Lecture 15 Flashcards
Modulating flow and pressure at the level of the tissues- micro control(2)
Myogenic response to stretch
endothelium dependent response to flow
Modulating flow and pressure at the level of the organ - local control
response to metabolic needs- metabolic hyperemia
Modulating flow and pressure at the level of the organism-macro control
involving the baroreflex- nerve pathways and hormones as mediators
Pressure changes in the vascular tree (4)
left ventricle is highest pressure and R atrium is almost at zero
diastolic pressure is the low of pulse pressure and systolic is the high
LV>arteries>arterioles>capillaries>venules/veins>R atrium
Vein pressure must be low in order to keep blood flowing
Factors that affect stroke volume(4)
COx TPR
CO=HRxSV
SV=EDV-ESV (contractility)
EDV-venous return
What are the points of control of blood pressure?(2)
Control of systemic arterial BP is MOST important mechanism for proper operation of cardiovascular system
control mechanisms designed to regulate arterial pressure called baroreflex
Components of the baroreflex (6)
stimulus sensory receptors ( high and low pressure) afferent pathways integrating center in CNS efferent pathways Effector organs
High pressure (arterial) baroreceptors(4)
are stretch receptors
respond rapidly to changes in pressure
buffer sudden changes
Adaptable- will get new set point
Location of arterial (high) baroreceptors and what they respond to(2)
aortic baroreceptors (aortic arch)- respond to pulsatile flow carotid sinus baroreceptors(collar of shirt)- response to non pulsatile stretch
Cardio pulmonary (low pressure) baroreceptors- what do they measure, where are they
pressure (stretch) receptors in atria at junctions of great veins and atria, ventricles and pulmonary veins
respond to absolute pressure (stretch) rather than change in pressure (venous return)
Nerve fibers from low pressure receptors run in _____ to ____________ in the brain
vagus nerve
medullary cardiovascular center
Afferent pathways of the baroreflex located within(2)
glossopharyngeal nerve CN9
vagus nerve CN10
Central integration of the baroreflex
Medullary Cardiovascular center in the brain stem
pressor regoin of medullary CV center provides
normal “tonic” sympathetic stimulation to blood vessels and heart
Depressor region of medullary CV center is
stimulated by baroreceptor firing and then inhibits sympathetic discharge from pressor region
Efferent Sympathetic nerve supply to
Heart: *SA node inc rate *myocardium inc force Blood vessels *arterioles inc TPR *veins inc venous return think fight or flight for heart and BV
Efferent parasympathetic nerve supply to
heart
*SA node dec rate
Sympathetic Nervous System
Neurotransmitter
Receptors
Neurotransmitter at the effector organ is NA (or circulating Adr)
Receptors on the effector organ
*alpha 1 or 2 (contraction)
*Beta 1 or 2 (relaxation)
Parasympathetic Nervous System
Neurotransmitter
Receptors
neurotransmitter at effector organ is Ach
Receptors on effector organ- Muscarinic receptors
Effector- HEART
change in force of contraction (inc)
sympathetic stimulation -> inc contractility (SV)
binding of NA to beta receptors -> inc Ca and inc force of contraction
effector- heart
change in heart rate (inc and dec)
sympathetic stimulation-> inc HR
parasympathetic stimulation-> dec HR
CO=HRxSV
Inc SV can be achieved by (2)
inc muscle length (venous return) (frank starling)
inc contractility by inc intracellular Ca during contraction
Vasoconstriction of the arterioles leads to
inc TPR
vasoconstriction of the veins leads to
inc venous return-> inc EDV-> inc SV
Gastrointestinal vasculature ratio alpha and beta
more alpha than beta
inc sympathetic drive-> vasoconstriction
Skeletal muscle vasculature ratio of alpha and beta
more beta than alpha
inc sympathetic drive will vasodilate (think fight or flight)
Response to a chronic fall in cardiac filling
inc sympathetic drive also leads to (4)
activation of RAAS
Na and water retention
inc blood volume
Release of ADH
