Chapter 19 Flashcards
Pulmonary circuit
Right side receives blood that has circulated through the body
Systemic circuit
Left side blood leaves it by way of another large artery aorta
Heart
With then mediastinum between two lungs more than half the heart is to the left of the bodies median plane
Pericardium
Isolates heart from other thoracic organs allows room to expand
Function of pericardial fluid
Lubricates the membranes and allows the heart to beat within minimal friction
Fibrous skeleton
Tissue concentrated in the walls between the heart chambers
Functions of fibrous skeleton
Provide structural support for the heart
Anchors the cardio sites and gives them something to pull against
Serves as electrical insulation between the arteria and the ventricles
Heart valves
To pump blood affectively to ensure a one-way flow
What closes the semi lunar valve’s
Changes in blood pressure that occur as a heart chambers contract and relax
Pathway of blood through the heart
Enters the right atrium from the superior and inferior venae cavae
Blood entering right atrium is oxygen poor
Flows from the right atrium through the right AV
Into the right ventricle through the pulmonary valve and exit through the pulmonary trunk
Pulmonary trunk splits into pulmonary arteries they carry blood to lungs where CO2 is unloaded and 02 is loaded
Blood is return to heart by vena cava
Blood enters the left atrium oxygen is Rich
Through the left AV valve into left ventricle then through the aortic valve and exits through ascending aorta
Now blood is in systemic circulation 02 will be unloaded and CO2 will be loaded
After gas exchange blood will be returned to the right atrium by superior and inferior vena cava
Where does the coronary sinus empty into
Empties blood into the right atrium
Myocardial infarction
A heart attack caused by a fatty deposit or blood clot in a coronary artery
Arterial anastomoses
Where two arteries come together and combined their blood flow to points farther down stream
Collateral circulation
The route points take that supply the heart tissue with blood if the primary route becomes obstructed
Autorhythmic
Doesn’t depend on nervous system for its rhythm heart has its own pace maker and electrical system
Cardiocyte
Short thick branched cells
Where are calcium ions admitted from to activate muscle contractions
T tubules admit calcium ions from the extracellular fluid
What is unique about the mitochondria
Large
Intercalated discs
Cardiocytes joined end to end by thick connections
Electrical junction
Form channels that allow ions to flow from the cytoplasm of one cardiocyte directly into the next
How is damaged cardiac muscle repaired
No satellite cells so repair is almost entirely by fibrosis
Why is cardiac muscle so vulnerable to oxygen deficiency
Cardiac muscle depends almost exclusively on aerobic respiration to make ATP
Is cardiac muscle prone to fatigue
No
Sympathetic fibers innervate which part of the heart
SA and AV node
Affects sympathetic innervation has on the heart
Control of contraction strength
Increases heart rate
What cranial nerves do parasympathetic fibers travel to the heart
Vagus nerves in the medulla oblongata
Parasympathetic fibers innervate which part of the heart
Synapse with postganglionic neuron’s in the epicardial surface and within the heart wall
Main effect of parasympathetic innervation
Reduce heart rate
Sequence of conduction
SA node pacemaker that initiates each heartbeat and determines the heart rate
Signals from the SA node spread throughout the atria
AV node acts as an electrical gateway to ventricles fiber skeleton acts as an insulator to prevent currents from getting to ventricles
AV bundle is pathway by which signals leave AV node
Purkinje fibers are nerve like and distribute the electrical excitation to cardiocytes of the ventricles
Sinus rhythm
Normal heartbeat triggered by the SA node
Pacemaker potential
Cells of the SA node slowly drift upward showing a gradual depolarization
Cardiac muscle duration
Long duration for action potential contraction and absolute refractory period
Skeletal muscle duration
Short action potential contraction absolute refractory period
Pressure in the atria and ventricles during ventricular filling
Ventricles expand pressure drops below that of the atria AV valves open blood flows into ventricles causing ventricular pressure to rise and atrial to fall
Pressure in the atria and ventricles during ejection
Ventricular pressure exceeds arterial pressure and forces semi lunar valves open
Dicrotic notch
Ventricular diastole blood from the aorta and pulmonary trunk briefly flow through the semi lunar valve’s
Backflow quickly fills creating a slight pressure rebound that appears as the notch of the aortic pressure curve
Stroke volume
Amount of blood each ventricle ejects about 70
End diastolic volume
At the end of ventricular filling each ventricle contains an EDV of about 130 mL of blood
End systolic volume
Blood remaining behind in ventricles
Cardiac output
Amount of blood ejected by each ventricle
Heart rate
Counting the number of pulses in 15 seconds multiply by four to get beats per minute
Positive inotropic agents
Raises heart rate
Negative inotropic Agents
Lowers heart rate
Cardiac reserve
Difference between maximum and resting cardiac output
Preload
Amount of tension in the ventricular myocardium immediately before it begins to contract
Frank starling law of the heart
The more the ventricles are stretched The harder they contract on the next beat
Contractility
How hard the myocardium contracts for a given preload cardio sites more responsive to stimulation
How do positive negative inotropic agents affect contractility
Positive increases contractility negative decreases
What is afterload
Sum of all forces a ventricle must overcome before it can Eject blood blood-pressure opposes the opening of these valves and thus limits stroke volume
