When human tissue, such as skin or a blood vessel, is torn or cut, the cells in the damaged region secrete a signal that activates specialized blood cells called platelets in the vicinity. As the platelets come in contact with one another, they begin to form a clot and release ad- ditional chemical signals to attract more platelets as well as other clotting factors until the bleeding is stopped. Which of the following correctly describes the feedback mechanism illustrated by the acti- vation of the platelets? A It is an example of positive feedback because the initial activation of the platelets causes the activation of additional platelets. B It is an example of negative feedback because the initial activation of the platelets is caused by a harmful stimulus. C It is an example of positive feedback because the ultimate result of initial platelet activa- tion causes the bleeding to stop. D It is an example of negative feedback because the initial activation of the platelets causes the additional activation of different clotting factors.

When human tissue, such as skin or a blood vessel, is torn or cut, the cells in the damaged region secrete a signal that activates specialized blood cells called platelets in the vicinity. As the platelets come in contact with one another, they begin to form a clot and release ad- ditional chemical signals to attract more platelets as well as other clotting factors until the bleeding is stopped. Which of the following correctly describes the feedback mechanism illustrated by the acti- vation of the platelets? A It is an example of positive feedback because the initial activation of the platelets causes the activation of additional platelets. B It is an example of negative feedback because the initial activation of the platelets is caused by a harmful stimulus. C It is an example of positive feedback because the ultimate result of initial platelet activa- tion causes the bleeding to stop. D It is an example of negative feedback because the initial activation of the platelets causes the additional activation of different clotting factors.

Human Biology (MindTap Course List)

11th Edition

ISBN:9781305112100

Author:Cecie Starr, Beverly McMillan

Publisher:Cecie Starr, Beverly McMillan

Chapter8: Blood

Section: Chapter Questions

Problem 5SQ: Which of the following statements about red blood cells is false? a. They live about 120 days before...

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Which of the following statements about red blood cells is false? a. They live about 120 days before being replaced. b. They lack a nucleus and other organelles when they are mature. c. They are replaced when the hormone EPO stimulates stem cells in bone marrow. d. They are replaced as part of a negative feedback loop in which kidney cells monitor blood oxygen levels e. All the above statements are true except b, because all cells require a nucleus in order to function properly.
Low doses of aspirin are commonly used to reduce the risk of arterial thrombosis in patients who have suffered myocardial infarction. Which one of the following steps in hemostasis is inhibited by aspirin? Aggregation of platelets| Adhesion of platelets to collagen Production of tissue factor Synthesis of von Willebrand factor Synthesis of antithrombin III|
When a blood vessel is injured or severed, the process leading to hemostasis is initiated. The first step in this process is vascular spasm. Platelets contribute to vasospasm in small vessel beds by which of the following mechanisms? (a)Elaboration of vascular endothelial growht factor (b)Presence of actin and mysoin in platelet cytoplasm (c) Production of thromboxanne A2 (d) Release of thrombosthenin (e) Synthesis of prostaglandins
Figure 33.21 State whether each of the following processes are regulated by a positive feedback loop or a negative feedback loop. A person feels satiated after eating a large meal. The blood has plenty of red blood cells. As a result, erythropoietin, a hormone that stimulates the production of new red blood cells, is no longer released from the kidney.
Nifedipine is an antihypertension medication that is also used to reduce the workload on the heart. The study below compares the effects of two different types of capsules used to administer the drug to patients (GITSred line, and Cotracten Xblue line). Each graph shows changes with time following initial administra- tion of the capsules. Figure A compares the levels of nifedipine in the blood with each capsule type. The ability of the different cap- sules to reduce workload on the heart by altering blood pressure or heart rate is shown in Figures B and C, respectively. Are elevated plasma levels of nifedipine(above 10 ng/mL) required for the drug to perform its actions? Source: M. J. Brown and C. B. Toal. 2008. Formulation of long-acting nifedipine tablets influences the heart rate and sympathetic nervous system response in hypertensive patients. British Journal of Clinical Pharmacology 65:646652.
Nifedipine is an antihypertension medication that is also used to reduce the workload on the heart. The study below compares the effects of two different types of capsules used to administer the drug to patients (GITSred line, and Cotracten Xblue line). Each graph shows changes with time following initial administra- tion of the capsules. Figure A compares the levels of nifedipine in the blood with each capsule type. The ability of the different cap- sules to reduce workload on the heart by altering blood pressure or heart rate is shown in Figures B and C, respectively. Which type of capsule would you expect to have fewer side effects? Source: M. J. Brown and C. B. Toal. 2008. Formulation of long-acting nifedipine tablets influences the heart rate and sympathetic nervous system response in hypertensive patients. British Journal of Clinical Pharmacology 65:646652.
Which of the following is most directly responsible for the increasein capillary permeability during the infl ammatory reaction?a. pain c. histamineb. white blood cells d. tissue damage
AB negative blood can be and can not be donated to which blood groups? Explain with reason.
A chemical called EDTA, like citrate, binds to (or “chelates”) Ca2+. Suppose a person had EDTA infused into their blood. What effect would this have on the intrinsic and extrinsic clotting pathways? How would these effects differ from the effects of aspirin on blood clotting?
Referring to the figure shown, the movement of glucose is from the lumen of the duodenum through an interstitial cell, out to the extracellular fluid, and into a capillary. What would happen if the action of the Na+–K+ pumps was reduced? A)The rate of flow of glucose into the interstitial cells would be increased. B)The direction of flow of glucose would be reversed. C)The rate of flow of glucose into the interstitial cells would be reduced. D)Nothing would differ: the movement of glucose would be the same as before the reversal.
Which of the following are mechanisms which prevent clotting under normal circumstances? Select all that apply. platelets are not released into the bloodstream until needed heparin and anti-thrombin circulate in the bloodstream vessels are coated with prostacyclin which repels platelets clotting enzymes are not released into the bloodstream until needed rapid blood flow
Outline or briefly describe the sequence of events that leads to blood coagulation.