What are the tiny contractile units within muscle cells called?

Correct Answer: C

Rationale: Sarcomeres are the smallest contractile units within muscle cells. They consist of overlapping filaments of actin and myosin proteins, which interact to produce muscle contractions. Myocytes are the entire muscle cells, myofibrils are bundles of protein filaments found within muscle cells, and tendons are tough connective tissues that connect muscles to bones. Therefore, sarcomeres specifically represent the contractile units responsible for muscle contraction, making them the correct answer in this context.

Correct Answer: B

Rationale: Cerebrospinal fluid is the protective fluid that surrounds the brain and spinal cord. It acts as a cushion to protect these vital organs from injury and provides nutrients to the nervous system. Blood, plasma, and myelin are not the fluids specifically surrounding the brain and spinal cord. Blood is found within blood vessels, plasma is the liquid component of blood, and myelin is a fatty substance that forms a protective sheath around nerve fibers.

Correct Answer: B

Rationale: Action potentials, the all-or-nothing electrical signals traveling along neurons, are generated by the movement of sodium and potassium ions across the neuronal membrane. This movement creates changes in the membrane potential, leading to the propagation of the electrical signal along the neuron. Glucose is a source of energy for neurons but is not directly involved in generating action potentials. Neurotransmitters are involved in communication between neurons but do not directly generate action potentials. Myelin is a fatty substance that insulates and speeds up the conduction of action potentials but does not generate them.

Correct Answer: D

Rationale: The endocrine system is responsible for producing hormones that regulate various bodily functions such as growth, metabolism, mood, and more. Facilitating digestion through muscle contractions is primarily the role of the muscular and nervous systems, not the endocrine system. Therefore, option D is the correct answer as it does not align with the functions typically attributed to the endocrine system. Choices A, B, and C are functions that are indeed associated with the endocrine system, making them incorrect answers in the context of this question.

Correct Answer: A

Rationale: The correct difference between type 1 and type 2 diabetes lies in their underlying causes. Type 1 diabetes is caused by the body's inability to produce insulin, while type 2 diabetes is characterized by insulin resistance, where the body doesn't effectively use the insulin it produces. Insulin resistance is a key feature of type 2 diabetes, distinguishing it from type 1 where insulin deficiency is the primary issue. Choices B, C, and D are incorrect. Type 1 and type 2 diabetes can both be chronic conditions, affecting individuals of different age groups, and typically require a combination of diet, exercise, and medication for management.