Cardiovascular System Flashcards
How many chambers and valves does the heart have?
4 chambers, 4 sets of valves form 2 pumps
What are the four chambers of the heart?
Right Atra
Right Ventricle
Left Atria
Left ventricle
What are the valves of the heart?
AV valves - tricuspid and bicuspid
Semi-lunar valves - aortic and pulmonary
Where does the pulmonary circulatory system go?
arteries to and veins from the lungs
Where does the systemic circulatory system go?
arteries to and veins from the rest of the body
Why is the heart separated into two distinct parts?
to separate oxygenated and deoxygenated blood
What are the 7 functions of the cardiovascular system?
- transport O2/CO2 from and to the lungs and tissues
- transport of nutrients: from intestine to tissues and from and to the liver and fat
- transport waste: from production to excretion sites
- transport heat: from inside to the skin
- transport hormones: endocrine glands to target cells
- carrying immune cells
- stabilize internal environment: buffer
What is the pericardium?
2 layers of connective tissue with a cavity
What is the function of the pericardium?
prevents overstretching of the heart
What are the names of the two layers of the pericardium?
Parietal layer (outside)
pericardial cavity
Visceral layer (inside)
What is the pericardial cavity filled with?
fluid, allows some movement
What is the function of the atria of the heart?
Serve as reservoirs, help transfer blood to the ventricles
What is the function of the ventricles?
propel blood into systemic and pulmonary circulation
What are the heart valves separated by?
muscular septum
What is the muscle tissue called of the heart?
myocardium
What is the endocardium?
epithelium covering the inner surface
What are the heart valves made out of?
fibrous connective tissue attached to a fibrous ring
What is the function of the valves of the heart?
allow blood to flow in only 1 direction
Where are the AV valves located?
bicuspid (mitral) valve on the left
tricuspid valve on the right
What is a special feature of the AV valves?
the free end of the AV valves attached to papillary muscle (chordae tendonae) in the ventricle (prevents inversion, limits movement)
Where are the semilunar valves located?
aortic: between left ventricle and aorta
pulmonary: between right ventricle and pulmonary artery
What is the mechanism for the opening and closing of valves?
passive mechanism, dependent on blood pressure
If the ventricles are relaxed, what will the valves do?
AV valves opened
If the ventricles are full, what will the valves do?
AV valves closed
If the ventricles contract, what will the valves do?
pressure higher than arterial pressure, aortic and pulmonary valves open
What is the function of the arteries?
convey blood from the heart to tissues and organs
Where does the pulmonary artery leave from the heart?
leaves the right ventricle to bring deoxygenated blood to the lungs
Where does the aortic artery leave from the heart?
leaves the left ventricle to bring oxygenated blood to the rest of the body
What is the function of the veins?
convey blood from the tissues and organs to the heart
Where does the vena cava come into the heart?
bring deoxygenated blood to the right atrium
Where does the pulmonary vein come into the heart?
brings oxygenated blood to the left atrium
Which arteries are elastic and why?
aortic and pulmonary arteries receive tremendous pressure from ventricle contractions
What are the function of small arteries?
deliver blood locally to arterioles and capillaries in tissues, control the pressure via tone of vessels smooth muscle
What is the function of the capillaries?
site of gas exchange nutrient etc.
What is the function of the venules?
collect blood from the capillaries
What is the function of the veins?
receive blood from venules and return it to the heart, change in tone will alter venous return
What are the different blood vessels
artery>small artery>capillaries>venules>veins
What are the similarities vs differences of the systemic vs pulmonary circulation?
both have arteries and veins
pulmonary - heart/lungs loop to oxygenate blood
- relatively low pressure, low resistance, highly distensible
systemic - distribution of oxygenated blood and nutrients throughout the body
- high pressure high resistance
Why is the left ventricular wall much thicker than the right?
Work performed by the left ventricle is 5-7 fold greater than right ventricle
What is the cardiac cycle?
repeating pattern of contraction and relaxation of the heart
What are the two basic stages of the cardiac cycle?
Systole - phase of contraction
Diastole - phase of relaxation/filling
What is the concept of two-step pumping?
both atria contract simultaneously - push blood in ventricles
right and left ventricles contract 0.1 to 0.2 seconds later
What are the steps of the cardiac cycle?
- Diastole
- atrial contraction
- isovolumic contraction
- ejection phase (systole)
- isolvolumic relaxation
What are the two types of cells that the myocardium is composed of?
contractile cells: 99% of cells, AP required for contraction
autorhythmic cells: modified non-contractile cells, concentrated in specific regions of the heart, spontaneously generate AP
What are gap junctions and what is their function?
adjacent cells in the heart are connected by water-filled pores forming open contractions (gap junctions), they allow ions to freely move from 1 cell to another, and electrical activity can pass from cell to cell
What is electrical conduction generated by?
autorhythmic cells (pacemaker cells)
What are the components of the electrical conduction system?
SA node
AV node
bundle of His and Purkinje fibers
What is the function of the SA node?
Command center (determines heart contraction)
rhythmical self-excitation
What is the function of the AV node?
autorhythmic ability but pace is slower so under SA control
gateway for electrical conduction between atria and ventricles
What is the function of the bundle of his and purkinje fibers?
help to quickly propagate electrical activity from the Av node to the rest of the ventricles
What are the three roles of the electrical system?
maintain appropriate heart rate
coordinate contraction of atria and ventricles
coordinate contraction of each chamber
What is the relevance of the electrical system?
use ECG to determine heart rhythm
problems with conduction - abnormal rhythm - arrhythmia
What are the steps to excitation of the heart?
- SA node self excitation (generation of APs)
- Aps propagate through atria = atrial contraction
- AV node activated by AP wave, transmit electrical activity to the bundle of his and purkinje fibers with a little delay (allows packing of blood in ventricles and closure of the AV valves)
- electrical activity propagate through ventricles - ventricular contraction
How is AP generated in the SA node?
cells from SA node gradually depolarize, this drift in potential is caused by the leakage of Na+ inside the cell and reduced diffusion of K+ outside the cell, when threshold is met, AP is generated, cycle is repeated
How does the ANS control the contraction of the SA node?
sympathetic fibers: reduce the time required to reach the threshold, faster pace
parasympathetic fibers: prolong the time required to reach the threshold, slower pace
How does the action potential actually reach the contractile cells in the heart to induce a contraction?
AP from authorythmic cells propagate to the contractile cells
Is there a stable RMP in autorhythmic cells and contractile cells?
authrhythmic cells do not have a stable RMP
contractile cells have a stable RMP
What is the difference between cardiac muscle AP from skeletal muscle AP?
cardiac muscle duration of AP is much longer, 100’s of a millisecond
the length of the refractory period in cardiac muscle is also longer
allows full contraction in heart to occur before another one, eleminates tetany or involuntary contractions
What are the states of the voltage gated channels of the heart cells at phase 1-5 of the cardiac cycle?
phase 1: Na+ closed, K+ closed, Ca+ closed
phase 2: Na+ open, K+ closed, Ca+ closed
phase 3: Na+ closed, K+ open, Ca+ closed
phase 4: Na+ closed, K+ (open), Ca+ open
phase 5: Na+ closed, K+ open, Ca+ closed
What are the five phases of the voltage-gated ion channels in cardiac muscle?
phase 1: RMP
phase 2: rapid depolarization, mainly due to influx of Na+
phase 3: short phase of repolarization; loss of K+ from the cell
phase 4: plateau phase - influx of Ca+ into cell
phase 5: repolarization phase - outward movement of K+ from cell
What are the steps to calcium stimulated calcium release during contraction coupling?
- depolarization
- voltage-gated Ca++ channels open
- Ca++ entry induces an avalanche of Ca++ release from sarcoplasmic reticulum
- large increase in intracellular Ca++ triggers contraction
- Ca++ pumped back in its pre-stimulation compartment
What does the sympathetic nervous system do in terms of control of heart contraction?
- stimulates the heart rate: firing of the SA node, velocity of the AV node conduction
- increase the contraction force: increases the release of Ca2+ from sarcoplasmic store
- reduces the contraction time: increases the speed of Ca2+ transport
- actions mediated by epinephrine/norepinephrine on beta-adrenergic receptors present in all cardiac cells
What does the parasympathetic nervous system do in terms of contraction of the heart?
- decreases heart rate: reduces firing of the SA node, decreases the velocity of the AV node conduction
- actions mediated by binding of acetylcholine of muscarinic receptors in autorhythmic cells: increase k+ permeability, hyperpolarization increase time required to reach the AP threshold
What does an ECG measure?
heart membrane potential throughout the cardiac cycle
How does an ECG work?
electrode place at different location on the skin will read the progression of the electric current wave
What are the three waves of the ECG?
P wave = depolarization of the atria
QRS wave = depolarization of the ventricles
T wave = repolarization of the ventricles
What is the base-apex lead configuration?
One lead on the left chest, second lead over the neck (jugular groove)
What are the two uses of the ECG?
- assessment of the heart rate and rhythm, measures intervals between cycle, contraction force (amplitude of waves), and rhythm (measures the intervals between each wave)
- detection of abnormalities
What is a slower and faster heart rate called?
Bradycardia = slower rate
tachycardia = faster rate
What does an abnormally long PQ interval indicate?
AV conduction problem
Draw out the graph for the events during a cardiac cycle (lecture 8)
refer to slides
What is the formula for cardiac output?
cardiac output = heartrate x stroke volume
What is a denervated heart rate?
the parasympathetic controls of the heart are lost resulting in a slow increase in heart rate due to the sympathetic action of adrenaline and noradrenaline
EDV
end-diastolic volume
ESV
end systolic volume
What is the formula for the volume of blood ejected per contraction?
EDV-ESV
What is EDV?
preload
- volume of blood present in the ventricles at the end of diastole
- linked to the work imposed on ventricles prior to contraction
What is ESV?
- residual volume of blood contained in ventricle after systole
- depends on the impedance to ejection of blood from ventricles
What does an increase in EDV result in?
increase in stroke volume
What is the Frank starling law of the heart?
as preload is increase, the contractility of the heart is increases which leads to increased stroke volume
increased stretch of cardiac muscle fibers at the end of diastole induce increase in contracility by enhancing binding of Ca2+ to troponin-C
under resting condition EDV stretches cardiac muscle to sub-optimal levels
What is the main factor that effect EDV?
venous return
increased venous return = increased EDV
decreased venous return = decreased EDV
What factors affect the venous return?
- dependent on the pressure difference between the large veins and the right atrium
- skeletal muscle pump: muscle contraction squeezes veins, pushes blood towards heart (valves in veins prevents backflow)
- respiratory activity (pump): increases abdominal pressure = transfer to abdominal veins, creates low pressure in thoracic cavity
- blood volume (more blood volume, more venous return)
- ANS (veins contain smooth muscle innervated by sympathetic fibers), increase in AP in nerve fibers cause a contraction which increases pressure in the veins and increases venous return
What factors affect afterload (ESV)?
- resistance the ventricles encounter during ejection
- contractility - higher contractility = lower ESV
- total peripheral resistance (TPR)
What are the important factors of blood vessels?
diameter
elasticity
contractility
Draw the table in lecture 8 of the various blood vessel characteristics
refer to lecture 8
What is the formula for flow?
Flow (Q) = Pressure difference (deltaP)/Resistance (R)
Is pressure higher in arteries or veins?
arteries
Which vessels are the bottlenecks of the circulation?
arterioles, main site of pressure/flow regulation as they have the most smooth muscle
What is flow?
the volume of fluid transported per time unit
What is the flow between 2 points dependent on?
the pressure difference between the two points and the resistance
What does resistance depend on?
- length of vessel
- radius of vessel (most important)
- viscosity of blood
Does pressure decrease through the arteries to the capillaries or increase?
decrease
How does the arterial pressure fluctuate during the cardiac cycle?
- when aortic valve opens during ventricular contraction there is a rapid flow of blood which increases the arterial pressure, the aorta absorbs some of the pressure and temporarily stores it
- when the aortic valves close during diastole no blood is flowing from the ventricle, energy is stored during the stretching of the aorta is released, the arterial pressure gradually decreases
Why are arteries elastic?
low resistance but high flow
recoil of walla limits the drop in pressure after systole
more continuous flow
What are the two types of arterial pressure during the cardiac cycle?
systolic pressure and diastolic pressure
Draw the aortic blood pressure profile during systole and diastole
refer to lecture 8
What is the difference between systolic and diastolic pressure?
pulse pressure
What occurs to the MBP during rest?
MBP closer to diastolic pressure (diastole longer)
What occurs to the MBP during exercise?
MBP closer to systolic pressure (diastole shorter)
MBP
mean blood pressure
What are the factors that influence arterial pressure?
- elasticity of the artery (low elasticity - high pressure)
- cardiac output (more blood from systole - higher pressure)
- respiration
- resistance to blood flow (main factor) - TPR depends on vasoconstriction of arterioles higher TPR = higher pressure
- blood volume
What are some characteristics of arterioles walls?
fewer elastic fibers but larger number of smooth muscle fibers
What is basal level constriction?
the control of the diameter of the arteriole walls
If the diameter of the arteriole wall decreases, does the resistance increase or decrease?
increases
What are the two levels of control of arteriolar resistance?
Autoregulation and extrinsic control factor
What is autoregulation?
controls blood flow to critical organs (a protective mechanism)
What are the two types of autoregulation?
- metabolic regulation: response to changes in metabolism (thus blood requirement), results to increase in diameter
- myogenic pressure autoregulation: vessels respond to changes in tone or stretch
What is extrinsic regulation?
regulates the peripheral pressure as a whole
What are the influence on the extrinsic regulation of vascular constriction
- vasoconstrictive influence
- sympathetic stimulation on alpha adrenergic receptors
- angiotensin 2
- arginin vasopressin
- vasodilatory influences (few)
- parasympathetic stimulation
How low is the pressure once blood enter the veins?
10 mm Hg
How does venous pressure increase to move blood upwards?
smooth muscles of veins, heart acts as a pump to suck blood upwards, skeletal muscle activity, respiratory pump
What happens when the pressure in the veins is too high?
fluid can leak out and accumulate in tissue which leads to an edema
What are baroreceptors?
sense stretching of arterial wall, have free nerve endings
Where are baroreceptors located?
aortic arch
carotid sinus
What is the arc of a baroreceptor?
- sensory fibers: ascend via vagus nerve, stretch increase = increase AP frequency
- integration center: cardiovascular center in the medulla oblongata
- motor fibers: ANS
- effectors: heart (rate and stroke volume), TPR (veins and arteries)
What is an example of baroreceptors in action?
changing from lying to standing: (venous return is lowered, blood pressure is lowered)
- decreased firing in stretch receptors
- decrease in parasympathetic activity, increased heart rate
- increased sympathetic activity, increased heart rate, stroke volume and vasoconstriction
What is atrial volume receptor reflex?
stretch receptors in wall of atra, regulates blood volume via ANS activity and neural input that controls thirst
What are three hormones that regulate BP?
- atrial natruiretic peptide (ANP) - synthesized in atrial all, increases Na+ extcretion
- renin - synthesized in kidney, increases aldosterone indirectly
- ADH - decreases water extraction (kidney)
How much blood is contained in the capillaries at a given time?
5%
how many blood cells can fit through the diameter of the capillary?
1
How many layers of endothelial cells is the capillaries?
1 cell layer thick
Are there openings between the endothelial cells of the capillaries?
yes
What does the density of the capillaries depend on?
metabolic activity of the tissue
What are metarterioles?
smallest arterioles
What do metarterioles possess?
rings of smooth muscle tissue that can open and close on demand
What happens to the rings of muscle tissue in metarterioles during exercise?
all open
Is the flow fast or slow in capillaries and why?
slow flow due to small diamter, this increases resistance and more exchange will occur
What are the function of the pores and clefts in capillaries?
allow transfer of water and lipid-insoluble molecules
What molecules can diffuse across the capillary freely?
lipid-soluble molecules
What are fenestrated capillaries and what do they do?
vesicles fuse to form large gaps across endothelial cell membrane allowing water and water-soluble macromolecules to pass
What is bulk flow?
mass movement of water and dissolved substances across the capillary walls, maintains fluid balance between intravascular and interstitial fluid
In bulk flow, what are the terms for the fluid going towards interstitial fluid and away?
towards interstitial fluid = filtration
towards the intravascular fluid (blood) = absorption
What is bulk flow dependent on?
- pressure gradients (hydrostatic and osmotic)
- permeability of vessels (porosity)
- size of diffusion surface
- blood flow
What is hydrostatic pressure?
filtration pressure
- pressure from heart -> arterioles -> capillaries
- pressure in interstitial fluid is close to 0
- pushes fluid out of vessel
What is oncotic (osmotic) pressure?
- due to big proteins that stay in vessel
- counter balances hydrostatic pressure
How are hydrostatic and oncotic pressures balanced?
in first portion - hydrostatic pressure is stronger (more fluid out)
toward the end - hydrostatic is less and if hydrostatic is less than oncotic, more fluid moves in
What are the 3 situations where the balance between hydrostatic and oncotic pressure in the capillaries can be effected?
arteriole dilation - hydrostatic pressure increases and no oncotic pressure is able to push fluid back in the capillaries
lower oncotic pressure - same as above
arteriole constriction - sooner than usual, oncotic pressure becomes higher than hydrostatic pressure (as it was lower in the first place) and more fluid flows into the capillaries
Where does fluid go inside and out?
picked up by the lymphatic system and drained to the large veins (lymphatic drainage), fluid that remains in blood goes back to the heart
What happens if the lymphatic system can’t keep up with the outflow?
edema
How does bulk flow help to stabilize blood volume during physiological cases?
blood loss = decrease in pressure = decrease in hydrostatic pressure = fluid enters back in
excess fluid intake = increase in pressure = increase in hydrostatic pressure = fluid accumulates in interstitial
low protein in plasma = lower oncotic = fluid out
high protein in plasma = higher oncotic = fluid in
What are the four mechanisms responsible for an edema formation?
- increased hydrostatic pressure in the blood vessels (increases hypertension/arterial pressure and increases venous pressure/right side heart failure)
- increased interstitial protein concentration (inflammation of capillaries, become leaky)
- decrease in oncotic pressure (loss of proteins, GI disease, liver disease)
- obstruction of lymphatic vessels
