Exam 2 Flashcards
What is a PVC?
When the heart contracts prematurely / extrasystole
How are parasympathetic impulses transmitted from the brain to the heart?
Cardioinhibitory center sends impulses through the vagus nerve to decrease HR
How are sympathetic impulses transmitted from the brain to the heart?
The cardioacceleratory center sends impulses through the sympathetic trunk - stimulates the SA node, AV node, myocardium, and the coronary arteries to increase HR and contractility
How do these autonomic systems change the heart rate?
Through the cardiac centers in the medulla oblongata
What does the PNS do to HR?
Can decelerate it
What is the role of artificial pacemakers?
Medical devices that decouple the atria and ventricles - can be programmed to change with changing energy demands and interrogates to with symptoms appear
What is partial heart block?
Only some impulses get through
What is total heart block?
No impulses get through, the ventricles beat at their own intrinsic rate - too slow for adequate tissue perfusion
Why can a PVC feel like a thud in the chest?
Afterwards, the heart has a slightly longer time to fill and the next normal contraction feels like a thud with more fluid
What is an ICD?
Implantable cardioverter defibrillator, devices that continually monitor heart rhythms, they will slow tachycardia and emit an electrical shock in the event of fibrillation
What is defibrillation?
electrically shocking the heart to depolarize the entire myocardium - ideally, the SA node begins to function normally and sinus rhythm is restored
What is fibrillation?
Rapid or irregular contractions of the heart
control of heart by SA node is disrupted
Fibrillation ventricles are not useful pumps
What is an arrhythmia?
Irregular heart rhythm resulting from a defect in the intrinsic conduction system
What is the intrinsic rate set by the AV bundle/Purkinje fibers?
30 beats per min
What is the intrinsic rate set by the AV node?
50 beats per min
What is the intrinsic rate set by the SA node?
75 beats per min
What is the only electrical connection between the atria and ventricles?
AV bundle
Why is there a delay at the AV node?
It allows the atria to complete their contraction
How long does it take an impulse to pass through the entire heart?
0.22s or 220ms
What is the sequence of excitation of the heart?
Sinoatrial node (SA Node)
Atrioventricular node (AV node)
AV bundle / Bundle of His
Right and left bundle branches
Punkinje fibers (subendocardial conducting network)
What is repolarization?
K+ channels open, K+ effluxes, cell’s interior becomes more negative
What is depolarization?
Ca2+ channels open (around -40mV), Ca2+ influxes leading to an AP
What is the intrinsic conduction system?
Noncontractile cells specialized to initiate and distribute impulses throughout the heart
What is the difference between cardiac myocytes and cardiac muscle regarding aerobic respiration?
cardiac myocytes are dense in mitochondria reflecting a great dependence on oxygen
Cardiac muscle is more adaptable to using different nutrient sources as fuel
What is tetany?
In cardiac muscle, the refractory period is longer than contraction to prevent tetany
What is summation?
Occurs in skeletal muscle because the refractory period is short than contraction
What is the absolute refractory period?
The period during an AP when an additional AP cannot be generated
What does depolarization do in cardiac muscle?
Depolarization opens special, slow flow Ca2+ channels in the cell membrane - the combination of extracellular Ca2+ and Ca2+ from the Sarcoplasmic Reticulum allows contraction
What is automaticity/audtorhythmicity?
The ability to spontaneously depolarize
self generated depolarizations travel throughout the heart via gap junctions
No neural input is needed for cardiac myocytes
What are pacemaker cells?
Self excitable, non-contractile cells, SA node
What is the coronary sinus?
cardiac veins merge to form coronary sinus
What is the bicuspid mitral valve?
1 of the 2 AV valves, between LA and LV, 2 flexible cusps
What branches off the descending aorta?
All other systemic arteries
What is the physiology of cardiac tamponade?
Compression of the heart by large amounts of inflammatory fluid in pericardial cavity
hearts ability to pump blood is reduced
Management: removal of excess fluid by syringe
How is calcium delivered?
Fewer, wider, T tubules, 1 per sarcomere, regulate calcium concentration
What are sarcomeres made of?
Myosin, actin, Z discs, A bands, and I bands
What are myosin and actin?
Thick and thin myofilaments part of the sarcomere
What is a functional syncytium?
When the myocardium acts as a single coordinated unit
What are gap junctions?
Part of the intercalated discs, allow ions to pass from cell to cell - transmitting current across the entire heart
What are desmosomes?
Part of intercalated discs, orevtns separation during contraction
What are intercalated discs?
Junctions that the plasma membranes of adjacent cardiac myocytes interlock at
What part of cardiac myocyte volume does large mitochondria account for?
25-35%
How does the cardiac muscle contract?
It contracts via the sliding filament mechanism - sarcomeres
What is the anatomy of the cardiac muscle?
striated like skeletal muscle
Contracts via sliding filament mechanism - sarcomeres
Cardiac myocytes are shorter and fatter than skeletal muscle cells - they are more branched and interconnected
Each myocyte has 1 or 2 centrally located nuclei
Large mitochondria account for 25-35% of cardiac myocyte volume
Cardiac myocytes push and pull on the cardiac skeleton striated like skeletal muscle
What is angina pectoris?
Thoracic pain caused by a fleeting deficiency in blood supply to myocardium
Causes increased physical al demands on heart (I.e. exercise), stress induced spasms of the coronary arteries, myocardial cells will weaken but not die
Where does the coronary sinus empty its blood?
It drains into the RA
What are the 3 major venous tributaries to the coronary sinus?
great cardiac vein from the anterior interventricular sulcus
Middle cardiac vein from the posterior interventricular sulcus
Small cardiac vein from the right inferior margin - anterior cardiac veins empty directly into the RA
What’s an anastomosis?
Cross connection between adjacent channel
When is the myocardium perfused - during ventricular systole or diastole?
Diastole
What are the symptoms of a myocardial infarction?
Male: chest squeezing, pressure, discomfort, shortness of breath, upper back pain, pain down at least 1 arm, jaw pain, feeling of fullness, and nausea
Female: chest discomfort, shortness of breath, upper back pain, pain down at least 1 arm, jaw pain, unexplained/extreme fatigue, fainting, vomiting, nausea, sudden dizziness
What medical condition results from a partial or complete blockage in the coronary circulation?
Myocardial infarction
What branches off the right coronary artery and what parts of the myocardium it supplies?
Serves the right side of the heart
right marginal artery; supplies myocardium of lateral right side of heart
Posterior interventricular artery: supplies the apex of heart and the posterior ventricular walls
What branches off the left coronary artery and what part of the myocardium does it supply?
Serves the left side of heart
anterior inter ventricular artery (left anterior descending artery): follows the anterior inter ventricular sulcus, supplies blood to the anterior walls of both ventricles and inter ventricular septum
Circumflex artery: supplies the LA and posterior wall of LV
Where do the coronary vessels exist on the surface of the heart?
R and l coronary arteries arise from base of aorta and travel around heart in the coronary sulcus
What is the function of coronary circulation?
In the epicardium, functional blood supply to myocardium
What blood is carried by pulmonary veins?
They carry oxygen-rich blood from the lungs to the LA
What is blood is carried by the pulmonary trunk/arteries?
Carries oxygen-poor blood from RV to lungs
What branches off the aortic arch?
Brachiocephalic trunk, L common carotid artery, and L subclavian artery
What branches off the ascending aorta?
R and L coronary arteries
What are exceptions to the oxygenation of the arteries and veins?
Pulmonary trunk (artery) carries oxygen-poor blood from arm to lungs
Pulmonary veins carry oxygen rich blood from lungs to LA
What do veins do for the circulatory loop?
Returns blood to the heart that is typically oxygen-poor
What do arteries do for the circulatory loop?
Carries blood away from heart that is typically oxygen rich
Which side of the heart pumps blood into the pulmonary circuit?
The right side is the pulmonary circuit pump, which is short and lower pressure
Which side of the heart pumps blood into the systemic circuit?
The left side is the systemic circuit pump, which is longer and has higher resistance
What are the dangers of stenotic valves?
They are stiff and narrows, constricting the heart’s openings
narrow openings force the heart to contract more forcefully
Mitral and aortic valves are often affected
What are the dangers of insufficient valves?
It forces the heart to repump the same blood multiples times, faulty valve increases heart workload - weakening the heart over time
leaky valves reduce efficiency of pumping heart
What causes SL valves to close?
Close as blood back flows toward the heart and fills the cusp
What causes SL valves to open?
Forced open as ventricles contract and pressure rises
What are the SL valves?
Includes aortic and pulmonary valves. They guard the bases of the large arteries emerging from each of the ventricles, preventing back-flow from vessel to ventricle
They open and close in response to changes in pressure; forced open as ventricles contract and pressure
What is a cusp?
Flap of endocardium
What is the tricuspid valve?
1 of the 2 AV valves, between RA and RV, 3 flexible cusps
What are the AV valves?
2 total (Tricuspid and mitral valves) that are located at each atrial ventricular junction, prevents backflow of blood into atria during ventricular contraction
How is blood propelled from ventricles?
Ventricular contraction propels blood out of the heart and into circulation
Blood propelled from RV is in pulmonary trunk
Blood propelled from LV is in the aorta
what is the difference between the left and right ventricles?
The left ventricle’s myocardial wall is 3x thicker than right ventricle
What are the ventricles?
They make up most of the volume of the heart and have much thicker myocardial walls than atria
includes trabeculae carneae and papillary muscles
What is the anatomy and physiology of the LA?
The walls are smooth and blood enters via the 4 pulmonary veins
What is the anatomy and physiology of the RA?
Anterior wall of RA is covered with bundles of muscles called pectinate muscles, blood enters RA via the coronary sinus, SVC, and IVC
What is the atria?
Small receiving chambers, generate only minimal contraction to push blood into the ventricles; includes right atrium, left atrium. and fossa ovalis
how many and what chambers are in the heart?
4 chambers, 2 atria, 2 ventricles
What is the chordae tendineae and its function?
Irregular ridges of muscle that lines the internal walls of ventricular chambers
What are papillary muscles and its function?
Muscles that project into ventricular chambers and play a role in valve function
What is the function of the auricles?
small wrinkled appendages that sit atop each atrium
Expands the volume capacity of the right and left atria as needed
What is the physiology of pericarditis?
The inflammation of the pericardium
beating heart runs against pericardial sac - audible sound produced
Sx; pain deep to the sternum
Leads to adhesions, impeded cardiac activity
What is the function of cardiac skeleton?
A reinforcing, dense network formed by CT fibers, skeleton prevents overstretching from continuous stresses and ensures that action potentials only spread along desired pathways
What is the endocardium?
The deepest layer of heart wall made of endothelium; lines the heart chambers, contiguous with lining of the great vessels
What is the myocardium?
The middle muscle layer of heart wall; composed of contracting, cardiac muscle, bulk of heart; cardiac muscles arranged in spiral bundle thethered to each other by crisscrossing CT fibers, cardiac skeleton
What is the epicardium?
It’s the visceral pericardium and most superficial layer of heart wall
What is the contents and function of pericardial cavity?
Space between parietal and visceral layers, filled with serous fluid, functions to reduce friction
What is visceral layer?
Layer of serous pericardium, lines the external surface of the heart
What is the parietal layer?
Layer of serous pericardium, lines internal surface of the fibrous pericardium
What is serous pericardium?
Deep to the fibrous pericardium, made of 2 thin layers
What is fibrous pericardium?
Loose fitting superficial part of the pericardium, made of DCT, protects the heart; keeps it from overfilling and anchors to mediastinum
What is the pericardium?
The double-walled sac that encloses the heart
Describe the apex of the heart
Points inferiority to left hip
Describe the base of the heart
Wide, flat, posterior surface, directed to right shoulder
Where is the heart located?
Within mediastinum, midline thoracic cavity between sternum and vertebral column, rests on diaphragm, 2/3 of mass to left of midstream, line
What is the shape of the heart?
Hollow cone-shaped structure
What size is the heart?
Less than a lb, human fist
Which side of the heart is the systemic circuit?
Left side (aortic valve, body, LA, LV)
Which side of the heart is the pulmonary circuit?
Right side (venae cavae, SVC, RA, RV)
Which side of the heart has oxygenated blood?
Left side of the heart receives oxygen-rich blood
Which side of the heart has deoxygenated blood?
right side of the heart receives oxygen-poor blood
What does the SNS do to HR?
Can accelerate it and increase contractility
