Hemodynamic Defense Response Flashcards
what is the main goal of the hemodynamic defense?
maintain cardiovascular integrity
what are the key systems involved in blood pressure control?
baroreceptor reflexes
sympathetic nervous system
renin angiotensin aldosterone system
antidiuretic hormone
what is the equation for cardiac output?
CO= stroke volume x heart rate
what is the equation for mean arterial pressure?
MAP= diastolic blood pressure + 1/3 of pulse pressure
what happens with mean arterial pressure during exercise?
it stays the same
what vessels determine peripheral vascular resistance?
arterioles
what is the major determinant of resistance?
radius of the vessel
what performs short term blood pressure control?
vasomotor center
baroreflexes and autonomic control
where is the vasomotor center located?
reticular substance of the medulla and lower pons
what is the sensory area of the vasomotor center?
nucleus solitarius
how does the vasodilator area of the vasomotor center perform?
inhibit vasoconstrictor activity with its fibers
where are high pressure baroreceptors located?
carotid sinus and aortic arch
what is the first line of defense to acute changes in blood pressure?
high pressure baroreceptors in carotid sinus and aortic arch
where are low pressure baroreceptors located?
large intrathoracic vessels and the heart
what is the stimulus for the low pressure baroreceptors?
increased stretch
what is the bainbridge reflex?
increased sympathetic outflow detected by low pressure baroreceptors (increased stretch) leads to an increase in heart rate
what are the specific responses to acute hypotension?
vasomotor center receives input from baroreceptor via cranial nerves IX and X: vasomotor center
nucleus solitarius conveys signal to vasoconstrictor and vasodilator centers
increased sympathetic activity: vasoconstriction, increased heart rate and contractility
what is the general response to acute hypotension?
increased cardiac output
restoration of normal blood pressure
what serves as the intermediate control of blood pressure?
epinephrine and norepinephrine
what are alpha1 receptors chiefly mediated by?
norepinephrine
what are beta1 receptors chiefly mediated by?
epinephrine
what is the net result of beta1 receptors being stimulated?
increased cardiac output
what type of blood pressure control does the renin angiotensin aldosterone system provide?
intermediate to long term
what are the causes of renin release?
renal sympathetic stimulation
decreased renal perfusion
decreased sodium delivery to the macula densa
what organ releases and produces renin?
kidney
where is angiotensinogen made?
liver
how do renin and angiotensinogen interact?
renin acts on angiotensinogen to make angiotensin-I (AT-I)
how is angiotensin-I converted into angiotensin-II (AT-II)?
angiotensin converting enzyme (ACE)
what are some stimuli of aldosterone?
angiotensin II
decreased sodium load at the macula densa
increased potassium
ACTH
why is antidiuretic hormone primarily released?
plasma hyperosmolarity (dehydration)
when is antidiuretic hormone inappropriately elevated?
in CHF
what is the response to antidiuretic hormone?
direct vasoconstriction
increased permeability to water in the distal tubule
what are the two natriuretic peptides?
atrial and brain natriuretic peptides
what stimulates the release of the natriuretic peptides?
stretch of the atria or ventricles
myocardial dysfunction
how are the natriuretic peptides activated?
proteolytic cleavage
what maintains cardiovascular integrity in the short term?
autonomic nervous system
what maintains cardiovascular integrity in the long term?
salt and water retention
what maintains cardiovascular integrity in the intermediate term?
humoral factors
what is the first line defense against rapid changes in blood pressure?
baroreceptor reflexes
how does the sympathetic nervous system control blood pressure?
rapid selective vasoconstriction and increased cardiac output
what timeline does the renin angiotensin aldosteron system work over?
intermediate and long term
how is peripheral vascular resistance decreased in exercise?
arteriolar vasodilation in skeletal muscle
what is poiseuille’s law?
R=8nL/(pi x r^4)
what controls peripheral vascular resistance acutely?
autonomic control: baroreceptors
metabolic, paracrine factors
what controls peripheral vascular resistance in intermediate and long-term?
sympathetic nervous system
angiotensin
vasopressin
endothelin
what does the vasomotor center transmit?
parasympathetic impulses through vagus to heart
sympathetic impulses through spinal cord and sympathetic nerves to vasculature and heart
what does the vasoconstrictor area of the vasomotor center do?
distributes fibers to cord: excited vasoconstrictor neurons of sympathetic nervous system
what do high pressure baroreceptors detect?
magnitude, rate of change of pressure-induced stretch of arterial wall
what is the response to increased stretch in the low pressure baroreceptors?
bainbridge reflex
decreased renin and AVP release: increase Na and H2O excretion
what is the pathway for secretion of epinephrine and norepinephrine?
adrenal medullary secretion of both
epi: alpha and beta
norepi: alpha
what is the stimulus to release epinephrine and norepinephrine?
generalized sympathetic nervous system stimulation
what does alpha1 stimulation by norepinephrine lead to?
increased peripheral vascular resistance and venous return to heart
arteriolar vasoconstriction
venous vasocnstriction
what does beta1 stimulation by epinephrine lead to?
increased chronotropy, inotropy, and lusitropy (relaxation): increased cardiac output
what is the response to angiotensin II?
vasoconstriction, thirst
kidney: conserve Na and H2O, efferent arteriolar vasoconstriction
aldosterone and ADH release
how does aldosterone work?
transcription of Na/K pumps in distal convoluted tubule
increased number of Na channels
increased potassium secretion into tubules
what is the response to aldosterone?
sodium and water retention, potassium excretion
myocardial remodeling and fibrosis
why is antidiuretic hormone released?
primary: plasma hyperosmolarity
also: decreased atrial stretch, angiotensin II, decreased arterial stretch
what is the response to antidiuretic hormone?
direct vasoconstriction
increased permeability to water in distal tubule
what do the intra-cardiac RAAS systems drive?
remodeling
progressive hypertrophy
fibrosis
what do the atrial and brain natriuretic peptides do?
diuretic effect
endogenous antagonists to RAAS
inhibit sympathetic nervous system and vasopressin
what do the natriuretic peptides do to blood pressure?
decrease it
