Session 5 Lectures Flashcards
What is the calculation for working out mean arterial bp ?
mean arterial BP = CO x TPR
and
mean arterial BP = diastole + 1/3 (systole - diastole)
What is the calculation for working out cardiac output?
CO = HR x SV
What are 3 locations of baroreceptors?
- Carotid sinus
- Aortic arch
- Afferent arteriole of kidney
How long does the baroreceptor help deal with hypertension?
For up to 15 minutes
It then resets back to the level it was previously at
Only works for acute changes in BP
What 4 neurohumoral pathways control circulating volume and BP?
- RAAS
- Sympathetic nervous system
- Anti-diuretic hormone (ADH)
- Atrial natriuretic peptide (ANP)
Where is renin released from?
From granular cells of juxtaglomerular apparatus
Give 3 factors that stimulate renin release
- Reduced sodium delivery into kidney
- Reduced pressure in the afferent arteriole (indicative of low blood volume)
- Sympathetic stimulation
What is the function of renin?
Converts angiotensinogen to angiotensin I
What converts angiotensin I to angiotensin II?
ACE (angiotensin converting enzymes)
Where are the main 2 types of angiontensin receptors?
Which produces main actions?
AT1 and AT2
AT1 receptor is where main actions produced from
Name the 5 sites of angiontensin receptors
- Kidney
- Arterioles
- Sympathetic NS
- Adrenal cortex
- Hypothalamus
What is the effect of angiotensin on arterioles?
Acts on smooth muscle receptors to cause vasoconstriction = increasing arterial BP
What is the effect of angiotensin on the kidney?
Increases sodium reabsorption and therefore water = increasing plasma volume and BP
What is the effect of angiotensin on the sympathetic NS?
Causing more noradrenaline to be released = increasing actions of sympathetic NS (increases renin release)
What is the effect of angiotensin on the adrenal cortex?
Stimulates aldosterone release
Aldosterone acts to increase sodium reabsorption by the kidneys
What is the effect of angiotensin on the hypothalamus?
Increases thirst sensation
Encourages fluid intake
What channel does aldosterone act on to increase sodium intake?
ENaC
Epithelial Sodium Channel
What effect do ACE have as well as conversion of angiotensin I to II?
They stimulate the breakdown of bradykinin to peptide fragments
This effects the vasodilation action of bradykinin
If bradykinin is not broken down what symptoms might a person
get?
Dry cough
How does stimulation of sympathetic nervous system increase BP?
It acts on smooth muscle receptors to cause vasoconstriction
Blood flow is reduced to kidney which stimulates renin release
When is anti-diuretic hormone stimulated?
When plasma osmolality increases or in severe hypovolaemia
It stimulates sodium reabsorption and water retention to increase plasma volume
Where is atrial natriuretic peptide synthesised and stored?
When is ANP released and what does it do?
In the atrial myocytes
They are released in response to stretch = the less the heart is filled the less they stretch and the less ANP released
ANP stimulates sodium excretion and prevents reabsorption
What effect do prostaglandins have?
Are they effective for a hypertensive patient?
They are vasodilators
They reduce sodium reabsorption and act as a buffer against excessive vasoconstriction to prevent damage to blood vessels
Not effective long term as they have a short half life