The Heart Flashcards
What is the pericardium?
A double walled sack around the heart
Parietal pericardium
Lines the internal surface of the fibrous pericardium
Visceral pericardium
Lines the surface of the heart
Homeostatic imbalance
Pericarditis
Inflammation of the pericardium, rough serous membrane, heart rubs against the pericardial sac. visceral and parietal pericardia stick together
Homeostatic imbalance
cardiac tamponade
Large amounts of inflammatory fluid compress the heart, limiting it’s pumping action (it must be drained)
Three layers of the heart wall
Epicardium- visceral layer of the pericardium
Myocardium- Cardiac muscle layer forming bulk of heart, fibrous skeleton of the heart
Endocardium- Endothelial layer of the inner myocardial surface
The way heart muscle is bundled allows it to function as a syncytium, what does that mean?
It “works together” as a single coordinated unit
What is the difference between the pulmonary circuit and the systemic circuit?
They going opposite direction one drop off oxygen, the other picks up the oxygen.
Coronary circulation
Functional blood supply to the heart muscle itself
Anastomoses
Also known as collateral routes, ensures blood delivery to the heart even if major vessels are obstructed
Homeostatic imbalance
angina pectoris
(Choked chest) thoracic pain caused by deficiency and blood delivery to myocardium
Homeostatic imbalance
myocardial infarction
A heart attack caused by lack of oxygen due to blockage of the coronary system, areas of cell death are repaired with scar tissue
Why is damaged cardiac muscle not replace?
Because muscle cells do not undergo mitosis because they are missing centrioles
Heart valves
Atrioventricular valves- Tricuspid, bicuspid(mitral)
semilunar valves: pulmonary and aortic
Heart valves function
They ensure unidirectional blood flow through the heart
Incompetent valve
Makes swishing sound, blood backflows or regurgitates through partially open valve
Stenotic valve
High-pitched sound or click because valvular opening is narrowed so bloodflow is restricted
Cardiac muscle
Striated, short, fat, branched and interconnected. connective tissue endomysium acts as tendon and insertion
Intercalated discs
Made of gap junctions and desmosomes. anchor cardiac cells together and allow free passage of ions
Autorhythmic cells
Create the action potential which travel through the gap junction to depolarize the contractile cells (slow sodium Fast calcium)
Contractile cells
Fast sodium slow calcium
What is the difference between autorhythmic cells and contractile cells
Autorhythmic set the pace uses calcium
Contractile cells like the rest of the heart use sodium to contract
Why must there be a 0.1 second delay between as SA and AV nodes
Because all heart chambers cannot squeeze at the same time
Sequence of electrical excitation to the heart
Intrinsic
- SA node generates impulse
- Atrial excitation begins
- Impulse delayed at AV node
- Impulse passes to heart apex
- Ventricular excitation begins
- Ventricular excitation complete
Arrhythmias
Irregular heart rhythm
Fibrillation
Rapid out of step contraction where control of heart rhythm is taken away by SA node fibrillating ventricles are useless pumps.
defibrillization is needed to shock heart and allow SA node to reestablish rhythm
Ectopic focus
SA node is replaced by another pacemaker like AV node
Junctional rhythm
Pace set by AV node usually 50 beats
Extrasystole
Hyperexcitable region of the heart causes premature contractions, before SA node initiates regular contraction
premature ventricular contraction PVC are most problematic
Heart block
Inability of ventricles to receive impulses from AV node. Total heart block-Ventricles forced to beat at own slow autorhythmic rate. To slow for adequate circulation
Total or partial heart block a pacemaker can recouple atria to ventricles
Extrinsic innervation of the heart
Sympathetic nerve- speeds up (100)
parasympathetic nerve- vagus nerve tells it to slow down
Why does parasympathetic nerve dominate control over the heart?
Parasympathetic controls because it maintains the heart rate
Cardiac output problem
CO= HR x SV
The amount of blood pumped by each ventricle in one minute
Stroke volume problem
SV= EDV - ESV
Stroke volume = end-diastolic volume - end-systolic volume
EDV is The amount of blood collected in a ventricle during diastole
ESV Is the amount of blood remaining in a ventricle after contraction
Stroke volume
preload
The amount the ventricles are stretched by contained blood
Stroke volume
Contractility
Cardiac cell contractile force due to factors other than EDV
Stroke volume
afterload
Back pressure exerted by blood in the large arteries leaving the heart
Frank-starling law
Preload is a critical factor in controlling stroke volume, cardiac muscle exhibits a length tension relationship. at rest, cardiac muscle cells are shorter than optimal length
Factors influencing stroke volume
positive inotropic agents
Negative inotropic agent
Positive- increase and contractility
Ex increased sympathetic stimuli, catecholeamines, calcium
Negative- Decrease in contractility
Ex acidosis, calcium channel blockers, extracellular vitamin K
Positive chronotropic factors
Increased heart rate
example tachycardia
Negative chronotropic factors
Decrease heart rate
example bradycardia
ANS vagal tone
Slowing heart rate PNS dominates the autonomic stimulation
Bainbridge reflex
Sympathetic reflexes initiated by increase blood in atria (increase venous return)
Stimulation of SA node
stimulate Baroreceptors in atria causing increased SNS stimulation
Hypocalcemia
Depresses heart rate
Hypercalcemia
Prolongs plateau phase and leads to spasms that do not allow heart to rest
Hypokalemia
Makes heart beat feebly and arrhythmically
Hyperkalemia
Interferes with depolarization by lowering action potential and may lead to heart block and cardiac arrest
Fetal heart structure
Foramen ovale
Connects the two atria
At birth becomes the fossa ovalus
Fetal heart structure
Ductus arteriosus
Connect pulmonary trunk and the aorta
After birth becomes ligamentum arteriosum
Why does the fetus heart structures have the foramen ovale and the ductus arteriosus?
To bypass the lungs before they are born
If you have a junctional rhythm what is absent on an ECG?
The P wave
If you have a partial heart block what is seen on an ECG?
More P waves than QRS waves
Fibrillation looks like what on an ECG?
Chaotic waves
P wave corresponds to ____ of a SA node; T wave corresponds to ___ ___
Depolarization, ventricular repolarization
Aortic valves sounds are heard where?
Second intercoastal space at right sternal margin
Pulmonary valve sounds are heard where?
Second intercostal space at left sternal margin
Where are bicuspid valve sounds heard
Over heart apex in fifth intercostal space in line with the middle of the clavicle
Where are tricuspid valves sounds heard?
Right sternal margin of the fifth intercostal space variation include over sternum or over left sternal margin in 5th intercostal space
