Heart Chambers
Left Atria: oxygen- rich blood from pulmonary veins -> left AV valve
Right Atria: oxygen poor blood from vena cavae -> right AV valves
Left Ventricle: oxygen rich blood, from right at--> semilunar valves
Right Ventricle: oxygen poor blood from rigth atrium-> pulmonary artery
Nodes
SA Node |
AV node |
Bundle of His |
SA node
initiates potential and leads
audtorhythmicity: 70 action potentials per minute
AV node
base of right atrium
audtorhythmicity: 50 A.P. / minute
follows SA node under normal conditions
Bundle of His
origin: AV node
projects to left and right ventricles
Purkinje Fibers
terminal fibers
extend from Bundle of His
follows faster SA node under normal conditions
Cardiac Cycle
Systole |
contraction |
Diastole |
relaxation |
End- diastolic volume |
volume of blood at end of diastole, max amount that chamber will hold |
Isovolumetric ventricular contraction |
during contraction, valves closed, no blood leaves, increase in chamber pressure |
Stroke volume |
amount of blood pumped out of chamber |
Isovolumetric ventricular relaxation |
chamber pressure decreases |
ACh: Parasympathetic release
SA Node |
Ach: inc. permeability to K+ by delaying inactivation of K+ channels -> more hyperpolarization |
AV Node |
inc permeability to K+, reduces excitability of node, delays response of input from SA node |
Atrial contractile cells |
shortens of action potentials: reducing Ca2+ permeability during plateau |
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Components
Heart |
Blood Vessels |
Blood |
Valves : one way
Right AV Valve |
Left AV valve |
Aortic/ Pulmonary valve |
tricuspid |
bicuspic |
semilunar |
Pathways
Interatrial |
cardiac cells pacemaker activity from right to left atrium |
Internodal |
cardiac cell pacemaker activity from SA to AV node |
AV nodal delay |
Slow through AV node due to thickness |
Action potential in Contractile cells
Resting potenial |
-90mV until excited |
Rising phase |
rapid, Na+ entry due to opening of fast Na+ channels, close K+ channels |
Repolarization |
at peak, open transient K+ efflux, inactivate Na+ channels |
Plateu |
Slow Ca2+ entry, open of L-type Ca2+ channels, reduce |
Falling phase |
K+ efflux, open voltage-gated K+ channels |
Resting Potential |
maintained by opening leaky K+ channels |
Heart Sounds
Murmer: |
turbulent flow of blood through malfunctioning valves |
Stenotic valve: |
whistling, stiff narrow valve |
Insufficient valve: |
swishing, structurally damaged valve |
Rheumatic fever: |
valvular stenosis, autoimmune disease |
Cardiac muscle type
Straited: |
striped lines |
Involuntary |
moves by itself |
Sarcomere
Z line |
sarcomere boundary |
A band |
thick filament with thin filament overlapp |
H zone |
where thin filaments don't reach |
M line |
middle, vertically down A band |
I band |
remaining thin filament that are not in A band |
Muscle
Myofibril: |
thin( actin) thick ( myosin), sarcomeres connected together |
Sarcomere: |
smallest unit of muscle cell, |
Myosin: |
cytoskeletal protein |
Thin filament |
actin, tropomyosin, troponin |
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Types of Muscle
Endocardium - thin/ interior of each chamber
Myocardium - middle layer, thickest, intercalated disks for connection
Epicardium - thin external membrane with pericardial fluid
Pacemaker Activity
Open funny channels:
NA+ inward and closes K+ outward
Reaches threshold of -40:
Open L-type Ca2+ and K+ channels
Action potential in Contractile cells
Electrical Activity
Autorhythmicity- capability to produce own rhythmic electrical activity due to Pacemaker activity
Only 1% of Cardiac cells
Excitation Contraction Coupling
Ca2+ entry into cystol |
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T-tubule |
contain: dyhyropyridine receptors-> open Ca2+ into cytosol |
#crossbridges proportional to cytosolic Ca2+ concentration |
Electrocardiogram
P wave |
depolarization of atria |
QRS complex |
depolarization of ventricles |
T- wave |
Repolarization of ventricles |
Cardiac Output
Cardiac Output: |
heart rate x stroke volume |
Heart rate: |
beats per minute, regulated by both parasympathetic and sympathetic nervous system |
Excitation Contraction Coupling
ACh |
- released by motor neuron axon binds to motor end plate |
- results in action potential that propagates to surface membrane and down t-tubule |
- triggers Ca2+ release from SR |
-Ca2+ released from lateral sacs |
- bind to troponin, tropomyosin moves aside to open actin binding site |
- myosin crossbridge attach to actin-> bend -> pull actin towards center of sarcomere |
- Ca2+ taken up by SR |
- tropomyosin goes back to blocking position. |
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