Bio Chapter 45

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Which type of hormone is lipid soluble?

Steroids

Which molecules determine the tissue specificity of hormones?

Receptors

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 producing second messengers.
They bind to receptors on the plasma membrane.
They act by affecting the transcription of genes.
They bind to DNA as soon as they enter a cell.

They 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?
Enhancer.
Promoter.
Zinc finger.
Hormone-response element (HRE).

Zinc finger; A zinc finger is a distinctive DNA-binding domain on some hormone receptors that is exposed when hormone-receptor complexes are formed.

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 transduction pathway.

True 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

Which of these is a nonsteroid hormone?
estrogen
testosterone
both estrogen and testosterone
oxytocin
epinephrine and oxytocin

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

Which of these extracellular signal molecules could diffuse through a plasma membrane and bind to an intracellular receptor?
estrogen
epinephrine
cellulose
oxytocin
starch

Estrogen

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; they effect 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 its secretion.

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.

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; The counter-regulatory 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.

What is the function of endocrine glands?

They release hormones into the bloodstream for distribution around the body

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?
It produces hormones that control the menstrual cycle.
The posterior portion is an extension of the hypothalamus.
The anterior pituitary is connected to the hypothalamus by blood vessels
Neurosecretory cells produce hormones that are stored in the anterior pituitary.

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 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.

What is true about endocrine glands and the hormones they produce?

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

Which of these glands secretes releasing hormones?
hypothalamus
adrenal cortex
thymus
ovaries
testes

Hypothalamus; The hypothalamus secretes both releasing and inhibiting hormones

Which of these hormones are responsible for the "fight or flight" response to danger?
insulin and glucagon
thyroxine and calcitonin
androgens and estrogens
antidiuretic hormone (ADH) and oxytocin
epinephrine and norepinephrine

E and NRE

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 (testosterone)

What hormone promotes water retention by the kidneys?

Antidiuretic hormone (ADH)

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)

Which hormone stimulates milk production?

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

Steroid and peptide hormones typically have in common

their requirement for travel through the bloodstream.

Shortly after ingesting a big plate of carbohydrate-rich pasta, you measure your blood’s hormone levels. What results would you expect, compared to before the meal?

High insulin, low glucagon

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