Cardiology Flashcards
How are cardiomyocytes connected?
The cardiac syncytium is a network of cardiomyocytes connected by** intercalated discs** that enable the rapid transmission of** electrical impulses** through the network, enabling the syncytium to act in a coordinated contraction of the myocardium.
Striated, lots of mitochondria, involuntary
Syncytium:a single cell or cytoplasmic mass containing several nuclei, formed by fusion of cells or by division of nuclei. (Cardiomyocytes however do not have multiple nuclei).
What are “specialized” cardiomyocytes?
Pacemaker cells, Purkinje Fibers: generate/conduct electrical impulses.
What is different in cardiac muscle cells than regular skeletal muscel cells?
Adapted to the slower and more sustained single contraction! Also large t-tubules form a DYAD with SR. LOTS of Ca2+.
This can be see in the PLATEAU in the AP graph of cardaic muscle cells.
2 types of junctions at intercalated discs?
1-Mechanical (Fascia adherens anchors actin) & desmosomes (bind intermediate filaments of adjoining cells)
2-gap junctions (ion flow bt cells, propagate APs to neighboring cells.
Gap junctions: …
connexins
(connect cardiomyocytes)
Desmosomes:
Cadherins
(adhere actin to plasma membrane)
What is inclued in cardiac muscle cells? for graphing ap purposes
Atrial, Ventricular, AND perkinje fibers (perkinje fibers are not pacemakers!)
Describe Phase 0,1,2,3,4 and what channels/gates open.
-90 to +20
Refractory periods in skeletal vs cardiac muscle? Average time for cardiac?
Cardiac muscle cell in ventricle: 0.25-0.30
Cardiac muscle cell in **atrium: 0.15 **(much shorter than ventricle).
As shown by the graph, the refractory period is much longer in cardiac cells because they hold the contraction longer.
Relative refractory in heart?
0.05, can happen but only with strong stimulus. It can be see in the early “premature” contraction.
“Extra heartbeats”/skip a beat.
Mechanisms invovling excitation-contraction coupling and relaxation in cardiac muscle?
“Calcium-Induced Calcium Release (CICR)”, AP–>Ca2+–>T-tubule–>DHPR channel–>RyR–>Ca2+ release from the SR–> contraction.
Ca2+ reuptake during cardiac muscle relaxation?
**SERCA 2A: **Sarcoplasmic Endoplasm Reticulum Ca2+ ATPase with PLB phopholamban attached take up Ca into the SR. OR it goes out and across the sarcolemmal membrane via a Na+/Ca2+ exchange pump. This is secondary active transport bc the na will follow out of the cell kia a Na/K pump again.
What are the components of the EKG graph?
Please Quit Rusty Smoking Trinkets
Look and study this graph, in particular the AV valves closing/ ejection and how that relates across the board.
Isovolumic/Isometric Contraction
Ventricular contraction begins, pressure rises up, AV valves close quickly.
*Cardiac muscle tension is INC but length of muscle fiber remains constant.
What percentage of blood is ejected rapidly and slowly?
first 1/3rd= 70% fast
last 2/3rds= 30% fast.
What pressures do the right and left ventricles need to slightly surpass in order for ejection through the semilunar valves to happen?
80 mmHg for left ventricle (larger bc its pumping to rest of body) and 8 for right ventricle!
Isovolumic (Isometric) relaxation
Pressure in ventricles return back to normal, AV valves open again, and the cycle will start again.
What is the internodal pathways? Bachmann’s bundle?
Where electric impulses from the SA node will travel in the right atrium and the left atrium respectively
PR segment
Time delay between atrial and ventricular ACTIVATION (AV node related)
16 seconds
PR Interval
Time interval from onset of atrial activation to onset of ventricular activation.
ST Segment/interval
time between ventricular depolarization and repolarization
QT interval
Length of ventricular depolarization and repolarization
Average bp
120/60
Systole/Diastyole