Intro Flashcards
Fibrous sac enclosing the heart
Pericardium (visceral & parietal)
Working cells of they heart (contractile cells)
Myocardial cells
- Actin
- Myosin
Conducting cells
- Pacemaker cells
* Electrical cells ( bundle branches and Purkinje fibers)
Role of gap jxns
Facilitate rapid conduction of electrical signals
Hold the cells together during contraction
Desmosomes
How is the heart regulated
Brain (ANS)
Hormones
Heart tissue (intrinsic firing)
Receptors (blood vessels, kidney, brain , heart)
Baroreceptor locations
- Aortic arch
* Carotid arteries
Cardioregulatory center in the brain is in the …
Medulla oblongata
ANS Cardioexcitatory
Sympathetic
ANS cardioinhibitory
Parasympathetic
Properties of myocardial cells
- Automaticity
- Excitability
- Conductivity
- Contractility
Types of myocardial cells
- Pacemaker cells
* Electrical conducting cells
Primary pacemaker
SA node
Polarized state of myocardial cells
Negative iNside
pOsitive Outside
Depolarization
Na+ in; depol. the cell, Ca+ enters also —> leads to devt. of AP
Repolarization
Na+, Ca+, K+ out restoring a net negative charge to the inside of the cells. Followed by refractory period
Refractory period
- Absolute: No matter what, can’t depol. the cell
* Relative: high enough stim. will depol. the cell
Limb leads
RA :always negative
LA :reference
LL :always positive
Bipolar leads
Have +ve and -ve electrodes (Limb leads)
Unipolar leads
only +ve electrode; reference point determined by EKG (Precordial/chest leads V1-V6 and augmented limb leads)
Direction of electrical signal
-ve to +ve with an upward deflection
Vectors
- Toward +ve electrode = upward
- Away from +ve electron = downward
- Parallel to = flat (isoelectric)
Sum of vectors
Electrical axis
Frontal plane leads
Limb leads
Augmented leads
