Dr. O'Quin Notes 4/25, 4/27
Dr. O'Quin Notes 4/25, 4/27 Bio 152
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This 7 page Class Notes was uploaded by Alena Comley on Monday May 2, 2016. The Class Notes belongs to Bio 152 at University of Kentucky taught by Dr. O'Quin in Spring 2016. Since its upload, it has received 8 views. For similar materials see Introductory Biology II in Biology at University of Kentucky.
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Date Created: 05/02/16
HEART STRUCTURE AND HEART FUNCTION Heart Evolution Animals with closed circulatory systems have hearts with at least two chambers: an atrium and a ventricle o The atrium is thin-walled and receives blood from the body o The ventricle is a thick-walled compartment that generates the force needed to propel blood throughout the body At the base of the vertebrate tree- fishes o In fishes, the circulatory system forms a single circuit- one loop to the gills and the body o Fishes have a two- chambered heart with one atrium and one ventricle o Blood pressure drops as the blood moves across the gills, however, it remains high enough to move through the rest of the circuit Next- land dwelling vertebrates CLICKER #1 In regards to circulation, what is an issue you think organisms faced with the move onto land? Drier atmosphere The force of gravity Changing seasons More direct sunlight ANSWER: B- the force of gravity With the move onto land, gravity caused problems with blood flow to elevated portions of the body As a result, we see the evolution of two separate pumping circuits: pulmonary and systemic o Pulmonary circulation is a lower-pressure circuit to and from the o Systemic circulation is a higher-pressure circuit to and from the rest of the body Amphibians have a three-chambered heart with two atria and one ventricle Their ventricle is not divided, so there is a mixing of oxygenated and deoxygenated blood Next- turtles, lizards, and snakes o They possess a two circuit, three chambered heart as well o They have a partially divided ventricle, which helps to minimize the mixing of blood o Another unique feature they have is a bypass vessel that helps to shunt blood away from pulmonary circulation and to systemic circulation when the organism is underwater and not breathing o In the lineage leading to crocodiles and birds, we see a two circuit, four-chambered heart o In crocodiles, we see two ventricles, however, we still observe the bypass of pulmonary circulation o Birds have two circuits and four chambers o This is also observed in mammals CLICKER #2 Which organism below has a partially divided ventricle and a lung bypass? o Fish o Crocodile o Frog o Turtle ANSWER: D- turtle Human Heart o Pulmonary circuit/circulation o Blood enters the right atrium on return from the body through the vena cava o Blood enters the right ventricle o Blood is pumped to the lungs from the right ventricle through the pulmonary artery o Next is systemic circulation o Blood returns to the left atrium form the lungs through the pulmonary veins o Blood enters the left ventricle o Blood is pumped to the body from the left ventricle through the aorta o Back to step 1 CLICKER #3 Where does blood flow after it leaves the left atrium? o Pulmonary veins o Left ventricle o Right atrium o Aorta ANSWER: B- left ventricle o If heart valves are damaged, blood can backflow and can be heard as a heart murmur o The fetal heart contains two shunts: the foramen ovale and the ductus arteriosis that allows the fetal blood to bypass the lungs o The partial pressures of gases vary throughout the human circulatory system Like other muscle cells, cardiac muscle cells contract in response to electrical signals In vertebrates, a group of cells called pacemaker cells are responsible for generating the initial electrical signal o These cells are located in the sinoatrial (SA) node CLICEKR #1 Why is the electrical signal delay important? A. It prevents deoxygenated blood from mixing with oxygenated blood. B. It allows the atria and ventricles to contract at the same time. C. It allows the ventricles to fill with blood from the atria before they contract. D. It allows the valves to open. E. Both A and B ANSWER: C- It allows the ventricles to fill with blood from the atria before they contract Cardiac muscle cells have specialized structures called intercalated discs o The discs form cell-to-cell connections that allow electrical signals to pass directly from one cardiac muscle cell to the next As blood moves through the capillaries, blood pressure drops dramatically This is because the total-cross sectional area of the vessels is higher in the capillaries than in the arteries A change in velocity is also observed because the same amount of blood is going through a larger area This feature is especially important because slower blood flow through the capillaries allows time for gas exchange to occur CLICKER #2 In the capillaries, velocity _____ because total cross sectional area _______. A. Increases; increases B. Increase; decreases C. Decreases; increases D. Decreases; decreases ANSWER: C- Decreases; increases Remember that homeostatic systems have three components- let's talk about these components in the context of blood pressure homeostasis Sensor: pressure-sensing receptors called baroreceptors detect changes in blood pressure o Their location in the arteries going towards the head is logical given that preserving blood flow to the brain (which is also the most elevated part) is important Integrator: the brain initializes a rapid three-component effector response if blood pressure drops Effector: (1) cardiac output increases via an increase in heart rate and increase in stroke volume o (2) arterioles constrict and divert blood to critical organs o (3) veins constrict, shifting blood volume to the heart and arteries to maintain flow to the organs This response is coordinated by the sympathetic nervous system and by hormones CLICKER #3 Which of the following does not happen to restore homeostasis when blood pressure drops? A. Veins dilate B. Stroke volume increases C. Blood is diverted to critical organs D. Heart rate increases ANSWER: A- Veins dilate Cardiovascular disease is a group of ailments that affect the heart and blood vessels o It is the number one cause of death in humans worldwide o Factors contributing to cardiovascular disease include age, tobacco use, poor diet, obesity, inactivity, and genetics o Arteriosclerosis occurs when blood vessels harden or lose elasticity o High-fat diets and the lack of physical activity can also cause the deposition of fatty plaques on the walls of the vessels o These two factors together (high-fat diets and lack of physical activity) cause increased blood pressure which weakens the arteries o Myocardial infarction occurs when the arteries that deliver blood and oxygen to the heart become blocked
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