Chapter 23: The Endocrine System

Question 1

What does the adrenal cortex secrete

Answer 1

Aldosterone, glucocorticoids, and sex homones

Question 2

What are the three layers of the Adrenal cortex, and what are their functions

Answer 2

The outer zona glomerulosa secretes only aldosterone, the inner zona reticularis secretes mostly androgens, and the middle zona fasciculata secretes mostly glucocorticoids.

Question 3

What is the main glucocorticoid secreted by the adrenal cortex?

Answer 3

Cortisol

Question 4

What does the adrenal medulla secrete?

Answer 4

catecholamines (epinephrine and norepinephrine)

Question 5

What do all steroid hormones start with

Answer 5

cholesterol

Question 6

What leads to the crossover effect

Answer 6

Steroid hormones have similar structures and binding sites on their receptors. This can lead one steroid to bind to a receptor for a related molecule

Question 7

Explain how the body manages the crossover effect in the renal tubule

Answer 7

Aldosterone and cortisol both bind to MRs. The cells in the renal tubule have an enzyme that converts cortisol to a less active form with low specificity, preventing the cross-over effect.

Question 8

what is the pathway for cortisol secretion called

Answer 8

The hypothalamic-pituitary-adrenal (HPA) pathway

Question 9

What is the HPA pathway

Answer 9

1. hypothalamic corticotropin-releasing hormone (CRH)
2. This is secreted into the hypothalamic-hypophyseal portal system and transported to the anterior pituitary
3. CRH stimulates release of adrenocorticotropic hormone (ACTH) from the anterior pituitary
4. ACTH acts on the adrenal cortex to promote synthesis and release of cortisol
5. Cortisol acts as a negative feedback signal, inhibiting ACTH and CRH secretion

Question 10

What carrier protein carries cortisol

Answer 10

corticosteroif-binding globulin (CBG)

Question 11

What is the most important metabolic effect of cortisol? How does this work?

Answer 11

Helps prevent hypoglycemia. When blood glucose decreases, it leads to the secretion of pancreatic glucagon (promotes glucogen and gluconeogenesis breakdown). Without cortisol, glucagon can’t respond.

Question 12

What are the metabolic effects of cortisol

Answer 12

1. promotes gluconeogenesis (generation of glucose through nutrients)
2. causes the breakdown of skeletal muscle proteins (to provide substrate for gluconeogenesis)
3. enhances lipolysis (same reason as above)
4. supresses the immune system
5. causes negative calcium balence (decreases intestinal Ca2+ absorption and increases renal Ca2+excretion.
6. influences brain function

Question 13

How does cortisol suppress the immune system?

Answer 13

preventing cytokine release and antibody production of WBC. Inhibits inflammatory response by decreasing leukocyte mobility and migration.

Question 14

What is the CRH family involved in

Answer 14

Inflammation, decrease food intake, onset of labor

Question 15

What are the two endocrine cell types in the thyroid gland

Answer 15

C cells- secerte calcitonin
Follicular cells- secerte thyroid hormone

Question 16

Where does the synthesis of thyroid hormones take place

Answer 16

in the thyroid follicles. Hallow section of each follicle is filled with colloid.

Question 17

Why do T3 and T4 have limited solubility in the plasma

Answer 17

they are lipophobic molecules.

Question 18

What are the 3 things that IGFs and GH do to stimulate growth

Answer 18

1. promote protein synthesis
2. increase blood glucose levels
3. Act on the bones to increase bone growth

Question 19

What is required for soft tissue growth

Answer 19

adequate amounts of GH, insulin (by providing glucose), and thyroid hormone (interacts with GH in protein synthesis and nervous tissue development.)

Question 20

What do osteoblasts do

Answer 20

produce enzymes and osteoids

Question 21

what do osteoclasts do

Answer 21

secrete acid that dissolves the calcified matrix

Question 22

How do osteoclasts and osteoblasts lengthen bone

Answer 22

osteoclasts sense damage, and then use acid to breakdown the bone. They die and then osteoblasts start rebuilding

Question 23

Describe the movement of Ca2+ from the lumen of the nephron or intestine to the ECF as active, passive, facilitated diffusion, and so on.

Question 24

What 3 compartments divide your total body Ca2+

Answer 24

1. Extracellular fluid
2. Intracellular CA2+
3. Extracellular matrix (bone)

Question 25

What 3 hormones control calcium balance

Answer 25

Parathyroid hormone (PTH), Calcitriol (vitamin D), Calcitonin

Question 26

What 3 ways do parathyroid hormones raise plasma Ca2+

Answer 26

1. indirectly increasaes intestinal absorption of Ca2+
2. Increases reabsorption of Ca2+ in the renal system
3. mobilizes calcium from bone

Question 27

Is PTH increased or decreased when the Ca2+ hormone is increased?

Answer 27

It decreases

Question 28

When is calcitonin levels increased

Answer 28

when plasma Ca2+ increases