Heart Lecture 2 Flashcards
Heart muscle contains numerous what for energy?
Mitochondria
Alternating bands of light and dark
striations
Heart controls itself so it is
involuntary
What hold fibres together
Intercalated discs
Tight cell junction for stability
Desmosome
Tube connecting cells, transmit substances, conduct electricity
Gap junctions
Self-excitable, beats itself
Autorhythmicity
Self-excitable fibres
Autorhythmic fibres
Network of specialized cells that cause contraction
Conducting system
Conducting system components order 1-5
- SA node
- Internodal pathways
- AV node
- AV bundle and branches
- Purkinje fibres
Cells that set pace of heart. SA node
Pacemaker cells
Pacemaker of heart, 60-100 bpm
Sinoatrial node (SA node)
Distributes signal to RA and LA
Internodal pathways
If SA node fails, can take over pacing. Slower. B/w atria and ventricles
Atrioventricular node
Transmit signal from AV node
AV bundle
Transmit signal to apex
Bundle branches
Conduction goes back up from Apex. Radiate upward
Purkinje fibres
Fires SA node if damaged or diseased
Artificial pacemaker
Purpose of cardiac muscle longer contraction
Avoid tetanic contraction (hold beat too long)
3 stages of cardiac muscle action potential
- rapid depolarization
- plateau (key)
- Repolarization
Contraction stages: sodium in, voltage-gated channels
Rapid depolarization
Contraction stages: membrane potential stays near 0 mV
Plateau
Slow calcium channels
slow to open/close more calcium entering
Contraction stages: slow calcium channels close, potassium out
Repolarization
Cardiac muscle energy type
Aerobic cellular respiration
Cardiac fuels for power
Fat, glucose
When heart uses lactic acid
During exercise
Creatine phosphate blood test used for
presence in bloodstream - heart attack
Recording of heart electrical currents
ECG
ECG reading: Atria firing off - atrial polarization
P wave
ECG: ventricular depolarization
QRS complex
ECG: Ventricular repolarization
T wave
Atria repolarizes when?
During QRS complex
ECG: Time difference b/w P and Q
P-Q interval
How much time in P-Q interval could mean damage
> 200msec
ECG: Start of QRS complex to end of T-wave
Q-T interval
Q-T interval too long could mean
Myocardial damage, ischemia
ECG: End of QRS to beginning T wave
S-T segment
S-T segment represents
End of depolarization, beginning of repolarization
Abnormal heart beat called
arrhythmia
Fast heart rate >100bpm
Tachycardia
Slow heart rate <60bpm
Bradycardia
Surprise atrial contraction
Premature atrial contraction
atria keep contracting early causing raised heart rate
Paroxymal atria tachycardia
Atria fluttering, not enough blood pump, ventricles working, mostly alright
Atrial Fibrillation
Which is worse? ventricular or atrial issues?
Ventricular
Ventricle prematurely contracts
Premature ventricular contractions
Ectopic pacemaker
Responsible for premature ventricular contractions
Cardiac arrest. Blood not pumping well, bad contractions
Ventricular fibulation
Cardiac cycle: contraction, blood leaves chamber
Systole
Cardiac cycle: Relax, chamber refills
Diastole
Sequence of contractions:
- Atrial Systole
- Ventricular systole
Atrial systole
Atria contract, push blood in ventricles
Ventricular systole
Ventricles contract, push blood into circuits (lungs or body)
typical Cardiac cycles lasts how long
800msec (0.8 sec)