Exam1Lec8Baroreceptor&ChemoreceptorRegulation Flashcards
Chief Complaint: “I get dizzy and sometimes faint when I get up out of bed”
History of Present Illness:
A 70-year-old female was admitted to the hospital after fainting while getting our of bed, and hitting her head on her nightstand. After regaining consciousness, she has indicated that for the past year or so, she often becomes dizzy when getting out of bed or standing up from her kitchen table and has fainted in the past.
What is the primary cause of the dizziness and fainting spells with getting out of bed?
low venous return> decr in pre-load >decr in contractility >decr in SV=>Decr in MBP>decr blood to brain
O2 not in brain
Chief Complaint: “I get dizzy and sometimes faint when I get up out of bed”
History of Present Illness:
A 70-year-old female was admitted to the hospital after fainting while getting our of bed, and hitting her head on her nightstand. After regaining consciousness, she has indicated that for the past year or so, she often becomes dizzy when getting out of bed or standing up from her kitchen table and has fainted in the past.
What cardiovascular reflex pathway is likely to be dysfunctional?
baroreceptor detects arterial BP
low Ca=compliance which decr w/ age affecting baroreceptors
Chief Complaint: “I get dizzy and sometimes faint when I get up out of bed”
History of Present Illness:
A 70-year-old female was admitted to the hospital after fainting while getting our of bed, and hitting her head on her nightstand. After regaining consciousness, she has indicated that for the past year or so, she often becomes dizzy when getting out of bed or standing up from her kitchen table and has fainted in the past.
How does standing up provoke these episodes?
rapid changes in BP due to changes in blood flow due to change in gravity
Incr blood flow to extremities
What do vascular reflexes sense?
change in Internal sensory-feedback systems that “sense” or detect changes in important circulatory parameters (i.e. blood pressure, O2 and CO2 levels, pH, temperature
How do vascular reflexes respond?
via neg feedback pathways that alter the tonic autonomic control of the heart and vasculature. (involves ANS)
ex: activity of parasymp (heart)/symp (bv) will incr or decr
Vascualr refelxes work to maintian and optimize what?
cardiovascular performance in rapidly changing physiological situations.
rapidly changing physiological situations.: posture change, exercise
What are the type of vascular reflexes?
Peripheral Baroreceptors
Peripheral Chemoreceptors
Central Chemoreceptors
Pulmonary stretch receptors
Hypothalamus (temperature sensors)
Arterial baroreceptros play a key role in what?
short-term (seconds to minute) adjustments of blood pressure when relatively abrupt changes in blood volume, cardiac output, or peripheral resistance occur.
Posture changes
Exercise
Hemorrhage (loss in bv)
Arterial Baroreceptors are located where?
Stretch (mechanoreceptrs) receptors located in the carotid sinuses and the aortic arch.
What do Arterial Baroreceptors detect
These stretch receptors detect physical deformations in the vessel wall due to blood pressure changes.
For Arterial Baroreceptors how are changes relayed?
Changes are relayed to the nucleus tractus solitarius (NTS) in the medulla via afferent nerve fibers.
The carotid barorectrpr afferent travels where
the sinus nerve to the glossopharyngeal nerve to the NTS
located at carotid sinus
The Aortic baroreceptor afferent travels where
afferents travel along the vagus nerve to the NTS
located at aortic arch
Carotid Sinus afferent firing increases
with ____ blood pressure
increased
At normal arterial pressures, carotid sinus afferent firing occurs mainly during what?
systole
At normal arterial pressures carotid aferent firing rate decreases during what?
late systole and diastole
Barareceptor stimulation ____ sympathetic activity and ____ parasymp activity
decr, incr
An increased baroreceptor firing rate leads to what?
leads to vasodilation and bradycardia.
What must work in conjunction to slow the heart rate?
The reduction in sympathetic firing is paralleled by an increase in parasympathetic outflow that slows the heart rate.
vagus decr hr
Explain sypmathetic negative feeback
- incr BP
- incr baroreceptor firing
- decr sympt discharge
- decr vasoconstriction
- decr BP back to set value
- and vice versa
Explain parasym neg feedback pathway
- Incr bp
- incr barorecp firing
- incr vagal discharge
- decr hr
- decr blood pressure
and vice versa
Adaption of barorecptors occurs when?
during long-term changes in mean arterial blood pressure (hypertension), having a decreased sensitivity to pressure changes,
barorector are NOT contantly firirng, they adapt and reset their midpoint to respond to incr and decr (midpt goes up for someone who is hypertensive)
Where are the “low pressure” baroreceptors located?
Mechanoreceptors located in
Atria
Pulmonary vessels
where bood is reterning in the heart
they also sense mechanical changes
What do low pressure baroreceptors detect?
Detects blood volume changes (pre-load)
sense filling/fullness (this will make is fire more)
For atrial mechanoreceptors , how do the afferent fibers run?
They run the vagus to the medulla
For atrial baroreceptors, increased stimulation (stretc) incr stimulation of the medullary centets causing what 2 things
decreased parasympathetic output to the heart
(increasing heart rate)
increased sympathetic output to the heart
(increasing heart rate)
Negative Feedback to reduce preload by increasing cardiac output
Peripheral chemoreceptors are organized into what 2 locations?
aortic and carotid bodies
What are aortic bodies and carotid bodies?
Highly vascularized cells (lots of cap, perfusing them) in the aortic arch and carotid sinus that are sensitive to blood O2, CO2, and pH .
they are more tunesd to O2 changes
Aortic bodies and carotid bodies are monstly involved in what?
Mostly involved in respiratory regulation, but they have some minor affect on the vasomotor centers in the medulla
incr cardiac out , incr perih resistance and shunt it toward pulm circuit
What is the primary role of central chemoreceptors?
respiratory regulation but also some Cardiovascular effects
What stimulates the central chemoreceptors and where?
What does this cause?
Incr blood CO2 that the signal is sent to the medulla
causes incr sympathetic outflow and vasoconstriction(shut blood to lungs) to increase venous return(o2)
Central more tuned to CO2 and ph changes
What reduces stimulates the central chemoreceptors and
What does this cause?
Increased ventilation causes decreased blood CO2 levels
causes reduced sympa outflow resulting in vasodilation
Does O2 tension have an effect on the central chemorecptors?
NO
Long term control of BP (hours to days) involved regualting what?
Systemic blood volume by the kidneys
What are the main hormonal mechanisms involved in long term BP regulation?
- ADH secretions
- renin-angiotensin-aldsosterone sysyem
- atrial natriuretic peptides
How do the hormones affect blood volume for long term BP regulation
volume by regulating salt and water retention/excretion from the kidneys.
this is how we control circulatory volume
90 -95% of hypertension cases are called? What does this mean?
Essential hypertension. No known origins or causes. some genetic influences are known.
What are the characteristics that we see with someone with essential hypertension?
mean BP?
CO?
TPR?
Renal resistance?
Mean blood pressure is increased 40-60%
Cardiac Output is near normal
TPR is increased 40-60%
Renal resistance is increased 2-4X
What is needed in someone with essential hypertension to excrete normal amounts of salt and water?
High blood pressure
Explain the pathway of response to posture change
slide 33/34
