Lecture 6:
Animal of the day: frog: African clawed frog, xenopus
· Found in fresh water lakes n streams, vegetarian but will take in animal protein, omnivores, love liver
· Spend entire life in water derive major oxygen supply from air, have lungs.
o Breating and pulling air into lungs is their main way of getting oxygen, lose co2 through the skin. Skin is highly vascular
· Skin secretes slimy smelly mucus, allows for escape, also have antibiotic effects,
· All vertebrate grops have closed circulatory system
· Many invertebrates have open circulatory system, although few have closed
· Open circulatory systems in insectes have a heart that is a long tube that stretches from the posterior to the anterior end of the insect
o Opening of the hearts many of them, are called ostia
o Peristaltic heart. Contraction moves from posterior towards the anterior
§ Blood enters aorta in the anterior end, which carries blood into brain then circulatory system becomes open
o Eventually blood gets back to the heart and the cycle occurs again
· This is a very successful plan, insects have been alive for a long time longer than us, so it has to be successful.
o Our way of circulating blood isn’t the only successful way to transport blood
· Cockroaches have aloform muscles that can contract, these muscles are outside wall of the heart and the other end is connected to the inside wall of the exoskeleton
o These aloform muscles contract rhythmically, this causes the volume of heart decreasing pressure which will cause the sucking up of blood from the outside
· Crayfish a different class of athropods, heart is not a tube, its an organ that is limited to some extent, but also has ostia,
o Instead of being peristaltic these hears are contractile
· Muscles contract when the muscle fibers depolarize….
· Myogenic hearts is what humans have, the signal to contract arises from the muscle it self.
o removing a myogenic heart from animal: heart continues to contract for hours even days
· Neurgenic hearts, signal to contract arises from the nervous system
o Removing a neurgenic heart from the animal, heart doesn’t contract
· Flow, Q=Pressure/Resistance
o In a closes system resistance is high. And high pressure
o Open circulatory systems have low resistance
Reletive amounts of fluids and solids in vertebrate body
· Plasma is 5%, interstital is 20%, intracellular 45% - all water
· Solids make up 30%
Fraction of total blood volume occupied by red blood cells
· Very uncommon to find blood cells in open circulatory systems
o Humans have about 50 percent of hematocrit occupied by red blood cells
o Bats also have 50 percent, dogs have 42 percent, brids have about 40-60 %
o Turtles have 19%
