Biology Homework Chapter 23: The Circulatory System II
Textbook assignment: Chapter 23: Circulation, sections 7-15.
- 23.7 Arteries, veins, and capillaries have different characteristics to support their varied functions. Arteries are thick-walled carriers with strong smooth muscle which can contract or expand to regulate blood flow, capillaries are thin-walled osmotic diffusion systems, veins are thick-walled, but don't have as much smooth muscle tissue and do have valves to prevent back-flow.
- 23.8 Blood pressure decreases with distance from the heart. It causes the rhythmic stretching of the vessels (pulse). Blood flow in the capillaries, where oxygen and CO_2 are exchanged with surrounding tissues, drops to almost zero cm/sec.
- 23.9 Blood pressure measurements is normal at 120mm Hg for systolic contractions and 70mm Hg for diastolic pressure (normal atmospheric pressure is about 760mm Hg). Deviations measured with a sphygmomanometer can be used to determine health problems.
- 23.10 The smooth muscle contractions of the arteries supports blood flow at distances from the heart; sphincters in the capillaries regulate the amount of blood flowing at any one time.
- 23.11 Thin walls in the capillaries allow water to diffuse through; some particles move through holes in the capillaries while others move across by exocytosis. Blood pressure pushes fluids out of the system, osmosis draws it in. This system uses negative feedback to keep concentration levels within acceptable boundaries: the rate of transport drops as concentrations rise.
- The lymphatic system absorbs and directs fluids that don't return directly through the capillaries the blood vessels. The lymph vessels dump this fluid back into the blood vessels at specific locations in the body so that the fluid can be filtered for wastes.
- 23.12 Blood includes cells (45%) and plasma (55%).
- Plasma is mostly water, but also carries hormones, electrolytes (charged or ionized minerals), critical proteins, clotting agents (platelets), and the red and white blood cells themselves.
- Red cells (erythrocytes) transport oxygen to cells, and carry some CO2 away from cells as waste. The "inner tube" shape maximizes the surface-to-volume ratio to facility rapid transport of oxygen across the cell membranes. Red cells are manufactured in the bone marrow. As they mature, they lose their nuclei, so by the time they are released into the blood system, they no longer have any nuclear DNA, and can't reproduce by mitosis. They also don't live longer than about 4 months, so your body must constant manufacture more.
- White blood (leukocytes) cells (also produced in the bone marrow) act as immunity agents.
- 23.13 The kidneys sense the amount of red blood cells in the blood they treat and release hormones to stimulate production as necessary. Too few blood cells creates a condition called anemia (this can also be caused by low iron amounts), where the blood does not carry enough oxygen for normal metabolic functions. Too many blood cells can also create "thick" blood, increasing blood pressure, stress on the heart, heart failure or stroke. High blood cell count is usually the result of blood doping, or taking drugs to increase athletic performance.
- 23.14 Blood clots when platelets exposed to air (usually because of an injury that breaks a blood vessel or capillaries) release hormones that cause platelets to stick together, forming complex fibrin plugs. Multiple proteins are involved in stimulating clotting, and genetic mutations in any one of the proteins can impair the clotting function (hemophilia).
- 23.15 Multipotent stem cells are cells that are not yet differentiated into a particular function. They offer ways to treat individuals with different diseases, including leukemia, a form of cancer that causes high levels of leucocytes, leading the body to attack itself over time. Until very recently, stem cells research was limited to only a few strains before ethical concerns shut down harvesting aborted fetuses for their stem cells. However, this limitation causes American scientists to seek ways to create stem cells from adult cells (since harvesting from grown adults is not harmful to the individual). As a result, medical techniques were developed so that doctors could use a patient's own stem cells to replace immune systems in the aftermath of cancer treatment, avoiding immune system rejection of foreign cells.
Read the following weblecture before chat: Blood
Take notes on any questions you have, and be prepared to discuss the lecture in chat.
Perform the study activity below:
Chat Preparation Activities
- Essay question: The Moodle forum for the session will assign a specific study question for you to prepare for chat. You need to read this question and post your answer before chat starts for this session.
- Mastery Exercise: The Moodle Mastery exercise for the chapter will contain sections related to our chat topic. Try to complete these before the chat starts, so that you can ask questions.
- Required: Complete the Mastery Exercise with a score of 85% or better.
- Optional: Test yourself with the textbook multiple choice questions and note any that you miss that still don't make sense. Bring questions to chat!
- Go to the Moodle and take the quiz for this chapter.
Read through the lab for this week; bring questions to chat on any aspect of the lab, whether you intend not perform it or not. If you decide to perform the lab, be sure to submit your report by the posted due date.
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