Week 1 - Short and Long Term Control of Blood Pressure Flashcards
What is the baroreflex and where are the baroreceptors?
change in pressure detected, sending nervous signal to counterract change. baroreceptors found in aortic arch and carotid sinus
Where do signals from baroreceptors go?
aortic arch sends through vagus nerve and carotid sinus sends through glossopharyngeal nerve. ends up in medulla oblongata - medullary cardiovascular centre.
How does parasympathetic system decrease heart rate?
sends signals to release acetylcholine, binding to cholinargic muscarinic receptors on SA and AV nodes, causing hyperpolarisation and longer time to get to threshold
How does sympathetic nervous system increase MAP?
adrenaline + noradrenaline released in blood:
- b2 receptors on ventricle increases contractility
- b1 receptors on SA and AV cause faster depolarisation
- a1 receptors on smooth muscle constricts vessels
all increase EDV
What is the role of cardiopulmonary baroreceptors?
found in atria and walls of lung vessels. detect stretch and cause response.
What is the role of central chemoreceptors?
detect increase in PaCO2 and decrease in PaO2 - trigger respiratory drive. more O2 in lungs, more blood needed to take it in. increase MAP
What is the role of muscle chemoreceptors and joint receptors in controlling blood pressure?
muscle chemoreceptors detect metabolite conc. changes. joint receptors detect joint movement
How are higher centres involved in vascular system?
hypothalamus coordinates response for thermoregulation. if too hot, tells medullary CVS to vasodilate so blood can be lost.
cerebral cortex may be involved - strong emotional stimuli like a phobia may cause fainting
What do we do that causes the valsalva manoeuvre?
defecating, weight lifting, popping our ears
How does the CVS respond to the valsalva manoeuvre, including all phases from start to end.
- you get increased thoracic pressure, decreasing pressure below diaphragm, causing reduced venous pressure. baroreceptors in aortic arch detect low MAP and sends signal to medullary CV centre.
- increases sympathetic tone - b1 in SA and AV node, contractility (b2), and a1 (vasoconstricton). these increase EDV and MAP. - then when manoeuvre stops, we have decreased thoracic pressure and increased below diaphragm pressure, causing rapid increase in SV and MAP.
- baroreflex now increases parasympathetic tone to reduce MAP. eventually gets back to normal.
How is the valsalva manoeuvre clinically relevant?
can be used to test autonomic function and baroreceptor reflex. reduced in elderly ppl and autonomic neuropathy (diabetes). people die when they poo
How the valsalva manoeuvre be dangerous?
elderly, obese and sedentary individuals may die when defecating as their heart cant take the strain and baroreceptors may lack sensitivity.
How is blood pressure controlled long term?
kidneys and hormone systems. not baroreflex - just short term.
How does transport in the kidney work in short?
afferent and efferent arterioles transport blood to and from kidneys. bowmans capsule filters blood and sends it through proximal tubule. goes through loop of henle and ends up in collecting duct.
What are the 3 hormone systems that regulate long term blood pressure?
- renin-angiotensin-aldosterone system
- anti diuretic hormone
- atrial natriuretic peptide and brain natriuretic peptide (ANP and BNP)
What is the cause of hypertension?
you’d think we know given our knowledge on MAP regulation. 5-10% is secondary - known cause. rest are primary and idiopathic - no known cause. knowledge of MAP mechanisms useful for treatment
How does the renin-angiotensin-aldosterone system work?
negative feedback. renin is produced by 3 mechanisms, and eventually converts to angiotensin II, which converts then has 3 mechsnisms.
What are the 3 triggers of renin production?
OVERALL, LOW BP
- sympathetic nerves caused by low BP stimulates juxtaglomerular cells in afferent arteriole, releasing renin
- decreased distesion of afferent arterioles (renal baroreflex) detects low MAP and increases sympathetic tone. same as above
- decreased delivery of Na+ and Cl- to macula densa. low BP means less filtration, so less ions exit at bowmans, and macula densa notices that. signals reduced MAP and triggers release of renin
How does angiotensin II cause increased MAP?
- stimulates release of aldosterone, increasing reabsorption of Na+ in loop of henle and causing more water retention. increases plasma volume and thus MAP.
- also stimulates release of ADH
- also is vasoconstrictor - increasing MAP
How is release of ADH triggered?
- Angiotensin
- decreased blood volume by baroreceptors. sends signals to medullar then pituitary gland releases
What does ADH do?
increases permeability of collecting duct to water to increase plasma volume and MAP
Where are ANP and BNP produced and released?
ANP (arterial natriuretic peptide) produced and released in myocardial cells in atira. BNP produced and release in myocardial cells in ventricles
What is the purpose of ANP and BNP?
detects high MAP and causes increased excretion of sodium, causing more water loss, reducing PV and MAP.
What triggers the release of ANP and BNP?
atria and ventricles distension - enlargement due to more blood - stretches.
