the ability of an organism to sense and react to changes in its body illustrates

ATI RN

ATI Anatomy and Physiology Online Practice

1. The ability of an organism to sense and react to changes in its body illustrates

A. circulation.
B. respiration.
C. responsiveness.
D. absorption

Correct answer: C.

Rationale: The correct answer is 'responsiveness.' Responsiveness refers to the ability of an organism to detect and respond to stimuli in its environment. In this context, it specifically relates to an organism's ability to sense and react to changes within its body. Choices A, B, and D are incorrect. Circulation refers to the movement of fluids within an organism, respiration is the process of exchanging gases, and absorption is the uptake of substances by cells or tissues.

2. Which of the following electrolytes plays an essential role in the clotting of blood?

A. sodium
B. magnesium
C. calcium
D. potassium

Correct answer: C

Rationale: Calcium plays an essential role in the clotting of blood by being involved in several steps of the coagulation process. It is necessary for the conversion of prothrombin to thrombin, which is a crucial step in forming blood clots. Sodium, magnesium, and potassium do not directly participate in the clotting cascade and are not associated with the coagulation process. Therefore, the correct answer is calcium.

3. In all organisms, what is the basic unit of structure and function?

A. the atom
B. the molecule
C. the macromolecule
D. the cell

Correct answer: D

Rationale: The correct answer is 'the cell.' Cells are considered the basic unit of structure and function in all living organisms. While atoms are the smallest units of matter, they do not represent the basic unit of structure and function in organisms. Molecules are made up of atoms and can vary in size and complexity, but they are not the fundamental unit of life. Macromolecules are large molecules essential for life processes, but they are composed of atoms and do not function as the basic unit of structure and function in organisms. Therefore, the cell, with its organelles and specialized functions, is the correct answer.

4. Which of the following is not an example of a homeostatic mechanism in the human body?

A. Shivering when the body temperature falls below normal.
B. Increasing heart rate and force of contraction when blood pressure falls.
C. Retaining fluid excessively.
D. Secreting insulin after a meal to return blood sugar concentration toward normal.

Correct answer: C

Rationale: The correct answer is C. Homeostatic mechanisms aim to maintain internal stability within the body. Choices A, B, and D all represent examples of homeostatic mechanisms. Shivering helps generate heat to raise body temperature back to normal levels. Increasing heart rate and force of contraction work to restore blood pressure. Insulin secretion after a meal helps regulate blood sugar levels. On the other hand, retaining fluid excessively can lead to fluid imbalance rather than maintaining internal stability, making it the incorrect choice.

5. Which of the following is a role of platelets in hemostasis?

A. formation of plugs
B. promotion of vasodilation
C. conversion of prothrombin to thrombin
D. activation of calcium

Correct answer: A

Rationale: Platelets play a crucial role in hemostasis by forming plugs to stop bleeding. Choice B is incorrect because platelets do not promote vasodilation; instead, they help in vasoconstriction. Choice C is incorrect as the conversion of prothrombin to thrombin is a function of the coagulation cascade involving various clotting factors, not platelets. Choice D is incorrect as platelets do not directly activate calcium; instead, they play a role in the activation of other clotting factors.