8. Endocrinology of calcium and phosphate homeostasis

Question 1

What is the significance of calcium phosphate for bones? - 2

Answer 1

1. provides the structural integrity of the bone
2. Ca phosphate is stored in bones and the bone is broken down when its needed for other biochemical processes

Question 2

What are 5 biochemical processes that require Ca ions? - 5

Answer 2

1. neuromusculat excitation
2. blood coagulation (clotting of blood when injured)
3. hormone secretion
4. enzyme activity
5. fertilization

Question 3

T or F - Ca is tightly regulated w/in the body due to how essential it is for metabolism

Answer 3

T

Question 4

a) in what form is Ca stored w/in the body
b) fill in the blanks = Ca__(PO4)__(OH)__

Answer 4

a) hydroxyapatite
b) 10, 6, 2

Question 5

Within soft tissues where is Ca stored? Which one has the least Ca storage? Why? - 3

Answer 5

1. intracellular
2. extracellular - least b/c it is tightly regulated thus is easier to regulate it when its w/in the cell then we it is free floating in the matrix

Question 6

What are the 3 forms that extracellular Ca takes? Assign the following percentages to each.
a) 40%? - 1
b) 50%? - 1
c) 10%? - 2

Answer 6

a) protein-bound
b) ionized (free)
c) combined w/ phosphate + citrate

Question 7

What are the 3 types of membranes that cellular Ca are associated w/? - 3

Answer 7

1. mitochondria
2. plasma mem (mem of the whole cell)
3. endoplasmic reticulum

Question 8

T or F - Ca is essential for life thus in order to keep it properly regulated it is only stored intracellularly until its needed

Answer 8

F - extracellular Ca does exist but it is still tightly regulated

Question 9

Total body Ca is maintained by the following. Explain each.
a) intake
b) output

Answer 9

a) diet = is absorbed via the small intestines which is regulated by hormones
b) kidneys = the Ca that is not used up is sent to the kidneys where it is urinated out

Question 10

T or F - while the body is able to produce Ca it is not very efficient at it thus is it better to get it from ones diet

Answer 10

F - body cannot produce Ca

Question 11

a) where is Ca mainly stored? - 1
b) how does it get there? - 2
c) how is Ca produced? - 2
d) Where does it go if its not being used? - 2

Answer 11

a) bones
b) using the ECF (extracellular fluid) or plasma
c) absorption through diet via small intestines
d) kidneys where its filtered out through urine

Question 12

If you are deficient in Ca where are the 2 places that it will be pulled out? Which one is the main source? - 3

Answer 12

a) bones or kidney
b) bones

Question 13

Why is there a constant movement of Ca w/in the body? - 2

Answer 13

is meant to distribute the proper ratios of Ca throughout the body in order to keep it stable

Question 14

What are the 3 hormones that regulate the movement of Ca? Which ones are essential for adults? - 5

Answer 14

1. PTH (parathyroid hormone) (sig for adults)
2. vit D3 = calcitriol (sig for adutls)
3. Calcitonin

Question 15

the PTH is very essential for Ca so if you were to remove the thyroid gland what would occur? - 2

Answer 15

it will not necessarily lead to death as long as you keep the parathyroid gland which is the part of the thyroid gland that produces PTH.

Question 16

Match the following parts of the larynx to the colours on this image
a) parathyroid glands
b) thyroid gland
c) trachea

Answer 16

a) green
b) blue
c) yellow

Question 17

What are the 2 cells in the parathyroid? Include their fxns - 4

Answer 17

1. chief cells = produce PTH
2. oxyphils = unkown

Question 18

Ans the following wrt the PTH
a) what tissue/organ produces it? - 1
b) what is its main fxn? - 1

Answer 18

a) the parathyroid gland
b) it raises Ca in the blood when plasma Ca levels are low

Question 19

a) What are the 3 mechanisms used to raise Ca in the blood?
b) which one is the primary mech?
c) what hormone raises Ca in blood?

Answer 19

a)
1. stimulate osteoclasts to resorb bone (break down)
2. stimulate kidneys to resorb Ca
3. activate Vit D (stim from kidney) which promotes the absorption of Ca by the intestines
b) 1
c) parathyroid hormone = PTH

Question 20

Describe the following terms wrt calcium phosphate homeostasis via the PTH
a) hypocalcemia - 2
b) hypercalcemia - 2

Answer 20

a) when Ca levels are too low resulting in INC secretion of PTH to bring it back up
b) when Ca levels are too high resulting in DEC secretion of PTH to bring it down

Question 21

What form does calcium take when stored in bone?

Answer 21

hydroxyapatite

Question 22

Describe the following cells wrt storage of Ca in bones
a) osteoblasts
b) osteoclasts

Answer 22

a) builds up Ca in the bones so it can be stored
b) breaks down bone in order to resorb Ca

Question 23

Match the following
a) osteoblasts
b) osteoclasts
1. Hydroxyapatite -> calcium phosphate
2. calcium phosphate -> hydroxyapatite

Answer 23

a) 2
b) 1

Question 24

Describe the 2 ways that stimulating the kidneys results in Ca resorption in the blood - 5

Answer 24

1. the kidney itself contains Ca that would normally be disposed of through urine but can be resorbed b/f that occurs
2. the kidneys produce enzymes that activate vit D3. Vit D promotes absorption in the intestines allowing more absorption of Ca from food/drink

Question 25

Put the following molecules in order wrt how the kidneys promote intestine absorption - 6 a) INC Ca b) 1,25-dihydroxyvitamin D3 c) 25-hydroxyvitamin D3 d) intestinal absorption e) INC 1alph-hydroxylase activity f) DEC ca

Answer 25

f -> e -> c -> b -> d -> a

Question 26

Where is the inactivated form of Vit D3 found in the body? - 1

Answer 26

the liver

Question 27

Put the following in order wrt the production/intake of Vit D3. Describe the 5 steps a) kidney b) fish/meat c) 7-Dehydrocholesterol d) cholecalciferol e) 1,25-dihydroxyvitamin D3 f) 25-hydroxvitamin D3 g) sunlight h) liver

Answer 27

1. our skin absorbs the g converting c -> d also known as vit D3 2. h takes both d + vit D3 from the ingestion of b 3. h convert d -> f 4. the a converts f -> e 5. e maintains the Ca homeostasis

Question 28

T or F - most production of Vit D comes from the ingestion of fish and meat

Answer 28

F - most comes from sunlight hitting the skin

Question 29

Which of the following is the active from of Vit D3 a) 25-hydroxyvitamin D3 b) Cholecalciferol c) 1,25-dihydroxyvitamin D3 d) 7-Dehydrocholesterol

Answer 29

c

Question 30

What are the 2 fxns of Vit D3 - 3

Answer 30

1. promoting intestinal absoption for Ca 2. promoting formation of osteoclasts which resorbs bone (break down)

Question 31

ANS the following wrt calcitonin a) where is it produced? b) what type of Ca levels does it respond to (high/low) c) What is it? d) What is its fxn? e) it appears to play a minor role in humans. How do we know this?

Answer 31

a) parafollicular cells of thyroid gland b) high c) a hormone d) reduces Ca levels e) if the thyroid gland is removed patient does not become hypercalcemic (high Ca in the blood) thus proving it not to be essential

Question 32

Draw a flow chart of how Calcitonin maintains Ca homeostasis. Include the following terms; bone, DEC Ca, INC Ca, neg feedback, Kidneys, inhibition of breaking down, calcitonin, stimulation of excretion, parafollicular cells, urine

Answer 32

Question 33

T or F - phosphate metabolism is controlled in an exact way as Ca due to them always remaining together

Answer 33

F - similar control but not as tightly monitored

Question 34

Describe the following wrt the parathyroid. Include what it causes a) hyperparathyroidism - 5 b) hypoparathyroidism - 4

Answer 34

a) when the parathyroid is too active - hypercalcemia (INC plasma Ca levels) - INC bone resorption (break down too much) - mineralization of soft tissues (resorption) - INC thirst due to INC urination b) when the parathyroid is under active - hypocalcemia (DEC plasma Ca levels) - ataxia = muscular weakness - cardiac arrhythmias

Question 35

describe the 2 following disorders of Vit D a) rickets - 3 b) osteomalacia - 3

Answer 35

a) low vit D in children causing bone pain, stunted growth, and deformities b) low vit D in adults causing reduction of bone quality due to excess reabsorption (break down)

Question 36

What are the 3 risk factors for osteomalacia (bone brittleness)

Answer 36

1. low Ca diet 2. lack of exercise 3. females a/f menopause

Question 37

Match the following w/ the image. How do you know a) osteoporosis b) normal

Answer 37

a) right b) left - much more bone loss in the right than the left

Question 38

What are the 3 treatments for osteoporosis (bone brittleness). Which one is the best

Answer 38

1. INC Ca intake 2. hormone therapy = PTH or calcitonin 3. prevents = exercise, vit D + calcium intake (best)