Ch. 9 Electrocardiography Flashcards
Electrocardiogram
Checks the electrical impulses of the heart and provides valuable information about the heart’s function
Depolarization
electrical stimulation of specialized cells that cause contraction
What does electrical stimulation do to the cardiac muscle cell membrane?
Depolarization
What does depolarization do to the membrane?
Makes the membrane more permeable to Na ions, allowing them to flow inward and creating a positive charge.
Automaticity
Ability to initiate its own electrical impulse.
Rhythmicity
Ability to repeat the cycle in synchrony with regularity
Conductivity
Ability to stretch as a single unit & then passively recoil while actively contracting
Cardiac mm cells are able to …
discharge an electrical stimulus without nerve stimulation
The Autonomic Nervous System effects on cardiac activity
Major influence on reflex cardiac activity via sympathetic and parasympathetic
Sympathetic division
- Discharges norepinephrine
- Acts on SA node, AV node, ventricles
- Stimulates adrenal gland to secrete catecholamines
- Increases HR, conduction velocity, contractility, irritability
Parasympathetic division
- Discharges acetylcholine
- Vagus nerve is main component in control of the heart
- General inhibitor on rate and conduction velocity
The conduction system
Composed of myocytes arranged in a pathway that spreads electrical activity throughout the four chambers
Pathway of Conduction system
- SA node
- Travels to left atrium via Bachmann bundle
- P wave = atrial depolarization
- Travels to AV node, atrial kick = P-R segment
- Travels to His bundle and bundle branches
- Travels to Purkinje fibers –ventricular contraction = QRS wave
- ST-segment repolarization
SA node
Found in the R. atrium and initiates electrical pulse
P wave
atrial depolarization, problems with the P wave pertains to the atria
