78, Blood pressure and venous return

Exam 3

what is perfusion pressure

the driving force of blood flow

what fluid exerts hydrostatic pressure in a confined space

any and all fluids

what is blood pressure

force per unit area that the blood exerts on the wall of the blood vessel

what is perfusion (flow through) pressure

the pressure gradient that promotes blood flow

what is invasive arterial blood pressure monitoring

placing a catheter within an artert and connected to a pressure transducer

provides constant measurements of SAP, DAP, and MAP

where us systolic on a blood pressure graph

the maximum point or peak on the curve

where is diastolic on a blood pressure graph

the minimum or lowest point

where is a pulse pressure found on a blood pressure graph

difference between systolic and diastolic

what is the MBP formula

DAP+1/3PP

what does the dicrotic notch represent

closure of the aortic valve

useful for interpreting waveform BP

what is indirect arterial blood pressure monitoring (NIBP)

estimation of arterial blood pressure using non-invasive techniques like a cuff or doppler

how does blood pressure change as the blood moves away from the body

decreases with distance

what vessel has the greatest resistance to blood flow

arterioles

what species has the highest blood pressure

avian

what species has the lowest blood pressure

rats

why do avians have the highest blood pressure

rapid heart rate and large heart sizes contribute to higher cardiac output than mammals

what is central venous pump regulatuon (right atrial pressure)

ability of heart to pump

tendency for blood to flow from the periphery to the heart

-3 to -5 or 0mmHg

what is peripheral venous pressure (Pv)

resistance in large veins (Rv) is almost absent

compression during the trajectory of the vein

4-6 mmHg

what is the equation for venous retrun

Peripheral venous pressure (Pv)- right atrial pressure (Pra) all divided by venous resistance (Rv)

what happens in the vesels if the heart cannot pump blood forward effectively

right arterial pressure may increase

reduces the pressure gradient driving venous return and can contribute to venous congestion

what r mechanisms assist in venous return

vis a tergo

thorax pump

skeletal muscle pump

valves

what is vis a tergo

the remnant pressure from the arterial side of circulation

what is the thorax pump used for

reduction of intrapleural pressure during inspiration

what is the skeletal muscular pump used for

compression/decompression

what is different about venous return in horses

there is a pumping mechanism in the hoof to send blood back up

how can pneumothorax affect venous return

normally inspiration decreases intrathoracic pressure, moving blood to heart

with pneumothorax the negative pressure is disrupted

venous return may decrease

what causes a rapid response in arterial blood pressure

neural mechanisms- autonomic nervous system

what causes an intermediate term response in blood pressure

hormonal- RAAS + ADH, ANP

what causes a long term regulation response in blood pressure

renal mechanisms- renal regulation

what factors cause acute local regulation of blood flow

myogenic

metabolic

endothelilal

what factor causes long term local regulation of blood flow

angiogenesis

what are the a1 receptors in the sympathetic nervous system

vascular smooth muscle, cause vasoconstriction

how does the vagus nerve affect heart rate

releases acetylcholine, which acts on M2 muscarinic receptors in SA and AV nodes

what is the sumamry affect of sympathetic system

increases blood pressure

what is the summary affect of parasympathetic

decreases heart rate

what neurotransmitter works on a1

norepinephrine> epinephrine

what NT works on B2 receptors

epinephrine

what NT works on a2 receptors

norepinephrine

what kind of loop is the baroreceptors reflex

negative feedback loop

where are arterial baroreceptors located

carotid sinus and aortic arch

what is the sensory pathway for the arterial baroreceptor reflex

glossopharyngeal nerve (CN 9) from the carotid suns and vagus nerve (CN 10) from the aortic arch

what is the integrative center for the arterial baroreceptor reflex

nucleus tractus solitarius (NTS) in the brainstem

what is the end result of the arterial baroreceptor reflex

reduced sympathetic activity and increased parasympathetic activity

reduced arterial pressure

what is the chemoreceptor reflex

caused by severe decrease in blood pressure and blood flow

stimulated by increase in PaO2, PCO2, and decrease in pH

activation of Quimoreceptors in aortic bodies and carotid

goes to vegas nerve pathway and glossopharyngeal nerve CN 9 and 10

into brain stem in the nucleus tractus soliarius and cardiovascular centers

cause increase contractility, change in HR and increased arterial blood pressure

how does the kidney control blood pressure

mostly through sodium reabsorption

how does angiogenesis affect blood flow long term

chronic tissue hypoxia stimulates VGEF release, promoting the growth of new capillaries and increasing tissue perfusion and oxygen delivery

what stimulates ANP release from the atria

Increased blood volume, increased venous return, and increased artial pressure

causes atrial stretch

how does ANP affect sodium and water excretion

ANP acts on kidney and decreases Na and water reabsorption, increases GFR

increase in natriuresis and dieuresis

how does ANP oppose RAAS

decreases renin release

decrease angiotensin 2

decreases aldosterone

what are the overall effects of ANP

decrease blood volume

decrease venous return

decrease cardiac output

decrease arterial pressure

what are the overall effects of RAAS

increase eblood volume

increase cardiac output

increase arterial pressure (MAP)

how does increased Na excretion from kidney decrease BP

increased sodium in urine increases amount of water in the urine

lowers blood sodium concentration which decreases extracellular fluid volume and decreases blood pressure

what happens in kidneys when blood pressure increases

increase sodium and water excretion

decreases blood volume

decreases cardiac output

decreases BP

what are the 3 acute mechanisms of local blood flow regulation

myogenic mechanism

metabolic mechanism

encothelium

what metabolic changes promote local vasodilation

decreased O2

increased CO3

increase H+

increase K+

adenosine

what endothelial mediators cause vasodilation

NO

PGI2

EDHF

how does the myogenic response regulate arterial blood flow

increase sheer stress and chemical mediators