Arterial Blood Pressure Regulation

Explain short-term blood pressure regulation and identify the key players

regulates BP within seconds to minutes

regulates blood vessel diameter, HR, and contractility

key players: baroreceptor reflex, chemoreceptor reflex, CNS-ischemic response, and atrial reflex

Briefly explain the baroreceptor reflex for hypotension and hypertension

hypotension: decreased BP → decreased firing frequency of baroreceptors → increased sympathetic activity and decreased parasympathetic activity → increased HR, SV, and BP

hypertension: increased BP → increased firing frequency of baroreceptors → decreased sympathetic activity and increased parasympathetic activity → decreased HR, SV, and BP

What is the valsalva maneuver and what do we use it for?

forceful ehalation against a closed airway

used to decrease HR

how it works: increased intrathoracic pressure → increased baroreceptor stretch -. increased baroreceptor firing → increased parasymp and decreased symp → decreased HR

What is a carotid massage and what is it used for?

massage the carotid sinus to stimulate the baroreceptors located there

used to lower HR

how it works: carotid massage stmulates an increase in BP → increase in baroreceptor firing → increase parasymp activity → decrease HR

What do chemoreceptors detect changes in?

blood O2, CO2, and pH

Explain the CNS-Ischemic Reflex

this is when there is a severe decrease in blood flow to the brain

how it works: decrease in cerebral blood flow → ischemia → CO2 accumulation → excitation of the neurons of vasomotor center → powerful vasoconstriction → increase in BP

Explain the Cushing Reflex

this is caused by a head injury, intracranial hemorrhage, CNS inflammation, increased CSF, or metabolic change

how it works: increased ICP → ischemia → incrased PCO2 and decreased pH → activates sympathetic → increased BP → activates baroreceptors → increased parasympathetic → decreased HR

Explain the Atrial Reflex / Bainbridge reflex

goal: maintain normal blood volume by attempting to eliminate excessive fluid in circulation

how it works: increased blood volume → increased atrial stretch → beta-fibers in atria activated → increased sympathetic activity → increased HR

Emilee think: within the heart we are trying to keep it good... so more fluid = need to pump out faster to keep up

Explain atrial stretch and Atrial Natriuretic Peptide (ANP)

this is with the kidney: causes vasodilation and a decrease in NA + reabsorption and dilates afferent renal arterioles and constricts efferent arterioles → diuresis

opposite of RAAS

Where are the baroreceptors located?

carotid sinus and aortic arch

Which cranial nerves are involved in the baroreceptor reflex? Where do they send their info?

CN IX (carotid) and CN X (aortic arch)

afferent signals go from the baroreceptors through the CNs to the nucleus tractus solitarius (NTS) of the medulla

What is the primary way that our body does long-term BP regulation?

The renin-angiotensin-aldosterone system (RAAS)

Briefly explain the RAAS system

decreased renal perfusion detected by baroreceptors in the AA and/or decreased NaCl (hyponatremia) detected by macula densa → juxtaglomerular cells secrete renin → renin converts angiotensinogen to angiotensin I → increased conversion of angiotensin I to angiotensin II → vasoconstriction and increased NA and H2O retention→ increased renal perfusion

What is a direct measurement of blood pressure that allows for continuouse collection of BP data and briefly how does it work?

telemetry

you implant a pressure catherter in the artery directly to measure BP

What are two other considerations with HTN?

white coat hypertension (normal in typical setting, elevated in clinic)

sex differences in BP regulation

Where are the renal baroreceptors located?

in the afferent arterioles

How does the kidney contribute to BP regulation and what is the net effect?

juxtaglomerular cells in the kidney produce renin, resulting in changes in salt and water retention

so the kidney can produce or not produce renin

What type of renal cells secrete renin?

juxtaglomerular cells

What are 3 factors that trigger renin secretion?

decreased renal perfusion (baroreceptors in AA)

decreased NaCl delivery to macula densa cells

increased renal sympathetic discharge