physio CV Flashcards
pressure gradients
difference of pressure between 2 locations
blood flows from high to low P
Pressure highest closest to ventricles and lower as furthur away (vena cava/atria)
blood flow is directly proportional to…
size of pressure gradient
greater pressure difference= greater flow, vice versa
resistance to blood flow caused by
friction (blood cells in contact with vessel walls and w/ eachother)
vascular resistance is determined by 3 things
vessel length (longer blood vessels= increase resistance)
internal vessel radius (decreasing radius- vasoconstriction= increase resistance) opposite
blood viscosity- proportional to hematocrit (the proportion of of the
blood volume that is red blood cells (more of this= increase viscosity)
resistance is mainly determined by…
changes to radius (small change to R= big change to resistance- ex: R from 2mm to 4mm= decrease in resistance by factor of 16x
relationship between velocity and cross sectional area
velocity is up when cross sectional area is down
water hose analogy
4 chambers of heart
l/r atria
l/r ventricle
3 layered walls of chambers
- endocardium: inner epithelium lining
2 myocardium: 99% are normal contractile cells and 1% that aren’t are called autorhthmic cells” that forms a network called conducting system
- epicardium (also called visceral pericardium)
outer surface lining
what surrounds and protects the heart and what it does to protect it
pericardial sac
prevents overdistension (stretch) of heart and anchors it to surrounding structures
the pericradial cavity space contains serous fluid that reduces the friction resulting from contractions
heart valves open in response to…
changes in pressure
-unidirectional so no back flow of blood
heart valves: atripventricular valves
includes tricuspid valve (R atrium and R vent)
and Bicuspid valve (L atrium and L vent)
open when ventricular pressure up during contraction. close when p down
ATB
heart valves: semilunar valves
between vent and larger arteries includes…
aortic semilunar valves (R aorta and R vent)
and pulmonary semilunar valve (L pulmonary trunk and L vent)
open when p high, vice versa
what do fibrous skeleton do
prevent collapse of valve openings
physically and electronically separate atria from vent
(so atria can contract as a unit and push blood down to vent. and so vent can contract as a unit and push blood up to aorta and pulmonary trunk/arteries)
conducting system
non contractile cells-
cardiac cells that create AP
conducting system parts: Sinoatrial node (Sa)
in R atrium
create atp at 100aps/min (fast- pacemaker of heart)
conducting system parts: atrioventicular node (AV)
in R atrium
slow ap (50ap’s/min) since only few gap junctions/ large diameter and delay so atria cintract and fully empty b4 vent contraction begins
interatrial vs internodal pathway
- carry signals from SA to left atrium
- carry signals from SA to AV node
AP pathway: internodal path
SA, AV NODE, AV BUNDLE, AV BUNDLE BRANCHES, PURKINJE FIBRES (terminal branches that transit AP’s to contractile cells)
treashold of pacemaker
-40
repolarization
k+ exiting
diastole vs systole
- relaxation and filling
2.contraction and emptying
frank starlings law
force of ejection (stroke volume)= directly proportional to the EDV
ie more blood coming in during diastole= more blood out during systole
venous return
amount of blood returning to the heart from veins
direct effects on edv and therefore on stroke volume and cardiac output
factors determining EDV (end diastole volume): neural control
up tension in vein walls decrease complience (bloot not pooling in veins) which also increase venous return (blood into heart) and EDV, SV (stroke v), and cardiac output
factors determining EDV (end diastole volume): skeletal muscle pump
one-way valves (no back flow- just blood towards heart)
facilitates venous control during exercise
not working at rest (sitting)
factors determining EDV (end diastole volume): respiratory pump
longer inhalation= up pressure= up venous return
afterload (what stroke volume depends on…)
depends on arterial pressure against what its pushing
semilunar valves only open when pressure is higher than aortic pressure
Mean arterial pressure up= aortic pressure up= more force is needed to eject
