Chapter 20 Flashcards
Location of heart
- Thoracic cavity in mediastinum
- Extends from
» Sternum to vertebral column
» First rib to diaphragm
» B/w lungs
Pericardium
- Membrane that surrounds and protects the hearts
- 2 layers
» Outer fibrous pericardium
» Inner serous pericardium: 2 layers, outer parietal layer and inner visceral layer
Pericardial cavity
Space b/w parietal and visceral layers, fluid filled
3 layers of the heart wall
- Epicardium
- Myocardium (myo=muscle)
- Endocardium
Type of tissue in myocardium
Cardiac muscle
4 chambers of heart
L atrium and ventricle, R atrium and ventricle
R atrium
Receives blood from
- Superior vena cava
- Inferior vena cava
- Coronary veins by way of coronary sinus
- Empties into right ventricle
R ventricle
- Receives blood from R atrium
- Pumps blood into lungs through pulmonary trunk (branches into R and L pulmonary arteries)
Tricuspid valve
- Valve between the R atrium and the R ventricle
- Aka atrioventricular valve/AV valve
- Closes when ventricle contracts, preventing flow of blood back into atrium
Pulmonary valve
- Pulmonary valve at base of pulmonary trunk
- Aka pulmonary semilunar (SL) valve
- Half moon shaped/closes when ventricle relaxes, preventing flow of blood back into the ventricle
L atrium
- Receives blood from the lung by way of pulmonary veins
- Then empties blood into L ventricle
L ventricle
- Receives blood from the L atrium
- Pumps blood all over body through aorta
Bicuspid valve
- Valve b/w L atrium and L ventricle
- Aka mitral valve/atriventricular valve (AV valve)
- Closes when ventricle contracts, preventing flow of blood back into the atrium
Aortic valve
- Aortic semilunar valve
- Closes when the ventricle relaxes thus preventing flow of blood back into the ventricle
Thickest wall of heart chambers and why this is an advantage
- Wall of left ventricle
- Higher forces needed to pump blood around the body compared to the pulmonary circuit
Fibrous skeleton of heart and how they aid in valve function
- 4 dense connective tissue rings that surround the valves and fuse to one another
- Prevents overstretching of valves, forms foundation for which heart valves attach
Heart murmur
Heart valves don’t function properly and don’t close completely, resulting in leakage and backflow
Delivers oxygen and nutrients to cardiac muscle tissue
Coronary arteries
Remove waste products from cardiac muscle tissue
Coronary veins
Conduction system
- Network of specialized cardiac muscle fibers that provide a path for ea. cycle of cardiac excitation to pass through the heart
- Ensures the heart chambers are stimulated/contract
Sequence for propagation through conduction sequence for action potentials
- Sinoatrial (SA) node
- Atrioventricular (AV) node
- Atrioventricular (AV) bundle (bundle of His)
- R and L bundle branches
- Perkinje fibers where the action potentials cause both ventricles to contract simultaneously
Sinoatrial (SA) node
- Pacemaker of heart
- Cells repeatedly depolarize spontaneously thus producing a pacemaker potential
- Triggers action potential when it reaches threshold
- Action potentials from the SA node propagate through other structures of the conduction
How autorhythmic fiber differs from ventricular contractile fiber
Has pacemaker potential which is constantly changing, contractile fiber has steady resting potential
Contractile fiber has a plateau after peak of depolarization (maintains depolarization a little longer/allows the ventricles to pump longer)
Function of autorhythmic fibers
- (In SA node) the natural pacemaker of heart
- Initiate action potentials most frequently
- Create/transmit action potential
Function of SA and AV node
- Where cardiac excitation begins
- Pacemaker potential
- Depolarize to threshold spontaneously
- Action potential slows considerably as a result of various diff. in cell structure
- Delay provides time for atria to empty their blood into the ventricles
Function of contractile fibers
- “Working” atrial and ventricular muscles
- Moves blood through cardiovascular system
What SA node’s rate of firing combined with influences from the nervous system and hormones will determine
Heart rate
Example of a hormone that decreases SA node firing, thus decreasing/incr. heart rate
Epinephrine?
Primary method of generating ATP for energy in cardiac muscle cells/how it differs from ATP production in skeletal muscles
Aerobic cellular respiration/uses creatine phosphate and anaerobic respiration in addition to aerobic respiration
Electrocardiogram (EEG or EKG)
- Recording of the electrical changes that occur with each heartbeat
- Shows each sequence of depolarizations and repolarizations
- Helps to detect problems in heart rhythm
P, QRS, and T wave/what they represent
- P: atrial depolarization (electrical excitation)
- QRS: ventricular depolarization (electrical excitation)
- T: ventricular repolarization (end of electrical excitation)
Cardiac cycle consists of
Contraction (systole) and relaxation (diastole) of both atria (simultaneously), rapidly followed by the contraction (systole) and relaxation (diastole) of both ventricles (simultaneously)
Blood pressure
Systolic: upper number, represents pressure in the arteries when the ventricles are contracting
Diastolic: lower number, represents pressure in arteries when ventricles are relaxing
Which pumps receive/push out blood
Atria receive, ventricles pump
- Right side of heart receives from the body and pumps to lungs
- Left side receives from lungs and pumps to body
Length of cardiac cycle in average adult and bpm
0.8 seconds, 75 bpm
Cardiac output (CO)
Volume of blood ejected from the left or right ventricle into the aorta or pulmonary trunk each minute
To calculate: CO(mL/min) = SV(mL/beat) x HR (bpm)
