Cardiac Cycle Flashcards
what is longer, Cardiac muscle action potential or skeletal muscle action potential/
cardiac muscle action potential
- Expand time necessary to develop force for the entire heart to contract
- Also includes Ca++ involvement in the process
Systole
period of ventricular contraction (pumping)
Diastole
period of ventricular relaxation (filling)
what are the 5 stages of the cardiac cycle?
- atriole systole begins: atrial contraction forces blood into ventricles
- ventricular systole (1st phase): ventricular contraction pushes AV valves closed
- Ventricular systole (2nd phase): semilunar valves open and blood is ejected
- ventricular diastole (early): semilunar valves close and blood flows into atria
- ventricular diastole (late): chambers relax and blood fills ventricles passively
Electrocardiogram
ECG: process of recording the electrical activity of the heart over a period of time
detects:
1. Irregular or abnormal heartbeats due to problems in the conduction system
2. Identify where in the heart muscle damage has occurred
Einthoven’s triangle
P-wave: atrial depolarization
QRS complex: ventricular depolarization
T wave: ventricular repolarization
Normal cardiac action potential is conducted through
the atria and ventricles, a characteristic sequence of voltage differences is created between the left forelimb and the right forelimb
PR interval
- atrial depolarization
- The cardiac action potential is being conducted through the AV node
- Time between depolarizations. PP interval can be used to measure atrial contractions per minute
RR interval
Time between ventricular depolarization. Used to measure ventricular contractions per minute
QT interval
ventricular action potential
Cardiac arrhythmias
caused by lack of the FORMATION of action potentials (sick sinus syndrome) or the conduction of action potentials (AV blocks)`
what are 2 cardiac arrhythmias?
- Bradycardia = slow heartbeat
- Tachycardia = fast heartbeat
what movements does action potentials make in the heart?
circular movement due to damage or blockage of the tissue. Can happen in both the atria and ventricles, can lead to fibrillation in with parts
Defibrillators
stimulates the entire heart to go into the refractory period
Tachycardia
- heart “palpitations”, dizziness, fainting or near-fainting, lightheadedness
- Can lead to ventricular or atrial fibrillations (irregular or fast HR)
Bradycardia
- fatigue, dizziness, lightheadedness, fainting or near-fainting spells
- Blood can pool in chambers and potentially start to clot
- Most pacemakers implanted are for too slow of a heartbeat
Parasympathetic acetylcholine
- binds to muscarinic receptors on the heart muscle
- Activation of the muscarinic receptor causes opening of additional K+ channels, making the cell “hyperpolarize” taking longer to reach threshold
Sympathetic norepinephrine
- binds to beta receptors
- Increases Ca++ channels and their permeability, decreasing the time it takes to reach threshold
Mechanical properties of the heart
Heart rate
Stroke volume
Cardiac output (CO)
Ejection fraction
Preload
Afterload
Contractility
Frank-starling mechanism
Factors on cardiac output
Adrenergic neurons
release norepinephrine (NE), sympathetic neuron
Adrenergic receptors
- alpha and beta receptors are on visceral effectors
Alpha 1 and beta 1 are excitatory
Alpha 2 and beta 2 are inhibitory
Beta 3 is on brown adipose tissue and involved in thermogenesis
Cholinergic neurons
- release acetylcholine (Ach)
- All sympathetic and parasympathetic preganglionic neurons, all parasympathetic postganglionic neurons
Cholinergic receptors
Nicotinic receptors are present in postganglionic neurons and motor endplate
Muscarinic receptors are present in membrane of all effectors (smooth, cardiac muscles, and glands)
Which of the following statements is true?
The period of contraction (systole), the heart pumps out blood through the arteries; during the period of relaxation (diastole), the heart fills with blood
The period of contraction (diastole), the heart pumps blood out through the arteries; during the period of relation (systole), the heart fills with blood
The period of contraction (systole), the heart pumps out blood through the arteries; during the period of relaxation (diastole), the heart fills with blood
During the early repolarization phase of cardiac muscles which of the following ion channels open and close?
K+ channels open and Na+ channels closed
Na+ channels open and K+ channels closed
K+ channels open and Na+ channels closed
Ventricular depolarization occurs during
P wave
QRS complex
T wave
QRS complex
Activation of the SV (sinoatrial) node would result in the:
P wave
QRS complex
T wave
P wave
Ventricular repolarization occurs during:
P wave
QRS complex
T wave
T wave
Atrial contraction occurs:
P wave
QRS complex
T wave
P wave
Memorize the ECG chart!
Memorize the ECG chart
