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Question 0

Osteoclasts

Answer 0

Large, multinucleated cells that breakdown/resorb calcium from previously formed bone by secreting hydrogen ions (dissolve the crystals) and hydrolytic enzymes (digest the osteoid).

Question 1

Osteoid

Answer 1

A collagen matrix in bone upon which minerals such as calcium and hydroxyapatite are deposited.

Question 2

Parathyroid Hormone (PTH)

Answer 2

Produced in the parathyroid glands.
The amount of PTH produced is directly related to calcium concentration. More is released when there is less calcium.
Actuating signal in calcium control

Question 3

PTH Actions

Answer 3

Increases resorption of bone by osteoclasts.
Stimulates formation of 1,25 dihydroxyvitamin D in the kidney.
Increases calcium reabsorption in the kidneys
Decreases the reabsorption of phosphate ions in the kidney.

Question 4

1,25-dihydroxyvitamin D (1,25-(OH)2D)

Answer 4

Active hormonal form of vitamin D.
Stimulates calcium absorption in the intestines.
Lipid soluble

Question 5

Calcitonin

Answer 5

Peptide hormone secreted by parafollicular cells in the thyroid.
Lowers calcium concentrations by inhibiting osteoclasts.
Stimulated by increased calcium concentrations.

Question 6

Rickets/osteomalacia

Answer 6

Conditions in which mineralization of the bone matrix is deficient. This causes the bones to be soft and break easily.
Often caused by a vitamin D deficiency.

Question 7

Osteoporosis

Answer 7

Disease where both the matrix and minerals in bone are lost due to an imbalance between resorption and formation.

Question 8

Primary hyperparathyroidism

Answer 8

Causes hypercalcemia.

Caused by a tumor on the parathyroid which secretes excess PTH.

Question 9

Humoral hypercalcemia of malignancy

Answer 9

Some malignant rumors release a PTH related peptide which is structurally similar to PTH and therefore has the same effects.

Question 10

Calcium sensing receptor (CaSR)

Answer 10

G couples receptor

Located in the plasma membrane of the parathyroid. Binds to calcium and lowers the release of PTH.

Question 11

Vitamin D receptor (VDR)

Answer 11

Nuclear receptor.

Question 12

Calcium steady state

Answer 12

Greater than zero. This allows control of calcium in both directions. If it was zero there could be no change when levels drop.

Question 13

Anagonist

Answer 13

Molecule that activates a receptor by binding to it.

Question 14

Antagonist

Answer 14

Molecule that does not activate the receptor when it binds.

Question 15

Positive Feedback

Answer 15

The goal is amplification.
Normally embedded in a larger system.
Can be unstable.

Question 16

Threshold

Answer 16

At threshold you will go to plateau.

Question 17

Oxytocin

Answer 17

Hormone peptide

Actuating signal in labor.

Question 18

Control variable

Answer 18

A system variable that is measured and controlled by a feedback loop.

Question 19

Comparator

Answer 19

Compares input variable to the set point. Creates the error signal and the actuating signal. Only in a negative feedback loop

Question 20

Effector

Answer 20

Changes the amount of a control variable present based on the actuating signal received from the comparator/controller.

Question 21

Actuating signal

Answer 21

Goes to the effector to cause a change in the control variable.
This is never zero so that the loop can also decrease levels

Question 22

Plateau

Answer 22

The maximum level of output variable in a positive feedback system.

Question 23

Mechanoreceptors

Answer 23

Neurons sensitive to force.