Circulation Flashcards
Week 11
What are circulatory systems used for?
Transporting oxygen and nutrients around the body and removing waste
What does the diversity in circulatory systems tell us about evolution?
That evolution does not follow overall optima, but local optima
What are the components of the circulatory system?
Heart, blood vessels and blood
What is the difference between arteries and veins?
Arteries carry blood away from the heart, veins carry blood to the heart
Why is the heart needed to act as a pump?
The second law of thermodynamics tells us that fluid moving along a vessel will inevitably stop
How does a heart create circulation?
By causing a pressure difference
How is the pressure inside the heart increased?
Muscle contractions
What is the heart’s contraction phase called?
Systole
What is the heart’s relaxation phase called?
Diastole
What is the difference between open and closed circulatory systems?
Closed systems have the blood enclosed in vessels at all times, wheras open systems have blood in vessels and in the hemocoel
What animals have an open circulatory system?
Insects, crustaceans, some molluscs and other invertebrates
What animals have a closed circulatory system?
Vertebrates and a few invertebrates
In the hemocoel, the combination of blood and interstitial fluid is called _____
Hemolymph
In open systems, what are ostia?
Small openings in the heart that allow blood to enter from the hemocoel
What does an insect plan look like?
One dorsal vessel, heart in abdomen (indestinguishable from dorsal vessel), blood pumped from posterior to anterior through the vessel
How can an insect’s circulatory system be so simple?
They breath through multiple trachea throughout the body surface, so they dont have to transport oxygen
What does a crustacean plan look like?
Simple heart pumps blood to hemocoel through 2 aorta. Collecting channels move blood to the gills to oxygenate and then to the space around the heart (not to the heart directly)
What does a bivalve (mollusc) plan look like?
Heart (2 atria, 1 ventricle), pumps blood through 2 aorta. Specialised vessels collect blood from gills.
What type of molluscs have a closed system?
Cephalopods
How many hearts does a cephalopod have?
Three: Two brachial hearts, one for each gill, and a systemic heart to pump blood to the body
What are capillaries?
Small blood vessels present in closed systems that deliver blood to tissues
Is pressure increased or decreased in capillaries?
Decreased pressure
Why do cephalopods need multiple hearts?
They are only simple and so produce a low differential pressure; one would be unable to distribute blood to both the gills and the body
How many chambers does a fish heart have? What are they?
4 chambers: sinus venosus, atrium, ventrical and bulbus arteriosus (conus arteriosus in sharks)
What is vertebrate circulatory apparatus divided into?
Respiratory and systemic circulation
Fish have a ‘single cycle circuit’. What does this mean?
Blood goes through respiratory and systemic circulation sequentially, without returning to the heart
What types of valves are present in a fish heart, keeping circulation in one direction?
Passive valves
How many chambers does an amphibian heart have?
What are they?
3 chambers: 2 atria and one ventricle
Amphibians are able to control how much deoxygenated blood goes into respiratory and systemic circulation. True or false?
True
In amphibians, where does gas exchange occur?
Lungs and skin
What might having one ventricle (amphibians and reptiles) lead to?
oxygenated and deoxygenated blood can mix
In amphibians, the skin delivers oxygenated blood to systemic veins. Why might this be beneficial?
It gives the blood supplying the heart a higher oxygen content, which is useful when the animal is underwater as the animal will be unable to use lungs but will still be able to use skin
How many chambers does a reptilian heart have? What are they?
3 chambers: 2 atria and one ventricle (ventricle has an incomplete septum).
Why is the incomplete septum in a reptilian heart beneficial?
It allows for less mixing of oxygenated and deoxygenated blood
How are crocodiles different from other reptiles?
They have a 4 chambered heart (complete septum between ventricles), but systemic arteries exit from both ventricles and connect, allowing for the blood to be selectively mixed
Mammals and birds have a ‘doulbe cycled circuit’. What does this mean?
Respiratory and systemic circulations are completely separate
In mammal and bird hearts, which ventricle is more muscular?
Left ventricle - maintains high pressure in systemic circulation
Which side of the heart pumps blood through respiratory circulation?
Right
Which side of the heart pumps blood through systemic circulation?
Left
What is pulmonary edema?
The alvioli in lungs become progressively filled with water
What is the Starling-Landis hypothesis?
There is a net loss of water from blood as it passes through the capillary network of tissues
What does complete ventricle separation allow for?
More efficient gas exchange in the lungs, and so more active lifestyles
O2 consumption ______ with exercise
Increases
What does Vo2 max stand for?
The maximal rate of oxygen consumption
What is vasodilation?
The diameter of blood vessels increase
What is vasoconstriction?
The diameter of blood vessels decrease
How does gravity affect blood pressure?
Increases pressure in the lower parts of teh body
How do tall animals combat the effect of gravity on blood?
Vasoconstriction in lower limbs when standing increases blood flow to the head; vasodilation when head is lowered to prevent too much blood flowing to the head
What do amphibians and reptiles use selective vasodilation for?
Direct blood to systemic tissues and away from lungs during diving
