Regulation of Fluid/Electrolyte Balance Flashcards
How much sodium is reabsorbed in the PCT?
65%
How much sodium is reabsorbed in the ascending loop of Henle?
25%
How much sodium is reabsorbed in the DCT?
8%
What hormones affect the volume of urine?
ADH, Aldosterone, ANP
What do ADH and Aldosterone do?
insert aquaporin and sodium channels causing urine to become concentrated and little
What does ANP do?
inhibits effects of ADH and Aldosterone - removes channels
What can a increase in BP trigger?
release of ANP
What can a decrease in BP trigger?
release of Aldosterone and ADH
What factors influence Glomerular Filtration Rate (GFR)?
- Glomerular Hydrostatic pressure
- Capsular hydrostatic pressure
- Glomerular Osmotic pressure
- Systemic blood pressure
- Renin-angiotensin-aldoterone system
- Disease
What does the juxta-glomerular apparatus do?
Measures and responds to changes in Na+ conc of the filtrate
What does the juxta-glomerular apparatus connect?
connects the distal convoluted tubule with the glomerulus
What are the cells of the juxta-glomerular apparatus?
macula densa
juxta-glomerular cells (modified smooth muscle cells)
mesangial cells
What is the role of the macula dense cells?
detect sodium concentration
What is the role of the juxta-glomerular cells
Adjust the diameter of the afferent arteriole via vasoconstriction or vasodilation
What is the role of the mesangial cells
supporting cells
What does blood pressure drive?
glomerular hydrostatic pressure
What do macula densa cells release to drive vasoconstriction during low BP?
prostaglandins
What do juxtaglomerular cells release to drive RAAS during low BP?
renin
What do macula densa cells release to drive vasodilation during high BP?
adenosine which directs juxta-glomerular cells to constrict the afferent arteriole
What are the steps of the renin- angiotensiogen system?
- Angiotensinogen released into circulation
- Renin converts angiotensinogen into Angiotensin I
- Angiotensinogen converting enzyme coverts angiotensin I into angiotensin II
- Angiotensin II potent vasoconstrictor – rapidly increases blood pressure
Where is ACE produced primarily?
in the vascular endothelium of lungs
Where does angiotensin 2 bind?
receptors on:
1. Arterioles - constriction
2. Hypothalamus- thirst (encourage fluid)
3. Pituitary gland – release of
ADH
4. Adrenal cortex-release of
aldosterone
Where is ANP released from?
atria of the heart
What causes the release of ANP?
baroreceptors detect rise of BP in heart
As kidney function decreases, what also decreases?
glomerular filtration rate (GFR)
What does the GFR tell the kidneys?
the systemic blood pressure
What are the consequences of reduced kidney function due to CKD?
o Inadequate removal of fluid and waste products of metabolism
o Inappropriate activation of RAAS (hypertension)
Why is CKD a high risk for cardiovascular?
hypertension
Why can hypertension cause CKD?
damage to glomerular capillaries due to high blood flow
Why is diabetes a high risk for CDK and cardiovascular?
hyperglycaemia affects bloodflow (low blood flow)
What are the causes of CDK?
- Hypertension
- Diabetes
- High Cholesterol
- Kidney Infections
- Glomerulonephritis
- Polycystic kidney disease
- Kidney stones
- Long-term use of NSAIDS
What are symptoms of CDK?
- Hypertension
- Nausea
- Oedema (ankles, hands or feet, lungs)
- Blood/protein in urine
- Anaemia
- Weak/painful bones
How can hypertension be regulated?
- Diet (reduce to salt intake)/weight loss
- Diuretics (furosemide)
- ACE inhibitors/angiotensin receptor blockers (ARBs)
- Aldosterone agonists (nuclear receptors or sodium channels)
Where does furosemide bind?
NKCC2
What % function is stage 5 CKD characterised by?
15%
What is required at stage 5 CKD?
transplant/ dialysis
What is dialysis?
Artificial removal of waste, solutes, water and toxins from blood
What are the types of dialysis?
- Haemodialysis
- Peritoneal dialysis
