Download BIOL 424 Circulation 1 I. Circulation A. Open

BIOL 424
Circulation 1
I. Circulation
A. Open
- most mollusks, all arthropods, invertebrate chordates
B. Closed
- jawed vertebrates, cephalopods
1. arteriovenous systems
2. ultrafiltration
3. lymphatic system
4. often divided
a. pulmonary
b. systemic
II. Vertebrate Heart
A. Chambers
1. fish
a. four chambers arranges in series
b. sinus venosus
c. bulbus arteriosus (bony fish)/conus arteriosus (elasmobranchs)
d. ventricle
2. amphibians
a. three chambers
b. transcutaneous respiration
3. non-crocodilian reptiles
a. five chambers
b. ventricle divided into 3 interconnected compartments
c. reptiles can shunt between circuits
4. birds and mammals
a. four completely separated chambers
b. no shunting between circuits except in utero
c. venae cavae empty into right atrium
B. Valves
1. AV valves
2. semilunar valves
a. pulmonary between right ventricle and pulmonary artery
b. aortic between left ventricle and aorta
C. Myocardium (3 types of fibers)
1. SA node fibers
a. weakly contractile
b. autorhythmic
c. slow conduction rate
2. bundle fibers
a. very large
b. in ventricular septum
c. fast conduction system
3. cardiomyocytes -bulk of heart
D. Heart wall
1. epicardium
2. myocardium
e. endocardium
III. Cardiac Cycle
A. Systole
1. atrial
2. ventricular
B. Diastole
C. Ventricular Systole
1. atria relaxed
2. ventricles contract--> pressure increases
- isovolumetric contraction
- ejection
3. AV valves closed
4. blood forced out of ventricles
a. portion of blood ejected
b. remaining volume is end-systolic volume
D. Ventricular diastole
1. pressure drops in ventricles to about 0 mmHg
- isovolumetric relaxation
2. blood flows from atria to ventricles
- rapid filling
3. atrial systole occurs just before ventricular systole
- completes ventricular filling end-diastolic volume