exam 4 heart Flashcards
What does the cardiovascular system include?
heart, blood vessels, blood, & lymphatic system (not really)
What is the heart?
approximately 1 pound with the size/shape of a closed fist; located in thoracic cavity slightly left of the midline
What is the heart’s base?
superior part which is flat
What is the heart’s apex?
inferior part which is pointed; rests on the diaphragm & touches the chest wall at the 5th intercostal space
What happens to the heart when using CPR?
the heart muscle is manually contracted/squeezed between bodies of vertebrae & ribs + sternum
What layers protect the heart?
fibrous pericardium & serous pericardium (parietal/visceral)
What is the fibrous pericardium?
tough, dense, fibrous connective tissue; protects heart & holds it in place
What is the serous pericardium?
thin, soft, delicate serous membrane folded into parietal & visceral surfaces
What is the parietal pericardium?
deeper surface; fuses to the inside of the fibrous pericardium
What is the visceral pericardium?
also called epicardium; anchors directly to the heart wall; can also be categorized as a layer in the wall of the heart
What is the pericardial cavity?
space separating the parietal & visceral pericardium; filled with 15 mL of pericardial fluid which serves as a lubricant to reduce friction
What is the myocardium?
muscle layer made of cardiac muscle cells; each cell is branched & contains 1 central nucleus & they are interwoven to provide strength & prevent this layer from tearing
How are adjacent cardiac cells anchored?
by many desmosomes & specialized gap junctions called intercalated disks which act to hold cells together while allowing electrical impulses to pass from 1 cell to another to help coordinate contraction of the myocardium
How are cardiac muscle cells autorhythmic?
they can contract spontaneously without electrical impulses; when these cells touch each other they contract as a unit
What is a syncytium?
the units in which cardiac muscle cells are arranged; this arrangement allows the heart to contract with a slight twist to properly pump blood
When the heart is damaged, what chemicals could leak from the cardiac muscle cells?
troponin & creatine phosphokinase
What is troponin?
it can leak into the blood; elevated levels indicate heart damage (usually a heart attack)
What is creatine phosphokinase?
an enzyme that cardiac muscle cells use during their metabolism; it leaks into blood when cells are damaged
What is the endocardium?
deepest layer lining the inside of the heart; made of endothelium which is a type of epithelium where the cells are flat & scale-like (squamous)
Why is the formation of the cells in the endocardium important?
the cells are close together making this lining slick so that blood zips through
What tissue forms the heart valves?
the endocardium; it is continuous with the linings of blood vessels
What is endocarditis?
occurs when the lining is inflamed which can cause blood clots along the now roughened surface which can lead to pulmonary embolism in the lung or a stroke
What is c-reactive protein?
released into the blood by the liver due to some type of blood vessel inflammation (endocarditis); elevated levels of this protein can indicate any type of blood vessel inflammation
What are the 2 main routes of blood flow through the heart?
pulmonary & systemic circulation
What is pulmonary circulation?
deoxygenated blood is pumped to the lungs; right side of the heart
Through what 3 sources does blood enter the heart during pulmonary circulation?
superior vena cava, inferior vena cava, & coronary sinus opening
What is the superior vena cava?
drains blood from above heart level
What is the inferior vena cava?
drains blood from below heart level
What is the coronary sinus opening?
drains blood from the myocardium
Where does the blood go after it enters the heart?
fills the atria & auricles
How does blood travel to the right ventricle?
by passing through the tricuspid valve; the right ventricle contracts from the apex upwards with a slight twisting motion
Where does blood flow when it exits the right ventricle?
into the pulmonary artery trunk which branches into the left & right pulmonary arteries that continue to the lungs
What is the pulmonary semilunar valve?
it snaps shut to prevent backflow of blood into the right ventricle (from PAT)
Why must some blood always remain in the ventricles?
to prevent the walls from collapsing
What is systemic circulation?
newly oxygenated blood from the lungs is pumped to all body systems; left side of heart
How does blood enter the heart during systemic circulation?
newly oxygenated blood in alveolar capillaries merges into 4 pulmonary veins
How does blood enter the left ventricle?
by going through the bicuspid valve; left ventricle contracts from apex upwards with a slight twisting motion to eject blood into the aorta
What is the aortic semilunar valve?
it snaps shut to prevent backflow from the aorta into the left ventricle
What are the 2 types of valves in the heart?
atrioventricular & semilunar valves
What are atrioventricular valves?
the tri & bi cuspid valves; they separate the atria & ventricles
What are atrioventricular valves made of?
soft flaps called cusps which grow out of the endocardium
What are chordae tendinae?
“heart strings” that anchor the cusps into the ventricles; they attach to papillary muscles
What are papillary muscles?
cone-shaped extensions from the ventricle wall to prevent the valve’s cusps from extending into the atria which prevents leakage of blood from ventricle into atrium
What are semilunar valves?
rigid valves that pop open due to force of blood as its ejected from ventricles; prevents leakage from “great vessels” (PAT & aorta) into ventricles
How is the “lub” heart sound heard?
from the closure of the tri & bi cuspid valves at the same time
How is the “dup” heart sound heard?
from the closure of the semilunar valves at the same time
What is a heart murmur?
when the heart sound is heard as a gurgle due to valve leakage
What is the heart’s conduction system?
groups of neurons that coordinate the contraction of the heart
What does the conduction system include?
SA node, AV node, AV bundle of His, bundle branches, & Purkinje fibers
What is the sinoatrial (SA) node?
a lump of nervous tissue in the right atrial wall slightly inferior to the opening of the superior vena cava
What does the SA node do?
sets basic heart rate at approximately 75 bpm which can be adjusted as needed; causes atria to contract at the same time
What is the atrioventricular (AV) node?
a lump of nervous tissue in the interatrial septum near the tricuspid valve; sends impulses to AV bundle of His
What is the atrioventricular (AV) bundle of His?
strand of nervous tissue in the superior part of interventricular septum; branches to form the bundle branches
What are the bundle branches?
strands of nervous tissue in the inferior portion of the interventricular septum; branches into Purkinje fibers
What are Purkinje fibers?
tiny branches that extend into lateral walls of the heart from apex upwards to ensure that contraction of the heart also occurs from apex upwards
When does heart failure occur?
when blood is not adequately ejected into the “great vessels”; often due to issues with conduction system or death/weakness of a portion of the heart wall
What are the 2 types of heart failure?
pulmonary & systemic
What is pulmonary heart failure?
occurs when the right side doesn’t fully eject blood which causes blood to back up into the right atrium & inferior vena cava
What happens as a result of pulmonary heart failure?
swelling of the extremities, especially feet, ankles, and legs; can cause serous fluid to leak from the skin (weeping heart failure)
What is systemic heart failure?
occurs when the left side doesn’t fully eject blood which causes blood to back up into the left atrium & 4 pulmonary veins
What happens as a result of systemic heart failure?
swelling of the alveolar capillaries which causes difficulty breathing
What is an electrocardiogram (EKG)?
graphical representation of impulses/electricity from the conduction system
What is the P wave on an EKG?
where depolarization of the atria occurs
What is the QRS complex on an EKG?
shows the repolarization of atria & the depolarization of ventricles
What is the T wave on an EKG?
where the repolarization of ventricles occurs
What happens at the place between the P wave & QRS complex?
depolarization of atria is completed
What happens at the place between the QRS complex & the T wave?
depolarization of ventricles is completed
What is cardiac output (CO)?
the amount of blood ejected by each ventricle per minute; typically 5250 mL/min or 5.25 L/min
How is CO calculated?
heart rate • stroke volume
What is stroke volume?
the volume of blood ejected with each heartbeat; contraction force
What is cardiac output influenced by?
intrinsic & extrinsic factors
What are intrinsic factors?
changing of heart rate or stroke volume
What are extrinsic factors?
events that somehow alter the intrinsic factors
How is sympathetic stimulation an extrinsic factor?
it increases heart rate & contraction force through cardiac nerves in the sympathetic division supplying the heart
How could sympathetic stimulation occur?
through fear, exercise, fever, excitement, most pain, etc.
What is epinephrine?
hormone from the adrenal glands that is released in severe sympathetic stimulation; its presence greatly increases cardiac output
How do high blood calcium levels affect cardiac output?
causes an increase in CO because it increases cross bridge formation in the cardiac muscle
How is parasympathetic stimulation an extrinsic factor?
it returns an elevated cardiac output to normal through cranial nerve X = vagus nerve
How does the vagus nerve affect cardiac output?
in severe abdominopelvic pain (kidney stones, appendicitis, etc.), the pain travels to the brain through the sensory part of vagus nerve & sends impulses back through vagus nerve to the heart causing a decrease in heart rate & stroke volume
How could the decrease in CO due to the vagus nerve be harmful?
can lead to a cardiac output that causes insufficient blood going to the brain causing someone to pass out
How do cold/freezing temperatures affect CO?
cause a decrease in cardiac output as body tries (unsuccessfully) to divert blood to our “vital” organs
How do high blood potassium levels affect CO?
alter the waves of depolarization in heart’s conduction system which decreases cardiac output
How does depression/grief affect CO?
decreases cardiac output
How does acidic blood pH affect CO?
acidic blood pH occurs if the brain’s respiratory centers do not respond to this acidity (because of the presence of drugs like opioids); this pH decreases cardiac output which can lead to death
What are baroreceptors?
masses of neurons found within the wall of the aortic arch & the wall of the common carotid arteries at the point where they branch into external & internal carotids
Why is it important that the great vessels can stretch & recoil?
large volumes of blood enter these vessels as ventricles contract, so they must be able to withstand the force
What do baroreceptors do?
monitor changes in blood pressure in the arteries they are located in, sending that information to the centers in the brain’s medulla which regulate cardiac output accordingly
How is pressure in the blood vessels expressed?
systole & diastole; these phases are monitored when blood pressure is taken
What is systole?
phase of contraction of atria & ventricles
What is atrial systole?
atria contract
What is ventricular systole?
ventricles contract
What is diastole?
phase of relaxation of atria or ventricles
What is atrial diastole?
atria relax & fill with blood
What is ventricular diastole?
ventricles relax & fill with blood
What is normal blood pressure?
120/80
