What is the responsibility of the somatic nervous system?

Correct Answer: C

Rationale: The somatic nervous system is responsible for controlling voluntary movements of skeletal muscles. This system communicates sensory information and controls voluntary movements, such as walking or reaching for objects. Breathing is primarily regulated by the autonomic nervous system, which functions involuntarily. Thought processes involve complex interactions between various regions of the brain and are not directly controlled by the somatic nervous system. Fear is an emotional response that involves the limbic system of the brain and the autonomic nervous system, not the somatic nervous system.

Correct Answer: A

Rationale: The correct answer is A: Platelets. Platelets are small cell fragments in the blood that play a crucial role in clotting. When there is an injury, platelets adhere to the site and release chemicals that help form a clot to prevent excessive bleeding. Red blood cells transport oxygen, antigens are substances that trigger an immune response, and plasma cells are a type of white blood cell involved in producing antibodies, none of which are primarily responsible for clotting.

Correct Answer: A

Rationale: The correct answer is A. The initial event in a primary immune response is the phagocytosis of pathogens by macrophages and the subsequent presentation of their antigens, which is crucial for initiating the adaptive immune response. Neutrophils (Choice B) are also involved in the innate immune response, but they typically respond after macrophages. B lymphocytes (Choice C) produce antibodies later in the adaptive immune response, and Helper T cells (Choice D) help in coordinating the immune response but are not the first cells to act in a primary immune response.

Correct Answer: C

Rationale: Sperm maturation occurs in the epididymis, a coiled tube located on the back of each testicle. In the epididymis, sperm gain motility and the ability to fertilize an egg. It serves as a storage site for mature sperm until ejaculation. The seminal vesicles and the prostate gland contribute fluids to semen, enhancing sperm viability and motility. The vas deferens is responsible for transporting mature sperm from the epididymis to the urethra during ejaculation, but it is not where sperm maturation takes place. Therefore, the correct answer is the epididymis.

Correct Answer: A

Rationale: The correct order of joint types, from least mobile to most mobile, is hinge, condyloid, saddle. A hinge joint allows movement in one plane (like a door hinge), a condyloid joint allows movement in two planes but not rotation (like the wrist), and a saddle joint allows movement in multiple directions (like the thumb). Choice A, 'Hinge, condyloid, saddle,' is the correct sequence as it accurately represents the order of increasing permitted motion in joints. Choices B, C, and D are incorrect because they do not follow the correct order of joint types from least mobile to most mobile as required by the question.