GUMES CV Flashcards
what are the layers of the pericardium
fibrous
parietal
parietal cavity
visceral
what attaches the free edges of the valves to the papillary muscle
chordae tendinae
what are the korotkoff sounds
sounds of blood flow, one is systole and the second is diastolic
what is the interventricular septum
the wall of tissue that separates the right and elft ventricles of the heart
what is atrial septal defect
the absence of a septum between the atria leading to mixing of oxygenated and deoxygenated blood
what is ventricular septal defect
defect in the ventricular septum leading to blood flow between the ventricles under pressure
what is atrioventricular septal defect
birth defect whcih leads to holes between the chambers of the heart
can also mean the valves that control the blood flow between these chambers may not be formed correctly
describe artery structure
thick outer wall
small lumen
thick layer of muscle and elastic fibres
describe capillary structure
very small lumen and wall made of a single layer of cells
describe vein structure
thin layer of muscle and elastic fibres, large lumen and fairly thin outer wall
what is found in arteriole walls
muscle
elastic fibre
fibrous tissue
how does the lumen of arteries vary
increases as a pulse of blood passes through
why are the walls of arteries strong and elastic
to withstand the pulsing of the blood and prevent bursting.
maintain high blood pressure and prevent blood flowing backward
what is the function of capillaries
supply all the cells with their requirements and take away waste products
describe the wall of capillaries
one cell thick
how wide is the lumen of a capillary
enough for a singel red blood cell to pass through
why do capillaries not need strong walls
most of the blood pressure has been lost
what can pass through the cells of capillary walls
white blood cells
why do capillaries have narrow lumens and thin walls
to bring blood into close contact with body tissue and allow diffusion of materials between the two
describe the pressure of blood as it returns to the heart
low
describe the walls of veins
thin
mainly fibrous
less muscle and elastic tissue than arteries
why is there a wide lumen on veins
offers less resistance to blood flow
where is the AV node
centre almost
what are the AV bundles
stretch down from the AV node to provide action potential to the myocardium
describe the conduction system of the heart
- SA node generates an impulse
- atrial excitation begins
- impulse is delayed at the AV node
- impulse passes to the heart apex
- ventricular excitation begins
- ventricular excitation completes
what is the order of propagation of the action potential
- SA node
- interatrial bundles
- internodal bundles
- av node
- av bundle
- right and left bundle branches
- purkinje fibres
what is the P wave
the activation of the atria
what is the PR interval
the time interval between the onset of atrial depolarisation and onset of ventricular depolarisation
what is the QRS complex
depolarisation of ventricles, consisting of the QR and S waves
what is the QT interval
the time interval between onset of ventricular depolarisation and end of ventricular repolarisation
what is the RR interval
time interval between the two QRS complexes
what is the T wave
ventricular depolarisation
what are the three phases of sinoatrial node action potential
4, 0 and 3
what is the first phase of the sinoatrial node action potential generation
phase 4
calcium enters and there is less potassium leaving the cell.
what occurs in phase 0 of sino atrial node conduction
calcium channels open
what occurs at stage 3 of the sino atrial node conduction
potassium leaves thereby making the charge more negative inside causing repolarisation
what is the pacemaker potential
when there is slow depolarisaiton of the SA node
when does the action potential occur for the SA node
phase 3
where on an ECG can the plateau of action potential be seen
ST segment
why is action potential referred to as fast response action potential
rapid depolarisation
what are the phases of the purkinje action potentials
0,1,2,3 and 4
what happens in phase 0 of purkinje action potential
- sodium and calcium channels open and there is fast influx of postivie ions
- potassium channels close to the intracellular charge stays positive
what happens in phase 1 of purkinje fibre action potential
there is initial repolarisation as there is now opening of potassium channels
what happens in phase 2 of purkinje fibre action potential
there is a plateau as the charge evens out since the calcium continues to enter the cell.
when does phase three of purkinje fibre action potential begin
once the calcium channels close and there is only potassium moving out of the cell to reduce the intracellular charge
what is phase three of purkinje fibre action potential
calcium channels are inactivated, potassium ions continue to move out
what occurs at phase four of purkinje action potential
true resting potential
what is the blood pressure measurement
systolic over diastolic
what is the average blood pressure
120/80 mmhg
what do arterioles do
dissipate the blood pressure
do arteries have valves
no
do veins have valves
yes
why do veins have valves
to direct blood flow against gravity
what is cardiac output
the volume of blood pumped by the heart per minute. a function of heart rate and stroke volume
what is the stroke volume
the volume of blood pumped out of the heart with each beat
what increases cardiac output
increased heart rate or stroke volume
what is the preload
the amount of blood entering the heart
what does preload affect
strength of contraction and stroke volume
what inervates the sinoatrial node
sympathetic and parasympathetic nerve fibres
what slows the pacemaker potential of the sinoatrial ndoe
acetylcholine
effect of acetylcholine on the heart rate
decrease
what increases the pacemaker potential of the sinoatrial node
noradrenaline
effect of noradrenaline on heart rate
increase
how does adrenaline release increase heart rate
enters the bloodstream and is delivered to the heart where it binds with sa node receptors to increase the heart rate
what innervates the ventricular myocardium
sympathetic nerve fibres
how does an increase in sympathetic activity lead to increased stroke volume
release of noradrenaline from the nerve fibres causes an increase in the strength of myocardial contraction
how does noradrenaline increase stroke volume
increases the intracellular concentration of calcium in myocardial cells, facilitating faster actin myosin cross bridging.
what is the mean arterial blood pressure
the average blood pressure pushing blood around the body
what is the pulse pressure
the difference between the systolic and diastolic blood pressures
which reflexes control blood pressure
baroreceptors and chemoreceptors
where are baroreceptors found
in the carotid sinus or in the aortic arch
what are baroreceptors sensitive to
change in stretch in arteries caused by increased pressure
what are chemoreceptors sensitive to
changes in blood oxygen, carbon dioxide and pH
where are chemoreceptors found
carotid bodies and aortic bodies
what decreases parasympathetic stimulation of the heart to increase heart raet
decreased blood oxygen and increases carbon dioxide
what increases sympathetic stimulation of the heart
decreases blood oxygen and pH and increased carbon dioxide
what is starlings law
if the heart chambers are intially distended with blood, the ensuing beat is more forceful than if the chambers were intially empty
why does force of contraction increase as the heart muscle stretches
filling of the chambers
what controls blood pressure
endothelial cells
elasticity effects
drugs
hydrostatis and oncotic pressure
active and reactive hyperaemia
what is blood flow affected by
- diameter of the tuble
- pressure gradient across the tube
- length of the tube
- viscosity of the fluid
why is deep vein thrombosis in the legs common
the veins have a low pressure gradient so flow is going to be slower
what causes angina
lack in oxygen to the heart leading to anaerobic respiration causing lactic acid production and pain
what can be used to treat angina
nitrates which are vasodilators and will increase oxygen delivery to the heart and relieve the pain of angina
which heart receptors does acetylcholine bind to
M2
where are beta one receptors found
heart
where are beta two receptors found
lungs
what is the composition of blood
55% plasma and 45% cells
what are the cells found in blood
red blood cells
white blood cells
platelets
what is the significance of the biconcave shape of red blood cells
- larger surface area for rapid gaseous exchange
- allows transport in the narrow capillaries as they have a bending movement
- allows expansion to accomodate fluid in hypotonic solutions
what happens to red blood cells in hypotonic solutions
they expand
what happens to red blood cells in isotonic solutions
they are normal
what happens to red blood cells in hypertonic solutions
shrink
what is the process of red blood cell turnover
they are formed in the bone marrow and go through the circulation, where 10% of hemolysis occurs, and then destroyed if they are 120 days old or damaged
where are red blood cells destroyed
by macrophages in the spleen liver and bone marrow
what happens after red blood cell breakdown
the iron from the heme is transported in circulation by transferrin along with amino acids and they are returned to bone marrow for new red blood cell formation
what happens to the biliverdin release from heme following red blood cell breakdown
converted to bilirubin and transported to the liver for bile excretion
what is erythropoietin
a hormone produced by kidney cells to stimulate red blood cell production
what does a decrease in red blood cells lead to
reduced oxygen delivery to cells including in the kidney, which triggers erythropoietin release to stimulate the stem cells in bone marrow to increase production of red blood cells
why does haemolysis occur if we transfuse incompatible blood types
antigens are attachments on red blood cells and the specific blood types have specific antigens to pair with the specific antibodies.
when incompatible blood types are transfused, the host antibodies identify the transfused antigens as foreign antigens, bind to them and cause haemolysis, ultimately rejecting the blood transfusion
what are the antigens found on blood type A
A
what are the antibodies for blood type A
anti B
explain the significance of rhesus factor in pregnancy
if a rh negative mother conceives an rh positive foetus, the mother develops anti rh antibodies and due to maternal circulation, the anti rh antibodies may attach the red blood cells of the rh foetus, causing haemolysis
what are risk factors for endocarditis
rheumatic valves
prosthetic valves
dental abscess
what are the micoorganisms involved in endocarditis
streptococcus viridans and staphylococcus aureus
what is the function of a valve in the heart
prevent the backflow of blood
why is the sinoatrial node considered the pacemaker of the heart
it generates an electrical stimulus causing contraction of the atria, initiating the cardiac cycle
what is systole
contraction of both ventricles
what is diastole
relaxation of both ventricles
what is auscultation
listening to the sounds of the heart
what is phase four of the sinoatrial node action potential
inward movement of sodium via leaky sodium channels, slow depolarisation
what is phase zero of sinoatrial node action potential
membrane potential threshold reached, action potential triggered leading to depolarisation, calcium channels open, calcium enters the cell
what is phase three of the sinoatrial node action potential
repolarisation, calcium channels close, potassium leaves the cell
what are the stages of ventricle action potential
4, 0, 1, 2, 3
stage four of ventricle action potential
resting membrane potential, sodium and calcium channels are closed but potassium are open to maintain the resting potential
stage 0 of ventricle action potential
action poential, rapid influx of sodium
stage 1 of ventricle actiokn potential
potassium channels open and potassium leaves, membrane potential is 0
stage 2 of ventricle action potential
plateau, calcium channels open, influx of calcium, potassium leaves, balance between the two
stage 3 of ventricle action potential
repolarisation, calcium channels close, potassium stays open
what is excitation contraction coupling
couple of the electric excitation brought by the action potential to the mechanical contraction of the cardiac myocytes and subsequently the myocardium
what is starlings law
the more the heart stretches, the stronger the force of contraction
what affects how much the heart stretches prior to contraction
duration of diastole, as the longer it is the more the ventricles will fill.
venous return, as the more blood there is being returned, the more it will fill
which branch of the nervous system modulates cardiac output
autonomic
what is inotropy
contractility
what is chronotropy
rate, frequency
what is lusitropy
rate of myocardial relaxation
what is dromotropy
conductivity of cardiac muscle
what does blood pressure mean
the force exerted by blood against any unit area of the vessel wall
what is systemic vascular resistance
the peripheral resistance
what is peripheral resistance
the resistance that must be overcome to push blood through the circulatory system
how do you calculate the mean arterial pressure
diatolic blood pressure plus one third of pulse pressure
what is cardiac output times by the peripheral resistance
mean arterial pressure
how can blood pressure be modified
acting on the alpha adrenoreceptors on the blood vessels
what does alpha one adrenoreceptor lead to
vasoconstriction
what is the hydrostatic pressure
the pressure exerted on the capillary wall by blood
how does fluid enter the interstitial space
through pores on the capillary walls
why does pressure exerted by blood decrease as blood moves along the capillary
because fluid is leaving via the pores
where are the baroreceptor impulses carried
to the medulla
why do baroreceptors not respond to hypertension
they are reset to the higher blood pressure level
