Cardiovascular System Pt.1 Flashcards
What is the main function of the CV system
Transport of nutrients, water, gases, wastes, immune cells, and hormones
What are the 2 main circulatory paths
Pulmonary (heart-lungs-heart, deoxygenated to oxygenated) and systemic (heart-body/brain-heart, oxygenated to deoxygenated)
Where do arteries and veins move blood
Arteries move it away from the heart, veins carry blood towards the heart
What is blood composed of
Plasma (water, ions, amino acids, proteins, lipids, gases), and cellular components
What are the cellular components of blood
Erythrocytes (red blood cells), leukocytes (white blood cells), and platelets (cell fragments)
What is another word for cardiac muscle
Myocardium
What are cardiac muscle cells called
Cardiomyocytes (autorhythmic and contractile)
Where does the signal to contract in the heart originate
The sinoatrial (SA) node
How are cardiocytes connected
Electrically via gap junctions in intercalated disks and physically via desmosomes (keep cells from pulling apart)
What percent of myocytes are contractile
99%
What is the pacemaker potential in authorhythmic cells
I(f) channels open at -60 mV, permeable to potassium and sodium but net Na influx allows slow depolarization (slope determines HR)
What is the AP due to in voltage-gated Ca and K channels
Ca++ is what really depolarizes the cell
What are the 3 unique characteristics of contractile cell APs
2 types of K channels, voltage-gated Ca channels, and much longer duration/refractory period to prevent summation of twitches (so blood can pump properly)
What are the steps of contractile cell APs
Resting membrane potential about -90: 1) Na channels open, 2) Na channels close and fast K channels open, 3) Ca channels open, fast K close, some slow K open (causes plateau), 4) Ca channels close and more slow K channels open
How does the electrical signal get from the atria to the ventricles
From SA node via internodal pathways to atrioventricular (AV) node
What is the ventricular conducting system
AV bundle/bundle of His goes to bundle branches and then to Purkinje fibers (apex to base)
How is an electrocardiogram taken
Einthoven’s triangle
What is an electrocardiogam
Summed electrical activity of all heart cells
What are waves of ECGs
Deflections above or below the baseline (P,Q,R,S,T)
What are segments of ECGs
Sections between two waves (P-R, S-T, etc)
What are intervals of ECGs
Combinations of waves and segments (PR, QT)
What does the P wave correspond with
Atrial depolarization (tells atria to contract/systole)
What does the P-R segment correspond with
Conduction through the AV node and bundle
What does the QRS complex correspond with
Ventricular depolarization (tells ventricles to contract/systole)
What does the T wave correspond with
Ventricular repolarization (tells ventricles to relax/diastole)
When does atrial repolarization happen on an ECG
Not visible but during QRS complex
What is bradycardia
Slower than normal HR
What is tachycardia
Faster than normal HR
What is a heart arrhythmia
Skipped or dropped beats, extra beats (premature ventricular contractions), and fibrillation (loss of coordinated electrical signaling and unorganized contraction)
What is ischemia
Heart condition that leads to tissue damage as the result of lack of blood and oxygen flow
What is a conduction block
Affects electrical signal conduction (slower than usual or not able to get through necessary tissues)
What increases pressure in the heart
Contraction/systole
What are the events of the cardiac cycle
1) Late diastole, 2) Atrial systole, 3) Isovolumic ventricular contraction, 4) Ventricular ejection, 5) Isovolumic ventricular relaxation
What happens during late diastole in the heart
Both atria and ventricles are relaxed, blood fills the atria and ventricles via gravity (AV valves open)
What happens during atrial systole
Last bit of blood is pushed into ventricles so they are filled with their EDV (end diastolic volume)
What happens during early (isovolumic) ventricular contraction
Ventricular pressure rises, AV valves close, causing “lub” S1 sound
What happens during ventricular ejection
Ventricles contract, pressure increases, SL valves open and blood is pushed into arteries, ESV (end systolic volume) left in ventricles
What happens in ventricular relaxation
Ventricular pressure decreases, closing semilunar valves, and causing the “dup” S2 valve
When do AV valves close
When pressure in the ventricles is greater than in the atria
When do SL valves open
When ventricular pressure is greater than aortic pressure
What is the dicrotic notch
Increased aortic pressure caused by backward suction from SL valves closing
What is the equation for cardiac output
Stroke volume times HR
What is cardiac output (CO)
Volume of blood pumped out by one ventricle (usually left) per minute
What is stroke volume
Volume (mL) of blood pumped by a ventricle per contraction (EDV-ESV)
What is heart rate
Number of heart beats per minute (bpm)
How can the vagus nerve alter heart rate
Vagus nerve activates parasympathetic neurons, increasing K efflux and decreasing Ca influx, hyper polarizing cell, decreasing HR
How does the sympathetic nervous system and adrenal medulla affect heart rate
SNS and adrenal medulla activate sympathetic neurons, release NE onto B-1 receptors of autorhythmic cells, increasing Na and Ca influx, increasing rate of depolarization, increasing HR
What is stroke volume determined by
Force of contraction in ventricular myocardium
What is the force of contraction in ventricular myocardium influenced by (for stroke volume)
Contractility and muscle fiber length at beginning of contraction (EDV)
What is contractility
Forcefulness of contraction of individual ventricular muscle fibers (Ca interaction with troponin)
What effect does sympathetic innervation have on contractility
Increases force of contraction in contractile cells due to Ca increase
What does NE and E bind to in contractile cells
B-1 receptors
What happens once B-1 receptors are bound to
cAMP 2nd messenger system is activated, phosphorylating voltage-gated Ca channels (increasing time they’re open) or phospholamban (increasing CA ATP-ase on SR and storing more CA in the SR)
What is the Frank-Starling law
Stroke volume increases as EDV increases because of preload (degree of stretch)
What is venous return
Amount of blood entering the heart through veins (influenced by skeletal muscle pump, respiratory pump, and venoconstriction)
What is the skeletal muscle pump
As muscles contract, they compress veins and force blood back to the heart (valves prevent back flow)
What is the respiratory pump
When the chest cavity decreases in volume, blood gets pushed into the heart
What pathway is activated by B-1 receptors to cause venous constriction
PLC-IP3 pathway
