which structure serves as the electrical stimulator of the cardiac muscle

ATI TEAS 7

Science TEAS Practice Test

1. Which structure serves as the electrical stimulator of the cardiac muscle?

A. The sinoatrial node
B. The left ventricle
C. The aorta
D. The tricuspid valve

Correct answer: A

Rationale: The correct answer is the sinoatrial node. This node, also referred to as the pacemaker of the heart, is responsible for initiating the electrical impulses that stimulate cardiac muscle contractions. It plays a crucial role in setting the pace and rhythm of the heart's contractions. Choices B, C, and D (the left ventricle, the aorta, and the tricuspid valve, respectively) do not serve as the primary electrical stimulator of the cardiac muscle. While the left ventricle is a chamber of the heart that pumps oxygenated blood to the body, the aorta is the main artery that carries blood away from the heart, and the tricuspid valve is a one-way valve that ensures blood flows properly through the heart, none of these structures initiate the electrical impulses that cause the cardiac muscle to contract.

2. What information can be obtained from the mass number of an element?

A. The number of protons in the nucleus
B. The total number of protons and neutrons
C. The number of electrons in the valence shell
D. The element's chemical reactivity

Correct answer: B

Rationale: The mass number of an element represents the total number of protons and neutrons in the nucleus. This information is crucial for determining the atomic mass of the element and understanding its stability and isotopes. The number of protons in the nucleus (option A) is represented by the atomic number, not the mass number. The number of electrons in the valence shell (option C) is related to the element's position in the periodic table and its chemical properties, but it is not directly determined by the mass number. The element's chemical reactivity (option D) is influenced by the number and arrangement of electrons in the atom's energy levels, not by the mass number.

3. What does the term 'dilution' refer to in a solution?

A. Adding more solvent to decrease concentration
B. Adding more solute to increase concentration
C. Reducing the temperature to increase solubility
D. Increasing pressure to increase solubility

Correct answer: A

Rationale: The term 'dilution' in a solution refers to adding more solvent to decrease the concentration of the solution. Dilution involves reducing the concentration of the solute in the solution by increasing the amount of solvent. Choice B is incorrect because adding more solute would increase the concentration, not decrease it. Choices C and D are also incorrect as they relate to factors affecting solubility, not dilution specifically. Therefore, choice A is the correct answer as it accurately defines the process of dilution in a solution.

4. Which of the following functions corresponds to the parasympathetic nervous system?

A. It stimulates the fight-or-flight response.
B. It increases heart rate.
C. It stimulates digestion.
D. It increases bronchiole dilation.

Correct answer: C

Rationale: The parasympathetic nervous system is often referred to as the 'rest and digest' system because it promotes activities that occur when the body is at rest, such as digestion. This system helps stimulate digestion by increasing gastrointestinal motility, secretion of digestive enzymes, and blood flow to the digestive organs. Choices A, B, and D are incorrect because they are functions associated with the sympathetic nervous system, which is responsible for the 'fight-or-flight' response, increasing heart rate, and dilating bronchioles to facilitate more oxygen intake during stressful situations.

5. Blood is carried away from the heart in large vessels known as which of the following?

A. Arteries
B. Arterioles
C. Veins
D. Venules

Correct answer: A

Rationale: The correct answer is A: Arteries. Arteries are the large blood vessels that carry blood away from the heart to various parts of the body. They have thick, muscular walls to withstand the high pressure generated by the heart's pumping action. Choice B, Arterioles, are smaller branches of arteries that further divide into capillaries. Choice C, Veins, carry blood back to the heart and have thinner walls compared to arteries. Choice D, Venules, are smaller veins that collect blood from capillaries and merge into larger veins.