CARDIOLOGY - Anatomy & Mechanical Physiology (Week 1) Flashcards
Main organs of cardiopulmonary system
heart and lungs
Blood supplies body with ___________ and _________, and carries away ________ and _________.
oxygen, nutrients
carbon dioxide, waste products
Heart
A hollow muscular organ producing a pumping action causing pressure changes that circulate blood throughout body
Base vs apex of heart
Base: more flat, broad
Apex: more conical, blunt
Heart acts as a double sided pump. What does this mean?
Means that pumping occurs on L and R side, which happens when muscular walls of each heart chamber contract (squuze) causing blood to be forced out of the chambers
Heart has ___ chambers. They are:
4
Right atrium
Left atrium
Right ventricle
Left ventricle
In individuals of average height and weight, what is the size/weight/shape of the heart?
Weight: ~453g (1 lb)
Size: ~an adult’s fist (12cm long x 9 cm wide x 6 cm deep)
Shape: blunt cone
Shape of heart in taller, thinner individuals?
Shape of heart in shorter, stalkier people?
taller, thinner ppl: elongated hearts
short people: heart is of greater width
Location of the heart
- lies obliquely (slanted) in the mediastinum
- anterior to the esophagus and vertebra
- posterior to the sternum
- approx 2/3 of heart’s mass is L of midline (sternum)
- approx 1/3 of heart’s mass is R of midline
- base is directed poserior and slightly superior; lies just below 2nd rib (2nd intercostal space)
- apex is directed anterio and slightly inferior; lies just below the 5th rib (5th intercostal space) ⇒ pointed downwards towards the left
Mediastinum
place between the lungs in thoracic cavity & extends from vertebral column to sternum
How many layers make up the heart wall? list from outer layer to inner layer
1) epicardium
2) myocardium
3) endocardium
Pericardium/pericardial sac
- Loose-fitting inextensible membrane sac which encases the heart
- sac made of white firbous tissue, but lined with a smooth membrane (which has parietal and visceral layer)
Pericardium contains 2 parts. What are they?
1) Fibrous pericardium - tough, loose-fitting and inelastic sac
2) Serous pericardium (space) - thinner and has 2 layers
- Parietal layer - lining inside of fibrous pericardium
- Visceral layer - aka the EPICARDIUM - adheres to outside of the heart
Between the parietal and visceral layer of the pericardial sac contains what?
small amount of pericardial/serous fluid (10-30mL)
Function of pericardial fluid
to act as a lubricant, reducing change of friction and allowing the heart to move within the pericardial save as it beats
there is no danger of irritation as long as serous membrane remains undamaged and produces serous fluid
Epicardium
- translates to “above heart”
- outer layer of the heart
- also the same as the visceral layer of the serous pericardium
Myocardium
- literally translates to “muscle heart”
- thick middle layer of the heart
- consists of contractile cells (non-autorhythmic) and pacemaker cells (autorhythmic)
- has striated involuntary cardiac muscle cells (myocytes) joined into a continuous mass by end-to-end gap junctions (basically creating tunnels) called intercalated discs
Function of myocardium
contracts rhythmically and continuously thus providing pumping action in order for blood to circulate systemically throughout the body
What is the unique feature about intercalated discs?
These end-to-end gap junctions form discs that are electrically coupled into a single functional unit called syncytium (meaning if one feels it, they all feel it)
syncytium allows action potential (electrical impulse) to pass from cell to cell along the entire heart wall thus stimulating heart contractions
Endocardium
- translates to “within heart”
- inner layer of the heart
- made of delicate lining, endothelial tissue
- also covers the inside of the myocardium
Label all the chambers and blood vessels
Upper chambers/receiving chambers are also known as
atria
Atria are separated by
interatrial septum
Myocardial walls of each atrium are not that thick. Why is this?
Because thick walls are not required as the blood is travelling a very short distance to the ventricles
Function of atria
- acts as reservoirs for blood
- when contracted, pushes blood into ventricles (atria contract and relax at the same time)
Atria receives blood from (veins/arteries). Specify the blood vessels that supply the RA and LA.
veins
RA: receives blood from superior and inferior vena cava, and coronary sinus (deoxygenated blood)
LA: receives blood from pulmonary veins (oxygenated blood)
Lower chambers/primary pumping chambers also known as
ventricles
Myocardial walls of each ventricle compared to atria
much thicker (and LV myocardial wall is thicker than RV because LV has to pump further )
Ventricles are separated by
interventricular septum
Function of LV
acts as a pump for blood (both contract and relax at the same time)
Ventricles receive blood from
atria
LV receives oxygenated blood
RV receives deoxygenated blood
Left ventricle is considered a (high/low) pressure pump. What is its function?
high pressure pump
function: pumps blood through aorta which ultimately travels to all cells in the body
RV is considered a (high/low) pressure pump. What is its function?
low pressure pump
pushes blood through pulmonary trunk then pulmonary arteries which enter capillaries of lungs where gas exchange takes place
Identify all the valves in the heart
Arterioventricular valves (AV vales) include
tricuspid valve
bicuspid (mitral) valve
Function of AV valves
- allows blood to flow from atria to ventricles
- permits flow of blood in a forward direction and prevent backflow into atria
semilunar valves include
pulmonic valve: between RV and pulmonary trunk
aortic vale: between LV and aortic arch
Function of semilunar/SL valves
- Pulmonic valve: allows blood flow from RV to pulmonary trunk
- Aortic valve: allows blood flow from LV to aortic arch
- SL valves permit blood flow in a forward diretion, prevents backflow down the ventricles from aorta and pulmonary arteries
Label the valves
The “heart sounds” heard through the stethoscope indicate what action in the heart?
heart valves closing
Heart murmur
an abnormal heart sound made as blood flows through a heart valve working incorrectly (i.e. improper closing, stenosis, etc.)
murmurs are typically due to malfunctioning mitral valve
Coronary arteries originate from what structure. Briefly describe the structure of the coronary arteries.
the aorta
just above aortic valve where the aorta exits the heart, runs along epicardial surface. Divides into small vessels as they penetrate myocardium and endocardial surface
Function of coronary arteries and how much blood does it deliver?
sole supplies of arterial blood to the heart
delivers approximately 200-250mL of blood to myocardium each minute
Left Coronary Artery (LCA) supply what % of blood to the heart?
Right Coronary Artery (RCA) supply what % of blood to the heart?
LCA: supplies 85%
RCA: supplies 15%
How do coronary arteries fill?
When aortic valve is open, blood flows through to body (as per usual).
When aortic valve is closed (during ventricular relaxation) - bacflow of blood closes the valve and fills coronary arteries
Label the coronary arteries in the diagram below.
RCA supplies blood to:
- RA
- RV
- inferior and posterior surface of LV in ~85% of ppl
- SA in 60% of people
- AV node in 85-90% of people
LAD supplies blood to:
- anterior of LV
- part of lateral surface of LV
- most of interventricular septum
Circumflex artery supplies blood to:
- LA
- part of lateral surface of LV
- inferior and posterior surface of LV in 15% of ppl
- SA node in 40% of ppl
- AV node in 10-15% of ppl
Label the cardiac veins in the following diagram
Describe the pathway in which blood that supplies the heart returns back to circulation
coronary arteries ⇒ cardiac veins ⇒ common venous channel (coronary sinus) ⇒ right atrium
Anastomosis
connection of one or more branches that exist ebtween arterioles to provide backup (collateral) circulation (so that in the event of a blockage, blood can still get to the heart through other channels)
Function of coronary capillaries
- allow for exchange of nutrients and metabolic waste
- merge to form coronary veins which empties into coronary sinus
Provider an overview of the circulatory system -how deoxygenated blood becomes oxygenated (i.e. what structures it goes into/out of).
Deoxygenated blood
- blood enters into RA from superior and inferior VC and coronary sinus
- RA empties most of its blood into RV and then when 70% is emptied into RV, atrial kick occurs to empty the remaining 30%
- high pressure of RV pushes tricuspid valve close, and pulmonary valve opens to allow blood towards pulmonary arteries & lungs
Oxygenated blood
- back from the lungs and into the LA from pulmonary veins
- LA ⇒ LV via bicuspid/mitral valve (again 70% blood enters before a mitral kick occurs to empty remaining 30%)
- high pressure of LV pushes bicuspid valve close, and opens aortic valve to allow blood to systemically move to all cells except gas exchange tissue
Cardiac cycle
refers to mechanical events that occur to pump blood
What are the two phases of the cardiac cycle?
Systole (ventricles contract and expel blood)
Diastole (ventricles relax and fill)
1st phase of diastole - what is this phase called and what is happening?
Rapid refilling - atria dumping blood into ventricles
- atria are full of blood, therefore have high pressure
- ventricles are empty (just expelled blood) therefore low pressure
- the difference in pressure causes AV valve to open and fill the ventricles
2nd phase of diastole - what is it called and what is happening during this phase?
Diastasis - slowing blood flow
- pressure in the atria and ventricles start to equalize
- ventricles fill and atria empty, so blood flows slow
- there is where 70% of blood is in ventricles, 30% is still in atria
3rd phase of diastole - what is it called and what is happening during this phase?
Atrial Kick - Atria contracting to squeeze remainder of blood into ventricles
- atria are essentially empty but still has a little bit remaining that needs to be delivered to ventricles (30%)
- atria therefore contract, squeezing on themselves ⇒ causes the remainder of blood into the ventricles
- atrial kick provides 15-30% (use 30% for testing purposes) of ventricular filling
1st phase of systole - what is it called and what is happening during this phase?
Isovolumetric contraction - ventricles squeezing (on itself to build pressure) but not pumping
- ventricles are full but the pressure in them is not high enough to open SL valves
- ventricles squeeze down on themselves to force muscular walls inwards, thereby putting pressure on the blood inside and causing ventricular pressure to rise
- NO blood flow occurs during this phase
2nd phase of systole - what is it called and what is happening during this phase?
Ventricular Ejection - pumping vigourously
- ventricles are under high pressure causing SL valves to open
- blood flows out and into pulmonary trunk and aorta
3rd phase of systole - what is this called and what is happening during this phase?
Protodiastole - pumping less
- ventricular contraction continues but blood flow slows as the ventricualr pressure falls (as it empties)
- aortic and pulmonary arteries pressure rise (as they fill)
4th phase of systole - what is it called and what is happening during this phase?
Isovolumetric relaxation - relaxing, valves are closing to end systole
- ventricular presure is low as blood has been pumped out
- ventricles relax
- aorta and pulmonary arteries now have high pressure
- no longer foward pressure from the ventricles
- some of the blood starts to flow backwards towards the valves closing them shut
Cardiac output
the amoutn of blood pumped by the left ventricle in 1 minute
Normal cardiac output range is ________.
What factors does cardiac output depend on?
4000-8000mL
depends on gender, body, age, and size
Formula for calculating cardiac output
CO = SV x HR
Stroke Volume
Avg amount?
the amount of blood ejected from the heart with each ventricular contraction
~70mL
Stroke volume is dependent on what 3 factors?
1) Preload
2) Afterload
3) Myocardial contractility (performance of the cardiac muscle)
Heart rate
number of times the left ventricle contracts in 1 minute; normal is 60-100
Preload
volume of blood returning to the heart (the amount of stretch on ventricles at the end of diastole)
During diastole (relaxation), blood flows from the _______ into the ______.
atria; ventricle
During preload, the volume of blood entering each ventricle is known as __________. The volume of blood is approximately __________.
end diastolic; around 120-130mL
When ventricles pump during systole (contraction), they don’t exactly empty entirely. The remaining volume is approximately ______, and this remaining volume of blood left in each ventricle after systole is known as _________.
50-60mL
end systolic
Ejection fraction
% of blood volume ejected in each cardiac cycle - a representation of LV performance
normal is 55-65%
calculated by EF = SV/EDV x 100
Afterload
the resistance against the heart muscle during its pump (aka peripheral vascular resistance)
i.e. the pressure that the heart must work against to eject blood during systole/contraction
An increase in resistance causes a ________ in stroke volume. Examples of resistance include:
decrease
Ex: HTN, aortic stenosis, hypothermia
A decrease in resistance causes an __________ in stroke volume. Examples that would cause a decrease in resistance include:
increase
ex. septic shock, anaphylactic shock, use of vasodilators, etc.
remember: less resistance = more can come out (like a garden hose)
The heart’s behaviours are controlled by what nervous system?
autonomic nervous system
ANS influences chronotropy, inotropy, and dromotropy. Define these terms.
Chronotropy: influences HR
Inotropy: influences contractility (blood volume)
Dromotropy: influences conductivity
ANS inntervates what in the heart?
atria and ventricles
Atria is controlled by what parts of the autonomic nervous system?
Controlled by a large number of sympathethic and parasympathetic nerve fibers
Ventricles are controlled by what parts of the ANS?
Controlled MAINLY by sympathetic nerve fibers
True or False. Autonomic nerve fibers help maintain cardiac output according to the metabolic needs of the body
True
Sympathetic control (Fight or flight response) influences the heart how?
increase HR and contractility
Parasympathetic control influences the heart how?
primarily by decrease HR and to a lesser extent, contractility
controlled through vagus nerve
What are the three parts of an autonomic pathway?
- preganglionic neuron (stemming from CNS)
- preganglion neuron synapsing (releasing NT) with postganglioninc neuron at the autonomic ganglion
- Postganglionic neuron release NT to target tissue
In sympathetic control, where do the neurons originate from and what chemical mediates this response?
Originates from: thoracolumbar region (CNS)
Mediated by: norepinephrine (secreted by adrenal gland)
Describe the sympathetic control pathway.
Preganglionic neuron originates from thoracolumbar region and is cholinergic (so secretes ACh)
⇒
synapses at autonomic ganglion (cholinergic nicotinic receptors) where preganglion neuron releases ACh into axon terminal
⇒
postganglionic neuron is adrenergic and acts on target tissue via alpha and beta receptors by releasing norepinephrine
Acetylcholine is considered:
a) +ve chronotropic
b) -ve chronotropic
c) +ve ionotropic
d) -ve ionotropic
e) A and C
b) -ve chronotropic
decreases HR
Norepinephrine is considered:
a) +ve chronotropic
b) -ve chronotropic
c) +ve ionotropic
d) -ve ionotropic
e) A and C
e) A and C
increases both HR and contractility
Parasympathetic response is controlled by what nerve?
vagus nerve
Describe the parasympathetic control pathway.
Preganglionic neurons (cholinergic) from craniosacral region of CNS synapse with cholinergic nicotonic receptors
⇒
Preganglionic neurons release ACh at autonomic ganglion (axon terminal)
⇒
Postganglionic neurons (cholinergic) are stimluated and conduct impulse to target tissue, acting on cholinergic muscarinic receptors via ACh
Parasympathetic control is mediated by what chemical?
Acetylcholine (ACh)
The act of closing the glottis (flap over trachea) or stimulation of the vagus nerve causes release of what chemical?
Acetylcholine
Lungs
large spongy organs located in the chest cavity, slightly behind and on either side of the heart
encased in protective pleural sac
Main function of lungs
remove CO2 from blood and replace it with oxygen
Trachea
hollow tube extending ~4.5 inch down and divides into 2 slightly smaller tubes (bronchi)
Bronchi enter the lungs (one on each side) and further divides into smaller tubes known as
bronchioles
alveoli
tiny sacs of tissue arranged in grape-like clusters and surrounded by capillaries; where gas exchange occurs
Hollow tubes of smooth muscle with primary function of transportation
Blood vessels
Perfusion
movement of blood through an organ or part of the body
Identify the function of:
arteries
veins
capillaries
Arteries: carry blood away from the heart
Veins: carry blood to the heart
Capillaries: where exchange of nutrients and waste products for body cells take place (one cell thick)
Peripheral veins
veins in arms/legs (contain tiny valves to prevent backflow of blood)
largest veins in the body
superior and inferior VC (these do not have valves)
ischemia
decreased supply of oxygen to tissue
Angina
caused by increased demand of oxygen in heart muscle
Classic Sx of angina
- vague dull ache
- indigestion (heart burn) not relieved with antacids
- pressure in chest
- crushing, squeezing chest tightness (“elephant” or “tight belt” around/on chest)
- can be localized or spread ot L shoulder, either arm, jaw, upper back
Atypical Sx of angina
- fatigue
- lack of Sx/pain
- pain in jaw/upper back
Angina is more likely to occur when (i.e. what factors exacerbate it)?
- after physical exercise
- after a large meal
- stressful situations
- extreme temps
Stable vs unstable angina
Stable: usually starts with physical exertion and is relieved with rest (treatment is nitro to relieve pain)
- can become unstable angina if episodes increase in frequency or severity
Unstable: not relieved by rest, more painful than usual, can cause N/V, difficulty breathing, sweating
- can indicate increased myocardial ischemia or decreased ability to tolerate ischemia
When cardiac output is abnormal, what will the heart try to do initially?
compensate (balance it out by changing SV or HR)
Signs and symptoms of poor cardiac output
- ashen, pale, cool clammy skin
- N/V
- dizziness, weakness, faintness
- tachycardia
- diaphoresis
- mild to severe chest pain
- unresponsiveness/altered LOC
- SOB
- hypotension
- dyspnea
- confusion/disorientation
- cyanosis (skin, lips, nail beds)
- decreased urinary output
What are the 3 phases of diastole?
1) Rapid refilling
2) Diastasis
3) Atrial Kick
What are the 4 phases of systole?
1) isovolumetric contraction
2) ventricular ejection
3) protodiastole
4) isovolumetric relaxation
