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Where is the hormone melatonin produced?
Melatonin is produced in the pineal gland which is a gland in the brain responsible for the body’s circadian rhythms and sleep/wake cycle. The concentration of melatonin peaks at night and causes us to fall asleep. Melatonin is degraded while we sleep so that when we wake up in the morning we start to produce it again throughout the day.
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The pancreas is responsible for regulating blood sugar levels through the release of insulin and glucagon. In Type I Diabetic individuals the body has high blood sugar due to the inability to produce insulin, which is responsible for lowering blood sugar. In an individual with Type II Diabetes the body produces insulin, however, the receptors have become insensitive to the presence of insulin. What effect will injecting additional insulin have in an individual with Type II Diabetes?
Because insulin receptors have been desensitized to insulin, the addition of more insulin will not have any effect. This is why Type II Diabetes is much more difficult to treat than Type I. The recommended course of action for individuals with Type II diabetes is to eat healthy and exercise.
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Which of the following is produced by the pituitary gland?
The hormones secreted by the pituitary gland are FLAT PEG: Follicle-stimulating hormone, luteinizing hormone, adrenocorticotropic hormone, thyroid-stimulating hormone, prolactin, endorphins, and growth hormone. Testosterone is produced in the testes in males, and in the adrenal gland in both males and females. Insulin is produced by the pancreas. Estrogen is produced by the ovaries in females, and in the adrenal gland in both males and females.
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While walking home from class one afternoon, you take a shortcut that leads you in front of a house that is guarded by a huge, barking dog. Unfortunately, you are terrified of dogs! Though the dog is unable to escape its yard, as you walk past you notice yourself breathing more quickly than normal and you can feel your heart racing and your palms sweating. Which of your glands is most likely responsible for your physiological reaction to the dog?
The adrenal gland is almost certainly responsible for your reaction, as this gland contains the adrenal medulla, which is capable of releasing epinephrine. During stressful situations, the sympathetic nervous system triggers the fight-or-flight response. During this response, sympathetic nerves stimulate the adrenal medulla, which then releases epinephrine. Epinephrine raises blood sugar levels and increases blood pressure, brain oxygen consumption, and heart rate. It prepares an individual to either fight a threat (such as a dog), or run away from it.
The anterior pituitary is capable of releasing a number of hormones including growth hormone, thyroid-stimulating hormone, and prolactin.
The pineal gland is involved in biorhythms and sleep patterns.
The adrenal cortex is stimulated by adrenocorticotropic hormone and releases corticosteroids in response to long-term stress, such as sleep or food deprivation.
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Which of the following hormones is not released by the anterior pituitary gland?
The anterior pituitary is responsible for releasing a large number of hormones; however, oxytocin is released by the posterior pituitary. Two of oxytocin's most important functions include stimulating uterus contractions and stimulating milk production by the mammary glands.
Prolactin stimulates milk release from the mammary glands.
Thyroid-stimulating hormone stimulates the release of hormones from the thyroid gland.
Growth hormone stimulates the growth of bones and stimulates the liver to release insulin-like growth factors.
It is important to note that at least one hormone from the hypothalamus is used to regulate each of the hormones released by the anterior pituitary—for example, the anterior pituitary gland will only release prolactin if the hypothalamus releases prolactin-releasing hormone.
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Chemical messengers released in the blood to stimulate or inhibit the function of another organs are known as __________.
A hormone is a chemical formed in one organ and carried by the blood to stimulate or inhibit the function of another organ.
Enzymes are protein molecules that carry out catalytic functions. Electrolytes are simply ions dissolved in solution. Second messengers are relay molecules between a signal and its ultimate effect, such as the molecules that carry signals from the cell membrane to the nucleus to affect transcription. Platelets are cell fragments in the blood that help form clots to heal injuries.
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Which of the following is not true of hormones?
Hormones are generally slow acting, spread throughout the body by the blood, and can affect a variety of tissues at once. Neurotransmitters on the other hand, are quick acting, localized, and affect only a specific cell. We would not expect hormones to affect only one cell or tissue at a time, as their wide distribution allows them to have multiple target areas.
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How do steroid hormones elicit a response from their target cells?
Steroids are nonpolar, which means that they are able to pass easily through cell membranes, but require a transport protein through the hydrophilic blood in order to do so. The steroid hormone then enters the nucleus and attaches to the DNA in order to increase the desired product at the level of transcription.
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Parathyroid hormone (PTH) is a peptide hormone responsible for increasing the concentration of calcium in the blood. This is accomplished by stimulating the activity of osteoclasts and removing calcium from the bones.
If a person has low blood calcium levels, what would you expect the level of PTH to be in the body?
A critical concept to understand about hormones in the body is negative feedback. Remember that hormones are not causing the body's condition, but rather, are responding to the body's condition. As a result, parathyroid hormone would be higher than normal in order to increase the concentration of calcium currently in the blood, correcting the existing deficiency.
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Which of these hormones is responsible for the secretion of testosterone in males?
Luteinizing hormone is responsible for the secretion of testosterone from leydig cells in the testes.
FSH is responsible for the proliferation of sertoli cells, which nurture sperm cell precursors. hGH is responsible for body growth, and is not responsible for testosterone formation. Oxytocin is responsible for increasing uterine contractions during pregnancy.
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__________ is released in response to low blood sugar levels, while __________ is released in response to high blood sugar levels.
Insulin is responsible for lowering blood sugar levels, and is therefore released when the body's blood sugar levels are too high. Glucagon is released in response to low blood sugar levels, and acts to increase sugar concentrations.
Thyroid hormones (T3 and T4) are released to increase the body's metabolic rate, but are not directly influenced by blood sugar levels.
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Which of these hormones stimulates secretion of cortisol?
Cortisol is a hormone secreted by the adrenal cortex. The adrenal cortex is first stimulated by adrenocorticotropic hormone, which is secreted from the anterior pituitary gland.
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Obesity can sometimes be caused by the slowing of the thyroid gland's production of thyroid hormones III and IV (T3 and T4), a condition known as hypothyroidism. Conversely, hyperthyroidism occurs when the thyroid overproduces T3 and T4. If T3 and T4 receptors became insensitive to the hormones, what effect would this have on the body?
The question tells us that slowed output of thyroid hormones can lead to obesity. One can safely assume that receptor insensitivity will have a similar effect. In either scenario, the T3 and T4 hormones are unable to elicit the proper response form the body. Similar to individuals with hypothyroidism, individuals with insensitive receptors would show slowed metabolism and increased weight gain.
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__________ is a critical hormone that controls heart rate and constriction of blood vessels. It is crucial in the fight-or-flight response.
Epinephrine, released from the adrenal gland, is important for the fight-or-flight response. During moments of stress, heart rate increases, pupils dilate, and blood vessels constrict in order to prepare for danger. All of this is controlled by epinephrine and norepinephrine, and is part of the sympathetic nervous system.
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__________, released from the __________, is the hormone responsible for controlling lactation in nursing women, as well as triggering labor in pregnant women.
Oxytocin is responsible for lactation in nursing women. When the nipple is stimulated, oxytocin is released from the posterior pituitary to cause lactation. During labor, release of oxytocin causes positive feedback on the hypothalamus, which causes further oxytocin release.
Luteinizing hormone and follicle-stimulating hormone are released from the anterior pituitary and function to regulate the menstrual cycle. Vasopressin is released from the posterior pituitary and helps to regulate blood pressure and water balance.
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Which steroid hormone is responsible for development of the secondary sexual characteristics in males, such as facial hair and deepening of the voice?
Testosterone is well known to be responsible for male secondary sexual characteristics. It also plays a key role in behavior, such as aggression. For example, during mating season in gorillas the testosterone levels in males raise significantly and lead to confrontations between males.
Progesterone and estrogen are responsible for female secondary sexual characteristics, while cortisol plays a role in the body's response to long-term stress.
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The corpus luteum releases progesterone to prevent menstruation from occurring; if an ovum is not fertilized, then menstruation occurs. What happens to progesterone levels if the ovum is not fertilized?
In order for menstruation to occur, progesterone levels must decrease. When fertilization does not occur, the corpus luteum ceases progesterone production, initiating menstruation. The corpus luteum then transitions into the corpus albicans and removed from the ovary in preparation for the new menstrual cycle.
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__________ is the hormone responsible for milk production in female mammals. It is released by the __________.
Prolactin is responsible for the production of milk, while oxytocin is responsible for the ejection of milk. The question asks for the hormone that causes production, so the answer is prolactin. Prolactin is released from the anterior pituitary.
Oxytocin is released from the posterior pituitary and the mammary glands are responsible for releasing milk.
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__________ causes testosterone production in males and triggers ovulation in females.
The hormone described in the question is luteinizing hormone (LH). If fertilization occurs, the LH levels will decrease and human chorionic gonadotropin (hCG) is released from the placenta to simulate LH function.
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A certain molecule is known to signal through an autocrine mechanism. What does this tell us about the hormone's behavior?
To answer this question, you must have an understanding of the differences between endocrine, paracrine, and autocrine functioning. This example, in which a molecule exhibits autocrine behavior, means that a cell releases a hormone that acts on itself. In paracrine signaling, the molecule does not act on the same cell, but does diffuse through tissue to reach nearby target cells. Finally, endocrine signaling refers to hormone molecules that are released and transported through the bloodstream to act on more faraway target cells in distant regions.
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