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Endo Repro 1 > Ca Homeostasis > Flashcards

Ca Homeostasis Flashcards

1
Q 
IC use of Ca
I
E
M
H
Plasma Ca use
 N
M
C
M
S
F
A

IC signal transduction
Enzyme action
Muscle contraction (excitation/contraction coupling)
Hormone/NT release (exocytosis)

Nerve/muscle excitability (nerve most important)
Membrane perm
Coagultion of blood
Maintain TJ
Synaptic transmission
Fxn integrity of bones/teeth
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2
Q

Fraction of Ca hormonally regulated

99% of total Ca is located in

IF Ca conc

Plasma (% as Ca++)
% protein bound
% unionized

% in IC fluid

A

Plasma free/ionized

Bone (CaPhos salts/hydroxyappetite)

<1, Ca

50
40
10

<1, Ca++ and protein bound

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3
Q

Free Ca in plasma

Normal value

Tightly _____ over long term

Continuous exchange w

A

9-10 mg

regulated

gut, kidney, bone

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4
Q

GI tract

Ca and PO4 ions are ___ via AT/diffusion

Only ____ is hormonally regulated

___ of ingested Ca absorbed

Majority is -____

If gastric empties too fast (gastrectomy)

Major determinant of net Ca uptake

affected by _____ to inc Ca in

A

absorbed in SI

AT

1/3

excreted in feces

less Ca is absorbed

Ca absorbtion

VD3, GI tract

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5
Q

Kidney

Filters _____ from plasma

Rate of excretion =

usually 99% of filtered Ca is

regulation of Ca occurs in

PTH helps to

A

Free Ca ions

rate of absorption from gut

reabsorbed (most in PT)

distal nephron (major site of regulation)

inc Ca reabsorption

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6
Q

Bone

Stable Ca pool

slow exchange w

regulated by

releases ____ to plasma

Labile Ca pool

rapid exchange from

A

bone remodeling

Osteoblasts (form) and osteoclasts (resorption)

Ca and PO4

readily available pool in bone fluid

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7
Q

Labile Ca pool

Osteocytes

Canaliculi

Osteocytic osteolysis
OC transfers ____ from ___ to ____

Mechanical stress inc, later

absence of ____ inhibits OB

A

Embedded OC

contain bone fluid & free Ca

Ca ions, bone fluid to plasma

flow of BF, osteocytic activation of bone remodeling

stress

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8
Q

Bone remodeling stage 1

PTH and 1,25 OH VD stimulate ______ to release

OB express receptors for

Mature OC express ___ receptors for RNKL released by

also express

OB cytokines activate

A

activation of OB

OB, MCSF, RANKL, IL1/IL6/TNFA

PTH, VD3

RANK, OB

calcitonin

OC recruitment, differentiation, activation

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9
Q

Boen remodeling stage 2

activated, mature OC secrete

____ to dissolve bone crystals, releasing

____ to break down exposed matrix

occurs for

A

H+, Ca and PO4

enzymes

2-4 wks

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10
Q

Bone remodeling stage 3/4

OB with reversal signal secrete _____, to suppress OC _____

synthesize ____, such as hydroxyproline and osteocalcin

Regulate

Complete bone formation takes

A

OPG, formatiom and activation

alkaline phosphatase, matrix proteins

mineralization

2-4 mnths

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11
Q

Regulation of OC osteolysis

_____ stimulate OC to inc _____ and transfer to circulation via

Inc _____ inc _____, which inc ______, ultimately inc

Dec ______ inc _______, dec ______

A

PTH/VD, Ca uptake, canaliculi

shear stress, fluid flow, OC RANKL release, OC activation

mechanical stress, inc osteocytic sclerostin release, dec OB function

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12
Q

Serum phosphate levels during the day

Most of ingested phosphate is

Primary site of phosphate homeostasis/regulation

Hormones that regulate Ca hoeostasis

P
A
C
G and I
G
T
A

vary widely

absorbed in GI tract

renal phosphate reabsorption

PTH
Active VD3 (1,25OH VD3)
Calcitonin
GH and IGF1
GC
TH
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13
Q

PTH prevents

secreted by

primary targets

fxn
acts via

Regulation
dec plasma free Ca
Inhibited by

this occurs via

A

hypoCa

Chief cells of 4 PT glands

bone (OB and OC), kidney

inc plasma Ca, dec plasma PO4
cAMP

inc PTH
inc plasma free Ca via NF

membrane Ca sensing receptor (CaSR)

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14
Q

Maximum response of PTH in bone requires

VD3 synth in

Final step in

1, 25OH VD3 aka

A

VD3

skin, liver, kidney

kidney

calcitriol

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15
Q

PTH actions

Bone (requires VD3)
Inc ____ and ____, resulting in inc _____

Kidney
_____ Ca reab
____ PO4 reab
____ calcitriol syn

Intestine

A

bone resorp and OC osteolysis, serum Ca/PO4

Inc
Dec (prevents CaPO4 in ST)
inc

no direct action

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16
Q

Active VD3 actions

Intestine

Bone

Acts via

A

inc Ca absorp by inc calbindin synth

permissive to PTH

nuclear receptor VDR

17
Q

Calcitriol synth control point

Renal 24 hydroxylase activation results in formation of

24 hydroxylase activated by high

A

kidney- PTH activates 1-hydroxylase to form VD3

24,25 OHD3

1,25OH VD3

18
Q

Plasma Ca levels are

inc/dec causes ____ in plasma PTH

A

very controlled

large change

19
Q

Pubertal growth spurt inc rate of

stimulated by ___ in F, ____ in males

mediated by ____ in both

High levels of __ causes epiphyseal closure

E2 throghout life

activates ____ and dec ____

postmenopasual ____ in E2, leading to

A

long bone growth

inc plasma E2, inc plasma T (eventually E2)

estrogen receptors

E2

protects bone

OB, cytokine

drop, bone loss/osteo

20
Q

In men, T leads to
decreases w

Calcitonin secreted by, fxn

Regulated by ____ to inc ___

Inhibits _____ which express

Plasma Ca can be regulated after _____ or with Calcitonin excess

Uses- tx of hyperCa with
Severe
Marker for

A

inc bone strength
age

C cells (parafollicular), lower Ca

Inc plasma Ca, calcitonin

OC, calcitonin receptors

thyroidectomy

excessive OC activity (Paget)
Osteo
medullary thyroid ca

21
Q

TH and bone turnover
High levels can cause

GC essential for

High levels cause
____ intestinal Ca absorp
____ renal Ca reabs
Inhibits

Excess GC can cause

Inc GH/IGF1 at puberty

A

inc
Osteo (HyperT)

normal Ca balance

hypoCa
dec
Dec
bone formation

osteo (cushing, high GC)

pubertal growth spurt

22
Q

Inc age ___ bone mass, inc

due to

2 phases of bone loss in

Phase 1 is

phase 2 is , also in

Estrogen loss contributes to bone loss in

A

dec, fractures

dec sex steroids

women, 1 in men

rapid, @ menopause

slower, men

elderly M/F

23
Q

Other causes of bone loss

Low ____ in YA
Peak bone mass at

____ GH/IGF1
____ TH or
_____ due to high glucose activating
Inad metabolism of ___, ususally in

M, M, A
Lack of
S, A
Drugs such as G, A (inc rate of VD3 conversion to inactive form)

A

peak bone mass, end puberty

dec
inc, GC
T1DM
VD3 to active form
Liver/kidney dz

Malabsorp, malnutr, anorexia
exercise
smoking, alcohol
GC, anticonvulsants

24
Q

HypoC

Primary_______, lab values
such as

P______, lab values
due to

____ def, labs

etiologies
Insufficient ______

Inad enzyme conversion to

inc rate of metabolism to, to treat

____ receptor defect

A

HypoPTH, low PTH/Ca, inc PO4
lost PT gland fxn

pseudohypoPTH, inc PTH/PO4, dec Ca
PTH receptor defect

Calcitriol, Inc PTH, low Ca/PO4

sun, intake, mal

active form (kidney/liver/1-OHase dz)

inactive form, epilepsy

25
Q

HypoCa causes

Renal faulure

____ PO4 excretion
____ PO4
_____1-OHase activity
______

A 
dec
inc
dec
dec
VD3, Ca
26
Q

HypoCa sx

O/R
inc N due to low Ca
H, t, C, T
S
D
T- death dye to
A 
osteomalacia (weak bones), ricketts
NM activity
Hyperactive reflexes, tingling, Chvosteks, Trousseas
Seizures
Dec myocardial act
Tetany- asphyx due to laryngospasm
27
Q

HyperCa causes

H, labs
Due to

Excessive ingestion of
labs

M, labs

due to tumors secreting
B
P____ to cross react w pth receptors and

A

HyperPTH, inc PTH/Ca, low PO4
tumor PT gland, ectopic tumor w PTH sec

Ca,VD3
dec PTH, high Ca/PO4

malignancy, low PTH/PO4, high Ca
bone mobilizing substance
PTHrP, activating them

28
Q

Sx of HyperCa

M, F, L
Neuropsych do w
P- Ca inc gastrin leading to
Calcified
C
A 
muscle weakness, fatigue, lethargy
depression, EEG changes, mem/pers problems
Peptic ulcers, GA secretion
calcified soft tissues
cardiac arrest

Endo Repro 1 (24 decks)

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