Download Cardiovascular System Notes

Cardiovascular System Notes
Basics
 CVS is composed of the heart & blood vessels
 Cardio- = heart
 -vascular = blood vessels
 Basic path: arteries arteriolescapillariesvenules veins
Pulmonary circuit: sends deoxygenated blood to the lungs to get O2 and get rid of CO2
Systemic Circuit: sends O2-rich blood & nutrients all over body; removes wastes
Path of blood
1. O2- poor blood to right atrium
2. Right atrium to right ventricle
3. Right ventricle pumps to lungs
4. Lungs to left atrium
5. Left atrium to left ventricle
6. Left ventricle to body
Structure of heart
 Hollow, cone-shaped muscular pump
 In thoracic cavity, on top of the diaphragm
 Size: approx. 14 cm long by 9 cm wide
 Pericardium = covering around heart
 Heart wall = epicardium (outer layer); myocardium (muscular middle layer); endocardium (inner
layer)
Chambers
 2 atria on top; thin walls; receive blood
 2 ventricles on bottom; thicker walls; pumps blood out into arteries
 Septum: wall that separates left & right sides
Valves
 Function: to ensure one-way blood flow
 A-V (atrioventricular) valves: tricuspid & mitral
o Tricuspid: on right; 3 cusps (flaps)
o Mitral: on left; a.k.a. bicuspid; only 2 cusps
 Pulmonary valve: between right ventricle & pulmonary artery; 3 cusps
 Aortic valve: at base of aorta and top of left ventricle; 3 cusps
Blood Supply
 Coronary arteries: First 2 branches of aorta; provide for the capillaries of the myocardium
 Cardiac veins: remove blood from myocardial capillaries
 Coronary sinus: empties into right atrium
Cardiac cycle
 Systole = contraction
 Diastole = relaxation
 Cycle = atrial systole / ventricular diastole ventricular systole / atrial diastole  both relax = a
complete heart beat
Heart sounds
 Through a stethoscope sounds like “lubb-dupp”
 Lubb = ventricular contraction; A-V valves closing
 Dupp = ventricular relaxation; pulmonary & aortic valves closing
 Murmur = abnormal heart sounds
Functional Syncytium
 Mass of merging cells that function as a unit
 Atrial walls and ventricular walls
Cardiac conduction system
 Fibers that initiate and distribute impulses throughout the myocardium
 Coordinates cardiac cycle
Sinoatrial node (S-A node)
 In right atrium near superior vena cava
 Initiates impulses that spread into myocardium and cause cardiac contractions
 A.k.a. the pacemaker
The Path
 S-A note  atrial syncytium  junctional fibers  A-V node  A-V bundle  bundle branches 
Purkinje fibers  ventricular syncytium
Electrocardiogram (ECG or EKG)
 Recording of electrical changes during cardiac cycle
 Muscle fibers are polarized between cycles
 P wave = depolarization of ventricles
 T wave = ventricles repolarizing
 P-Q interval = time between beginning of P
wave and beginning of QRS complex; time for
impulse to travel from S-A node through A-V
node
Regulation of Cardiac Cycle
 cells need more blood during certain times, like
strenuous exercise
 Parasympathetic or sympathetic nerve fibers
“tell” the heart to increase heart rate
 Temperature changes can affect HR (colder =
slower HR)
 Ions affect HR (Ca+2, K+)
Blood Vessels
 Closed circuit
 Tubes that carry blood from the heart to the cells and back
 Includes: arteries, arterioles capillaries, venules, veins
Arteries & Arterioles
 Carry blood away from the heart
 Under high pressure
 Arteries are larger
 Arterioles are smaller and branched
 Contain muscle in the artery wall
 Vasoconstriction: contraction of the artery
 Vasodilation: increase diameter of the vessel
 Aorta = largest diameter artery
Capillaries
 Smallest diameter blood vessel
 Connect to arterioles and venules
 Where exchange of gases and nutrients happens between blood and cells
 Happens by osmosis, diffusion and filtration
Veins and venules
 Carry blood back to heart
 Veins are larger than venules
 Lower pressure than in arteries and arterioles
 Less muscle in the wall than arteries
 Many contain valves
Blood pressure
 Force blood exerts against the inner walls of blood vessels
 Systolic pressure: max pressure during ventricular contraction
 Diastolic pressure: lower pressure during ventricular relaxation
 Influenced by stroke volume / cardiac output, blood volume, peripheral resistance, viscosity
 Normal = 120 / 80 (+/ - 20)