cardiovascular system Flashcards
Arteries, arterioles and capillaries carry blood going ______ the heart
away from
venules and veins carry blood going _______ the heart
towards
What are the 3 layers that make up arterial walls? (from in to out)
- tunica interna
- tunica media
- tunica externa
What makes up the tunica externa?
connective tissues
What makes up the tunica media?
smooth muscle
What makes up the tunica interna?
- innermost endothelium
- basement membrane
- internal elastic lamina
What happens to arteries during ventricle contraction?
the pressure of blood rises, and they expand
What happens to arteries during ventricle relaxation?
the pressure of blood falls, and they recoil
What is Angiogenesis?
the formation of new blood vessels from venules
What is arteriovenous anastomoses?
when blood from the arterioles passes directly into the venules without going through the capillaries
What is vasoconstriction, and what does it do to the rate of blood flow?
the contraction of smooth muscle within the arteries; decreases blood flow
What is vasodilation, and what does it do to the rate of blood flow?
the relaxation of smooth muscle within the arteries; increases blood flow
What’s the difference between continuous and discontinuous capillaries?
- continuous capillaries have closely joins adjacent endothelial cells, and permit the passage of molecules between blood and interstitial fluid
- discontinuous capillaries have a great distance between adjacent endothelial cells, and prevent the passage of molecules (they also create cavities in their respective organ)
Continuous capillaries are found in…
- muscles
- lungs
- adipose tissues
- central nervous system (contribute to blood-brain barrier)
Fenestrated capillaries are found in…
- kidneys
- intestines
- endocrine glands
What are fenestrated capillaries?
capillaries that contain wide intercellular pore covered by mucoprotein, and restrict the passage of molecules
What are the 3 types of capillaries?
- continuous
- discontinuous
- fenestrated
Discontinuous capillaries are found in…
- bone marrow
- liver
- spleen
What are is the role of capillaries?
location of gas exchange
Veins _____ as they accumulate more blood
expand
What is the role of a venous valve?
to ensure one-way blood flow to the heart
What is the skeletal muscle pump?
- contraction of muscles help return blood to the heart
- essential in lower limbs
- increases during physical activity
What is the abdomen’s equivalent to muscles in the skeletal muscle pump?
the diagram
What are the 4 chambers in the heart?
- right atrium
- left atrium
- right ventricle
- left ventricle
What is the role of the atria?
receive blood from the venous system
What is the role of the ventricles?
pump blood into the arteriole system
the atria and ventricles are separated by the…
fibrous skeleton
Describe the steps of pulmonary circulation (with deoxygenated blood starting within the muscles)
- blood travels through the veins, and enters the superior/inferior vena cava, which brings it to the right atrium
- blood passes through the tricuspid valve, and is pumped into the right ventricle
- blood passes through the pulmonary valve, and is pumped into the pulmonary truck
- blood travels through the pulmonary arteries, and is re-oxygenated in the lungs
Describe the steps of systematic circulation (with oxygenated blood beginning in the lungs)
- the pulmonary vein transports the blood to the left atrium
- blood passes through the bicuspid/mitral valve, and is pumped into the left ventricle
- blood passes through the aortic valve, and is pumped into the aorta
- blood enters the arteries, and is pumped to the body
The _____ ventricle is ______ than the right ventricle because…..
left ventricle is thicker than the right because it has the work harder
What’s an Atrioventricular Valve (AV)? What is its function?
a valve embedded within the fibrous skeleton that prevents back flow of blood from the ventricle into the atrium
What are the 2 kinds of atrioventricular valves, and where are they located?
- tricuspid valve; between the right atrium and ventricle
- bicuspid valve; between the left atrium and ventricle.
How many flaps does the tricuspid valve have?
3
How many flaps does the bicuspid valve have?
2
What’s the role of a Semilunar Valve?
opens during ventricular contraction, and closes during relaxation to prevent back flow into the ventricles
The “lub-dub” sound heart during a heart beat refers to…
- “lub” : atrioventricular valve closing (systole)
- “dub” : semilunar valve closing (diastole)
What’s a heart murmur?
abnormal sounds during the cardiac cycle, typically due to defective heart valves
rheumatic endocarditis is a heart murmur causes by…
rheumatic fever
mitral stenosis causes a heart murmur due to…
a thickened and calcified mitral valve
mitral valve prolapse causes a heart murmur due to…
blood flowing backwards into the left atrium
septal defects cause heart murmurs due to…
holes in the septum
papillary muscles…
- connect to the AV valves by chordae tendineae
- cause the closing of valves due to pressure increases
The cardiac cycle consists of…
- contraction of ventricles (systole)
- relaxation of ventricles (diastole)
What is end-diastolic volume?
the total volume of blood in the ventricles at the end of diastole
What is stroke volume?
2/3 of the volume in the ventricles (amount ejected during systole)
> AKA the amount of blood coming from the ventricle in 1 heartbeat
Where is most of the blood in the body at any given time?
the venous system
What are the 2 kinds of semilunar valves?
- pulmonary valve
- aortic valve
What is the end-systolic volume?
1/3 of the volume in the ventricles (initial amount in the ventricles)
What does automaticity refer to?
the automatic nature of the heart
What are the primary (1) and secondary/ectopic (2) pacemakers of the heart?
- Sinoatrial/SA node (primary)
- Atrioventricular/AV node (secondary)
- Purkinje fibers (secondary)
Why are the atrioventricular/AV node and Purkinje fibers secondary pacemakers?
they’re typically suppressed by the sinoatrial/SA node
Secondary/ectopic pacemakers produce a rhythm ______ than normal sinus rhythm
slower
What happens during pacemaker potential/diastolic depolarization?
> production of 1 heart beat
- during diastole, the sinoatrial/SA node exhibits a slow spontaneous depolarization
- Na+ ions flood through HCN channels in the plasma membrane and sarcoplasmic reticulum, creating a depolarization
- Once threshold value is reached, Ca2+ channels open, producing the upward phase of action potential
- The Ca2+ triggers calcium-induced calcium release in the sarcoplasmic reticulum
- Repolarization is then reached by opening of K+ channels
What is a myocardial action potential, and how is it produced?
- myocardial cells produce their own action potentials when stimulated by the SA node
- stimulation by the SA node causes FAST opening of Na+ channels, and SLOW opening of Ca2+ channels
Why do myocardial action potentials last longer than normal ones?
slow Ca2+ channels maintain depolarization for longer (plateau phase)
Describe the process of electrical conduction through the heart
- SA node creates action potential which spreads to the right and left atria via gap junctions
- action potential passes to the AV node on the interartrial septum
- action potential passes through the atrioventricular bundle/bundle of His in the interventricular septum
- action potential divides left and right, and is passed to Purkinje fibers
- action potential spreads from the endocardium to the epicardium, which causes simultaneous contraction of the ventricles
What are the 3 distinct ECG waves (in order of appearance on the graph)?
- P wave
- QRS wave
- T wave
What does the P wave represent?
the spread of atrial depolarization
What does the QRS complex represent?
spread of depolarization into the ventricles
What does the T wave represent?
repolarization of the ventricles
Which section of the heart has the fastest conduction rate?
Purkinje Fibers
What is an electrocardiogram?
recording of potential differences generated by the heart conducted to bodily surfaces
What does the peak of an electrocardiogram wave mean?
the respective section of the heart is at 50% depolarization
What is coronary artery disease?
- buildup of plaque in one or more of the 3 coronary arteries
- restricts blood flow to the heart, causing chest pain or angia
What is bradycardia?
slower than average heart rate (<60bpm)
What is tachycardia?
faster than average heart rate (>100bpm)
What is ventricular fibrillation?
chaotic heart rhythm and rate
What’s a myocardial cell?
heart muscle cell
myocardial cells are…(5)
- short
- branched
- interconnected
- striated
-connected via electrical synapses/gap junctions
What is the grabby boi called?
myosin :3
Each myocardial muscle fiber is composed of subunits known as…
myofibrils (extend in parallel rows from one fiber to another, and are tightly packed together)
What are the components of myofibrils, and what kind of filaments do they contain?
- A band (thick and half thin filaments)
- I bands (thin filaments)
What are thin filaments made of?
actin
What are thick filaments made of?
myosin
What is the H band?
the portion of the A band that only contains thick filament
What is the Z disk?
- thin filament that penetrate surround thick filament in a hexagonal arrangent
What is a sacromere?
From Z disc to Z disc (contains 2 half I bands and an A band)
A Tintin filament consists of…
- amino-terminal end bound to a Z disk
- a “spring” portion that extends through the I band
- a long portion bound to thick filament up until the M line
Where is the M line, and what is it’s role?
the center of the thick filaments/A band, anchors the thick filaments during contraction
What happens (to sarcomeres, A bands, I bands, and H bands) during myocardial contraction?
- sarcomeres shorten in length
- A bands move closer together
- I bands decrease in length (thin filaments DON’T shorten, they slide between thick filaments)
- H bands decrease in length
What do cross bridges do?
they produce sliding filaments
What are the components of cross bridges?
- myosin contains 2 globular heads oriented opposite to those on the other side, each containing ATP-binding sites and actin binding sites
How do cross bridges work?
- myosin functions as an ATPase enzyme, and converts ATP to ADP + Pi
- The Pi causes a conformational change, and the head binds to actin, and pulls the thin filament in
- After the contraction, ADP is released, a new ATP is bound
- The cycle repeats again for the next contraction
Do all cross bridges contract at the same time? Why or why not?
No, power strokes are not synchronous
What 2 proteins act to regulates cross bridges?
- tropomyosin
- troponin
What are the 3 subunits of troponin, and what do they do?
- troponin I: inhibits actin binding
- troponin T: binds tropomyosin
- troponin C: binds Ca2+
What is Ca2+’s role in cardiac muscle contraction
- When Ca2+ binds troponin, a conformational change occurs, which moves tropomyosin, and allows the globular heads to bind and undergo a power stroke
What does tropomyosin do?
physically blocks myosin heads from binding in resting state
What are the 3 main differences between cardiac and skeletal muscle?
- skeletal requires stimulation from nerves, whereas cardiac produces its own action potentials
- skeletal are long and fibrous, myocardial are short, branched and interconnected
- skeletal have direct excitation-contraction coupling, cardiac have voltage gated Ca2+ release channels
