Short-term Control of Blood Pressure Flashcards
What are the three causes of changes in blood flow that occur during normal day to day life? (3)
- Tidal breathing
- Changes in body position
- Valsalva maneuver
What are some of the normal physiological mechanisms that maintain blood flow in response to day to day changes? (4)
- Vascular auto-regulation
- Baro-receptor mediated effects
- Central nervous system ischemic response effects
- Renal baro-receptor mediated effects
What are some of the abnormal responses that can be seen in the short term control of BP? (4)
- Abnormal auto-regulatory effects
- Autonomic dysfunction
- Drop in BP too large
- Pulsus parodoxus (and tidal breathing)
What happens if the body senses alterations in flow and BP?
Triggers compensatory mechanisms to maintain flow and BP.
How does changing body posture affect BP?
Effects of gravity on venous return
How does the valsalva maneuver affect BP?
Increases intrathoracic pressure = decreases venous return
What is vascular autoregulation?
Local blood flow maintained relatively constant despite an increased BP.
What is the response of vascular autoregulation when BP is increased?
Increased BP - stretch of arteriolar muscles - vasoconstriction - decreased flow
What is the response of vascular autoregulation when BP is decreased?
Decreased BP - increased vasodilator metabolites - increased flow
Where are the baro-receptors found?
Carotid, aortic, renal baro-receptors
What effect do the baro-receptors have on BP?
Baroreceptors pick up decreased blood pressure
= activate SNS
- vasoconstriction, increased heart rate, increased cardiac contractility
= increased cardiac output and increased BP
The baroreceptors work in synergy with what other response?
CNS ischemic response
What does the cerebral ischemic response protect against?
The cerebral ischemic response safeguards cerebral perfusion
What does VMC stand for?
Vasomotor center
What is effect of the cerebral ischemic response?
Massive decrease in BP = Greatly decreased cerebral blood flow = Increased PCO2, Increased H+ = Activation of VMC = Increased sympathetic response = (intense vasoconstriction) Increased HR, Increased TPR = RESTORES BP
What are the renal BR mediated RAAS effects?
Decreased blood pressure:
- Renin release
- Aldosterone release
What is the effect of renin on BP?
Renin converts Angiotensinogen to Angiotensin I = converted by ACE (in lungs) to Angiotensin II = VASOCONSTRICTION = increased TPR
What is the effect of aldosterone on BP?
Aldosterone causes increased Na+ re-absorption in kidney (Na+ and H2O resorption) = increased plasma volume = increased venous return = Frank-Starling effect = Increased stroke volume = Increased CO
What are the two causes of abnormal responses to changes in BP?
- Autonomic dysfunction
2. Drop in flow or BP too large for ANS to cope
What are the consequences of abnormal responses to changes in BP?
Dizziness, fainting and syncope
What are the signs and symptoms of compensatory changes following acute drops in blood flow and BP?
Pallor, sweating, tachycardia, nausea
all due to sympathetic activation
What are the two types of autonomic dysfunction abnormal responses?
- Neurological
2. Emotional (vasovagal)
What are some causes of neurological autonomic dysfunction?
- Neuropathies (DM, strokes)
2. Blood clots in the VMC
Explain vasovagal syncope:
Activation of hypothalamus - activation of PSNS - increased vagal firing - decreased HR - venodilation (venous pooling) - decreased venous return - decreased stroke volume - decreased BP (vasodilation also = decreased BP)
