Cardio 1 Flashcards
What are the 4 chambers?
- Right atrium
- Left atrium
- Right ventricle
- Left ventricle
What are the atria & ventricles separated by?
‘atrioventricular valves (AV)’
1. Left AV valve = mitral (bicuspid) valve
-between LA & LV
2. Right AV valve = tricuspid valve
[inlet valves = let blood go in ventricles]
What are semilunar valves?
between ventricles & arteries
1. Aortic valve
-between LV & aorta
2. Pulmonary valve
-between RV & pulmonary artery
[outlet valves = let blood out of ventricles]
What is atria & its functions?
-thin wall
-low pressure
1. Elastic reservoir & conduit from venous bed to ventricle
2. Booster pump enhancing ventricular filling
3. Assist AV valve closure before ventricular systole
Describe the ventricle.
-most of hearts weight
-main pumping force to whole body
1. RV
-propels blood through pulmonary circulation = pulmonary artery
2. LV
-propels blood through systemic circulation = aorta
[LV & RV separated by ventricular septum/wall]
Describe the pathway of blood flow to the right side of the heart.
- Deoxy (blue) blood from body returns to heart through cranial & caudal vena cava (1)
- Blood from vena cava flows in RA (2) & then into RV (3)
- From RV to the pulmonary arteries (4 & 5) to the lungs to be oxygenated
vena cava -> RA -> RV -> pulmonary artery -> lungs
Describe the pathway of blood flow through the left side of the heart.
- Oxy (red) blood goes back to the heart via the pulmonary veins
- Blood from pulmonary veins flows in LA (7) & then into the LV (8)
- From the LV, blood goes through aorta (9 & 10) to the rest of the body to be used by organs/tissues
pulmonary veins -> LA -> LV -> aorta -> body
Describe the whole pathway of blood through the heart.
Vena cava -> RA -> RV -> pulmonary artery -> lungs -> pulmonary vein -> LA -> LV -> aorta -> body
What happens electrically when the SA node is not working properly?
Normal HR: 70-120
*Abnormal HR: 28-229
*episodes of weakness/collapses
*heart stoppages of 6.85s long
Describe the cardiac fibers capacity for self-excitation.
-automatic rhythmic discharge
>contraction of myocardial cells
-all fibers of heart conduction system can act as pacemakers
1. SA node = 70-80
2. AV node = 40-60
3. Purkinje fibers = 15-40
Describe the conduction system of the heart.
- SA node generates impulses
- Impulse pauses at AV node
- AV bundle connects atria to ventricles
- Bundle branches to conduct impulses through interventricular septum
- Purkinje fibers depol the contractile cells of both ventricles
Describe the AP shape at various locations.
-SA & AV node = slow AP
-atrial & ventricular muscle = fast AP
Why is the sinus node considered the normal pacemaker of the heart?
-specialized cardiac muscle
-in RA
-fibers have no contractile muscle filaments
-connect w atrial muscle fibers = AP can spread into atrial muscle wall
Describe the AP of the sinus node.
-ends of sinus nodal fibers connect directly with atrial muscle fibers
-AP spread through atrial muscle mass & then to AV node
-velocity conduction = 0.3m/sec
Describe the AV node.
-delays impulse conduction from atria to ventricles
-allows time for atria to empty blood into ventricles before ventricular contraction begins
-delay at beginning of AV bundle also
>due to specific fibers having less gap junctions
>increased resistance to conduction of excitatory ions
Describe purkinje fibers.
-lead AV node impulses through AV bundle (bundle of His) into ventricles
-transmission velocity in ventricular purkinje system is fast = 1.5-4.0 m/sec
-instant transmission of cardiac impulse through remainder of ventricular muscle
Describe the bundle of His.
-AV bundle
-only forward conduction from atria to ventricles
-atrial muscle separated from ventricular muscle by fibrous skeleton
-act as insulators to prevent passage of cardiac impulse between atrial & ventricular muscle through abnormal routes
Describe the AV bundle branches.
-AV bundle passes down in ventricular septum & divides into L & R bundles branches
>branches lie beneath endocardium
-branches spread toward apex of ventricle
-branches course sidewise around each ventricular chamber & back toward base of heart
-ends of purkinje fibers penetrate muscle mass = continuous with cardiac fibers
time from entering cardiac impulse into bundle branch until reaches end = 0.03s
What happens once the impulse reaches the end of Purkinje fibers?
-transmitted through ventricles by muscle fibers
-cardiac muscle wraps around heart in double spiral (fibrous septa between layers)
-cardiac impulse angulates toward surface along direction of spirals
transmission velocity in ventricles = 1.5-4 m/s
Describe the conduction velocity during cardiac electrical conduction.
- SA node depol
- Electrical activity goes to AV node via intermodal pathways
- Depol spreads across atria (conduction slows through AV node)
- Depol moves through ventricular conducting system to apex of heart
- Depol goes up from apex
