origin of the heartbeat Flashcards
what cells does the conduction system of the heart have
non contractile cells
properties of the non contractile cells of the conduction system of the heart
- larger than standard cardiomyocytes
- fewer contractile proteins
- More glycogen and mitochondria
-
No intercalated discs - Connected by desmosomes and gap junctions
what are pacemaker cells
myocardial cells of the SA and AV nodes
what is synchronization
the action potential is conducted down the conduction system as an electrical impulse
what apparatus to measure heart rate
ECG (electrocardiogram)
properties of normal cardiac cells
- Self contracting
- Single nucleus
- There are intercalated discs
○ It composes of desmosomes and gap junctions - Gap junctions provide passage for ions and small molecules
- Desmosomes and adhere junctions provide mechanical continuity
- High mitochondrial density - a continuous supply of ATP is needed to support contraction
They are striated
what does intercalated disc consists of
gap junction and desmosomes
process of cardiac conduction
Cardiac conduction
Phase 4 = Resting potential
Phase 0 = Rapid depolarisation phase
Na+ channels open and membrane
potential becomes positive (+50 mV)
Phase 1
= Slow-release K+ current (Ito) small drop in membrane potential triggering phase 2
Phase 2 = Plateau phase
Ca2+ influx balances out K+ efflux;
component of effective refractory period
when Ca2+ influx stimulates intracellular
Ca2+ release initiating contraction; no
further action potential can occur (absolute
refractory period)
Phase 3 = Repolarisation -
Rapid K + efflux returns membrane potential
back to -70 mV
explain systolic
Systole/systolic
- chambers are contracting
- Chambers are emptying
explain diastolic
Diastole/diastolic
- chambers are relaxed
- Chambers are filling up
process of the cardiac cycle
The cardiac cycle
- Atrial contraction
- the atria contract, pushing the blood into ventricles
- Isovolumetric contraction-The ventricles begin to contract, but all heart valves are closed, so no blood is ejected yet
- Rapid ejection
- Once ventricular pressure exceeds the pressure in the aorta and pulmonary artery, the aortic and pulmonary valves open, allowing blood to be ejected rapidly from the ventricles
- Reduced ejection
- The rate of ejection slows down as the ventricles continue to contract but with decreasing force
- Isovolumetric relaxation
- After the ejection phase, the ventricles relax, but all valves (atrioventricular and semilunar) are closed
- Rapid filling
- The atrioventricular (AV) valves (mitral and tricuspid valves) open when ventricular pressure falls below atrial pressure, allowing blood to flow rapidly from the atria into the ventricles.
- Reduced filling
This phase is characterized by a slower rate of filling as the blood continues to enter the ventricles but at a diminishing speed
what is the lub-dub sounds
Lub-dub
Lub - closure of the atrioventricular valves
Dub - closure of the semilunar valves
how many heart sound does horse have each cycle
4
how many heart sound does dogs and cats have each cycle
2
PQRST
P waves - atrial depolarisation
QRS complex - depolarisation of the ventricles
T wave - repolarisation of the ventricles
