Biology: Chapter 5

Question 1

Peptide Hormones

Answer 1

-made up of amino acids
-Peptide hormone is considered the first messenger; it binds to the receptor and triggers the transmission of a second signal, known as the second messenger
-Effects of peptide hormones are usually rapid but short-lived because hormones act through second messenger cascades
-Peptides are generally water-soluble meaning that peptide hormones can travel freely in the bloodstream and don’t require carriers

Question 2

Steroid hormones

Answer 2

-usually end in -one, -ol, or -oid
-Derived from nonpolar molecules so can easily cross the cell membrane; their receptors are usually intracellular (in the cytosol) or intranuclear (in the nucleus)
-Upon binding to receptor, steroid hormone-receptor complexes undergo conformational changes; receptor can then bind directly to DNA
-Effects of steroid hormones are slower but longer lived than peptide hormones because steroid hormones participate in gene regulation
-Not water-soluble so they must be carried by proteins in the bloodstream to travel around the body; generally inactive while attached to a carrier protein and must dissociate from the carrier to function

Question 3

Amino-Acid derivative hormones

Answer 3

-derived from one or two amino acids, usually with a few additional modifications
-Less common than peptide and steroid hormones, but include some of the most important hormones discussed including epinephrine, norepinephrine, triiodothyronine, and thyroxine

Question 4

Direct hormones

Answer 4

-secreted and then act directly on a target tissue

Question 5

Tropic hormones

Answer 5

-require an intermediate to act
-usually originate in the brain and anterior pituitary gland, allowing for the coordination of multiple processes within the body

Question 6

Hypothalamus

Answer 6

-The bridge between the nervous system and endocrine systems
-Regulates the pituitary gland through tropic hormones which allows hypothalamus to have organism-wide effect
-Controls the pituitary through paracrine release of hormones into a portal system that directly connects the two organs
-The release of hormones by the hypothalamus is regulated by negative feedback

Question 7

Interactions between hypothalamus and anterior pituitary

Answer 7

–Hypothalamus secretes compounds into the hypophyseal portal system, which is a blood vessel system that directly connects the hypothalamus with the anterior pituitary gland
-Once hormones have been released from the hypothalamus into this portal bloodstream, they travel down the pituitary stalk and bind to receptors in the anterior pituitary, stimulating the release of other hormones
-Each of the tropic hormones then causes the release of another hormone from an endocrine gland that has negative feedback effects

Question 8

Interactions between hypothalamus and posterior pituitary

Answer 8

-doesn’t receive tropic hormones through the hypophyseal portal system
-Neurons in the hypothalamus send their axons down the pituitary stalk directly into the posterior pituitary, which can then release oxytocin and antidiuretic hormone

Question 9

Oxytocin

Answer 9

-received from the hypothalamus and stored here
-stimulates uterine contractions during labor, as well as milk letdown during lactation

Question 10

Antidiuretic hormone

Answer 10

-received from the hypothalamus and stored here
-increases reabsorption of water in the collecting ducts of the kidneys; secreted in response to increased plasma osmolarity or increased concentration of solutes within the blood

Question 11

4 tropic hormones of the anterior pituitary gland

Answer 11

-Follicle-stimulating hormone (FSH)
-Luteinizing hormone (LH)
-Adrenocorticotropic hormone (ACTH)
-Thyroid-stimulating hormone (TSH)

Question 12

3 direct hormones of the anterior pituitary gland

Answer 12

-Prolactin
-Endorphins
-Growth hormone (GH)

Question 13

Thyroid

Answer 13

-Controlled by thyroid-stimulating hormone from the anterior pituitary
-sets basal metabolic rate by releasing triiodothyronine (T3) and thyroxine (T4)
-promotes calcium homeostasis by releasing calcitonin

Question 14

Cacitonin

Answer 14

-decreases plasma calcium levels in three ways: by increasing calcium excretion from the kidneys, by decreasing calcium absorption from the gut, and by increasing storage of calcium in the bone
-High levels of calcium in the blood stimulate secretion from C-cells

Question 15

Parathyroid glands

Answer 15

-four small pea-sized structures that sit on the posterior surface of the thyroid
-Parathyroid hormone (PTH) is produced
-Promotes phosphorus homeostasis by increasing the resorption of phosphate from bone and reducing reabsorption of phosphate in the kidney
-Activates vitamin D

Question 16

Parathyroid hormone (PTH)

Answer 16

-raises blood calcium levels
-Decreases excretion of calcium by the kidneys, increases absorption of calcium in the gut, and increases bone reabsorption
-As levels of plasma calcium rise, PTH secretion is decreased

Question 17

Adrenal cortex

Answer 17

secretes corticosteroids; steroid hormones that can be divided into three functional classes

Question 18

Corticosteroids

Answer 18

steroid hormones that can be divided into three functional classes: Glucocorticoids, Mineralocorticoids, and Cortical sex hormones

Question 19

Glucocorticoids

Answer 19

-regulate glucose levels and affect protein metabolism
-These hormones raise blood glucose by increasing gluconeogenesis and decreasing protein synthesis
-Release is under the control of ACTH

Question 20

Mineralocorticoids

Answer 20

-used in salt and water homeostasis
-Aldosterone increases the sodium reabsorption in the distal convoluted tubule and collecting duct of the nephron, water follows the sodium cations into the bloodstream, increasing blood volume and pressure
-Aldosterone also decreases the reabsorption of potassium and hydrogen ions in these same segments of nephron which promotes their excretion in the urine

Question 21

Cortical Sex Hormones

Answer 21

-androgens and estrogens
-made by adrenal glands

Question 22

Adrenal medulla

Answer 22

-Nestled inside the adrenal cortex
-Responsible for the production of the sympathetic hormones epinephrine and norepinephrine

Question 23

Pineal Gland

Answer 23

-Has both exocrine and endocrine functions
-Exocrine tissues secrete substances directly into ducts; the pancreas produces a number of digestive enzymes
-Located deep within the brain and secretes the hormone melatonin

Question 24

Endocrine

Answer 24

small clusters of hormone-producing cells are grouped together into islets of Langerhans throughout the pancreas

Question 25

3 Types of cells in Islets of Langerhans

Answer 25

-alpha secretes glucagon
-beta secretes insulin
-delta secretes somatostatin