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Veterinary medicine year 2 > Nutrition > Flashcards

Nutrition Flashcards

1
Q

Where is phosphate used in the Body

A

DNA and RNA
NADP
ATP
Phosphate esters
Receptor and intracellular messenger function
Hydroxyapatite

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2
Q

What are the locations of phosphate in the body?

A

Bone
Intracellular organic molecules
Extracellular fluid

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3
Q

How does the law of mass action apply to calcium and PO4

A

High concentrations of either or both in a solution will form insoluble precipitates
Homeostasis aims to keep Ca and PO4 at levels suitable for mineralisation of bone but not soft tissue mineralisation

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4
Q

How is phosphate controlled?

A

Absorb more phosphate by calcitriol
Intestinal pho abs promoted by 1,25 Dihydroxy vitamin D (calcitriol)
Renal absorption PCT and DCT

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5
Q

How is phosphate excreted by the body?

A

PTH promotes renal PO4 losses
Salivary losses and recycling by cattle
FGF-23

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6
Q

What is FGF-23?

A

Fibroblast growth factor 23
Phosphophaeteamic peptide secreted by the bone in response to circulating phosphate
Phosphaturetic - promotes loss of phosphate

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7
Q

FGF-23 effect on calcitriol

A

Anti alpha 1 hydroxylase (inhibits the release of calcitriol)

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8
Q

Effect of FGF-23 on PTH

A

Anti PTH so stops the release of PTH

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9
Q

How can phosphate deficiencies occur and how does this present?

A

Herbivores grazing pasture without grain
Bone mineralisation and Pica

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10
Q

What occurs if there is an excess of dietary phosphate?

A

Associated with calcium deficiency
Ideally Ca:P ratio is Ca>P

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11
Q

Which factors control phosphate release?

A

Dietary intake and absorption
Calcitriol
PTH
Renal tubular resorption
Phosphatonins

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12
Q

How does Hyperphosphataemia occur?

A

Reduced GFR
Calcitriol = intestinal absorption (vit D toxicity)
Hypoparathyroidism
Increased bone turnover

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13
Q

Clinical presentation of hyperphosphataemia

A

Decrease calcitriol
Secondary renal hyperparathyroidism
Osteopenia, Osteomalacia, rubber jaw
Soft tissue mineralisation
Can cause hypocalcaemia as PO4 binds to calcium

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14
Q

How does increase phosphate = secondary renal hyperparathyroidism?

A

dec GFR-> red PO4 clearance-> inc serum PO4= FGF-23 release
Complex Ca inc but ionised Ca decrease
Ionised Ca dec = inc PTH so bone resorption
Tubular damage+ FGF23 = Dec calcitriol
Polyuria
Poor appetite and decreased calcitriol = poor uptake of calcium

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15
Q

How can secondary renal hyperparathyroidism be treated?

A

Therapeutic calcitriol

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16
Q

What Bran- disease?

A

Equine secondary hyperparathyroidism

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17
Q

What is the pathophysiology of Bran disease?

A

Low Ca and High phosphorus graind
Low Ca:P ratio
FGF23 decreases calcitriokl
Ionised Ca dec so ~PTH inc = bone resorption
Bone loss from the skull = swelling

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18
Q

How can PO4 be restricted?

A

PO4 restricted diets
PO4 binders - oral antacids - lanthanum carbonate

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19
Q

What is ruminant urolithiasis?

A

At risk - sheep, goats and fattening beef
High grain diets with high Phosphorus
Uroliths contain Struvite and apatite
Causes alkaline urine
Surgical treatmetn

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20
Q

Where do ruminant urolithiasis occur?

A

Urethral diverticulum

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21
Q

How does hypophosphotaemia occur?

A

Increased PTH
Dietary deficiency in PO4
Milk fever and eclampsia
Lack of calcitriol
Insulin promotes uptake into cells

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22
Q

Faconi syndrome

A

PCT defect

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23
Q

What is the clinical presentation of hypophosphataemia?

A

Muscle weakness and pain
Haemolytic anaemia, ATP dependent membrane
Inc oxygen binging -> hypoxia
Poor growth
Poor milk yields
Low fertility

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24
Q

What is the treatment for down cows?

A

IV phosphorous
often treatment with calcium alone will correct via PTH and GI function

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25
How can phosphate levels be diagnosed?
Serum/ plasma phosphorus (cells might burst w hypo so could create false increase) Urea, creatine as evidence of renal dysfunction Total calcium , ionised calcium and albumin
26
Where is calcium found in the blood?
Bound to plasma proteins Complexes (citrate) Ionised calcium
27
How should the interpretation of total plasma calcium change with hypoproteinemia?
Total lower but ionised unchanged Dont interpret low ca as hypocalcaemia Ignore if low ca = Low albumin
28
What are the 4 major actions of the parathyroid hormone?
Bone - fast phase get ca from bone fluid Bone - slow phase gets Ca from bone Kidney - reabsorption in tubules for more Ca Intestine- indirect effect through activation of vit D to get calcium
29
Calcitonin
Hormone with opposite actions to PTH Secreted from thyroid cells
30
Describe the effects of PTH on phosphorous homeostasis
Promotes Renal loss of phosphorous Promotes absorption of phosphorous from the GI tract and release from bone
31
How would a parathyroid tumour affect different structures of the body?
Fast and slow bone resorption High plasma Ca Low plasma phosphorous In the urine calcium is retained and phosphorus will be excreted
32
What would be the outcome of an animal on a high phosphorous diet with little Ca?
Nutritional secondary parathyroidism, increased FGF bine resorption, rubber jaw and big head
33
Describe the process of calcitriol stimulated absorption by intestinal cells
Calcium channel proteins (luminal) Calcium binding protein (calbindin) Calcium ATPase pumps (basolateral)
34
What role calcium play in nerve conduction?
Depolarisation - Membrane is permeable to Na ions which flow inwards Repolarisation- Na channels close, K chanels more perm so K outwards = normal negative resting membrane potential
35
What effect would a calcium deficit have on nerve conduction?
Sodium voltage gated channels open very easily because calcium binds to exterior channel to change electrical state nerve fibre excitable Nerves fire repetitively without stimulation All occurs when ionised calcium drops below 50%
36
Muscle tetany
Tetanic contraction of the muscles When occurs in resp system can be fatal
37
What role does calcium play in the neuromuscular synapse?
AP opens voltage gated Ca channels at NM synapse Incr Ca conc in terminal Inc rate of ACh vesicles fusion Exocytosis of ACh into synaptic terminal ACh binds to ACh gated ion channels in post sy Influx of Na+ = end plate potential = AP
38
What mechanism contracts skeletal muscles
Excitation contraction coupling AP from Muscle surface-> transverse tubules Ca released in myofibrils from SR Ca binds to troponin C = contraction Inhib affect of troponin tropomyosin complex on actin inhibited by Ca= musc contraction
39
What mechanism contracts smooth muscle?
Similar to skeletal muscle contraction Initiation is increase in intracellular Ca+ Nerve or hormonally regulated No troponin instead calmodulin Calmodulin binds with 4 Ca ions Calmodulin Ca complex activated myosin kinase Myosin kinase phosphorylates reg chain on myosin head which binds actin filament
40
What is the mechanism by which cardiac muscle contracts?
Excitation contraction coupling AP spreads over muscle membrane via T tubules T tubule AP acts on longitudinal sarcoplasmic tbules = release of Ca from SR into musc sarcopalsm Ca -> myofibrils Myosin -> actin = muscle contraction
41
How do structural differences between skeletal and cardiac muscle affect response to ECF calcium concentrations?
Skeletal musc have closed T tubules so Ca is released from SR so not affected as much by ECF ca conc Cardiac musc- Open T tubules so ECF into interstitium to T tubules Cardiac calcium directly related to ECF calcium conc
42
How is calcium involved in inc cardiac contractility induced by catecholamines?
Norepinephrine = cardiac musc fibre to be more permeable to ca Inc contractile strength
43
What clinical signs would be seen in skeletal muscle of a bitch with eclampsia?
Ionised Ca in blood drops Ca deficit = permeability changes to voltage gated Ca2+ and Na+ Inc influx of Na+ so excitable cells means lower threshold and more musc contractions = tetanic muscle contractions Tremors, twitching, musc spasm, stiffness, ataxia
44
role of FGF23
Promotes renal losses of phosphorus
45
High blood phosphorous leads to what parathyroid state?
Secondary hyperparathyroidism
46
What can go wrong to cause hypercalcaemia?
Inc PTH activitt Activity of PTH like substances Increased Vit D activity Osteolysis HyperAC
47
How is calcium homeostasis maintained?
PTH negative feedback - inc when low Ca dec when high Ca Active vitamin D3 (calcitriol)- promoted by PTH, Inhibited by FGF-23
48
What is PTH related peptide?
PTH related protein - same biological activity as PTH Peptide hormone that shares 60% homology with PTH
49
What is PTH rp produced by?
Cartilage Bone Muscle Epithelium CNS Specific tumours
50
What are the differential diagnoses for hypercalcaemia?
HARD IONS Hyperparathyroidism Addisons Renal Vit D Idiopathic Osteolysis Neoplasia Spurious
51
What are the causes of HyperCa in dogs?
1. Malignancy 2. hypoadrenocorticism 3. Primary hyperparathyroidism 4. Chronic renal failure 5. Vitamin D toxicosis 6. Granulomatous diseases
52
What are the causes of HyperCa in cats?
1. Idiopathic hypercalcaemia 2. Renal failure 3. Malignancy 4. Primary hyperparathyroidism
53
What are the causes of total hyperCa in horses?
Chronic renal failure Vitamin D toxicosis Hypercalcaemia of malignancy Primary HyperPT
54
What are the clinical signs of hyperCa?
PUPD Weakness Anorexia, vomiting constipation Musc twitching, shiverign seizures Bradycarda, cardiac arrhythmias (inc cont, dec excitability)
55
How is palpation carried out with suspicion for hyperCa?
lymph nodes Anal sac masses Other masses - neoplasia and granulomas Angiostrongylus - imaging and faceal exam Haematomas
56
What are the lab tests for hypercalcaemia?
Total calcium Ionised calcium Phosphorus PTH PTH rp Vitamin D
57
What is hypervitaminosis D?
Increased Ca x P product causes soft tissue mineralisation
58
How is PTH independent hyperCa investigated?
Low PTH and high iCa No initial clinical appearance of neoplasia Tests PTHro 25 hydroxyvitamin D (calcidiol) 1, 25 dihydroxy vitamin D (calcitriol)
59
Calcidiol
25 hydroxy vitamin D
60
Calcitriol
1,25 dihydroxy vitamin D
61
What is the role of calcium?
Muscle contraction Decrease neurone sodium permeability Mediate ACh release
62
What pathology is associated with hypocalcaemia?
Inc iritability Dec smooth musc contraction reduced cardiac musc contraction Decreased skeletal muscle contraction
63
What are the clinical signs of milk fever?
Reduced muscle contractions - Skeletal affects posture adn gait - Smooth - repro tract and GI tract - Cardiac - heart and circulation
64
What is the pathophysiology of milk fever?
In dairy cows calving Ca demand rapidly increases Ca loss through milk Ca in plasma to PTH PTH increase - inc Ca resorption from bone Calcitriol increase to SI more Ca absorption
65
Why does metabolic alkalosis predispose to milk fever?
High cation diets can cause milk fever as they induce metabolic alkalosis Reduced the ability of cow to maintain calcium Metabolic alkalosis blocks binding of Ca to albumin and decreases ionised calcium
66
How can milk fever be prevented?
Calcium restriction during close up transition dry period Dietary cation anion balance Oral supplementation with calcium at calving

Veterinary medicine year 2 (23 decks)

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