Shake It Off
Describe the Atrioventricular Bundles
Wave of depolarization goes down the atrioventricular bundles
Describe Purkinje Fibers
Carry wave of depolarization into walls of ventricles and cause depolarization
Describe how the electrical conduction system creates cardiac contractions that efficiently move blood through the heart (8 steps)
1. Each heartbeat starts with depolarization of sinoatrial node
2. A wave of depolarization sweeps across both atria and they contract as a unit
3. The wave of depolarization reaches the atrioventricular node and depolarizes it
4. Atrioventricular node holds depolarization for a fraction of a second and then lets it move on
5. Wave of depolarization goes down the atrioventricular bundles
6. Wave splits at bundle branches and goes to apex of the heart
7. At apex, bundles of Purkinje Fibers which spread out through the myocardium of the ventricles
8. Purkinje fibers carry wave of depolarization into walls of ventricles and cause depolarization
What is an Electrocardiogram
Reading of electrical activity within the heart muscle
DRAW: A normal EKG
You will have included P wave, QRS, T wave
What is going on at the baseline of an EKG?
What is going on at the P Wave of an EKG?
Depolarization of atria
What is going on at the QRS Complex of an EKG?
Caused by repolarization of the atria combined with the depolarization of the ventricles
What is going on at the T Wave of an EKG?
Repolarization of ventricles
What causes the Lub in the heartbeat?
Caused by atrioventricular valves slamming shut plus large arteries vibrate
What causes the Dub in a heartbeat?
Caused by semilunar valves shutting
When does Lub occur in an EKG?
When QRS complex occurs
When does Dub occur in an EKG?
Right around T Wave
What is cardiac output
Amount of blood the heart pumps in a unit of time
What 2 factors decide cardiac output?
1. Stroke Volume
2. Heart Rate
What is the mathematical equation for cardiac output?
Cardiac Output= Stroke volume X Heart rate
What are the 3 parts of Stroke Volume?
1. Preload
2. Contractility
3. Afterload
Define Preload
Amount of blood pushed into the chamber prior to contraction
Define Contracility
Strength of the contraction of the walls
Define Afterload
Pressure in blood vessels that the blood must overcome to flow
What 5 things affect Heart Rate?
1. ANS
2. Hormones
3. Ions in blood
4. Age
5. Body temperature
How does the ANS affect heart rate? (5)
1. Neurons from ANS
2. Sympathetic branch innervates SA node and releases norepinephrine on the node
3. Norepinephrine makes heart rate go up
4. Parasympathetic branch innervates SA node and releases acetylcholine on the SA node
5. Acetylcholine causes heart rate to go down by blocking calcium entry into cells
What hormones affect Heart Rate and how? (2)
1. Epinephrine and Norepinephrine: cause heart rate to go up
2.T3 and T4: cause heart rate to go up
How do ions in the blood affect heart rate? (2)
1. Calcium causes heart rate to go up
2. Sodium and Potassium in excess levels descrease heart rate
How does age affect heart rate? (3)
1. Babies have high heart rate
2. Adults have normal heart rate
3. Elderly have higher heart rate