Chapter 45 Homework

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.

_____ are the main male hormones.

Androgens Androgens, such as testosterone, are the main male hormones

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.

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 produce gigantism.

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.

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.

What is the function of endocrine glands?

They release hormones into the bloodstream for distribution around the body. Endocrine glands release hormones into the bloodstream for distribution to distant cells in the body.

Suppose that a woman had to have part of her thyroid gland surgically removed. She would most likely suffer from a condition known as hypothyroidism due to too little thyroid function. Predict how this woman's hypothyroidism would affect prolactin levels in her body. Which choice describes how surgical hypothyroidism would likely affect prolactin levels?

Thyroid hormones levels decrease, TRH levels increase, and PRL levels increase. Surgical removal of all or part of the thyroid can result in hypothyroidism, or undersecretion of the thyroid hormones T3 and T4. Thyroid hormones have a negative feedback effect on the production of thyroid-releasing hormone (TRH) by the hypothalamus: When T3 and T4 levels decrease, TRH levels increase. TRH has a stimulatory effect on the anterior pituitary's production of both thyroid-stimulating hormone (TSH) and prolactin (PRL). Therefore, when thyroid hormone levels decrease, TRH levels increase, stimulating the secretion of PRL. When hypothyroidism causes an increased level of prolactin in the blood, a condition known as hyperprolactinemia may result. Symptoms can include abnormal menstrual cycles and infertility (in women), sexual dysfunction (in men), and headache (in both women and men). Many types of cells have prolactin receptors, and few patients with hyperprolactinemia produce milk.

True or false? The homeostatic system for blood calcium concentration is maintained by the hormones calcitonin and parathyroid hormone.

True

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.

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 conservation.

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 hormone opposes the action of parathyroid hormone?

calcitonin Parathyroid hormone increases blood calcium levels; calcitonin lowers blood calcium levels.

Hormones are _____.

chemical signals between cells, transported in blood or hemolymph Hormones are secreted into body fluids, usually blood, and communicate developmental and regulatory messages within the body.

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 its secretion.

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.

Which of these is a nonsteroid hormone?

epinephrine and oxytocin

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.

Adrenocorticotropic hormone (ACTH) triggers the release of _____ in response to stress.

glucocorticoids In response to stress, ACTH stimulates the adrenal cortex to secrete glucocorticoids.

Among insects, the metamorphic transition from pupal form to adult form is associated with _____.

high levels of ecdysteroids and reduced levels of juvenile hormone The ecdysteroids are produced by the prothoracic gland and the juvenile hormone is secreted by the corpora allata.

Which of these glands secretes releasing hormones?

hypothalamus The hypothalamus secretes both releasing and inhibiting hormones.

Each of the following phrases describes the structure, function, or regulation of either the hypothalamus, posterior pituitary, or anterior pituitary.

hypothalamus - integrates nervous and endocrine systems; synthesizes oxytocin and ADH (antidiuretic hormone) posterior pituitary - is an extension of the hypothalamus; releases oxytocin and ADH (antidiuretic hormone) anterior pituitary - regulated by hormones released into portal blood vessels; synthesizes and releases TSH [thyroid-stimulating hormone (thyrotropin)]; synthesizes and releases PRL (prolactin) Prolactin (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. In 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).

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.

Which hormone stimulates hormone production by the ovaries and testes?

luteinizing hormone (LH) LH stimulates hormone production by both the ovaries and testes.

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 hormone stimulates milk production?

prolactin Prolactin, secreted by the anterior pituitary, stimulates milk production by the mammary glands.

Steroid hormone-receptor complexes act in _____.

the nucleus Steroid hormone-receptor complexes bind to DNA, where they affect transcription.

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 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 This is the primary reason that steroid hormones usually act slowly.