off and it takes time for gene products to build up or become depleted
This is the primary reason that steroid hormones usually act slowly.
Steroid hormone-receptor complexes act in _____.
A. the nucleus
B. lysosomes
C. vesicles
D. the cytoplasm
E. the plasma membrane
A. the nucleus
Steroid hormone-receptor complexes bind to DNA, where they affect transcription.
What property of steroid hormones allows them to cross the phospholipid bilayer?
A. Steroid hormones can act in very small concentrations and very few molecules of steroids need to cross the lipid bilayer.
B. Steroid hormones are lipid soluble and easily cross the phospholipid bilayer.
C. Steroid hormones act on cells close to where they were produced and very few molecules are required to travel such a short distance to cross the lipid bilayer.
D. Steroid hormones act on the same cells in which they are produced and, therefore, are within the cell they are acting upon.
B. Steroid hormones are lipid soluble and easily cross the phospholipid bilayer.
Growth factors are local regulators that _____.
A. bind to cell-surface receptors and stimulate growth and development of target cells
B. convey messages between nerve cells
C. are found on the surface of cancer cells and stimulate abnormal cell division
D. are modified fatty acids that stimulate bone and cartilage growth
A. bind to cell-surface receptors and stimulate growth and development of target cells
Different body cells can respond differently to the same peptide hormones because _____.
A. different target cells have different sets of genes
B. the hormone is chemically altered in different ways as it travels through the circulatory system
C. the circulatory system regulates responses to hormones by routing the hormones to specific targets
D. a target cell's response is determined by the components of its signal transduction pathways
D. a target cell's response is determined by the components of its signal transduction pathways
Maintaining homeostasis
An animal’s body maintains a relatively constant internal environment. How is this accomplished? It is surprisingly similar to the way a thermostat and heating system maintain a relatively constant temperature inside a room.
Drag the terms on the left to the appropriate blanks on the right to complete the sentences. Not all terms will be used.
The maintenance of a relatively constant internal environment is known as homeostasis. To achieve homeostasis, the body has a wide variety of sensors that detect and trigger responses to different stimuli.
Negative feedback, in which the body’s response reduces the stimulus, is an important mechanism for maintaining homeostasis.
Controlling blood glucose levels
In the animation, you saw that both high blood glucose levels and low blood glucose levels are stimuli that trigger specific responses by the body. These responses cause blood glucose levels to return to their normal range. In this activity, you will explore how this happens. Drag the labels to their appropriate locations on the diagram.
Insulin and glucagon 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.
Diabetes: Disrupting blood glucose homeostasis
In the disorder diabetes mellitus, the body is unable to maintain homeostasis of blood glucose. There are two major types of diabetes, type 1 and type 2.
The graphs below show blood levels of glucose and insulin in three patients after each has consumed a sugary soft drink. Use the graphs to identify which patient is healthy, which has type 1 diabetes, and which has type 2 diabetes.
Drag the labels to their appropriate locations above the graphs.
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.
When the beta cells of the pancreas release insulin into the blood, _____.
A. the skeletal muscles and the adipose cells take up glucose at a faster rate
B. the kidneys begin gluconeogenesis
C. the alpha cells of the pancreas release glucose into the blood
D. the liver catabolizes glycogen
A. the skeletal muscles and the adipose cells take up glucose at a faster rate
Oxytocin secretion and milk release from the mammary glands of lactating female mammals are initiated by _____.
A. estrogens from the ovaries
B. a hormone released by the anterior pituitary gland in response to the smell of the baby
C. the physical sensation of the baby sucking at the nipple
D. the secretion of the pancreatic hormone called glucagon
E. the level of fullness in the breast, based on the rate of milk synthesis
C. 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 anterior and posterior lobes of the pituitary differ in that _____.
A. the anterior lobe of the pituitary is nervous tissue that connects directly to the brain whereas the posterior pituitary is derived from non-neural tissues
B. the posterior lobe of the pituitary operates independently of the brain whereas the anterior lobe is directly dependent on brain activity
C. many anterior pituitary hormones regulate other endocrine glands whereas posterior pituitary hormones regulate nonendocrine tissues
D. the posterior pituitary gland synthesizes oxytocin and antidiuretic hormone whereas the anterior lobe receives all of its hormone products in the blood
E. the anterior lobe of the pituitary receives neuronal impulses from brain cells whereas the posterior lobe receives blood-borne hormones
C. many anterior pituitary hormones regulate other endocrine glands whereas posterior pituitary hormones regulate nonendocrine tissues
Anterior pituitary hormones FSH and LH (ovaries and testes), TSH (thyroid), and ACTH (adrenal cortex) stimulate endocrine glands; posterior pituitary hormones ADH (kidney tubules) and oxytocin (mammary glands, uterine tissues, brain) regulate nonendocrine tissues.
Hormones secreted by the posterior pituitary gland are made in the _____.
A. hypothalamus
B. medulla oblongata
C. cerebellum
D. thalamus
A. hypothalamus
Injury localized to the hypothalamus would most likely disrupt _____.
A. executive functions, such as decision making
B. short-term memory
C. coordination during locomotion
D. regulation of body temperature
D. regulation of body temperature
Portal blood vessels connect two capillary beds found in the _____.
A. hypothalamus and thalamus
B. posterior pituitary and thyroid gland
C. anterior pituitary and posterior pituitary
D. hypothalamus and anterior pituitary
D. hypothalamus and anterior pituitary
The body's reaction to PTH (parathyroid hormone), raising plasma levels of calcium, can be opposed by _____.
A. calcitonin
B. growth hormone
C. epinephrine
D. thyroxine
A. calcitonin
DES is called an "endocrine disrupting chemical" because it structurally resembles, and interferes with, the endocrine secretions of the _____.
A. hypothalamus
B. thyroid gland
C. adrenal medulla
D. ovaries
D. ovaries
Of the following types of molecules, which can function as both neurotransmitters and hormones?
A. second messengers
B. glucocorticoids
C. adipocytes
D. catecholamines
D. catecholamines
Which of these glands secretes releasing hormones?
A. hypothalamus
B. adrenal cortex
C. thymus
D. ovaries
E. testes
A. hypothalamus
The hypothalamus secretes both releasing and inhibiting hormones.
Which of these hormones are responsible for the "fight or flight" response to danger?
A. insulin and glucagon
B. thyroxine and calcitonin
C. androgens and estrogens
D. antidiuretic hormone (ADH) and oxytocin
E. epinephrine and norepinephrine
E. 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.
A. melatonin
B. insulin
C. glucocorticoids
D. thymosin
E. parathyroid hormone
In response to stress, ACTH stimulates the adrenal cortex to secrete glucocorticoids.
C. glucocorticoids
_____ are the main male hormones.
A. Progesterones
B. Mineralocorticoids
C. Androgens
D. Luteinizing hormones
E. Estrogens
C. Androgens
Androgens, such as testosterone, are the main male hormones.
What hormone promotes water retention by the kidneys?
A. follicle-stimulating hormone (FSH)
B. prolactin
C. antidiuretic hormone (ADH)
D. melatonin
E. glucagon
C. antidiuretic hormone (ADH)
A diuretic promotes water loss; thus it makes sense that ADH (secreted by the anterior pituitary) promotes water conservation.
Which hormone opposes the action of parathyroid hormone?
A. calcitonin
B. insulin
C. thyroxine
D. thymosin
E. glucagon
A. calcitonin
Parathyroid hormone increases blood calcium levels; calcitonin lowers blood calcium levels.
Which hormone stimulates hormone production by the ovaries and testes?
A. progesterone
B. testosterone
C. glucocorticoids
D. luteinizing hormone (LH)
E. estrogens
D. luteinizing hormone (LH)
LH stimulates hormone production by both the ovaries and testes.
Which hormone stimulates milk production?
A. parathyroid hormone
B. mineralocorticoids
C. prolactin
D. thyroid-stimulating hormone (TSH)
E. thymosin
C. prolactin
Prolactin, secreted by the anterior pituitary, stimulates milk production by the mammary glands.
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 _____.
A. insulin
B. prolactin
C. estrogen
D. melatonin
E. epinephrine
D. melatonin
Melatonin is produced by the pineal gland, but only at night; its production is regulated to some extent by day length.
People with type II diabetes mellitus have defective insulin receptors that cannot respond to insulin properly. Relative to normal individuals, what would be the effect on blood glucose levels under conditions of chronic stress that kept blood cortisol levels high? There would be _____.
A. less decrease in blood glucose levels in individuals with type II diabetes mellitus than in normal individuals
B. a greater increase in blood glucose levels in individuals with type II diabetes mellitus than in normal individuals
C. be a greater decrease in blood glucose levels in individuals with type II diabetes mellitus than in normal individuals
D. less increase in blood glucose levels in individuals with type II diabetes mellitus than in normal individuals
B. a greater increase in blood glucose levels in individuals with type II diabetes mellitus than in normal individuals
A disease that destroys the adrenal cortex should lead to an increase in the plasma levels of _____.
A. glucocorticoid hormones
B. acetylcholine
C. adrenocorticotropic hormone (ACTH)
D. epinephrine
C. adrenocorticotropic hormone (ACTH)
In an experiment, rats' ovaries were removed immediately after impregnation and then the rats were divided into two groups. Treatments and results are summarized in the table above. The results most likely occurred because progesterone exerts an effect on the _____.
A. gestation period of rats
B. metabolism of the uterus
C. general health of the rat
D. number of eggs fertilized
B. metabolism of the uterus
Vertebrates have two major communication and control systems: the endocrine system and the nervous system. Choose the correct statement describing the coordination of these systems.
A. Epinephrine functions as a hormone in the endocrine system and as a neurotransmitter in the nervous system.
B. The parathryroid gland is a fused endocrine and neuroendocrine gland.
C. The adrenal cortex secretes hormones in response to nervous stimulation.
A. Epinephrine functions as a hormone in the endocrine system and as a neurotransmitter in the nervous system.
The same is true of norepinephrine. Read about adrenal hormones.
Glucose homeostasis is maintained by two antagonistic hormones, insulin and glucagon. Select the correct statement about these hormones.
A. Each of these hormones operates in a simple neuroendocrine pathway.
B. Each of these hormones operates in a simple endocrine pathway.
C. The two hormones interact in a hormone cascade pathway.
C. The two hormones interact in a hormone cascade pathway.
Read about simple hormone pathways and control of blood glucose.