Bio 209 Ch 20A
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How much blood does the heart pump each minute throughout the body?
5 liters/min and our body has approx. 5-6 liters of blood
Describe the heart and its location
- Cone shaped about the size of a first
- - Base is formed by atria and has broad posterior surface
- - Apex is formed by left ventricle and has a pointed tip
Located in mediastinum
Where are the Base and Apex located?
Apex: left side, resting on diaphragm
Describe the Pericardium and its function
Membrane that surrounds & protects the heart
It confines heart to its location in mediastinum
Describe the Fibrous Pericardium & its function
Superficial layer of Pericardium
It prevents overstretching of the heart by attaching to diaphragm & BV
Describe the Serous Pericardium & its function
- 2 Layers:
- - Parietal: fused to fibrous pericardium
- - Visceral/Epicardium: adheres to surface of heart
- Pericardial Cavity: space between parietal & visceral
- Pericardial Fluid: slippy fluid that reduces friction during contraction
What are the three layers of the heart?
What layer of the heart is the outermost layer?
What layer is the thickest layer and describe its function?
Myocardium: middle layer of the heart that is responsible for contraction of the heart
What layer does the Endocardium sit and what is its function?
Innermost layer, and it provides slippery surface that prevents friction as blood passes through within the chambers and valves
Name the heart chamers (2)
Atria & Ventricles
Which part of the heart chamber receives blood and describe its structure?
Atria: these are the upper heart chambers that contain auricles (pouch-like structures on anterior surface and slightly increases amount of blood it can hold)
Which part of the heart chambers distribute blood & describe its structure?
Ventricles: these are the lower heart chambers
What three veins carry blood to the Right Atrium?
- Superior Vena Cava
- Inferior Vena Cava
- Coronary Sinus
What artery (from the Right Ventricle) is blood pumped?
Which veins carry blood from the lungs to the Left Atrium?
Where does blood pass through from the Left Ventricle?
Describe the Sulci on the surface of the heart
- Sulci are grooves that contain BV & fat:
- - Coronary Sulcus: deep groove encircling heart, separating atria & ventricles
- - Anterior Interventricular Sulcus: shallow groove on anterior surface of heart separating R & L ventricles
- - Posterior Interventricular Sulcus: continues AIS on posterior surface and separates R & L ventricles
What are the two heart valves?
Atrioventricular Valves & Semilunar Valves
Describe the structure and function of the Atrioventricular Valves
Tricuspid Valve (R Atrioventricular): three cusps, located between R Atrium & R Ventricle
Bicuspid Valve (L Atrioventricular): two cusps, located between L Atrium & L Ventricle
Chordae Tendinae attaches cusps to papillary muscles
Describe the structure & function of the Semilunar Valves
Pulmonary Semilunar Valve: between R Ventricle & Pulmonary Trunk
Aortic Semilunar Valve: between L Ventricle & Aorta
Semilunar Valves eject blood into Aorta
Describe the blood pathway thru R heart
1. Inferior Vena Cava
to Superior Vena Cava
to Coronary Sinus
into R atrium
- 2. Right Atrioventricular Valve into R Ventricle
- 3. Pulmonary Valve into Pulmonary Trunk
4. Enters Pulmonary Arteries
Describe the blood pathway thru L heart
1. Pulmonary Veins into L Atrium
2. Left Atriventricular into L Ventricle
3. Aoric Valve into Aorta to body tissues
Compare the thickness of the myocardium of each chamber
Thicker - L Ventricle
Thinner - R Ventricle
How does thickness of myocardium relate to function of each chamber?
Thickness indicates amount of force it contracts - the thicker the muscle, the stronger the contraction
R Ventricle pumps blood into lungs, therefore its walls are thinner
L Ventricle pumps to the rest of the body, therefore its walls are thicker
Narrowing of heart valve opening that decreases flow of blood
Failure of valve to close completely allowing backflow of blood
How does Rheumatic Fever affect the heart?
It damages/destroys heart valves
Describe the pathway of blood thru Pulmonary Circulation (Right Side of heart)
1. Oxygen-poor blood pumped from R Ventricle
into Pulmonary Trunk
2. Pulmonary Arteries
- 3. Oxygen is added, Carbon Dioxide is removed
4. Pulmonary Veins to Left Atrium
Describe the pathway of blood thru Systemic Circulation (Left Side of the heart)
1. Oxygen-rich blood pumped from Left Ventricle into Aorta
2. Systemic Arteries to different body areas
3. Enters Capillaries, loses Oxygen & gains Carbon Dioxide
4. Returns to Systemic Veins to Right Atrium
What is the function of Coronary Circulation?
Supply blood to the heart wall
What are some of the effects of blockage of coronary arteries?
- Myocardial Ischemia
- Myocardial Infarction
What's the function of Autorhythmic Cells?
1. Spontaneously generates Action Potentials
3. Form conduction system
What are the components of the Conduction System?
1. Sinoatrial Node
2. Atrioventricular Node
3. Atrioventricular Bundle
4. Bundle Branches
5. Purkinje Fibers
Describe the Sinoatrial (SA) Node of the Conduction System
- - Right atrial wall near superior vena cava
- - Unstable resting membrane potential- Action Potentials initiated by SA node spread to both atria via gap junctions
- - Spreads to AV Node
Describe the Atrioventricular (AV) Node of the Conduction System
- - Interatrial Septum
- - Spreads to AV Bundle (bundle of His)
Describe the Atrioventricular (AV) Bundle of the Conduction System
- - Conducts Action Potential from Atria to Ventricles
- - AV Bundles allow Action Potential to spread from atria to ventricles (because atria is electrically insulated from ventricles)
- - Spreads to Right & Left Bundle Branches
Describe the Right & Left Bundle Branches of the Conduction System
- - Interventricular Septum
- - Propogated along bundle branches towards Apex- Enters Perkinje Fibers at Apex
Describe the Perkinje Fibers of the Conduction System
- - Conduct Action Potential upwards to remainder of Ventricular Myocardium
- - Ventricles contract and blood is ejected to Semilunar Valves
What is the pacemaker of the heart?
Sinoatrial Node (SA Node)
Define Ectopic Pacemaker
Site other than SA Node is pacemaker due to damaged SA Node (Slow HR)
What effect does the ANS have on the heart?
- Modifies Action Potentials the SA Node generates by:
- - Sympathetic: increases HR by increased Action Potential
- - Parasympathetic: decreases HR by decreased Action Potential
Describe the stages of the Cardiac Muscle Cell Action Potential
1. Depolarization: opening of Voltage-Gated fast Na channels and Na enters cell
2. Plateau (Sustained Depolarization): opening of Voltage-Gated Ca channels and Ca enters cell
3. Repolarization: opening of Voltage-Gated K channels and K leaves cell
Why is the Refractory Period length important in the cardiac muscle?
Tetanus can't occur in cardiac muscle fibers because Refractory Period lasts longer than the contraction itself
What is ECG?
Electrocardiogram - a record currents generated by Action Potentials in the heart
What are the components of a ECG?
- P Wave: atrial depolarization
- QRS Complex: ventricular depolarization (atrial repolarization)
time between atrial action potential to ventricular action potential (elongated in heart block)
time between ventricular depolarization to ventricular repolarization (elongated in myocardial damage)
Correlation of ECG and Atrial Systole
- - Follows P Wave
- - Precedes ventricular systole, adding amount of blood to ventricles
Correlation of ECG and Ventricular Systole
- - Follows QRS Complex (atrial diastole)
- - Dystole follows T Wave
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