Section 39.4.2 (Exam 4) Hormones

Question 1

Why is regulation of calcium levels in blood critical to body function?

Answer 1

Not enough calcium can lead to a overexcited nervous system (muscle spasms and seizures)

Too much calcium can lead to a depressed nervous system (muscles weaken, including the heart)

Question 2

What mechanisms does our body have for changing blood calcium levels?

Answer 2

Deposition or reabsorption of bone

Excretion or retention of Ca by kidneys

Absorption of Ca from digestive tract

Question 3

Which three hormones control the mechanisms for regulating blood calcium levels?

Answer 3

Calcitonin

Parathyroid hormone (PTH or Parathormone)

Calcitriol

Question 4

How is the bone continuously remodeled?

Answer 4

Osteoclasts break down bone and release Ca into the blood

Osteoblasts take up Ca and deposit it in new bone

Question 5

Describe calcitonin.

Answer 5

released by the thyroid; lowers blood Ca by regulating bone turnover

Question 6

How does calcitonin regulate bone turnover?

Answer 6

Calcitonin decreases the activity of osteoclasts and thus favors removal of calcium from the blood and deposition in bone by osteoblasts

Question 7

Describe parathyroid hormone (PTH).

Answer 7

Secreted by the parathyroid glands to increase blood calcium

Works both on bones and kidneys

Most important hormone in calcium regulation

Question 8

When is PTH synthesized and released?

Answer 8

When blood calcium levels are low

Question 8

How does PTH affect the kidneys?

Answer 8

PTH stimulates the kidneys to reabsorb calcium that is being excreted through the urine

Question 8

Does PTH favor osteoclasts or osteoblasts?

Answer 8

Since PTH functions to increase blood calcium, it favors osteoclasts which break down bone to release calcium into the blood.

Question 9

Describe calcitriol.

Answer 9

In the liver and kidneys, PTH activates conversion of calciferol (Vitamin D) to calcitriol.

Calcitriol functions to absorb calcium from food in the gut.

Question 10

PTH also stimulates the release of phosphate from bone. What are the effects of this?

Answer 10

Small increases in Ca and phosphate in the blood can result in precipitation of calcium phosphate salts

This can result in kidney stones and hardening of arteries (Ca deposits)

Question 11

How does PTH counter the negative effects of too much phosphate released from the bone?

Answer 11

PTH also acts on the kidneys to increase the elimination of phosphate via the urine

Question 12

What is type 1 diabetes?

Answer 12

Diabetes mellitus

Lack of the protein hormone insulin

Question 13

How does insulin enable glucose intake by the cells?

Answer 13

Glucose transporters are controlled by insulin. When insulin binds to cell receptors, the insulin signaling pathway begins, which signals vesicles containing GLUT4-transporters to release the transporters which then move to the cell membrane and facilitate glucose uptake

When insulin is not present, transporters are returned to the cytoplasm, and glucose uptake is inhibited

Question 14

What is adult onset/type 2 diabetes associated with and caused by?

Answer 14

Associated with:
- Obesity
- high carbohydrate consumption
- lack of exercise

Caused by:
- Low production of insulin
- Insensitivity to insulin

Question 15

What are the are the Islets of Langerhans?

Answer 15

Endocrine cells in the pancreas that produce 3 hormones:

Alpha cells produce glucagon

Beta cells produce insulin

Delta cells produce somatostatin

Question 16

What happens if blood glucose falls substantially below normal?

Answer 16

alpha cells release glucagon, which stimulates liver to convert glycogen to glucose

Question 17

What are the paracrine functions of somatostatin?

Answer 17

Inhibits release of both insulin and glucagon

Slows digestive activities to extend the period of nutrient absorption

Question 18

What is the function of hypothalamic somatostatin or growth hormone inhibiting hormone (GHIH)?

Answer 18

Inhibits release of growth hormone and thyrotropin by the anterior pituitary