L16: Cardiovascular system I Flashcards
three principal components of circulatory system
blood, heart, blood vessels
cardio system function is impacted by
endocrine system, nervous system, kidneys
blood is made of
formed elements and plasma
formed elements
cells and cell fragments
how do you separate blood components?
high speed centrifugation
% of plasma in blood
55%
blood constituents are moved through the body by
bulk flow
white blood cells?
leukocytes
function of leukocytes
immune response
cell fragments?
platelets
buffy coat?
leykocytes and platelets
hematocrit?
erythrocytes, 38-46%
erythrocytes
red blood cells
cardiovascular system is composed of __
two circuits
both circuits originate and terminate ____
in the heart
inside the heart, blood flows ___
from atrium to the ventricle
blood ___ pass between either of the atria or ventricles
does not
deoxygenated blood moves __
from the right ventricle into the pulmonary circulation to the lungs, gases are exchanged, and oxygenated blood returns to the left atrium
oxygenated blood moves ___
from the left ventricle into systemic circulation, through all organs, and deoxygenated returns to right atrium
blood vessels are divided into ___
arteries, arterioles, capillaries, venules, and veins
arteries carry blood ___ the heart
away from
veins carry blood ___ the heart
to
how do liquids flow?
flow down pressure gradients from high pressure to low pressure
blood can flow only if __
one region develops higher pressure than other regions
what creates high pressure?
heart contraction
where is the highest pressure?
aorta
where is the lowest pressure?
venae cavae
why does the blood pressure go down?
friction between fluid and blood vessel walls
flow formula
F = deltaP/R
resistance of fluid depends on
radius of the tube, length of the tube, and viscosity of the fluid
Poiseuille’s Law:
R = 8Ln/pi*r^4
the main variable in blood vessels
radius of a tube
vasoconstriction
a decrease in blood vessel diameter that decreases blood flow through the vessel
vasodilation
an increase in blood vessel diameter that increases blood flow through the vessel
three main layers of the heart
outer pericardium, inner epicardium, and myocardium
the narrow space between outer and inner layers is filed with
a watery fluid that serves as lubricant
what layer is composed of cardiac muscle?
myocardium
cardiac muscles
faintly striated, branched, mononucleated, connected by disks
every cardiac muscle cell contracts __
with every beat of the heart
what creates one-way flow through the heart?
AV valves
atrioventricular AV valves
act as one-way valves permitting the flow of blood only from atria to the ventricles
the left AV valve
has two flaps and is called the bicupsid valve
the right AV valve
has three flaps and is called the tricupsid valve
a muscular wall that separates the two ventricles
interventricular septum
semi-lunar valves
permit blood to flow into the arteries during ventricular contraction but prevent blood from moving in the opposite direction during ventricular relaxation
the opening of the right ventricle into the pulmonary artery contains
pulmonary semi-lunar valve
the opening of the left ventricle into the aorta contains
aortic semi-lunar valve
how do heart valves act?
in a passive manner, they are open or closed depending upon the pressure differences across them
during ventricular contraction,
AV valves remain closed , while semi-lunar valves are open
during ventricular relaxation,
AV valves are open, but semi-lunar valves remain closed
does the blood in chambers exchange nutrients or products with the myocardial cells?
NO
myocardial cells receive their blood supply via
coronary arteries
coronary arteries
branching network around myocardial cells from aorta including arteries, arterioles, capillaries, venules, and veins
most of the cardiac veins drain into
a coronary sinus, which empties into the right atrium
parasympathetic nervous system controls heart by
innervating cells of the atria using acetylcholine
sympathetic nervous system control heart by
innervating the entire heart using norepinephrine
what are the receptors for acetylcholine in the heart?
muscarinic receptors
what are the receptors for norepinephrine in the heart?
mostly beta-adrenergic
efficient pumping of blood requires
atria contract first, followed almost immediately by the ventricles
the initial excitation of one cardiac cell to excitation of all cardiac cells is due to
gap junctions
the initial depolarization arises from
the sinoatrial node (SA node)
where is SA node located
right atrium, near the entrance of the superior vena cava
the action potential spreads
from the SA node throughout the atria and ventricles
step 1 of heart excitation
atrial excitation begins due to depolarization of SA node
step 2 of heart excitation
atrial excitation ends with rapid conduction of depolarization, right and left atria contract at the same time
the link between atrial and ventricular depolarization
atrioventricular node (AV node)
where is the AV node located?
the base of the right atrium
sole electrical connection
a connection between atria and ventricles, formed by the AV node and the bundle of His (AV bundle)
step 3 of heart excitation
ventricular excitation begins: slow propagation through the AV node
depolarization of the AV node transmits action potentials
down the Bundle of His, to the bundle branches, to the Purkinji fibers, and finally to the ventricular myocardial cells
step 4 of heart excitation
ventricular excitation complete: depolarization and contraction to begin earlier in the apex of the ventricles and then spread upwards
the result of ventricular excitation upwards
a contraction that moved blood up toward the semi-lunar valves
what does the delay in the propagation of action potentials through the AV node allow for?
a completion of atrial contraction
pacemaker potential
slow depolarization due to both opening of Na+ channels and closing of K+ channels; the membrane potential is never a flat line
depolarization
the action potential begins when the pacemaker potential reaches threshold; depolarization is due to Ca2+ influx through Ca2+ channels
repolarization
Ca2+ channels inactivating and K+ channels opening; this allow K+ efflux, which brings the membrane potential back to its negative voltage
