lecture 1: Guyton chapter 9 Flashcards
the heart is approximately the size of your…
fist
what is the location of the heart?
The superior surface of the diaphragm
Left of the midline
Anterior to the vertebral column, posterior to the sternum
true or false: the left and ride side of the heart are the same
false; they are anatomically and functionally separate
what does it mean for the heart to be a dual pump
right=lungs
left=systemic
what ensures that the blood from the left and right sides of the heart does not mix.
The interventricular septum
true or false: even if the left and right sides are separated, the heart contracts in a coordinated fashion.
explain
true
the atria contract together and the ventricles contract together….
the left side of the heart is coupled in…
parrallel
blood goes to diff capilaries depending on where its needed
the right side of the heart is coupled in …
series
only goes from heart lungs and back top heart
which side is a low pressure system
right side (doesn’t have to go as far)
which side is a high pressure system
left (pump oxygenated blood to entire body)
why is the left side a high pressure system
must overcome systemic pressure
explain the pathway of blood through the body
1) O2 deficient blood returns from body via sup and inf vena cava
2) enters right atrium
Tricuspid valve
3) enters right ventricle
4) goes to pulmonary artery
5) goes to lungs
6) blood is oxygenated
=PULMONARY CIRC.
7) blood comes back through pulmonary veins
8) blood goes to left atrium
Bicuspid valve
9) blood goes to left ventricle
10) blood goes to aorta
11) circulates to the body
=systemic circulation
what is the lining that covers the heart
pericardium
what is the pericardium
a double walled sac around the heart
what are the 2 layers of pericardium
1) superficial fibrous pericardium
2) a deep 2 layer serous pericardium
what are the 2 layers of the deep serous pericardium
parietal layer and visceral layer
where does the parietal layer line
the interal surface of the fibrous pericardium
where does the visceral layer line
lines the surface of the heart
what is another name for the visceral layer
the epicardium
what are the visceral and parietal layers separated by?
fluid filled pericardia cavity
what are the 3 functions of the pericardium
Protects and anchors the heart
Prevents overfilling of the heart with blood
Allows for the heart to work in a relatively friction-free environment
what allows for the heart to work in a relatively friction-free environment
the pericardial space that is fluid filled
what are the 3 types of cardiac muscle
atrial muscle (the chambers that receive the blood) ventricle muscle (chambers that eject special excitatory and conductive muscle fibers
what is the difference between cardiac and skeletal muscle contraction
Atrial and ventricular types of muscle contract in much the same way as skeletal muscle
However, the duration of contraction is much longer
why is heart muscle contraction longer than skeletal muscle
heart needs time to fill after blood ejection
true or false: cardiac muscle is smooth
false its branched and striated
where is the nucleus of cardiac muscle
centrally located
what are muscle cells of the heart called
myocutes (cardiomyocytes)
or myofibrils
what is the outside membrane of the cardiac muscle called
sarcolemma
true or false: Cardiac muscles have the same arrangement of actin and myosin, and the same bands, zones and Z discs as skeletal muscles forming sarcomeres.
true that what make it striated
which has less sarcoplasmic reticulum: cardiac or skeletal
cardiac
where does cardiac muscle get its calcium from and why
from extracellular flued for contraction (they have large t tubyles)
beacuse lsss sarcoplasmic retulum
which has larger T tubule diamters: cardiac or sckeletal
cardiac (5 times greater diameter0
what does it mean for cardiac muscle to act as a syncytium
cardiomytocites are electrically connected to the next cell
coordinated contraction of muscles along their entire length
true or false: Cardiac muscle fibers are made up of many individual cells connected in series
false
in series AND and in parallel with one another
explain intercalated disks
cell membranes separating and anchoring individual muscle cells from one another
At each intercalated disc, the cell membranes have fused
at the intercalated disks, the cell mebranes are smoothe>
false
they are rough which allows for increased surface area
where is one cardiac cell connected to the other>
at the intercalated disk
what are the fucntions of gap junctions
Gap junctions allow almost free diffusion of ions
Action potentials travel easily from one cardiac muscle cell to the next
what helps speed the conduction of AP in heart muscle
the syncitum of main heart muscles
true or false: there is an atrial and ventricle syncytium?
true
explain atrial and ventricular syncytium
the atrial syncytium means that the conduction only occurs and diffuses through atrial cells
simular to ventricular
true or false, the atrium and ventricle are separated
true by a fibrous tissue
why is it importance that there is a dual syncytium for atrium and ventricles
allows atrium to contract a bit before ventricles (ventricles will be relaxed while blood flows from contracted atrium) to bill the heart with as much as possible)
what does This division of the muscle of the heart into two functional syncytium allows
allows the atria to contract a short time ahead of ventricular contraction
what does the myocardium consist of
interlacing bundles of cardiac muscle fibers arranged spirally around the circumference of the heart.
what is the advantage of the bundles being spiral
the cardiac muscle contracts & shortens, a twisting effect is produced, efficiently pushing blood upwards towards the exit of the major arteries of the heart.
what is the AP in ventricular muscle fiber
-85 mV
after initial spike, the membrane remains depolarized for 0.2 s, what does that cause?
plateau
what does the presence of this plateau in the AP cause in terms of ventricular contraction>
ventricular contraction to last as much as 15 times as long in cardiac muscle as in skeletal muscle
what are the 5 phases of action potenial in cardiac muscles
phase 0: membrane is depolarixe by fast NA channels and slow CA channel
phase 1: K+ cahnnels open once the mebrane is positive
=begining to repolarize
phase 2: platuea occurs because efflux of K+=influx of ca+
phase 3: K+ channels open alow and membrane repolaises
phase 4: resiting membrane potential
the cardiac cycle consists of
diastole and systole
what is diastole
of a period of relaxation (diastole) during which the heart fills with blood and the cardiomyocytes re-establish the Na+/K+/Ca2+ gradient
what is systole
contraction
ejects blood
what is each cardiac cycle initiated by
initiated by a spontaneous generation of an action potential in the sinus node
=special excitatory cells depolarize by themsevles
the AP is conducted where
in the atria, the AV bundles and the venetcles
true or false: there is A delay of more than 0.1 sec during passage of the cardiac impulse from the atria to contract ahead of ventricular contraction
yes and that causes
Thus atria pump more blood into the ventricles prior to ejection
true or false: blood does not flow continually from vena cava to atria
false, blood flows continually
what percentage of blood flows directly through the atrai into ventricels even before contraction
80%
atrial contraction causes an additional BLANK to fill the ventricles
20% filling of blood
what is the a wave caused by
pressure change in atria caused by atrial contraction
what is the c wave occur
occurs when ventricles begin to contact
pulls a bit on the atrium as well since they are attached so affects pressure
when does v wave occur
towards the end of ventricular contraction
because as it relaxes, sicne it is attached to the atrium, it causes the pressure oin the atrium to change
true or false: walls of the atria are thicker than walls of the ventricles and why
false, ventricles are thicker because they are ejecting blood
which wall is thicker: left or right ventricle
left is thicker because it is a high pressure system
when does aortic pressure start to increase
during systole after the aortic valve opens
when does aortic pressure decrease
towards end of ejection pahse
what is the relationship between aortic pressure and ventricular volume
as aortic pressure increases, ventricular volume decreases
after the aortic valve closes, what develops and why
incisura develops due to a sudden back-flow towards the left ventricle
(pulse wave gets bounced off by systemic resistance
what does the insura supply
the back flow supplies the heart
Why does aortic pressure start to decrease during diastole?
elasticity of the aorta
why is it important to always have some blood in the ventricles
1) makes it easier to refill for next cardiac cycle
2) w/o blood, ventricle could colapse
explain why as volume is increase in the ventricle, pressure isn’t increase in ventricle
heart is expanding
what is the end diastolic volume
when the heart is filled with blood
=preload
at a given volume, after the heart filled, what happens
isovolumic contraction (ie./ ventricle contracts, pressure is building,
during the period of ejection, is pressure constant ?
Almost constant but not really because the heart needs to contract against a lesser and lesser amount of blood
what is the end systolic volume
after load (all the blood has been ejected)
what happens after all the blood has been ejected
isovolumic relaxation, ventricles relax so pressure decreases
what is ejection volume (stroke volume)
end diastole-end systolic
what is the ejection fraction
stroke volume/diastolic
what are normal ejection fraction values
50 - 60% at rest; > 80% during exercise and < 40% during disease
what is the frank starling mechanism
An intrinsic ability of the heart to adjust and adapt the volume change of blood
explain the frank starling mechanism
Within physiological limits the heart pumps all the blood that returns without excessive damming in the veins.
Extra stretch on cardiac myocytes makes actin and myosin filaments find a more optimal degree for force generation.
=ribber band effect forces blood out and not contractility
true or false: the heart only contract s sympathetic nerves
false, it has parasympathetic nerves (mostly valgus nerve)
where is the parasympathetic nerves located
around the atrium
explain the function of the parasympathtic nerves
relaxes the heart rate (since contraction happens in atrium)
explain the sympathetic nerves
effects hr and contractility (how forceful)
excitation of the heart happens by what nerves
sympathetic nerves
what can the excitation of the heart do to the heart rate
go from 70 to 180-200
true or false: sympathetic nerves only affect the HR
false, Sympathetic stimulation also increases the force of heart contraction to as much as double, thereby increasing the volume of blood pumped.
Under normal conditions, sympathetic nerve fibers to the heart discharge BLANK at a slow rate which causes…
continuously
This maintains pumping at about 30% above ‘normal’ heart rate with no sympathetic stimulation
true ro false: Strong parasympathetic stimulation (PS) can stop the heart for a few seconds
true
at rest, what is responsible for beating rest
parasympthetic
where are the vagal fibers mainly distributed
to the atria and not much to the ventricles (where power of contraction occurs
