into (heart) Flashcards
The cardiovascular system (CV) consists of:
- Blood
- Heart
- Blood vessels
is the pump that circulates the blood through
an estimated
- 60,000 miles of BV
- HR 100,000 times/day
- 35 millions times/year
- Pumps 5 L/minute, 14,000 L/day, 10 million L/year
- The heart
Anatomy of the Heart
Located in the mediastinum – anatomical region
extending from the sternum to the vertebral column, the
first rib and between the lungs
• Apex at tip of left ventricle
• Base is posterior surface
• Anterior surface deep to sternum and ribs
• Inferior surface between apex and right border
• Right border faces right lung
• Left border (pulmonary border) faces left lung
Because heart is situated between two rigid structure (vertebral column and sternum) external pressure on the chest can be used to force blood out of the heart and into the circulation
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Membrane surrounding and protecting the heart
– Confines while still allowing free movement
Pericardium
tough, inelastic, dense irregular
connective tissue – prevents overstretching, protection,
anchorage
Fibrous pericardium
thinner, more delicate membrane
– double layer (parietal layer fused to fibrous
pericardium, visceral layer also called epicardium)
Serous pericardium
Pericardial fluid reduces friction – secreted into ____
pericardial cavity
Visceral layer of serous pericardium
– Smooth, slippery texture to outermost surface
Epicardium (external layer)
95% of heart is cardiac muscle
Myocardium
Smooth lining for chambers of heart, valves and
continuous with lining of large blood vessels
Endocardium (inner layer)
receiving chambers
2 atria-Auricles increase capacity
– pumping chambers
– 2 ventricles
- Contain coronary blood vessels
- Coronary sulcus
- Anterior interventricular sulcus
- Posterior interventricular sulcus
Sulci – grooves
– Receives blood from • Superior vena cava • Inferior vena cava • Coronary sinus – Interatrial septum has fossa ovalis • Remnant of foramen ovale – Blood passes through tricuspid valve (right atrioventricular valve) into right ventricle
Right Atrium
Forms anterior surface of heart
– Trabeculae carneae – ridges formed by raised
bundles of cardiac muscle fiber
• Part of conduction system of the heart
– Tricuspid valve connected to chordae tendinae
connected to papillary muscles
– Interventricular septum
– Blood leaves through pulmonary valve (pulmonary
semilunar valve) into pulmonary trunk and then
right and left pulmonary arteries
Right Ventricle
About the same thickness as right atrium
– Receives blood from the lungs through pulmonary
veins
– Passes through bicuspid/ mitral/ left
atrioventricular valve into left ventricle
Left Atrium
Thickest chamber of the heart
– Forms apex
– Blood passes through aortic valve (aortic
semilunar valve) into ascending aorta
– Some blood flows into coronary arteries,
remainder to body
Left Ventricle
attached to papillary muscles
Chordae tendinae
left ventriclde
During fetal life ductus arteriosus shunts blood
from pulmonary trunk to aorta (lung bypass)
closes after birth with remnant
– called ligamentum
arteriosum(left venticle)
Thin-walled atria deliver blood under less pressure
to ventricles
Myocardial thickness
pumps blood to lungs
• Shorter distance, lower pressure, less resistance
– Right ventricle
pumps blood to body
works harder to maintain same rate of blood flow as right ventricle
• Longer distance, higher pressure, more resistance
Left ventricle
that forms a structural foundation for
the heart valves, prevents overstretching valves, forms point of insertion for muscle bundles, and is electrical insulator between atria and ventricles
Dense connective tissue
– Atria contracts/ ventricle relaxed
• AV valve opens, cusps project into ventricle
• In ventricle, papillary muscles are relaxed and chordae
tendinae slack
– Atria relaxed/ ventricle contracts
• Pressure drives cusps upward until edges meet and
close opening
• Papillary muscles contract tightening chordae tendinae
– Prevents regurgitation
Atrioventricular valves
Tricuspid and bicuspid valves
Heart valves and circulation of blood
-Valves open and close in response to ___________________as the heart contracts
and relaxes to ensure a one way flow of blood.
pressure changes
– Aortic and pulmonary valves
– Valves open when pressure in ventricle exceeds
pressure in arteries
– As ventricles relax, some backflow permitted but
blood fills valve cusps closing them tightly
Semilunar valves
- Left side of heart
- Receives blood from lungs
- Ejects blood into aorta
- Systemic arteries, arterioles
- Gas and nutrient exchange in systemic capillaries
- Systemic venules and veins lead back to right atrium
– Systemic circuit
Right side of heart
• Receives blood from systemic circulation
• Ejects blood into pulmonary trunk then pulmonary arteries
• Gas exchange in pulmonary capillaries
• Pulmonary veins takes blood to left atrium
– Pulmonary circuit
No valves guarding entrance to atria
– As atria contracts, compresses and closes opening (t/f)
true
steps of blood flow
- right atrium(deoxygenated blood)
- tricuspid valve-right ventricle
- pulmonanry valve-pulmonary blood and arteries
- in pulmonary capillaries-blood loses c02 and gains oxygen
- pulmonary veins-oxygenated blood
- left atrium
- bicuspid valve-left atrium
- aortic valve-aorta and systematic arteries
- systematic capillaries blood loses 02 and gains co2
has its own network of blood vessels
Myocardium
branch from ascending aorta
– Coronary arteries
provide alternate routes or collateral
circuits
• Allows heart muscle to receive sufficient oxygen even if an artery is partially blocked
Anastomoses
Collects in coronary sinus
• Empties into right atrium
Coronary veins
• Histology
– Shorter and less circular than skeletal muscle fibers
– Branching gives “stair-step” appearance
– Usually one centrally located nucleus
– Ends of fibers connected by intercalated discs
– Discs contain desmosomes (hold fibers together) and gap
junctions (allow action potential conduction from one fiber to
the next)
– Mitochondria are larger and more numerous than skeletal
muscle
– Same arrangement of actin and myosin
Cardiac Muscle Tissue and the Cardiac
Conduction System
Specialized cardiac muscle fibers
– Self-excitable
– Repeatedly generate action potentials that trigger
heart contractions
Autorhythmic Fibers
Autorhythmic Fibers 2 important functions
- Act as pacemaker
2. Form conduction system
Conduction system
- Begins in sinoatrial (SA) node in right atrial wall
• Propagates through atria via gap junctions
• Atria contact - Reaches atrioventricular (AV) node in interatrial septum
- Enters atrioventricular (AV) bundle (Bundle of His)
• Only site where action potentials can conduct from atria to
ventricles due to fibrous skeleton - Enters right and left bundle branches which extends through
interventricular septum toward apex - Finally, large diameter Purkinje fibers conduct action potential
to remainder of ventricular myocardium
• Ventricles contract
5 sequence of conduction system
- sinoatrial node
- atrioventricle node
- atrioventricle bundle
- r/l bundle branches(right ventricle
- purkinge fibers
node acts as natural pacemaker
– Faster than other autorhythmic fibers
– Initiates 100 times per second
sinoatrial node
Nerve impulses from ___modify timing
and strength of each heartbeat
– Do not establish fundamental rhythm
autonomic nervous
system (ANS) and hormones
3 steps Action potential initiated by SA node spreads out to excite “working” fibers called contractile fibers
- Depolarization
- Plateau
- Repolarization
– contractile fibers have stable resting membrane potential • Voltage-gated fast Na+ channels open – Na+ flows in • Then deactivate and Na+ inflow decreases
- Depolarization
period of maintained depolarization
• Due in part to opening of voltage-gated slow Ca2+
channels – Ca2+ moves from interstitial fluid into cytosol
• Ultimately triggers contraction
• Depolarization sustained due to voltage-gated K+
channels balancing Ca2+ inflow with K+ outflow
Plateau
– recovery of resting membrane potential
❑ Resembles that in other excitable cells
❑ Additional voltage-gated K+ channels open
❑ Outflow K+ of restores negative resting membrane potential
❑ Calcium channels closing
Repolarization
time interval during which second contraction cannot be triggered – Lasts longer than contraction itself – Tetanus (maintained contraction) cannot occur ❑ Blood flow would cease
Refractory period
Composite record of action potentials produced by all the heart
muscle fibers
– Compare tracings from different leads with one another and with
normal records
– 3 recognizable waves
• P, QRS, and T
Electrocardiogram
6 Correlation of ECG Waves and Systole
– Systole – contraction/ diastole – relaxation
1. Cardiac action potential arises in SA node
• P wave appears
2. Atrial contraction/ atrial systole
3. Action potential enters AV bundle and out over ventricles
• QRS complex
• Masks atrial repolarization
4. Contraction of ventricles/ ventricular systole
• Begins shortly after QRS complex appears and continues during S-T
segment
5. Repolarization of ventricular fibers
• T wave
6. Ventricular relaxation/ diastole
contraction phase
Systole
relaxation phase
Diastole
consists of the SYSTOLE and DIASTOLE of both atria, rapidly followed by the SYSTOLE and DIASTOLE of both ventricles. - PRESSURE and VOLUME changes during the cardiac cycle - during a cardiac cycle ATRIA and VENTRICLES alternately contract and relax forcing BLOOD from areas of HIGH pressure to areas of LOW pressure
cardiac cycle
During, atrial systole ___ are relaxed
ventricles
– During ventricle systole ___ are relaxed
atria
All events associated with one heartbeat
• Systole and diastole of atria and ventricles
• In each cycle, atria and ventricles alternately contract
and relax
– During atrial systole, ventricles are relaxed
– During ventricle systole, atria are relaxed
• Forces blood from higher pressure to lower pressure
• During relaxation period, both atria and ventricles are
relaxed
– The faster the heart beats, the shorter the relaxation period
– Systole and diastole lengths shorten slightly
Cardiac Cycle
Auscultation • Sound of \_\_\_ comes primarily from blood turbulence caused by closing of heart valves • 4 heart sounds in each cardiac cycle – only 2 loud enough to be heard – Lubb – AV valves close – Dupp – SL valves close
heartbeat
volume of blood ejected from left (or right)
ventricle into aorta (or pulmonary trunk) each minute
___stroke volume (SV) x heart rate (HR)
• In typical resting male
– 5.25L/min = 70mL/beat x 75 beats/min
• Entire blood volume flows through pulmonary and
systemic circuits each minute
cardiac output
difference between maximum CO and
CO at rest
– Average cardiac reserve 4-5 times resting value
• Cardiac reserve –
Regulation of stroke volume
– 3 factors ensure left and right ventricles pump equal volumes of blood
- Preload
- Contractility
- Afterload
Degree of stretch on the heart before it contracts
– Greater preload increases the force of contraction
• Preload proportional to end-diastolic volume (EDV)
- Preload
the more the heart fills with blood during diastole, the greater the force of contraction during systole
Frank-Starling law of the heart
– 2 factors determine EDV
- Duration of ventricular diastole
- Venous return – volume of blood returning to right
ventricle
increase contractility • Often promote Ca2+ inflow during cardiac action potential • Increases stroke volume • Epinephrine, norepinephrine, digitalis
– Positive inotropic agents
decrease contractility
• Anoxia, acidosis, some anesthetics, and increased K+
in interstitial fluid
Negative inotropic agents
– Pressure that must be overcome before a
semilunar valve can open
– Increase in ___ causes stroke volume to
decrease
• Blood remains in ventricle at the end of systole
– Hypertension and atherosclerosis increase
afterload
afterload
Cardiac output depends on heart rate and stroke volume
– Adjustments in heart rate important in short-term control of cardiac output and blood pressure
– Autonomic nervous system and epinephrine/ norepinephrine most important
Regulation of Heart Beat
Originates in cardiovascular center of medulla oblongata
– Increases or decreases frequency of nerve impulses in both sympathetic and parasympathetic branches of ANS
Autonomic regulation
Noreprinephrine has 2 separate effects
- In SA and AV node speeds rate of spontaneous depolarization
- In contractile fibers enhances Ca2+ entry increasing contractility
release acetylcholine which decreases
heart rate by slowing rate of spontaneous depolarization
Parasympathetic nerves
Chemical regulation of heart rate
Hormones
• Epinephrine and norepinephrine increase heart rate and contractility
• Thyroid hormones also increase heart rate and contractility
– Cations
• Ionic imbalance can compromise pumping effectiveness
• Relative concentration of K+
, Ca2+ and Na+ important
Heart develops from mesodermal cells called the
cardiogenic area
Heart develops from mesodermal cells called the cardiogenic area which in turn forms a pair of elongated
strands
cardiogenic cords.
The cords will eventually
form the and they in turn form the
primitive heart tube
endocardial tubes
The cords will eventually
form the endocardial tubes and they in turn form the ____
primitive heart tube
The primitive heart tube develops into 5 distinct regions including: (from tail end to
head end)
- Sinus venosus: forms part of the R. atrium, coronary sinus and SA node.
- Atrium: forms a part of the R. & L. atria and auricles.
- Ventricle: forms the L. ventricle and a part of the R. ventricle.
- Bulbus cordis: forms a part of the R. ventricle
- Truncus arteriosus: forms the pulmonary trunk and ascending aorta.
(t/f) There is also a bending during the heart development that brings the primitive heart tube to the adult heart position.
true
divide the primitive
atrioventricular canal into R. & L. atrioventricular canals separating the R. &. L.
atria from R. & L. ventricles respectively
Mesodermal thickenings known as endocardial cushions
Interatrial septum partitions the primitive atrium and forms the R. & L. atria but
initially a ___
forms in this septum that before birth
allows most blood entering the R. atrium to pass into the L. atrium
foramen ovale
Interatrial septum partitions the primitive atrium and forms the R. & L. atria but
initially a foramen called foramen ovale forms in this septum that before birth
allows most blood entering the R. atrium to pass into the L. atrium. It will be closed
after birth but it remnants forms the _______
fossa ovalis on interatrial septum
lungs
- pump pulmonary circulation- blood from heart and go up to each lung
- it receives deoxygenated (superior /inferior vena cava,coronary sinus)blood from the body and send it to the lungs for oxygenation.
path of blood/diagram of blood flow
Right side of the heart-
pump for the systemic circulation. it pumps oxygenated blood from the lungs out into the vessels of the body.
left atrium-receive red, oxygenated blood from the lungs via the pulmonary veins.
Left side of the heart-
- right atrium- deoxygenated- superior/inferior vena cava,coronary sinus
-tricuspid valve to close prevent backflow into the right atrium
-beginning of pulmonary circulation- right ventricle-deoxygenated- contraction
3.pulmonary trunk- semilunar valve close- prevent back flow into right ventricle - Right / Left pulmonary capillaries of the right/ left lung
right side of pulmonary circulation- deoxygenated
- right ventricle-deoxygenated- contraction
5.pulmonary veins-left atrium-oxygenated- end of pulmonary circulation
-bicuspid valve/mitral valve open/left atrioventricular valve
6.left ventricle- full of blood - begining of systemetic circulation
-bicuspid valve is close prevent backflow left atrium
-contraction
7.2 semilunar valves to open and push to the aorta- aorta and beggining of pulmonary trunk
8. aorta goes to the body
right atrium- end of systemic the circulation
9. in systemic capillaries loses oxygen and gains co2
• Fibers within the network are connected by thickening of sarclomma called ___ which hold the fibers and gap junction that allows action potention to conduct from one muscle fibre to another.
intercalated
because they are self-excitable. they repeatedly generate spontaneous action potential that then trigger heart contraction.
These cells act as a pace maker to set the rhythm of electrical excitation for the contraction of the entire heart
they form the conduction sysytem the route for propogating action potential through the heart muscle. This specific pathway of conduction ensures that cardiac chambers become stimulated to contract in the coordinated manner.
Autorhythmic cells
atrial depolarization - spread impulse from SA node over atria.
p wave-
rapid venticular depolarization- spread of impulse through ventricles
QRS complex-
ventricular repolarization
t wave-
represent the time when ventricular contractile fibers are depolarized during the plateau phase of the action potential
s-t segment end of s to the beginning of T
- represent the time from venticular depolarization end of ventricular repolarization.
correlation of ecg waves with atrial and ventricular systole
The Q- T segment
- depolarization of the sa node causes atrial depolarization
- atrial depolarization results in atrial systole. as the atria contrract the increase pressyre on the blood forces it through the open av valves int the ventricles
- atrial systole contributes a final 25 ml of blood to the volume already in each ventricle (105 ml. the end of atrial systole is also the end of diastole is end diastolic volume at this point each ventricle contains 130 ml of blood
- The qrs complex marks the onset of ventricular depolarization
- vetricukar depolarization causes ventricular systole
contraction of the ventricles rises the pressure on the blood forcing it up against the av valves to push tem closed.
For 0.05 seconds cusps of the valves all four av and sl valves are closed.this is isovolumetric contraction.
- cotinued contraction causes the ventricular pressure to exceed aortic pressure and the SL valves open allowing blood to flow out in the aorta- same for pulmonanry side. this is the ventricular ejection phase.
- the Left and right ventricles each eject about 70 ml of blood into aorta/pulmonary arterty which leaves 60 ml remaining in each ventricle-end systolic volume
- t wave in ecg marks onset of ventricular repolarization.
- ventricular repolarization causes ventricular diastole. as pressure in ventricles falls blood will flow back to area of lower pressure pushing the sl valves closed. rebound off the closed cusps of the aortic valve produce the dicrotic wave on the aortic pressure curve. After Sl valve close there is brief interval where ventricular blood volume does not change because all 4 valves are closed. -isovolumentric relaxation phase.
- as the ventricles relax falls below atrial pressure and the av valves open marking the beginning of ventricular filling. The major part of the filling occurs right after the Av nvalves ope. prior to this blood has been flowing into and collecting in the relaxed into and collecting in the relaxed atria and as soon as the valves open, it is dumped into ventricles-
at the end of relaxation period the ventricles are 3/4 full. then we get a P wave amd it all starts again.
first heart sound lubb- closing av valve after ventricular systole begins
dupp- closing of the sl valves- end of ventricular systole
heart murmur- foramen ovales open
cardiac Output-is the volume of blood ejected from the left ventricle into aorta pulmonary trunk each minute
Cardiac output- equals the stroke volume the volume of vlood ejected by the ventricle woth each contaction multiply by the heart rate(beats/min) the number of beats per minute
CO=SVx HR
SV=70ml x beats per minute Regulation of heart rate autonomic regulation of the heart central control of the cardiovascular system stems from the cardiovascular center in the medulla oblongata limbic system input increase HR even before activity by sending impulses to CV center
sympathethic impulses increase heart rate and force of contraction.parasymtpathetic impulses decreas heart rate
from thw thoracic level of spinal cord, cardiac accelerator nerves extend out to Sa node AV node and myocardium to trigger the relase of norepinephrine.
is the ratio between the maximum cardiac output a person can achive the cardiac output
cardiac reserve-
Cations (na ,K, CA also effect heart rate
elevated k and na in blood decrese heart rate and contractility because excess na blocks ca2 inflow during action potential to decrease the force of contraction. excess K blocks the generation of action potential. increased interstitial ca2 speed hr and heart contractility.
babies have much higher resting hear rates, women are slightly higher than men, athletes are lower than couch potaotoes.
heat (fever,exercise speds up the depolarization of sa node and increase Hr while hypothermia lower hr and slows strength of contraction reducing the tissue demands for 02
exercise and the heart
a person cv fitness can be improbed with reguar fitnes-20mins to increase co and elevates metablic rate
several weeks of training results in maximal cardiac outut and oxygen delivers to tissues.
regular exercise also decrease anxiety and depression,controls weight and increases fibrinolytic activity ( reduces blood clotting.
-sustained exercise increased oxygen demand in muscles.
tachcardia-elevated heart rate
bradycardia-decrease heart rate
heart rate is affected hormones- epinephrine , norepinephrine and thyroid hormones. epinephrine and noreepinephrine are also released from the adrenal medulla and act as the same way as with sympathtic stimulation
thyroid hormones also enhanced heart rate and contractility
Norepinephrine speed the rate of spotaneous depolarization of the fibers in SA and av node to increase heart rate. it also enhances the entry of CA2 through the channels to increase contractility of the myocardium. the result is increased sv and co, this increase in contractility offsets the decrease in preload.
Parsympathethic impulses arrive at the heart via the right and left vagus nerves(CNX and release acetycholine to decrease the heart rate by slowing the rate of spontaneous depolarization at the nodes.PArasympathetic impulses have the little effect on contractility of the venticles..
vagus nerves-acetycholine
montior the position of your limbs and as you start to move them around faster with exercise, nerve impulse are sent to the CV centere to stimulate in HR at the onset of activity
Proprioceptors-
- monitor presuure changes- detect the amount of the presure of the stretching in major arteries and veins ehich relates to the presuure of blood through blood vessels. they are located in the arch of aorta and carotid sinus.
Barorecetors
monitor chemical changes in the levels of O2 and Co 2 in the blood
chemoreceptors
