Blood Pressure Control and Hypertension Flashcards
How is BP controlled in the short-term?
relatively neural and usually due to the baroreflex
What is the baroreflex?
The baroreflex is associated with BP homeostasis and is a form of negative feedback. It takes place in the arterial baroreceptors and the brainstem autonomic centres.
What are the baroreceptors? Where are they situated?
They are situated in the carotid sinus (which is thin walled and highly innervated within the internal carotid artery) as well as the aortic arch. With a greater degree of stretch comes greater firing which responds very quickly. (within one cardiac cycle)
What is the Brainstem Cardiovascular Control Centre?
This is situated in the medulla and has both pressor and depressor centres, operating via sympathetic and parasympathetic nerves.
What is the baroreflex buffer and how is the baroreflex reset?
The baroreflex ‘buffer’ refers to the baroreflex’s ability to stabilise pressure and smooth out variations that can occur due to posture, eating, defecation and noise.
Resetting the baroreflex requires 1-2 days for the threshold for baroreflex firing to adjust/reset to new pressure levels.
What are chemoreceptors?
These receptors respond to very low oxygen levels. They are situated in carotid and aortic bodies outside of the arteries and are stimulated at very low MAP (low flow; low oxygen; high carbon dioxide, low pH)
Explain Correlating factors with respect to BP.
Sex & BP: Men have higher BP than Women (males: mean = 94; females: mean = 89)
Age & BP: blood pressure rises with age
Body size & BP: bigger body mass leads to a higher BP
Diurnal Variation: lower BP at night (20mmHg); less variability at night; less sympathetic activity at night
Seasonal Variation: Summer pressures are about 2mmHg lower than winter
What is hypertension?
Hypertension is simply the upper end of the distribution (high BP). It is defined by an arbitrary and falling cut-off.
Explain the population paradox surrounding High BP.
A population paradox can be seen in that in a population, more deaths occur in the larger number of people at moderate risk than in the small number of people at the highest risk.
