72: Long Term Control of Blood Pressure/Hypertension Flashcards
BP has a “set point”
_____tension = systolic pressure is below 90 mm Hg
_____tension = sustained elevated arterial pressure of 140/90 or higher
Transient elevations are normal and can be caused by fever, physical exertion, and emotional upset. Chronic elevation is a major cause of heart failure, vascular disease, renal failure, and stroke
BP has a “set point”
Hypotension = systolic pressure is below 90 mm Hg
Hypertension = sustained elevated arterial pressure of 140/90 or higher
Transient elevations are normal and can be caused by fever, physical exertion, and emotional upset. Chronic elevation is a major cause of heart failure, vascular disease, renal failure, and stroke
_____ (most important) is the major regulator of total Na content and long term MAP, ANS, ADH, ANP.
RAAS (most important) is the major regulator of total Na content and long term MAP, ANS, ADH, ANP.
Changes in Arterial Blood Pressure (ABP):
____ (low gain) = Baroreceptor reflex – cardiac and vascular
_____ = Renal actions – PVR
_____ = Renal salt and water excretion
Rapid mechanism have _____ gain than slower, long term renal mechanism of volume control.
Changes in Arterial Blood Pressure (ABP):
Fast (low gain) = Baroreceptor reflex – cardiac and vascular
Intermediate = Renal actions – PVR
Slow = Renal salt and water excretion
Rapid mechanism have lower gain than slower, long term renal mechanism of volume control.
Kidneys act directly and indirectly to maintain long-term blood pressure:
Direct renal mechanism alters _____ volume
Indirect renal mechanism involves the _____ mechanism (Juxtaglomerular apparatus)
Kidneys act directly and indirectly to maintain long-term blood pressure:
Direct renal mechanism alters blood volume
Indirect renal mechanism involves the renin-angiotensin mechanism (Juxtaglomerular apparatus)
Macula _____ is the collective name for a specialised group of epithelial cells in the initial portion of the distal tubules.
Juxtaglomerular cells (granular cells) produce _____. JGA is located and the junction of Afferent arteriole, Ascending Limb of PCT, and DCT.
Mesangial cell: provide anchor, may be involved in response to _____ tension as contain actin + myosin and may act under sympathetic stimulation
Macula densa is the collective name for a specialised group of epithelial cells in the initial portion of the distal tubules.
Juxtaglomerular cells (granular cells) produce Renin. JGA is located and the junction of Afferent arteriole, Ascending Limb of PCT, and DCT.
Mesangial cell: provide anchor, may be involved in response to hypotension as contain actin + myosin and may act under sympathetic stimulation
Declining BP causes the release of renin, which triggers the release of _____
Angiotensin II is a potent vaso _____ that stimulates _____ secretion
Aldosterone enhances renal reabsorption of _____ and _____ ADH release
RAAS has almost ____ capacity. It is ____ a neural reflex!
Declining BP causes the release of renin, which triggers the release of angiotensin II
Angiotensin II is a potent vasoconstrictor that stimulates aldosterone secretion
Aldosterone enhances renal reabsorption of sodium and stimulates ADH release
RAAS has almost unlimited capacity. It is not a neural reflex!
Renin secretion:
Neural baroreceptors signal via renal _____ to granular cells in JGA.
INTRA-renal baroreceptors in _____ arterioles (granular cells) can function without innervation.
Sodium chloride delivery to _____ of JGA. Osmotic swelling releases transmitter that _____ renin secretion.
Redundancy of systems reflects importance.
Renin secretion:
Neural baroreceptors signal via renal sympathetics to granular cells in JGA.
INTRA-renal baroreceptors in afferent arterioles (granular cells) can function without innervation.
Sodium chloride delivery to macula densa of JGA. Osmotic swelling releases transmitter that inhibit renin secretion.
Redundancy of systems reflects importance.
Renin-angiotensin-aldosterone mechanism:
Renin acts as a proteolytic enzyme which acts on a plasma a2 – globulin formed by the liver called _____ and converts it into decapeptide called angiotensin I (AI).
Angiotensin I (AI) is converted into octapeptide called angiotensin II (AII) by _____ mainly in the lungs.
Renin-angiotensin-aldosterone mechanism:
Renin acts as a proteolytic enzyme which acts on a plasma a2 – globulin formed by the liver called angiotensinogen and converts it into decapeptide called angiotensin I (AI).
Angiotensin I (AI) is converted into octapeptide called angiotensin II (AII) by angiotensin converting enzyme (ACE) mainly in the lungs.
AII is a powerful vaso _____ – increases peripheral vascular resistance.
- A II _____ mesangial cells – reduces GFR
- A II stimulates the secretion of _____ – stimulates proximal Na-H exchange, increases blood volume (pressure naturesis and diuresis).
Angiotensin II acts as negative feedback to _____ renin production on granular cells by binding to angiotensin II receptors on granular cells to decrease intracellular Ca which inhibits renin.
AII is a powerful vasoconstrictor – increases peripheral vascular resistance.
- A II constricts mesangial cells – reduces GFR
- A II stimulates the secretion of Aldosterone – stimulates proximal Na-H exchange, increases blood volume (pressure naturesis and diuresis).
Angiotensin II acts as negative feedback to inhibit renin production on granular cells by binding to angiotensin II receptors on granular cells to decrease intracellular Ca which inhibits renin.
- The _____ are ultimately responsible for maintaining the setpoint for BP in the long term.
Sympathectomy has _____ impact in NORMALS.
Guyton experiments in dogs with cut neural pathways
BUT in resistant HTN, _____ tone may have a greater influence.
- Baroreceptor reflex effective as _____ term buffer to maintain setpoint for BP
- The KIDNEYS are ultimately responsible for maintaining the setpoint for BP in the long term.
Sympathectomy has little impact in NORMALS.
Guyton experiments in dogs with cut neural pathways
BUT in resistant HTN, sympathetic tone may have a greater influence.
- Baroreceptor reflex effective as short term buffer to maintain setpoint for BP
The main factors influencing blood pressure are:
Cardiac output (CO)
Peripheral resistance (PR)
Blood volume
Blood pressure = __?
Blood pressure = CO x PVR
The kidneys: regulate Na content, hence osmotic content, hence ECF volume, hence BP
Osmolarity = osmoles/volume
Volume = osmoles/osmolarity
ECF determined by total osmotic content & 90% of osmotic content is ___.
The kidneys: regulate Na content, hence osmotic content, hence ECF volume, hence BP
Osmolarity = osmoles/volume
Volume = osmoles/osmolarity
ECF determined by total osmotic content & 90% of osmotic content is Na.
Control of Sodium content:
Pressure changes at detection sites are indirect clues to Na content:
Neural baroreceptors signal via renal _____
INTRA-renal baroreceptors in _____ arterioles
Sodium chloride delivery to _____ of JGA
Effectors include:
Change in _____: sympathetic nerve activity (_____) and Angiotensin-2 (_____)
Anti-diuretic Hormone and Atrial Naturetic Peptide sometimes
Control of Sodium content:
Pressure changes at detection sites are indirect clues to Na content:
Neural baroreceptors signal via renal sympathetics
INTRA-renal baroreceptors in afferent arterioles
Sodium chloride delivery to macula densa of JGA
Effectors include:
Change in GFR: sympathetic nerve activity (minor) and Angiotensin-2 (major)
Anti-diuretic Hormone and Atrial Naturetic Peptide sometimes
Aldosterone stimulates Na reabsorption in cortical connecting _____ and collecting _____. Influences about _____% of total filtered sodium.
Aldosterone stimulates Na reabsorption in cortical connecting tubules and collecting ducts. Influences about 2% of total filtered sodium–BUT VERY IMPORTANT.
Renin is an enzyme. Angiotensin II only persists in the blood for 1 or 2 minutes, inactivated by angiotensin_____, but has multiple potential actions .
Renin is an enzyme. Angiotensin II only persists in the blood for 1 or 2 minutes, inactivated by angiotensinases, but has multiple potential actions .
