SM 116a - Regulation of Arterial Pressure Flashcards
Low pressure baroreceptors:
Location:
Stimulus:
Response:
-
Location:
- Right atrium
-
Stimulus:
- Increased right atrial volume = activation
-
Response Goal = decrease blood volume
-
Secrete ANP
- Vasodilation
- Excretion of Na+, H2O from kidney
- Increase HR (Bainbridge reflex)
- Increase CO -> increase renal perfusion -> increase excretion of Na+, H2O
- Renal vasodilation
- Decreased ADH (vasopresin) secretion
- Decreased H2O reabsorption in kidneys
-
Secrete ANP
What are the 3 coordinating centers in the brain that send efferent signals as part of the baroreceptor reflex?
- Cardiac Decelerator activation
- Cardiac Accelerator inhibition
- Vasoconstrictor Center inhibition
Note: All of the above recieve input from the nucleus tractus solitarius, which recieves afferent signals from sensors
According to Starling’s law, how does increased plamsa volume affect stroke volume?
What mechanism in the body normally blunts this response?
Starling’s law indicates that increasing plasma volume will lead to increased stroke volume. Basically, preload increases strength of contraction
Activation of the baroreceptor reflex will blunt this response as plasma volume increases
- Stimulation of cardiac decelerator
- Inhibition of cardiac accelerator, vasoconstrictor
- Increased ANP secretion to promote excretion of H2O and Na+
What is the equation that estimates mean arterial pressure (MAP)?
MAP = HR * SV * SVR
- HR = Heart Rate
- SV = Stroke Volume
- SVR = Systemic Vascular Resistance
OR
MAP = (2 * DBP + SBP)/3
What is the major central chemoreceptor?
What is its overall function?
Central chemoreceptors detect…
- Increases in pCO2
Activation of these receptors signals to increase oxygen perfusion to the brain
- Dis-inhibtion of the vasoconstriction center
- Increased peripheral vasoconstriction shunts blood to the brain
- Increased arterial pressure: Cushing reaction
- Increasing arterial pressure makes flow to the brain the “path of least resistance”
- Bradycardia
Which coordinating center in the brain recieves afferent signals from baroreceptors in the body?
Nucleus tractus solitarius
High pressure baroreceptors:
Location:
Stimulus:
Response:
-
Location
- Carotid sinus
- Aortic arch
-
Stimulus:
- Stretch (signals high pressure)
- Carotid begins firing at 50 mmHg
- Aortic arch begins firing at 110 mmHg
- Stretch (signals high pressure)
-
Response:
- Increased stretch = increased rate of firing
- Carotid signals to glossopharyngeal nerve
- Aortic signals to vagus nerve
- Activate parasympathetic signals and reduce sympathetic signals to lower blood pressure
- Increased stretch = increased rate of firing
Describe the sympathetic effector pathways of the baroreceptor reflex
Activation of baroreceptors ->
- Inhibition of the cardiac accelerator
- Slow SA node firing
- Decrease HR
- Decrease BP
- Decrease contractility
- Slow SA node firing
- Inhibition of the vasoconstrictor response
- Decrease systemic vascular resistance (TPR)
- Increase unstressed volume
- Decrease preload
- Decrease contractility
- Decrease CO
- Decrease BP
- Decrease systemic vascular resistance (TPR)
What are the three major classes of peripheral chemoreceptors?
What is their overall function?
Peripheral chemoreceptors can detect…
- Decreased pO2
- Increased pCO2
- Decreases in pH
When these receptros are activated, they signal to…
- Increase ventilation
- Increase HR (reflex tachycardia)
What are the differences between the carotid and aortic arch baroreceptors?
Both are high pressure baroreceptors
- Carotid
- Activated at 50 mmHg
- Saturation at lower pressure than aortic arch
- Signals to glossopharyngeal nerve (CN IX)
- Aortic Arch
- Activated at 110 mmHg
- Signals to vagus nerve (CN X)
Describe the Cushing reflex
The Cushing reaction functions to maintain perfusion of blood to the brain, even when intracranial pressure increases
- If intracranial pressure increases, blood will typically flow down the path of least resistance and skip the brian
- This leads to increased pCO2 in the brain, sensed by central chemoreceptors
- The central chemoreceptors cause disinhibition of the vasoconstriction center
- -> intense perhipheral vasoconstriction
-
-> increased blood flow to the brain: now the path of least resistance
- This usually causes increased arterial pressure and bradycardia
What are some signs of the Cushing reflex that we can easily measure?
Why is this clinically significant?
Signs of the cushing relex
- Increased systolic blood pressure
- Bradycardia
- Irregular respiration
This is clinically significant because it indicates increased intracranial pressure; usually not a good thing
List the components of the general neural arc reflex
- Sensors send afferent pathways to a coordinating center (ex: brain)
- A coordinating center integrates signals from the afferent pathways and sends efferent signals to effectors
- Effectors recieve efferent signals an denact physiologic changes
- The sensors detect these changes, and feed back to the coordinating center via afferent pathways
Describe the parasympathetic effector pathways of the baroreceptor reflex
Activation of baroreceptors -> Activation of the cardiac decelerator
- Slows SA node firing
- Decrease HR
- Decrease BP
Describe the components of the baroreceptor reflex
- Sensors
-
High pressure baroreceptors
- Carotid
- Aortic Arch
-
High pressure baroreceptors
- Coordinating center
- Nucleus tractus soliarius in the medulla of the brain
- Parasympathetic: Activated
- (1) Cardiac Decelerator
- Sympathetic: Inhibited
- (2) Cardiac Acelerator
- (3) Vasoconstrictor Center
- Effectors
-
1) Inhibitory signaling to SA node
- Slow HR
- Decrease BP
-
2) Decreased excitatory signaling to SA node
- Decrease contractility
- Slow HR
- Decrease BP
-
3) Decreased systemicc vascular resistance
- Increase unstressed volume
- Decrease preload
- Decrease CO
- Decrease BP
-
1) Inhibitory signaling to SA node
What is the physiological basis for increased HR in response to both decreased and increased circulating volume?
- Baroreceptor Reflex (opposite): Increased HR in response to decreased circulating volume
- Relief of stretch on atrial receptors -> tachycardia to help increase blood pressure
- Bainbridge Reflex: Increasd HR in response to increased circulating volume
- Stretch of low pressure baroreceptors -> tachycardia to increase perfusion to the kidneys, to facilitate the excretion of Na+ and H2O
