Circulatory Systems Flashcards
What maximizes surface area for gas exchange?
tracheae, gills, and lungs
Open circulatory systems
the blood or circulating fluid is not kept separate from the tissue fluid so a pump helps propel the fluid into vessels and the fluid leaves the vessels to trickle through the tissues
-arthropods, mollusks, and other invertebrates use this
Pros/cons of open circulatory systems
-pros: work well for circulation of nutrients and waste
-cons: not rapid and efficient for gas exchange if metabolic rate is high
Tracheal system
puts a limit on the size of the organism bc passive diffusion of gases down the tubes can only go so far
Closed circulatory system
-keeps the blood and tissue fluid separate
-one or more muscular hearts and a branching network of vessels move the blood
-direction of blood flow is controlled by one-way valves
Advantages of closed circulatory system
-blood flow, nutrient delivery and waste removal are more rapid
-closed systems can regulate blood flow to specific tissues
-cellular elements and large molecules that aid in transport can be kept within the vessels
Components of blood
RBCs, WBCs, and platelets
Hematocrit
a measure of the cellular portions as a percentage of the total blood volume
Plasma
contains gases, ions, nutrients, proteins, hormones, and other stuff
Blood cells
made from pluripotent stem cells in the bone marrow
-lymphocytes, monocytes, erythrocytes, and platelets
Erythrocytes
biconcave, flexible discs packed w/ hemoglobin which carries O2
Platelets
broken off cell fragments from megakaryocytes (stem cells in bone marrow) that contain enzymes and chemicals necessary for blood clotting
Clotting
- vessel damage
- vascular spasm
- platelet activation (plug)
- conversion of prothrombin to thrombin
- activates polymerization of fibrinogen into fibrin threads
- forms a meshwork to stabilize plug and provide a base for scar tissue
Hemophilia
genetic disorder in which one or more of the clotting factors do not work
Capillary beds
lie between arterioles and venules and exchange materials btwn blood and tissue fluid thru their thin walls
Precapillary sphincters
made of smooth muscles at the entrance to capillary beds that regulate blood flow into capillaries
fenestrations
fine holes in capillary walls, small molecules leak through but large molecules are retained
Blood pressure…
squeezes water and small solutes out of the capillaries
Osmotic pressure…
draws water back into the capillary w/ HCO3- and CO2
How is blood flow regulated in veins?
contraction of skeletal muscle pushes blood toward heart because one-way valves in veins prevent backflow
Varicose veins
when the veins become stretched and valves can no longer do their job > increased blood
African lungfish
-modified gill arteries: direct some of the blood coming from the heart to the lung and a new vessel carries oxygenated blood from the lung back to the heart
-divided atria keeps blood streams separate
Ventricle and arterial contraction
- atria contract
- ventricles contract, AV valves close, pressure in ventricles builds up until aortic and pulmonary valves open
- blood is pumped out of ventricles into aorta and pulmonary artery
- ventricles relax, pressure in ventricles fall, pressure is greater in aorta, aortic and pulmonary valves close
- Ventricles fill back up with blood
What is the primary pacemaker of the heart?
sinoatrial node (located at the juncture of the superior vena cava and the right atrium)
What does a normal heartbeat begin with?
an AP in the SA that spread through the atrial cells causing them to contract in unison
Atrioventricular node
stimulated by depolarization of the atria; generate and conduct APs to the ventricles through Bundle of His (to Purkinje fibers)
What do Purkinje fibers do?
evenly distribute the AP throughout the ventricular muscle
Why do the ventricles contract after the atria?
because of the delay in action potentials from the SA node and AV node
Ventricular muscle cell action potentials (2 phases)
- initiated by voltage-gated NA+ channels opening
- voltage-gated Ca2+ channels open and don’t close quickly allowing ventricular muscle cells to continue contracting
Atherosclerosis
What: smooth internal lining of arteries becomes damaged and deposits of lipids and cholesterol (plaque) can form; plaque becomes infiltrated w/ fibrous connective tissue and calcium deposits, which makes the artery wall less elastic and narrows the lumen of artery
Result: heart attack or stroke
Thrombus
blood clot made of platelets and pieces of plaque broken off
Types of strokes
- Ischemic: an embolus lodges in the brain and block blood flow
- Hemorrhagic: rupture of a blood vessel in the brain
Good cholesterol vs bad cholesterol
good: high-density lipoproteins (reduce deposition of cholesterol in arterial plaques)
bad: low-density lipoproteins (increase deposition)
