52.1 The Control of Systemic Arterial Blood Pressure Flashcards
What provides short-term regulation for arterial blood pressure?
Baroreceptor reflex
circulation as a closed system
Describe the receptors, ganglia and afferent nerves involved in the baroreflex.
Carotid sinus baroreceptors:
- Via the petrosal ganglia
- Glossopharyngeal nerve (IX)
Aortic arch baroreceptors:
- Via the nodose ganglia
- Vagus nerve (X)
What type of receptors are involved in the baroreflex?
Baroreceptors -> These detect transmural pressure, not flow
What are the atrial baroreceptors?
↑-pressure receptors in carotid sinus + aortic arch
*Innervated by glossopharyngeal/ vagus nerve respectively
What are the cardiopulmonary baroreceptors?
↓-pressure receptors in atria + adjacent large veins.
What does stimulation of the low pressure baroreceptors lead to?
Triggers secretion of ADH, angiotensin and aldosterone (increase salt and water reabsorption in the kidney to raise BP)
Where do the afferent nerves of the baroreflex synapse in the brain?
Nucleus tractus soltarius (NTS) -> This is in the medulla
Describe the efferent target organs of the baroreflex.
Parasympathetic:
- Heart
Sympathetic:
- Heart
- Blood vessels
- Kidney
Is the normal stability of ABP independent or dependent of local flows to organs and tissues?
It is independent of local flows to organs and tissues.
How is ABP regulated in the long term?
By renal pressure natriuresis (sodium excretion) and diuresis (water loss) to keep blood volume at 5L with circulation as an open system.
What is Guyton’s hypothesis/ physical equilibrium model?
Guyton’s hypothesis → ↑ renal perfusion pressure → ↑ Na+ excretion → ↑ water loss → ↓ ECF → ↓ BP
What is the mechanism of Guyton’s hypothesis?
Mechanism unclear → 2 hypotheses:
*↑ renal perfusion → ↑ GFR + Tubular flow rate → ↓ time for water/ Na+ reabsorption → ↑ excretion.
*↑ renal perfusion pressure → ↑ shear stress → ↑ NO production → ↑ medullary washout
Which system is in control of long term blood pressure regulation?
Renin-angiotensin-aldosterone axis (RAAS)
What is typical blood pressure?
120/80mmHg
Which blood pressure is defined as being hypertensive?
Three consecutive readings of over 140/90 at home (monitored 24 hours at home where two readings are taken every day)
What are the BP targets for those > 80, and <80?
- <140/90 mmHg in patients aged <80
*<150/90 in patients aged ≥ 80
How can hypertension be classified?
1o → essential HT (95%)
*Heterogeneous disease
*Precise + ultimate causes undetermined despite multiple genetic, hormonal, nervous, + environmental factors + lifestyle linked to HT.
2o → 5%. Known cause
*Renal disease (e.g. renal stenosis/ diabetic nephropathy)
*Endocrine disorders (e.g. Conn’s syndrome - 1o hyperaldosteronism/ Cushing’s disease - pituitary adenoma → ↑ ACTH → ↑ cortisol)
What are type 1 and type 2 HT according to NICE?
*Type 1 HT
<55 y/o
associated w ↑ renin levels + vasoconstriction
*Type 2 HT
>55y/o or African-Caribbean family origin
associated w/ ↓ renin levels + ↑ circulating volume