Reading 4 (130-135) Flashcards
In a heart, the ____ ventricle creates _____ to propel the blood through the _______ to the _________. Once the blood is ______ by the lungs and return to the heart, the _____ ventricle creates a _____ pressure that propels the blood through the ______ and systemic arteries to the organs and muscles of the body.
In a heart, the RIGHT ventricle creates PRESSURE to propel the blood through the PULMONARY ARTERIES to the LUNGS. Once the blood is OXYGENATED by the lungs and return to the heart, the LEFT ventricle creates a GREATER pressure that propels the blood through the ______ and systemic arteries to the organs and muscles of the body.
The composition of the walls of the large arteries give them the ability to ______ and _____ which dampens the dramatic pressure changes created when the ventricles ____ blood into aorta.
The composition of the walls of the large arteries give them the ability to DISTEND and RECOIL which dampens the dramatic pressure changes created when the ventricles EJECT blood into aorta.
As the arteries close heart distend with each ventricular _______, they ____ the rest of the arterial system from the large ____ waves generated by the ventricles.
As the arteries close heart distend with each ventricular CONTRACTION, they CUSHION the rest of the arterial system from the large PRESSURE waves generated by the ventricles.
______, one of the fibrous molecules that composes the arterial walls, _____ easily and uniformly distributes the pressure created by the ventricle across the artery wall. As the pressure in the artery and diameter of the artery ______, the force inside the artery is gradually transferred to the more rigid ______ fibers that are also components of the arterial wall
ELASTIN, one of the fibrous molecules that composes the arterial walls, STRETCHES easily and uniformly distributes the pressure created by the ventricle across the artery wall. As the pressure in the artery and diameter of the artery INCREASE, the force inside the artery is gradually transferred to the more rigid COLLAGEN fibers that are also components of the arterial wall
When large arteries are ____ and pressure inside the arteries is stored in the arterial walls, the arteries fxn as pressure ______ that are ready to release pressure for moving blood when the arterial walls _____.
When large arteries are EXPANDED and pressure inside the arteries is stored in the arterial walls, the arteries fxn as pressure RESERVOIR that are ready to release pressure for moving blood when the arterial walls RECOIL.
The recoil of the arteries releases ____ which propels the blood from the _____ arteries to the _____ arteries. Even tho large ____ waves generated by ventricles are reduced by the _____ of the aorta and other large arteries, the _____ recoil of the large arteries still causes the pulsatile flow of blood to occur in _____ arteries and arterioles. Blood flow smooths to continuous _____ flow when blood reaches the _______
The recoil of the arteries releases PRESSURE which propels the blood from the LARGER arteries to the SMALLER arteries. Even tho large PRESSURE waves generated by ventricles are reduced by the DISTENSION of the aorta and other large arteries, the PULSATILE recoil of the large arteries still causes the pulsatile flow of blood to occur in SMALLER arteries and arterioles. Blood flow smooths to continuous LAMINAR flow when blood reaches the CAPILLARY BEDS
The autoregulatory response is mediated by two sets of ______ that are involved in the regulation of ______ and ____.
The autoregulatory response is mediated by two sets of BARORECEPTORS that are involved in the regulation of BLOOD PRESSURE and CARDIAC FXN.
The arterial baroreceptors, which are found in the _____ and _____ are responsible for regulating _______ and ______ through sympathetic and parasympathetic chanells stemming from the ____.
The arterial baroreceptors, which are found in the CAROTID SINUS and AORTIC ARCH are responsible for regulating HR and CARDIAC CONTRACTILITY through sympathetic and parasympathetic channels stemming from the CNS.
The cardio-pulmonary baroreceptors are found in the _____, _____, and ______. With slight decreases in BP below normal values there is a _____ effect seen in the ____ region of the body (hypovolemia), which causes a decrease in ____. This dec in CVP triggers the cardiopulmonary baroreflex to elicit a _______ response in the muscles associated with a decrease in ______ and an increase in _______, allow for greater VR.
The cardio-pulmonary baroreceptors are found in the RIGHT ATRIUM, VENTRICLES, and PULMONARY ARTERIES. With slight decreases in BP below normal values there is a VENOUS POOLING effect seen in the LOWER region of the body (hypovolemia), which causes a decrease in CENTRAL VENOUS PRESSURE (CVP). This dec in CVP triggers the cardiopulmonary baroreflex to elicit a SYMPATHETIC MEDIATED VASOCONSTRICTOR response in the muscles associated with a decrease in VENOUS COMPLIANCE and an increase in PERIPHERAL VASCULAR RESISTANCE, allowing for greater VR.
Theres some controversy regarding at what levels of _____ the cardiopulmonary baroreflex is present, as compared to the arterial baroreflex. Postulated the _______ baroreflexes respond primarily to _____ levels of stress (simulated lower body neg pressure [LBNP] <20 mmHg)
Theres some controversy regarding at what levels of ORTHOSTATIC PRESSURE the cardiopulmonary baroreflex is present, as compared to the arterial baroreflex. Postulated the CARDIO-PULMONARY baroreflexes respond primarily to LOWER levels of stress (simulated lower body neg pressure [LBNP] <20 mmHg)
With greater dec in MABP as seen in the ____ posture, the arterial BR firing rate is ___, causing a sympathetic nervous system mediated arterial _____ and both PNS and SNS mediated ____ in HR. Initial inc in HR is due to _____ of PNS activity. Inc in HR exceeding ~100bpm mediated by _____. _____ BR act as first line of defence to protect against major decrements in MABP during transition from _____ to _____ position. Both reflexes allow for adequate ______ to maintain blood flow to brain, preventing ______.
With greater dec in MABP as seen in the UPRIGHT posture, the arterial BR firing rate is REDUCED, causing a sympathetic nervous system mediated arterial VASOCONSTRICTION and both PNS and SNS mediated INCREASE in HR. Initial inc in HR is due to WITHDRAWL of PNS activity. Inc in HR exceeding ~100bpm mediated by SNS. ARTERIAL BR act as first line of defence to protect against major decrements in MABP during transition from SUPINE to UPRIGHT position. Both reflexes allow for adequate VR to maintain blood flow to brain, preventing SYNCOPE.
What is orthostatic stress
Force of gravity acting upon body while in upright position
What happens when theres inability of body to adapt to orthostatic stress
Result in gravitational-induced venous pooling below heart w/rapid fall in BP leading o cerebral ischemia and loss of consciousness (SYNCOPE)
What is syncope
Body’s final defence mechanism during severe drops in BP due to orthostatic stress (orthostatic hypotension)
Pro of syncope (fainting)
Causes person to collapse back into supine position allowing for blood remobilization and restore consciousness
Whats first defence against venous pooling
Muscle pump = contractions of leg muscles propel sequestered venous blood back to heart
When is muscle pump active
Initial transition to upright position and if body remains in motion
What is 2nd line of defence against orthostatic intolerance
Changes in neurovascular control
Example of neurovascular changes
rapid changes in total peripheral resistance (vasoconstriction) limiting flow to extremities and splanchnic vascular region while promoting passive emptying.
What is TPR mathematically
Difference btwn mean arterial pressure and central venous pressure, divided by CO
What are the delayed humoral effects to orthostatic stress
Activation of sympathetic system (mediating release of epinephrine and ADH), renin-angiotensin-aldosterone system
- humoral mechanisms highly effective for altering blood volume and sympathetic tone over longer bouts orthostatic stress
During quiet standing, sympathetic BP DOES/DOES NOT fall and DBP often ____, CO ______ due to impaired heart filling; only partially offset by inc in HR. Also ____ in cerebral blood flow (~6%) due to cerebrovascular autoregulation process being at its lower limit.
During quiet standing, sympathetic BP DOES NOT fall and DBP often RISES, CO DECREASES due to impaired heart filling; only partially offset by inc in HR. Also DECREASE in cerebral blood flow (~6%) due to cerebrovascular autoregulation process being at its lower limit.
Standing results in pooling of _____ blood in lower extremities and splanchnic circulation
Standing results in pooling of 500mL to 1000mL blood in lower extremities and splanchnic circulation
In patients w/previous history of syncope, head-up tilt induced orthostatic stress serves as stimulus for
induction of vasovagal hypotension
Describe the dec in BP with HUT
- BP dec linear fashion w/inc tilt
- Dec most in early transition to HUT
- Associated w/change in perfusion pressure across body
- initial transition to HUT there’s venous pooling effect seen in legs as MABP significantly drops due to orthostatic stress being placed upon vasculature
HUP of what degree to elicit central hypovolemia effect
80 degrees
CPP?
cerebral perfusion pressure
What are signs of presyncope
Dizziness, nausea, sweating, light-headedness, weakness
What is orthostatic hypotension defined as
Reduction in systolic BP of at least 20mmHg or reduction in DBP of at least 10 mmHg, during 1st 3 mins of standing or HUT of 60 degrees on tilt table
When standing how does MABP change in feet and brain
- from heart to feet = inc MABP ~100mmHg
- from heart to brain = dec MABP ~30mmHg
When orthostatic hypotension is exhibited, what 2 possible mechanisms occur that inhibit blood flow back to heart and brain
- Failure of autoregulatory system in eliciting counter changes in vasculature n HR to counter fall in MABP
- Reduction in central blood volume, which leads to central hypovolemia. High venous compliance, peripheral vasodilation, muscle atrophy all factors associated w/central hypovolemia (low VR)
What is a valsalva maneuvar
Force expiration against closed glottis
What does force expiration against closed glottis cause
Changes in intrathoracic pressure that dramatically affect VR, CO, arterial pressure, and HR
What movements can cause a valsalva maneuvar
- weightlifting
- rapid, max application of force over short duration movements
- staining while having bowel movement
A valsalva maneuvar _____ abdominal and thoracic cavities and is thought to ____ muscle action
A valsalva maneuvar STABILIZES abdominal and thoracic cavities and is thought to ENHANCE muscle action
Describe the phases in a prolonged valsalva manuver
Phase I: ONSET of strain. Inc SBP and DBP due to transmission of intrathoracic pressure to left heart and aorta. Baroreceptors may sense inc in BP and the HR may dec to compensate
Phase IIa: during CONTINUED strain. Inc in SBP and DBP rapidly reversed and falls below normal resting values due to decreased VR caused by collapse of thoracic veins due by inc intrathoracic pressure.
Phase IIb: The resulting dec in BP are sensed by baroreceptors, there’s reflex mediated inc in HR, and a peripheral vasoconstriction which prevents further dec in BPs
Phase III: immediately AFTER release of STRAIN. Further dec in BP as pressure surrounding left heart aorta suddenly dec. May be additional inc in HR during this phase caused by additional stimulation of baroreceptors
Phase IV: occurs at TIME of the ARTERIAL PRESSURE OVERSHOOT. After intrathoracic pressure suddenly reduced, there’s large inc in VR which results in large inc in stroke volume. This along w/still-existing peripheral vasoconstriction, causes ARTERIAL PRESSURE OVERSHOOT LASTS 4-8 SECONDS. The baroreceptor reflex is then activated resulting in dec in BP and slowing of HR back towards normal
