1. The involuntary, rhythmic contractions of the heart muscle are controlled by a specialized group of cells located in the:

A. Lungs
B. Brain
C. Spinal cord
D. Sinoatrial node (located within the heart)

Correct answer: D

Rationale: The correct answer is D: Sinoatrial node (located within the heart). The sinoatrial node, also known as the heart's natural pacemaker, is a cluster of specialized cells within the heart that controls the heart rate by initiating the electrical impulses that regulate the heart's contractions. The lungs (A), brain (B), and spinal cord (C) do not directly control the rhythmic contractions of the heart muscle. Therefore, the sinoatrial node is the specific anatomical location responsible for regulating the heart's rhythmic contractions, making it the correct answer.

2. Autoimmune diseases occur when the immune system mistakenly attacks healthy body tissues. What is a potential cause of autoimmune diseases?

A. Deficiency in essential vitamins and minerals
B. Exposure to environmental toxins
C. Breakdown in immune cell self-tolerance mechanisms
D. All of the above

Correct answer: C

Rationale: The correct answer is C. Autoimmune diseases are triggered by a breakdown in immune cell self-tolerance mechanisms, where the immune system fails to recognize 'self' from 'non-self' cells, leading to attacks on healthy tissues. While deficiencies in essential vitamins and minerals or exposure to environmental toxins can impact immune function, the root cause of autoimmune diseases is primarily attributed to the breakdown in self-tolerance mechanisms. This breakdown can be influenced by genetic predisposition, environmental factors, and other triggers, leading to the development of autoimmune conditions.

3. Simplify the expression: -5 + (-8)

A. -13
B. 8
C. 13
D. -5

Correct answer: A

Rationale: Combine the negative signs by adding them together. -5 + (-8) = -13

4. What is the common name for the compound CHâ‚ƒCOOH?

A. Acetic acid
B. Formic acid
C. Butyric acid
D. Propionic acid

Correct answer: A

Rationale: CHâ‚ƒCOOH is commonly known as acetic acid. The other choices represent different organic acids.

5. Which of the following is a redox reaction?

A. 2H2 + O2 â†’ 2H2O
B. Zn + 2HCl â†’ ZnCl2 + H2
C. 2NaCl â†’ 2Na + Cl2
D. CH4 + 2O2 â†’ CO2 + 2H2O

Correct answer: b

Rationale: The oxidation state of Zn changes from 0 to +2, indicating a redox reaction.

6. The process of bone formation and breakdown is called:

A. Ossification
B. Resorption
C. Remodeling
D. All of the above

Correct answer: C

Rationale: The correct answer is C: 'Remodeling.' Bone remodeling is the continuous process of bone formation (ossification) and breakdown (resorption). Ossification refers to the formation of bone tissue, while resorption is the breakdown and removal of old bone tissue. The term 'remodeling' encompasses both of these processes, making it the most appropriate choice. While ossification and resorption are part of bone remodeling, they do not cover the entire process on their own, hence 'All of the above' is incorrect.