The Cardiovascular System: The Heart Flashcards
Describe size and location of heart
a. Approx size of fist
b. Superior of diaphragm, between lungs
c. 2/3 to the left, 1/3 to the right
Name the protective sac of the heart
Pericardium
Two atria are separated by; two ventricles are separated by
a. Interatrial septum
b. Interventricular septum
What covers outer atria? What is their function
a. Auricules
b. Increase atrial volume, store extra blood
What encircles the junction of the atria and ventricles?
a. Atrioventricular groove
b. aka. AV groove or coronary sulcus
The Atria are also known as
receiving chambers
Walls of the atria are ridged by what muscles?
Pectinate muscles
Name the vessels entering the right atrium
a. Superior vena cava
b. Inferior vena cava
c. Coronary sinus
Name the vessels entering the left atrium
Right and left pulmonary veins
The Ventricles are also known as
The pumping (discharging) chambers
Walls of the ventricles are ridged by what?
Trabeculae carneae
What anchors the chordae tendineae?
Papillary muscles
What attaches the papillary muscles to the AV valves?
Chordae tendineae
What is the purpose of atrioventricular (AV) valves?
Prevent backflow into the atria when ventricles contract
What are the two atrioventricular (AV) valves?
a. Tricuspid valve (right)
b. Bicuspid/Mitral valve (right)
What connects the AV valve cusps to the papillary muscles?
Chordae tendineae
What is the purpose of semilunar valves?
Prevent backflow into the ventricles when ventricles relax.
What are the two semilunar valves?
a. Aortic semilunar valve
b. Pulmonary semilunar valve
Name the two heart pumps and name of their circuit tracts
a. Right: pulmonary circuit- carries blood to and from the lungs
b. Left: systemic circuit- carries blood to and from all body tissues
Describe pathway of blood through the heart
vena cavae > right atrium > tricuspid valve > right ventricle > pulmonary semilunar valve > pulmonary trunk > pulmonary arteries > LUNGS > pulmonary veins > left atrium > bicuspid valve > left ventricle > aortic semilunar valve > aorta > systemic circulation > venous return to vena cavae
Name the serous pericardium and heart wall layers from superficial to deep
a. Pericardium layers:
i. Fibrous pericardium layer: protects, anchors, and prevents overfilling
ii. Parietal pericardium layer
iii. Visceral pericardium layer/epicardium
b. Heart wall layers:
i. Visceral pericardium layer/epicardium
ii. Myocardium: thick, spiral bundles of cardiac muscle cells
iii. Endocardium: lines the chambers, continuous with endothelium (tunica intima) of blood vessels
What is the function of coronary circulation
Feed or provide functional blood to the heart muscle itself
Name the arteries and veins of the coronary circulation and destination
a. Arteries: Right and left coronary artery (in atrioventricular groove or coronary sulcus) carry oxygenated blood to the myocardium for gas exchange
b. Veins: Smaller veins travel through the myocardium and end up in the great cardiac vein. Great cardiac vein enters the coronary sinus
Name and describe two homeostatic imbalances
a. Angina pectoris- thoracic pain caused by deficiency in blood (ischemia) delivery to the myocardium
b. Myocardial infarction (heart attack)- prolonged ischemia/hypoxia, areas of cell death repaired with noncontractile scar tissue
Describe muscle cells aka fibers
a. Striated, bifurcated, and interconnected
b. 25-33% of volume is mitochondria
Describe why cardiac muscle behaves as a functional syncytium
a. Intercalated discs, desmosomes prevent cell from separating
b. Gap junction allows ions to pass; electrically couple adjacent cells ensure cells fire together
Depolarization of the heart is _____ and ________.
a. Autorhythmic
b. Spontaneous
What percentage of cardiac cells have automaticity? What are their names?
a. About 1%
b. Pacemakers
Describe the cardiac muscle contraction
a. Depolarization opens fast Na+ channels in the sarcolemma
b. Reversal of membrane potential from -90 mV to +30 mV
c. Depolarization also opens slow Ca2+ channels in the sarcolemma
d. Ca2+ surge prolongs the depolarization phase (plateau)
e. Repolarization results from inactivation of Ca2+ channels and opening of K+ channels
What is the intrinsic cardiac conduction system?
A network of non-contractile (autorhythmic) pacemaker cells that initiate and distribute impulses to coordinate the depolarization and contraction of the heart
Describe the autorhythmic action potential
a. Autorhythmic cells have unstable pacemaker potentials due to slow Na+ channels that remain open aka Na+ drip(always being depolarized)
b. When the pacemaker potential reaches threshold (-40 mV), Ca2+ channels open
c. Rapid Ca2+ influx produces the spike of the action potential
d. Repolarization results from inactivation of Ca2+ channels and opening of K+ channels
What is another word for cardiac contraction and relaxation?
a. Sytole – contraction
b. Diastole – relaxation
What percentage of blood flows passively into ventricles vs being delivered by atrial?
a. 80% passive
b. 20% delivered
Describe Sinoatrial (SA) node
a. Depolarizes faster than any other part of the myocardium, setting a sinus rhythm
b. Generates impulses about 75 times/minute
c. AP’s generated every 0.8 sec (=800 ms)
d. Electrical signal sent from SA node take 100ma to travel across both atria
Describe Atrioventricular (AV) node
a. Turned on by atrial activity
b. Delays impulses from SA node approximately 0.1 second = 100ms
c. Depolarizes 50 times per minute in absence of SA node input (junctional rhythm). Fires 75bpm if SA node is working.
d. Sends signal to AV bundle (of HIS)
Describe Atrioventricular (AV) bundle (bundle of His)
a. Only electrical connection between the atria and ventricles
b. Sends signal down left and right bundle branches
Describe Right and left bundle branches (of bundle of His)
Two pathways in the interventricular septum that carry the impulses toward the apex of the heart
Describe Purkinje fibers
a. Complete the pathway into the apex and ventricular walls
b. AV bundle and Purkinje fibers depolarize only 30 times per minute in absence of AV node input.
c. Extend into papillary
Describe sequence of cardiac electrical excitation
a. Sinoatrial (SA) node generates impulses
b. The impulses pause (0.1 sec) at the Atrioventricular (AV) node
c. Atrioventricular (AV) bundle (bundle of His) connects the atria to the ventricles
d. Right and left bundle branches conduct the impulses through the interventricular septum
e. Purkinje fibers depolarize the contractile cells of both ventricles
Name heart sounds and what they are associated with
a. Lub- AV close and beginning of ventricular systole
b. Dub- SL valves close at the beginning of ventricular diastole
Name of abnormal heart sounds and what they indicate
a. Heart murmurs
b. Valve problems
Defects in the intrinsic conduction system may result in what?
a. Arrhythmias: irregular heart rhythms
b. Fibrillation: rapid, irregular contractions; useless for pumping blood
A defective SA node may result in what?
Ectopic focus- abnormal pacemaker takes over
A defective AV may result in what?
Heart block- Few or no impulses from Sa node reach the ventricles. Results in few or no impulses from SA node reaching the ventricles.
The heartbeat is modified by the _______ system.
ANS
Cardiac centers located in the medulla oblongata innervate where?
a. Cardioacceleratory center innervates SA and AV nodes through sympathetic neurons
b. Cardioinhibitory centers inhibits SA and AV nodes through parasympathetic fibers in the vagus nerves
What is an electrocardiogram (ECG or EKG)?
A composite of all the action potentials generated in the heart (3 waves)
Name each wave of the electrocardiogram and it’s significance
a. P wave: depolarization of SA node
i. Atria systole
ii. Ventrical diastole
b. QRS complex: Ventricular depolarization
i. Atria diastole
ii. Ventrical diastole
c. T wave: Ventrical repolarization
i. Both diastole
What is cardiac output (CO) and how do you calculate it?
a. Volume of blood pumped by each ventricle in one minute
b. CO= heart rate (HR) x stroke volume (SV)
i. HR= number of beats per minute
ii. SV= volume of blood pumped out by a ventricle with each beat
Equation of cardiac output (CO) at rest, maximal, and minimal
a. Co (ml/min) = HR (75 beats/min) x SV (70 ml/beat) = 5.25 L/min
b. Maximal Co is 4-5x resting in a nonathletic person
c. Maximal CO may reach 35 L/min (6-7x resting) in trained athletes
Describe Frank-Starling law of the heart
a. Discusses degree of stretch of cardiac muscle cells before they contract
b. Increased venous return distends (stretches) the ventricles and increases contraction force, thus increasing stroke volume
What are some simple factors that influence heart rate?
a. Age
b. Gender
c. Exercise
d. Body temperature
Describe two homeostatic imbalances based on BPM
a. Tachycardia: abnormally fast heart rate (>100 bpm)
i. May lead to fibrillation if persistent
b. Bradycardia: heart rate slower than 60 bpm
i. May result in grossly inadequate blood circulation
ii. May be desirable result of endurance training
Describe two fetal heart structures that bypass (shunt) pulmonary circulation
a. Foramen ovale- connects the two atria (close at 1 year old)
1. Patent foramen ovale means foramen didn’t close and could lead to migranes
b. Ductus arteriosus- connects the pulmonary trunk and the aorta
1. Turns into ligamentum arteriosum
What is located between the parietal pericardium layer and visceral pericardium layer?
The pericardial cavity filled with pericardial fluid. Function is to decrease friction. Pericardial cavity is not considered a layer, so if he asks for the 3rd pericardium layer on the test, the answer would be the visceral pericardium layer.
What is the name for a long rest period in cardiac muscle contraction?
Absolute refractory period
