CVS: Control Of Blood Pressure Flashcards
How is blood pressure regulated in the shorter term?
Baroreceptor reflex:
They adjust sympathetic and parasympathetic inputs to the heart to alter CO They also adjust sympathetic input to peripheral resistance vessels to alter TPR.
Where are baroreceptors found?
- Aortic arch
- Carotid sinus
Why do the baroreceptors not control sustained increases in blood pressure?
They become insensitive.
Name the 4 neurohumeral pathways which control circulating volume and hence blood pressure.
- Renin- angiotensin-aldosterone system
- Sympathetic nervous system
- Antidiuretic hormone
- Atrial natriuretic peptide
Where us renin released from?
Juxtaglomerular apparatus (JGA)
Name 3 factors which stimulate renin release.
- Reduced na|Cl o distal tubule
- Reduced perfusion pressure
- Sympathetic stimulation of JGA
What are the consequences of the RAAS system?
Acts to increase BP.
- Vasoconstriction
- Stimulates Na+ readsorbtion
- Stimulates aldosterone (which then stimulates sodium readsorbtion)
Which is the main Ang II receptor?
AT1
What type of receptor is AT1?
G-protein coupled
What channel does aldosterone act on and what is the molecular mechanism it stimulates?
ENaC: activates apical Na+ channel and apical k+ channel (hence sodium is readsorbed and potassium is lost)
Name 2 substrates that ACE acts on.
- Angiotensin I
2. bradykinin
What is the role of bradykinin?
Vasodilator actions, hence its break down reduces vasodilation.
Describe how direct sympathetic stimulation at the kidneys increase blood pressure.
- Acts on arterioles to reduce renal blood flow
- Stimulates granule cells of afferent arteriole to release renin
- Stimulates sodium readsorption from PCT
What is the main function of antidiuretic hormone?
Formation of concentrated urine by retaining water to control plasma osmolarity.
What is the main function of natriuretic peptides?
Promotes sodium excretion to lower blood pressure.
When are natriuretic peptides released?
They’re synthesised and stored in myocytes and released in response to stretch.
What is the role of postaglandins?
- Act as vasodilators
- Locally acting enhance glomerular filtration and reduce sodium reabsorbtion
- Act as a buffer to excessive vasoconstriction produced by SNS and RAAS
Define hypertension.
Sustained increase in blood pressure.
What is the clinical range of stage 1 hypertension?
> 140/90 mmHg
What is the clinical range of stage 2 hypertension?
> 160/100 mmHg
What is the clinical range of severe hypertension?
> 180 systolic or >110 diastolic
Give some examples of causes of secondary hypertension.
- Renovascular disease
- Chronic renal disease
- Hyperaldosteronism
- Cushing’s sundrome
Name some none-pharmacological approaches to treating hypertension.
- Exercise
- Diet
- Reduce sodium intake
- Reduced alcohol intake
What drugs can be used to treat hypertension?
- ACE inhibitors
- Ang II receptor antagonists
- L-type calcium blockers
- Alpha-1 receptor blocker (can cause posteral hypotension)
- Diuretics
