Thirst Flashcards
3 processes kidney uses to conserve bicarbonate levels
Secretion of H+
Reabsorption if filtered HCO3-
Production of new HCO3-
Normal levels of pH, H, PCO2 and HCO3-
7.4;40;40;24
What happens in respiratory acidosis
Co2 retention drives equilibrium to the right
Therefore both h and HCO3- conc increase
The increased h conc results in acidosis
pH<7.35 and pco2>45mmHg
What happens in respiratory alkalosis
Excessive co2 removal drives equilibrium to the left
Both H and HCO3- conc fall
The decreased h conc results in alkalosis
pH>7.45 and pco2<35mmHg
Metabolic acidosis
HCO3 depleted
First priority: compensation - return pH regardless of HCO3 and pco2 conc
Second priority - correction - HCO3 and pco2
What happens in metabolic alkalosis
Loss of h+ or addition of base, causes HCO3- conc to rise
Ph>7.45 and HCO3 conc is high
What are fed and fasted state?
1. Fed state Shortly after a meal, when new nutrients are available Metabolism in anabolic 2. Fasted state Body needs to draw upon its fuel stores Metabolism is catabolic
Key hormones involved in regulating metabolism
Insulin
Glucagon
Adrenaline and noradrenaline
Which hormone drives the fed state, how is it secreted and what does it do?
Insulin secreted by b-cells in response to elevated levels of blood glucose and the parasympathetic nervous system
- Stimulates glycogen synthesis in liver and muscles
- Stimulates uptake of glucose into muscles and adipose tissue
- Stimulates glycolysis and hence fatty acid synthesis
- Stimulates triglycerides formation in fat tissue
- Stimulates protein synthesis in muscle
Which hormone drives the fasting state, how is it secreted and what does it do?
Glucagon secreted from alpha cells in the pancreas when glucose conc is low
main target is liver, where it:
- Stimulates release of glucose from glycogen
- Stimulates gluconeogenesis but inhibits glucose incorporation into glycogen
Where are adrenaline and noradrenaline secreted from and what do they do?
Secreted by adrenal medulla and neurones of the sympathetic nervous system when blood glucose falls
- Drive breakdown of glycogen and triglycerides
- glycogenolytic action mainly on muscle
- decrease glucose uptake by muscle so fatty acids are used as fuel
- Increase glucagon secretion and inhibit insulin secretion
What is type 1 diabetes?
Insulin dependent
Autoimmune condition in which beta cells of pancreas are destroyed
Therefore little insulin can be secreted in response to increase in blood glucose conc
Treated by injecting insulin when required
What is type 2 diabetes?
Late age of onset
Normally less severe than type 1
Tissues are insensitive to the effects of insulin
What are the three elements that maintain the acid-base balance?
- buffering
- lungs
- kidneys
what is the equation for pH?
pH is proportional to bicarbonate ion concentration divided by partial pressure of carbon dioxide
How is acid base balance regulated?
Return to homeostasis via:
- compensation: first priority, restore pH ASAP irrespective of [HCO3-] and PCO2
- correction: second priority, restore [HCO3-] and PCO2
Reduction of free [H+] in solution by:
- chemical buffers
- ventilation changes (PCO2)
- renal system changes
Why are patients with diabetic ketoacidosis thirsty?
Defect in insulin secretion leads to
• Glucose not metabolised
• Fats metabolised as fuel and form ketoacids
• Blood becomes acidotic
• Kidneys eliminate ketoacids in urine
• High glucose conc in ECF dehydrates ICF via osmosis
• High glucose conc in urine causes osmotic diuresis (i.e., glucose in tubules causes reduction in resorption of fluid –> high vol dilute urine
What does the breakdown of fats result in?
- breakdown of fatty acids leads to the formation of ketone bodies
- this is because acetyl-CoA formed in lipolysis cannot enter the citric acid cycle
- therefore the acetyl-coA is converted to ketone bodies
metformin functions
- increasing insulin sensitivity
- Acts to reduce gluconeogenesis in the liver,
- Increases glucose uptake and utilisation in skeletal muscle
- Slightly delays carbohydrate absorption in the gut.
- Increases fatty acid oxidation - reducing circulating LDL and VLDL
Metformin mechanism of action
- It acts on the mitochondria to change the ratio of AMP to ATP
- ↑ AMP:ATP ratios activate AMP-activated protein kinase
- Inhibits glucagon signaling and gluconeogenic pathways
- AMPK increases transcription of genes important for glucose transport fatty oxidatin and inhibits fatty acid synthesis
what are Incretins
- Glucagon-like peptide-1 (GLP-1) is secreted by L-cells in the gut
- Gastric inhibitory peptide (GIP) secreted by K-cells in gut
- stimulate insulin biosynthesis/ secretion, inhibit glucagon secretion in pancreas, delay gastric emptying, increase cardiac output and increase brain satiety signals.
What are sulphonylureas?
- older class of orally-active hypoglycemic drugs.
- interfere with beta cell ion channels to potentiate insulin secretion.
- Well tolerated but can lead to weight gain by stimulating appetite.
What are gliptins?
- Enhance endogenous incretin effects by blocking DPP-4
- Lowers blood glucose by increasing first phase of insulin response after meals.
Major predictors of poor patient adherence to treatment and medication
Presence of psychological problems, particularly depression
Presence of cognitive impairment
Treatment of asymptomatic disease
Inadequate follow-up or discharge planning
Side effects of medication
Patient’s lack of belief in benefit of treatment
Patient’s lack of insight into the illness
Poor provider–patient relationship
Presence of barriers to care or medications
Missed appointments
Complexity of treatment
Cost of medication, co-payment, or both
