the heart - mech events of the cardiac cycle Flashcards
how is cardiac muscle connected
through intercalated disks with Gap junctions
how is the AP of skeletal muscle different from cardiac
skeletal have a shorter AP
Skeletal can do tetanus
what happens during the plateau phase of cardiac muscle AP
trigger Ca enters the cells
what is the roll of the HEart
The pump that moves the blood
how is cardiac activity expressed
Cardiac output (amount of blood moved per unit time)
what is the average cardiac output
5 liters a minute
what caues the first heart sound
Closure of the AV valves
what causes the second heart sound
closure of the Aortic and pulmonary valves
what is stenosis
Narrowing
what is regurgitation
insufficiency (leaky)
what causes murmurs
stenosis
regurgitation
septal defects
when do you hear stensosi
When valves are open
when do you hear regurgitation
When valves are closed
how are the system and pulmonary circulations plumbed
in series
how are organs in systemic circulation plumbed
Parallel
what is systole
Ventricle contraction
what is diastole
Ventricles relaxed
what causes the valves of the heart to open
Pressure differences on both sides of the heart
how much filling is passive is ventricle
80%
what does the final portion of filling of the ventricles
Artrial kick
what happens in isovolumetric contraction
both valves closed (aortic pressure is higher than the ventricle)
raising of ventricular contraction
how do you know something is isovolumic contraction
both valves closed
volume is non-changing
when does QRS happen relative to ventricular contraction
QRS preceeds ventricular contraction
what is the eq for cardiac output
Heart ratexStroke volume
what pumps more blood, the Right or Left heart
pump both the same amount
what pumps higher pressure, Right or left heart
Left heart is higher pressure
what does parasympa and sympa affect in the heart
Parasympa closes funny channels
Sympa opens funny channels
how can hormones affect the heart
release of Epinephrine leads to an increase in HR
how can one speed up heart rate
deliver more sympa hormone (epinephrine) more sympa neurotransmitter (norepinephrine)
decrease release of parasympa neuro (acetylcholine)
can parasympa change stroke volume
No
what are the three factors influencing stroke volume
Preload
Sympa input to the ventricles
Afterload
what is preload
The volume of blood in the ventricles just before contraction
- end diastolic volume
what is afterload
the pressure against which the ventricle epumps
why does preload increase stroke volume
increased stretch of ventricle aligns actin and myosin to a more optimal pattern of overlap
how to further increase stroke volume beyond preload
preload+ sympa signals
how does sympa signals lead to higher stroke volume
causes ventricles to relax more rapidly
- more time to refill
causes ventricles to contract more rapidly
what does sympa do inside the mycardial cell to increase stroke volume
Regulates/increases Ca
what is the frank-starling mechanism
increased preload leads to increased stroke volume
does preload change the amount of inracellular ca
no`
can you increase stroke volume and increase heart rate separately
No, not under normal circumstances
how can one measure cardiac function
Thermodilution cardiac output Angiography Echocardiogram MRI ejection fraction
what is ejection fraction
Measure of contractility
what is the formula for ejection fraction
(End diastolic volume-end systolic volume)/ End diastolic volume
what is hypertrophic cardiomyopathy
increased heart wall thickness
myocardial disarray
- specifically interfer with blood ejection
what are the symptoms of hypertrophic cardiomyopathy
Angina
Arrhythmias
Sudden cardiac death
