CVS Basics Flashcards
Functions of the CVS (5)
O2 and CO2 Transport Nutrients Metabolites Hormones Heat
Heart pumps are in series because
output must be equal
Most vascular beds are in parallel because
All tissues get oxygenated blood
Regional redirection of blood
Flow = change in ?
pressure / resistance
Flow is controlled by
radius of arterioles (selectively redirects flow)
Arterioles act as
taps controlling the resistance (therefore flow) to each vascular bed
The aorta is an
elastic artery
The aorta has
wide lumen
elastic wall
damp pressure variations
Arteries are
muscular
Arteries have
wide lumen
strong non-elastic wall
low resistance conduit
Arterioles act as
resistance vessels, so control resistance and flow
Arterioles have
narrow lumen
thick contractile wall
(allow regional redirection of blood)
Capillaries act as
exchange vessels
Capillaries have
narrow lumen
thin wall
Venules and veins act as
capacitance vessels
so allow fractional distribution of blood between veins and rest of circulation
Venules/veins have
wide lumen
distensible wall
The left heart contains what valves?
mitral valve
aortic valve
The right heart contain what valves?
tricuspid valve
pulmonary valve
Describe the function of the heart, arteries, veins and capillaries (respectively)
Heart = a pump Arteries = distribute blood from heart Capillaries = exchange nutrients Veins = collect and return blood to heart
Function of the lymphatics is to
drain excess extracellular fluid from tissues
The heart lies in the
mediastinum
The mediastinum is
an area of the thoracic cavity between pleural sacs
In relation to the sternum, the heart lies
1/3rd to the right, 2/3rd to the left
The apex beat can be found at
the 5th intercostal space, midclavicular line
Anterior relations of the heart are
sternum and costal cartilages 4 - 7
anterior edges of lungs and pleurae
thymic remnants
When does the thymus disappear?
After adolescence
Posterior relations of the heart are
Oesophagus
Descending aorta
Thoracic vertebrae 5 - 8
Lateral relations of the heart are
the lungs
the phrenic nerve(s)
Inferior relations of the heart are
central tendon of diaphragm
Situs Inversus is when
everything is the opposite way round to normal
The three layers of the heart wall are
Endocardium (innermost)
Myocardium (middle)
Epicardium (outermost)
The endocardium is made up of (in order)
epithelium
basement membrane
connective tissues
The myocardium is made up of
muscle
The epicardium is made up of (in order)
connective tissue
basement membrane
epithelium
Functions of endocardium
lines heart chambers
forms valves
The endocardium
is simple squamous
sits on connective tissue
The myocardium
closes down chamber lumens
has rich capillary bed
has lots of mitochondria
The myocardium contains
cardiac muscle (myocytes) which are connected by intercalated discs
Intercalated discs are
complex junctions that connect myocytes
Desmosomes…
connect at horizontal interface
bind myocytes together
Gap Junctions…
connect vertically
are for electrical communication
essential to co-ord cardiac cycle
Epicardium is the
outer layer of the heart wall
The epicardium epithelium is the same layer as
the visceral layer of serous pericardium
The epicardium contains
main branches of coronary arteries
may be fatty
Name the four heart chambers
right atrium
right ventricle
left atrium
left ventricle
Functions of heart valves
control direction of blood flow
work passively
create heart sounds
Chordae terminae and papillary muscles prevent
valve failure
Valve abnormalities include narrowing (______) and widening (______)
Also, infection called _______
stenosis
incompetence
bacterial endocarditis
aortic and pulmonary valves are _____ valves with ___ cusps
semilunar
3
The mitral valve is also known as the
bicuspid valve (2 cusps)
The tricuspid and bicuspid valves are also known as
atrio-ventricular valves
Aortic stenosis =
Causes =
failure of aortic valve to close
back flow of blood into left ventricle
Electrical insulation in the heart
atria from ventricles
myocardium from great vessels
purlinje fibres
Describe the coronary arteries during systole
openings in aortic sinuses shielded by aortic valve cusps
Describe the coronary arteries during diastole
elastic recoil of aorta closes aortic valve, blood enter coronary arteries
At diastole, when myocardium relaxes
blood can flow into capillaries
The heart hangs by the ________ within the __________________
great vessels
fibrous pericardium
Attachments of the heart include
central tendon of diaphragm
sternum
roots of great vessels
The serous pericardium contains
epithelium pericardial fluid (lubricant)
The visceral layer is bound to
the heart
The parietal layer is bound to
the fibrous pericardium
Visceral and parietal layers are continuous so give
a closed bag for the heart
freedom to move during cardiac cycle
In the non-pacemaker potential, the RMP has
high resting K+
In the non-pacemaker potential, the initial depolarisation causes an
increase in Na+
The plateau in the non-pacemaker potential is caused by
an increase in Ca2+
a decrease in K+
The depolarisation in the non-pacemaker potential is caused by
decrease in Ca2+
increase in K+
In the pace-maker potential, an increase in Ca2+ causes
an action potential
Three changes to cause pacemaker potential =
gradual decrease in K+
early increase in Na+
late increase in Ca2+
Two drugs that effect contraction force of the heart are
Ca2+ channel blockers
Cardiac glycosides
Ca2+ channel blockers
decrease force of contraction
Cardiac glycosides
increase force of contraction
Temperature increases
about 10 beats/min/degreeC
Hyperkalemia (high plasma K+) causes
fibrillation
heart block
Hypokalemia (low plasma K+) causes
fibrillation heart block (anomalous)
Hypercalemia (high plasma Ca2+) causes
increased HR
increase force of contraction
Hypocalemia (low plasma Ca2+) causes
decreased HR
decreased force of contraction
The senatorial node acts as the
pacemaker
The atrioventricular node acts as the
delay box
Purkinje fibres do what, and are where?
Rapid conduction to ventricles
Spread from node to rest of heart (ventricles, IV septum etc)
The action potential in a single myocyte evokes what?
A very small extracellular electrical potential
The P wave corresponds to
atrial depolarisation
The QRS complex corresponds to
ventricular depolarisation
(
The T wave corresponds to
ventricular repolarisation
The U wave (sometimes heard) is the
depolarisation of Purkinje fibres (and other specialised cells)
The PR interval is what, and takes how long?
time taken from atrial depol to ventricular depol
0.12 - 0.2 seconds (3 to 5 small boxes on ECG strip)
The QT interval is the
time spent in ventricular depolarisation and depolarisation
maximum 0.42 seconds
The settings on an ECG should be
paper speed: 25mm/sec
calibration: 1mV = 1 cm
The following ECG leads show be placed where: Red Yellow Green Black
right wrist
left wrist
left ankle
right ankle
The C1 lead goes
4th ic space, right sternal edge
The C2 leads goes
4th ic space, left sternal edge
The C4 lead goes
5th left ic space, midclavicular line (apex)
The C3 lead goes
midway between C2 and C4
C5 goes
in line with C4
anterior midaxillary line
C6 goes
in line with C4
midaxillary line
What is essential for a good ECG recording?
Patient comfortable, skin exposed Not shivering (no movements) Dry skin (no sweat)
Compare the action potentials or cardiac muscle, to skeletal muscle
Cardiac had longer action potential than skeletal
The RMP of cardiac muscle =
leak of K+
The initial depolarisation =
increased Na+ permeability
The plateau is due to
Increased Ca2+
Decreased K+ permeability
The depolarisation =
decreased Ca2+
increase K+ permeability
Standard limb leads look at
events in vertical/frontal plane
Precordial (chest) leads look at
events in the horizontal/transverse plane
30 large squares on a rhythm strip =
6 seconds
1 large (5mm) square =
0.2 seconds
STEMI stands for
ST Elevated Myocardial Infarction
NSTEMI stands for
Non ST Elevated Myocardial Infarction
Which is worse, a STEMI or a NSTEMI?
a STEMI
What is happening to the atria during a P wave?
depolarisation
contraction
increased pressure
atrial systole
The P wave goes on to cause
an increase in ventricular volume
During the QRS complex, what is happening?
ventricular depolarisation
ventricles contract
ventricular systole begins
What opens the semi-lunar valve (opens aortic valve)?
Enough pressure in ventricles pushing valve open
When the valves open:
ventricular volume ________ and blood leaves when they _________
decreases
contract
During the T wave
repol. of ventricles
ventricles relax
drop in pressure
What causes the 1st heart sound, the ‘lub’?
Closing of atrioventricular valves (mitral, tricuspid)
What causes the 2nd heart sound, the ‘dub’?
Semi-lunar valves close (aortia, pulmonary)
What does the SA node do and where is it found?
Pace-maker, automatically makes impulses
Right atrium
SA node stands for
sinoatrial node
AV node stands for
atrioventricular node
The Av node in between
the atria and the ventricles
makes automatic impulses
The Purkinje fibres
extend from nodes
spread signals to rest of ventricle
Afterload =
load against which muscle tries to contract
What effect does the parasympathetic system have on SV?
Little effect on contraction strength or SV
Starlings Law states that
energy of contraction is proportional to initial length of the cardiac muscle fibre
Sympathetic nerves release ___________ that act on ___________, which ___________ contractility
nor(adrenaline)
B1-receptors on myocytes
increase
CO (cardiac output) =
HR x SV
Heart rate
Symp supply =
Parasymp supple =
increases HR
decreases HR
Preload increases
SV
Afterload decreases
SV
SV increased by
preload
symp supply
Measure arterial pressure by
auscultation of Korotkoff sounds using stethoscope and sphygmomanometer
Pressure in veins is _______ so change in P driving blood back to heart is _______
low
low
Does gravity effect driving pressure from arteries to veins?
No
Height of jugular collapse = 0 - 5 = ?
confusion
Height of jugular collapse = 20 = ?
anger
venomotor tone =
state of contraction of smooth muscle
central venous pressure can be estimated by
jugular collapse
venous pressure and return are influenced by
gravity
skeletal muscle & resp pump
venomotor tone
systemic filling P
Darcy’s Law states that flow is
equal to change in pressure / resistance
