ati teas 7 science

Correct Answer: B

Rationale: The correct answer is B: Protons and neutrons only. Electrons are not found in the nucleus, as they orbit around the nucleus in electron shells. Protons and neutrons are the subatomic particles found within the nucleus of an atom. Protons have a positive charge, while neutrons are neutral. The nucleus contains almost all of the atom's mass and is positively charged due to the presence of protons. Choice A is incorrect because electrons are not part of the nucleus. Choice C is incorrect because electrons are not present in the nucleus. Choice D is incorrect as protons and neutrons are indeed constituents of the atomic nucleus.

Correct Answer: A

Rationale: The correct answer is A: Calcitonin. Calcitonin is produced by the thyroid gland and functions to lower blood calcium levels by promoting calcium deposition in bones and inhibiting calcium reabsorption in the kidneys. This hormone opposes the action of parathyroid hormone (PTH), which increases blood calcium levels by promoting calcium release from bones and increasing calcium reabsorption in the kidneys. Thyroxine is a thyroid hormone that regulates metabolism and growth, not calcium levels. Insulin is a hormone produced by the pancreas that regulates blood sugar levels, not calcium levels. Thus, A is the correct answer as it directly regulates calcium levels in the blood through its actions on bones and kidneys.

Correct Answer: A

Rationale: The correct answer is A: Neuron. Neurons are specialized cells that transmit electrical impulses in the nervous system. They consist of a cell body, dendrites to receive signals, an axon to transmit signals, and synaptic terminals to communicate with other neurons. The axon is the long fiber that carries the electrical impulses away from the cell body. Myelin is a fatty substance that insulates and speeds up signal transmission along the axon. Dendrites receive signals from other neurons and transmit them towards the cell body. Therefore, the neuron is the fundamental structure responsible for transmitting electrical impulses, making it the correct answer.

Correct Answer: D

Rationale: The correct answer is D: Dependent, y. In experimental design, the dependent variable is the variable being measured as a possible effect, and it is typically plotted on the y-axis of a graph. This variable is what researchers are observing or testing to see if it changes in response to the manipulation of the independent variable. The independent variable, on the other hand, is what is being manipulated or controlled in the experiment and is usually plotted on the x-axis. Therefore, in a standard experimental design setup, the dependent variable is represented on the y-axis to show the relationship between it and the independent variable on the x-axis. Choices A, B, and C are incorrect because they do not align with the conventional practice of plotting the dependent variable on the y-axis.

Correct Answer: D

Rationale: Certainly! The correct answer is D because saltatory conduction is faster than normal nerve conduction (A), occurs from one node of Ranvier to the next (B), and only occurs in myelinated neurons (C). This process involves the rapid transmission of action potentials in myelinated axons, where the impulse "jumps" from one node of Ranvier to the next, skipping the myelinated regions in between. This allows for faster conduction speeds compared to continuous conduction in unmyelinated neurons. Therefore, all of the statements in options A, B, and C are accurate descriptions of saltatory conduction, making option D the correct choice.