Renal 7 Flashcards
What is secretion of K+ for
Acts directly on adrenal cortex protecting body from hyperkalemia
What are 4 causes of aldosterone release
- Decreased BP
- Increased osmolarity
- Large drops in plasma Na
- Increases in K
How does decreased BP release aldosterone
Initiate a pathway that results in production of angiotensin which triggers aldosterone release
How does increased osmolarity trigger release of aldosterone
Acts directly on adrenal cortex during dehydration
Renin angiotensin system (RAS)
Multi step pathway for maintaining BP
- day to day aldosterone secretion
What is the multi step pathway of the renin angiotensin system
- Decrease BP causes release of renin from granular cells
- renin cleaves angiotensin to ANG I then converted to ANGII by ACE
- ANG II travels to adrenal cortex and stimulates production of aldosterone
What does the renin-angiotensin pathway begin with
Renin secretion (enzyme)
What secretes renin
Granular cells
How is renin secretion indirectly stimulate
Sense when GFR decreases:
2. Sympathetic neurons activated by CVCC when BP decreased terminated on granular cells
3. Paracrine feedback (prostaglandins) from macula densa cells signal granular cells to secrete
What is the direct stimuli that cause renin secretion
Low BP in renal arterioles cause granular cells to secrete in response to less stretch
What are granular cells also known as
Juxtaglomerular cells
What is renin’s main role
Convert an inactive angiotensin, into angiotensin I
What is angiotensin
Plasma protein constantly circulating in blood
What is ACE
Angiotensin converting enzyme
- enzyme produced in blood vessel endothelium
What are angiotensin II receptors
G protein coupled receptors
Effects of ANG II
- Increased sympathetic (increased CO + BP, vasoconstriction)
- Proximal tubule Na reabsorption
- Thirst
- AVP secretion, increased H20 absorption
How does ANG II increase proximal tubule Na reabsorption
Stimulates an apical Na/H+ exchanger
What do pharmaceutical companies use ACE inhibitors for
Treatment of hypertension
What does natriuretic peptide (ANP) promote
Na+ and water excretion
Less vasopressin
Peptide produced and secreted by specialized myocardial cells in atria
Atrial natriuretic peptide
What caused release of ANP
Increased blood volume causes increased stretch of atria causing myocardial cells to release
What is the ANP receptor
Enzymatic membrane bound receptor acting through cGMP second messenger system
Affects of ANP in kidney
Relaxes afferent arterioles to increase GFR
Reduce renin release from granular cells, reduce aldosterone and ANG II
Reduce Na reabsorption
Affects of ANP at hypothalamus
Reduces AVP release
Inhibit thirst
Affects of ANP at adrenal cortex
Inhibits aldosterone release
Affects of ANP at medulla
Acts on CVCC to decrease BP
Why is potassium balance complicated
Reabsorbed and secreted
Where is K+ reabsorbed
Proximal tubule and ascending limb of loop
Where is K+ secreted
Distal tubule and cortical collecting duct
At normal K+ excretion
Reabsorption is less than filtered
Low K+ does what to aldosterone
Decreases aldosterone
Reducing secretion which reduces excretion
High K+ stimulates what
Aldosterone release
Increases secretion and excretion
Alterations in body K levels affects what
The resting membrane potential of all cells
Increased K+ in ECF
Hyperkalemia
Reduced efflux from cell, more K+ retained
Causes hyper excitation
Low K+ around cell
Hypokalemia
Increased K+ leakage
Hyperpolarizes cell causing larger stimulus to reach threshold
Where is potassium balance especially important
Excitable tissues such as heart and skeletal muscles
What does hypokalemia cause
Muscle weakness because more difficult for hyperpolarized motor neurons and muscles to fire APs
What is effects of hyperkalemia
More dangerous, initially leads to hyperexcitability
Eventually cells unable to repolarize and become less excitable
Arythmias in heart
What can disturbances in K+ balance result from
Kidney dysfunction, eating disorders, diarrhea, diuretics
Behavioural responses are critical for
Restoring to normal state, when ECF volume decreases or osmolarity deviates
What are only way to replace los water and increase Na+ content
Drinking water and eating salt
What causes relief of thirst
Act of drinking water, water does not have to be absorbed
Receptors in mouth/pharynx respond and decrease thirst and AVP release
What stimulates thirst center in hypothalamus
Increase blood osmolarity, decreased blood volume, decreased blood pressure, dry mouth
