Lecture 28 10/24/23 Flashcards
(26 cards)
How does blood pressure relate to cardiac output and systemic vascular resistance?
BP = CO x SVR
What are the characteristics of baroreceptors?
-found within carotid sinus and aortic arch
-respond to vessel distention/increases in BP
What type of control does the arterial baroreflex have over BP?
short term
What is the result of baroreceptor activation?
-decrease in heart rate
-vasodilation
Why is the arterial baroreflex only involved in short term BP control?
-sustained increases in BP “resent” the baroreceptors
-baroreceptors become used to long term higher pressure and no longer correct it
What things are able to stimulate the excitatory chemoreceptor reflex?
-low O2
-high CO2
-low pH
What is the result of excitatory chemoreceptor reflex stimulation?
-increase in sympathetic tone
-increase in arterial pressure
When is the excitatory chemoreceptor reflex most important/relevant?
-at lower BP
-during disease states
What are the characteristics of autonomic control of vascular resistance?
-CNS vasomotor center
-afferents from baroreceptors, chemoreceptors, and metaboreceptors
How do metaboreceptors work?
-metabolites build up when CO is inadequate
-metaboreceptors sense metabolites
-contractility and heart rate are increased
What are the important receptors for autonomic control of vascular resistance?
-alpha 1: vasoconstriction
-beta 2: vasodilation
Where are alpha receptors found?
-GI
-skin
-kidneys
(tissues that can have blood diverted away during fight or flight)
What occurs as a result of beta-1 receptor stimulation?
-increased contractility
-increased heart rate
-increased rate of myocardial relaxation
What is the Cushing’s response?
-reflex-mediated increase in systemic arterial pressure
-occurs as a result of increased CNS pressure
Which system has long term control over BP?
renin-angiotensin-aldosterone system
What is the stimuli for renin release?
diminished cardiac performance
-renal hypotension
-beta-adrenergic activation
-decreased renal sodium delivery
Where in the kidney is diminished cardiac performance sensed?
juxtaglomerular apparatus
What are the main things caused by angiotensin II?
-vasoconstriction
-aldosterone release -> sodium/water retention
Why is water retention necessary during diminished cardiac performance?
water retention leads to increased intravascular volume, which increases venous return and CO
How are extracellular fluid volume (ECF) and BP related?
increase in extracellular fluid volume = increase in systemic arterial BP
What is the most important determinant of extracellular fluid volume?
sodium
What determines ECF?
-dietary intake of sodium and water
-renal excretion
What is pressure diuresis?
-increase in ECF causes an increase in CO and arterial BP
-increase in renal loss of water and sodium
What are the characteristics of natriuretic peptides?
-cause natriuresis and vasodilation
-come from the atria and ventricles
-stimulus for release is increased wall tension/cardiac stretch
