CARDIOLOGY FOUNDATIONS Flashcards
Branches of the aorta
brachiocephalic
left common cartoid
left subclavian
Layers of the heart wall (inner to outer)
heart chamber
endocardium
myocardium
visceral pericardium
pericardial space
parietal pericardium
What is the fiborous skeleton
made from dense connective tissue
surrounds the valves of the heart and merges with the interventricular septum
prevents the spread of action potentials from the atria to ventricles
when is the bicuspid valve important
during systole
chordae tendineae close and open valves
Difference between the semilunar valves and bicuspid and mitral valves
No chordae tendinae
rely on pressure gradient for opening and closing
blood flow through the heart
RA deoxy
tricuspid valve
RA
pulm semi lunar valve
pulm trunk and pulm arteries
pulm caps, blood looses CO2 and gains O2
Pulm veins
LA
bicuspid
LV
aortic semilunar
aorta and systemic arteries
in systemic circulation
SVC,IVC, coronary sinus
where do the L and R side coronary arteries originate from
aortic root sinus
coronary artery supply to SA node
RCA 55% LCA 45%
CORONARY ARTERY SUPPLY AV NODE
RCA 90% LCA 10%
L VENTRICLE CORONARY SUPPLY
LAD 50%
RCA25%
CX 25%
TUNICA INTIMA MEDIA AND ADVENTITIA
intima- most internal. made from endotheliial cells, elastic, in contact with blood
media- thickest layer, smooth muscle, elastin, innervated by the sns
adventitia- external, elastic and collagen
PRESSURE IN VESSELS
- Aorta 100mmhg
- Arteries 100-40mmhg
- Arterioles 40-25mmhg
- Capillaries 25-12mmhg
- Venules 12-8mmhg
- Veins 10-5mmhg
- Vena cave 2mmhg
- R. atrium 0mmhg
Blood colloid oncotic pressure
the osmotic pressure exerted by large molecules, serves to hold water within the vascular space. It is normally created by plasma proteins, namely albumin, that do not diffuse readily across the capillary membrane
Interstitial Fluid Osmotic pressure
the (pulling) pressure that causes the reabsorption of fluids from the interstitial fluid back into the capillaries.
hydrostatic
pushing out from intravascular space
Net filtration pressure
=osmotic + hydrostatic pressure
two factors that affect resistance in perfusion
arteriolar radius
blood viscosity
preload
initial stretching of the cardiac myocytes (muscle cells) prior to contraction
factors that determine perfusion
HR
SV
Radius of vessels
blood viscosity
SV = HR X CO
CO X RESISTANCE = BP
Starling’s law (Frank–Starling law)
A law that states that the stroke volume of the heart increases in response to an increase in the volume of blood filling the heart (the end diastolic volume)
what does contractility rely on
calcium into the cytoplasm
SNS innvervation
afterload
The amount of pressure the LV has to contract against to push blood out of the aorta and into systemic circulation
where are baroreceptors found
aortic arch and cartoid sinus
how do baroreceptors work
stretch receptors
increase or decrease firing rate
send messages to cardiovascular control in medulla
sympathetic or parasympathetic activity sent to heart and blood vessels
SA NODE LOCATION
Epicardial surface
close to SVC
what is the bachmanns bundle
also called the interatrial bundle
conducts impulses from the right to left atrium
AV NODE LOCATION
lower right side of the interatrial septum
how long does av node delay impulses
0.1 sec
WHY does AV node delay
-less gap junctions (open channels that allow flow of iosn from one cell to another, less = slower conduction)
-small size of junctional conducting cells
-connective tissue interspersed among conducting cells (connective tissue is non conducting)
2 pathways from AV NODE + refractory periods
-slow pathway (w short refractory period)
-fast pathway (with long refractory period)
Bundle of HIS
Penetrates through fibrous skeletion and allows for conduction from the atria to ventricles
cardiomyocytes structure
striated
contain actin and myosin
contains lots of mitochondria
what is a desmosome
link myocytes together
what is a gap junction
intercalated discs join each cardiomyocyte together
Within the intercalated discs are gap junctions
-gap junctions are intercellular membranes which directly join the cytoplasm of two cardiomyocytes
- they permit the direct passage of ions from one myocyte to another, thereby allowing action potentials to spread quickly
- the result is the heart contracting as a unit, a type of ‘functional syncytium’
Ions outside vs inside the cell
outside - higher ca2++, Na+ and CI
inside- higher K+
Fast vs slow cardiac cells
Fast type myocardial action potentials
* Occurs in atrial and ventricular working contractile myocytes
* Stable resting membrane potential
* Upstroke of depolarisation and downstroke of repolarisation occurs faster
* Steep slopes
Slow type myocardial action potentials
* Occur in pacemaker/nodal cells (SA/AV nodes)
* Spontaneously depolarise between action potentials due to unstable resting potential = automaticity
* The upstroke of depolarisation and downstroke of repolarisation happens more slowly
* Gradual sloping
relative refractory period
around phase 3 if the signal is strong enough another action potential can be generated
excitation contraction coupling
= How electricity converts to contraction
* Calcium engages with sarcomeres to initiate contraction
* Calcium binds to troponin
* Actin and myosin binding = contraction
Parasympathetic and sympathetic effects on the AV node
HR is dependant on phase 4, if the slope is steeper our HR increases, if it is gradual our HR decreases
Which leads are bipolar and unipolar
- 3 standard limb leads (lead 1, lead 2 and lead 3) which are bipolar
- 3 augmented limb leads (aVR, aVL, aVF) which are unipolar
- 6 chest leads (precordial leads) which record electrical activity in the horizontal plane, these are unipolar