Regulation of Arterial Blood Pressure and Blood Volume Flashcards
What types of receptors help regulate release of hormones to regulate flow and pressure?
Arterial and cardiopulmonary baroreceptors
Arterial chemoreceptors
Pulmonary stretch receptors
Chemosensitive receptors in heart and viscera
‘Ergoreceptors’ in skeletal muscle (metabolites produced during exercise)
Trigeminal receptors (exposure of face to water, “diving reflex”)
What are baroreceptors?
Sensory nerve endings that signal the CNS to changes in arterial blood pressure
How do baroreceptors function?
1) they inhibit sympathetic activity and promote parasympathetic activity
2) they serve as a negative feedback mechanism to changes in blood pressure
What two neural pathways are involved in sensing changes in blood pressure?
Carotid sinus nerves (CN IX)
Aortic depressor nerves (CN X)
What factors determine baroreceptor activity?
1) Mean arterial pressure
2) Rate of change in pressure [fast changes trigger fast response]
3) Large artery compliance
What is the pressure threshold for a baroreceptor?
The minimum pressure at which baroreceptors fire (usually 40-60 mm Hg)
What is the sensitivity of a baroreceptor?
The slope of an activity-pressure relationship; sensitivity is usually highest near baseline
What is the saturation pressure?
The pressure above which baroreceptors no longer fire with increasing intensity
How does a baroreceptor respond to increasing arterial blood pressure?
It sends signals to the CNS that will ultimately promote:
1) increased parasympathetic activity
2) decreased sympathetic activity
3) decreased vasopressin release
How does a baroreceptor respond to decreasing arterial blood pressure?
It sends signals to the CNS that will ultimately promote:
1) decreased parasympathetic activity
2) increased sympathetic activity
3) increased vasopressin release
What happens to baroreceptors during sustained changes in blood pressure?
Baroreceptors adapt to the sustained changes as a new normal
How are baroreceptors affected in chronic hypertension?
Their activity reduces and their sensitivity to changes reduces
What other conditions can reduce baroreceptor effectiveness?
atherosclerosis, myocardial ischemia and infarction, heart failure, diabetes mellitus, obesity, and aging
What are consequences in the reduction of baroreceptor sensitivity?
1) Increased variability in blood pressures
2) Increased risk of arrhythmias and sudden heart death
3) Promotes high sympathetic activity
Which receptors are primarily responsible for detecting volume changes?
Cardiopulmonary (vagal afferent) baroreceptors
How do cardiopulmonary receptors respond to diminished blood volume?
Promote pathways that:
1) Increase sympathetic activity
2) Increase vasopressin
How do cardiopulmonary receptors respond to heightened blood volume?
Promote pathways that:
1) Reduce sympathetic activity
2) Reduce vasopressin
What are long term factors that influence blood volume and pressure?
1) Renal mechanisms–fluid and sodium retention
2) Arterial wall thickening
3) Neurohormonal/paracrine effects
4) Environmental factors
5) Genetics
What is the role of the carotid body cell?
A glomus cell detects changes in oxygen, carbon dioxide, and pH in the blood.
What is the effect of glomus cell activation?
The CNS promotes increased respiration, sympathetic activity to increase vascular resistance, and parasympathetic activity to decrease heart rate; the change in ventilation will negate the latter two.
What is the Bezold-Jarisch reflex?
Certain conditions like ischemia promote chemoreceptors that trigger both vagal and sympathetic afferent activity. The sympathetic system will attempt to increase heart rate and arterial pressure whereas the parasympathetic system will try to slow these down
How does a patient with the Bezold-Jarisch reflex happening present?
Has bradycardia and hypopnea
