Long Term BP Control-Exam 1 Flashcards
What is the main function of long term bp control?
Keeps MAP constant over long period; tied into control of body fluid volume
What does increased volume in arteries and veins result in?
Pressure in arteries and veins will increase, assuming no change in vascular compliance
What does increased venous return result in?
Increased preload, increased SV, increased CO, increased bp; assuming no change in SVR
Small changes in cardiac output can cause what?
Large change in blood pressure
5 to 10 % increase in CO can raise MAP from 100mmHg to what?
150 mmHg
What is the relationship between CBV and MAP?
Increasing CBV will increased MAP
Decreasing CBV will decrease MAP
Fluid Intake = Fluid Output
Constant CBV
Fluid Intake > Fluid Output
Increased CBV
Fluid Intake < Fluid Output
Decreased CBV
Salt Intake = Salt Output
Constant CBV
Salt Intake > Salt Output
Increased CBV
Salt Intake < Salt Output
Decreased CBV
Under normal circumstances, fluid and salt output is controlled by what organ?
Kidneys
What is the normal fluid intake?
2300 mls /day
What amount of fluid intake is synthesized by oxidation of carbohydrates?
200 mls /day
What amount of fluid intake is ingested fluids?
2100 mls/ day
What is the normal fluid loss/ output?
2300 mls / day
What amount of fluid loss is insensible loss via respiratory tract and skin (not sweat)?
700 mls/ day
What amount of fluid loss is sweat?
100 mls / day
What amount of fluid loss is feces?
100 mls/ day
What amount of fluid loss is urine?
1400 mls/ day
Renal Output Equation
Output = Filtration - Reabsorption
What factors affect filtration?
MAP, Renal Blood Flow, pressure in glomerular capillaries, oncotic pressure in glomerular capillaries
What factors affect reabsorption?
Concentration of angiotensin II, aldosterone, ADH (all increase rate of absorption)
What does 50 mmHg on the pressure diuresis curve refelct?
0 Urine Output
What does 90mmHg on the pressure diuresis curve reflect?
Normal U/o
What does 150 mmHG on the pressure diuresis curve refelect?
U/O over 4x normal
What happens short term and long term with increased SVR?
Acute: Change in MAP
Chronic: MAP returns to normal, no change in SVR
What will happen to the renal function curve if intrarenal vascular resistance is increased?
Shift of the renal function curve to the right which will result in a change in the baseline MAP; problem is change in renal vascular resistance not the change in overall SVR
BeriBeri
body does not have enough thiamine (B1)
Paget’s disease
involves abnormal bone destruction and regrowth, which results in deformity.
What does renin start as?
Prorenin
Where is prorenin produced/ stored?
Juxtaglomerular cells (walls of afferent arterioles) of the kidneys
What causes the splitting of prorenin into renin?
Decrease in pressure
Where is renin released?
Lumen of the afferent arterioles; circulates to the rest of hte body
How long does renin remain in the blood?
30 to 60 minutes, where it acts on the plasma protein called renin substrate (angiotensinogen) to release angiotensin I
What’s another name for renin substrate?
Angiotensinogen
Angiotensin I
mild vasoconstrictor; produces minimal changes in vascular constriction
Where is angiotensin I carried to?
Lungs
What happens to angiotensin I when it is carried to the lungs?
ACE mediates formation of angiotensin II
Where is ACE present?
Endothelial cells
How long does angiotensin II persist before being deactivated by variety of blood/tissue enzymes known as angiotensinases?
Persists for 1-2 minutes
Angiotensin II
potent vasoconstrictor of arterioles/ minor constriction of veins
Interacts w/ kidneys resulting in increasing salt and water reabsorption
Causes adrenal gland to secrete aldosterone
What does aldosterone do?
Increases salt and water reabsorption
What is the response time of the renin-angiotensin system vasoconstrictor?
20 minutes; will take secondary effect several days for maximal effect
Is it easier to excrete water or salt?
Water
What is the definition of hypertension?
MAP greater than 110 mmHg
Diastolic > 90 mmHg
Systolic > 135 mmHg
Why does HTN shorten lifespan?
Excess workload on the heart
Damage to blood vessels of brain
Injury to kidneys
What are the causes of HTN?
Volume loading
Renin-Angiotensin imbalance
Combination volume loading / vasoconstriction
Types of HTN
Primary
Essential
Goldblatt HTN
Renin-Angiotensin Imbalance
Only one kidney and it has a constriction of renal art.
Kidney senses decrease in pressure and renin/angio system stimulated
Two-Kidney Goldblatt
HTN will occur even if one kidney normal, other kidney has obstruction of renal artery
What will happen to the obstructed kidney in two-kidney Goldblatt?
Increases reabsorption of water and salt due to lower pressure in tubular capillaries; release renin resulting in overall increase in angiotensin ii and aldosterone
What occurs with renal pressure in two-kidney goldblatt?
Normal in obstructed kidney
Higher than normal in non-obstructed kidney
B/c angiotensin ii will increase SVR and MAP
What happens with salt and water reabsorption in two-kidney goldblatt?
Angiotensin ii and aldosterone will increase salt and water reabsorption for both kidneys
What percent of HTN patients have essential HTN?
90-95%
What is the cause of essential HTN?
unknown
What are the symptoms of essential HTN?
Excess weight gain/ obesity account for large percentage of risk for developing HTN (65 - 75% )
What is typically the first line of Tx in essential HTN?
Weight loss/ exercise
What are the main characteristics of essential HTN?
Increased CO
Increased sympathetic activity (kidneys)
Increased levels of angiotensin ii and aldosterone
Impairment of renal function
Why is there increased CO in essential HTN?
Support extra fat tissue
Support increased metabolic demand of major organs
Why is there increased sympathetic activity of kidneys in essential HTN?
Hormone released from fat cells stimulate regions of hypothalamus that provide excitatory stimulation of vasomotor center
How much are levels of angiotensin ii and aldosterone increased in obese patients?
2- 3x normal
Why is there impairment of renal function in essential HTN?
Requires higher pressure to remove normal amounts of salt and water
Must give drugs that improve renal function, can’t just decrease MAP
Tx for Essential HTN
Lifestyles modifications
Vasodilator drugs
Drugs that reduce reabsorption of salt and water
What is the primary target of vasodilator drugs in essential HTN?
renal arterioles; inhibits sympathetic signals to kidneys, block sympthetic neurotransmitter on renal vasculature and renal tubules, direct relaxation of renal vasculature smooth muscle, block action of renin-angiotensin system
Why do you tx essential htn with drugs that reduce resorption of salt and water?
Blocks active transport of sodium in tubules