fish heart - replaced simple tubular hearts 

• tube w/ 4 chambers
  • atrium/sinus venosus - 1st 2 chambers, for collection
  • ventricle/conus arteriosus - last 2 chambers, for pumping
• order of contraction - sinus venosus >> atrium >> ventricle >> conus arteriosus
• blood passes through gills after going through heart >> much of pressure from pumping lost

amphibian/reptile heart - has 2 separate circulations due to lungs

• pulmonary circulation - between heart and lungs
• systemic circulation - between heart, rest of body
• allows for pumping fully oxygenated blood
• separated atriums prevent oxygenated/deoxygenated blood from mixing
• aorta - major artery of systemic circulation
• cutaneous respiration - breathing through the skin

mammalian/bird hearts - 4 chambered heart w/ separate atria/ventricles 

• right atrium receives deoxygenated blood >> right ventricle pumps blood to lungs
• left atrium receives oxygenated blood >> left ventricle pumps blood to body
• double circulation - atrium/ventricles contract at same time
• both ventricles must pump same amount of blood
• heartbeats start in sinoatrial node (able to depolarize w/o neural activation from brain)

cardiac cycle - 2 separate pumping systems in a single organ 

• diastole (rest) >> systole (contraction)
• atrioventricular valves - between atria/ventricles
  • prevents blood backflow
  • tricuspid valve - on right side
  • bicuspid (mitral) valve - on left side
• semilunar valves - between ventricles and arteries
  • pulmonary valve - on right side
  • aortic valve - on left side
• coronary arteries - first arteries off the aorta, supplies heart
  • superior vena cava - drains upper body
  • inferior vena cava - drains lower body
• sphygmomanometer - measures blood pressure
  • pressure must be large enough to push blood through capillaries, but not cause damage to arteries
  • systolic pressure - peak pressure during contraction
  • diastolic pressure - minimum pressure between heartbeats
  • hypertension - condition w/ very strong contractions
• SA node depolarization >> AV (atrioventricular) depolarization >> bundle of His depolarization >> Purkinje fiber depolarization >> ventricle contraction
  • pace-making cell - fire action potentials on their own periodically
  • fibers blocked >> atria/ventricles don’t beat together
  • electrocardiogram (ECG/EKG) - records the depolarization through the heart
  • P wave = atrial depolarization
  • QRS complex = ventricular depolarization
  • T wave = ventricular repolarization (covers up atrial repolarization)

cardiac output - blood volume pumped by each ventricle per minute 

• equal to amount of blood that travels through systemic/pulmonary circulations per minute
• increase heart rate, blood volume, vasoconstriction >> increase blood pressure
  • baroreceptors - sense blood pressure changes
  • antidiuretic hormone (ADH) - aka vasopressin, stimulates kidneys to hold more water
  • aldosterone - maintains Na+, water retention in kidneys
  • atrial natriuretic hormone - secreted by the heart, lowers blood volume/pressure by getting rid of Na+ and water
  • nitric oxide - causes blood vessels to relax/dilate

cardiovascular diseases - leading cause of death in US 

• arrhythmia - missing a heartbeat
• fibrillation - desynchronized contraction of cardiac fibers
  • atrial fibrillation - decreases filling of ventricles >> not fatal
  • ventricular fibrillation - decreases amount of blood pumped to body >> could be fatal
• heart attacks (cardial infarction) - due to lack of blood reaching a part of the heart
  • caused by blood clots
• angina pectoris “chest pain”, not as severe as a heart attack
• stroke - blood doesn’t reach the brain properly
  • effects depend on location of stroke in brain
• atherosclerosis - accumulation of fat, muscle, or cholesterol in arteries
  • reduces blood flow
• arteriosclerosis - hardening of arteries
  • calcium deposits in artery walls