Nokea
How do efferent fibers exit the spinal cord?
- A. Through the anterior aspect
- B. Through the dorsal aspect
- C. Through the ventral aspect
- D. Through the lateral aspect
Correct Answer: C
Rationale: Efferent fibers, which carry motor commands, exit the spinal cord through the ventral aspect, also known as the anterior aspect. The correct answer is C, 'Through the ventral aspect.' Efferent fibers exiting through the ventral aspect are responsible for carrying motor commands from the spinal cord to the muscles and glands. Choices A, B, and D are incorrect. Efferent fibers do not exit through the dorsal, lateral, or anterior aspects of the spinal cord.
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Which of the following describes a reflex arc?
- A. The storage and recall of memory
- B. The maintenance of visual and auditory acuity
- C. The autoregulation of heart rate and blood pressure
- D. A stimulus and response controlled by the spinal cord
Correct Answer: D
Rationale: Choice D correctly describes a reflex arc. A reflex arc is a neural pathway that controls a reflex action. It involves a specific sequence of events that occur in response to a stimulus, which is rapidly and involuntarily processed by the spinal cord. The spinal cord coordinates the quick processing of sensory input and the generation of a motor response without involving the brain, allowing for rapid protective responses. Choices A, B, and C are incorrect because they do not accurately describe a reflex arc. A reflex arc is specifically related to the rapid and involuntary response to a stimulus through neural pathways involving the spinal cord, not memory storage, visual and auditory acuity maintenance, or heart rate and blood pressure autoregulation.
How does the Law of Conservation of Mass apply to this reaction: 2H₂ + O₂ → 2H₂O?
- A. Electrons are not lost.
- B. The hydrogen does not lose mass.
- C. New water molecules are formed.
- D. There is no decrease or increase in matter.
Correct Answer: D
Rationale: The Law of Conservation of Mass states that matter cannot be created or destroyed in a chemical reaction. In the given reaction, 2 moles of hydrogen combine with 1 mole of oxygen to form 2 moles of water. The total mass of the reactants (hydrogen and oxygen) is equal to the total mass of the products (water), meaning there is no decrease or increase in matter. The total mass of the system remains constant, demonstrating the conservation of mass. Choices A, B, and C are incorrect because the conservation of mass does not specifically relate to electrons, individual elements (like hydrogen), or the formation of new molecules; instead, it focuses on the overall mass of the system before and after the reaction.
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.
Which valve prevents blood from entering the left atrium when the ventricles contract?
- A. Pulmonary valve
- B. Tricuspid valve
- C. Mitral valve
- D. Aortic valve
Correct Answer: C
Rationale: The correct answer is the mitral valve, also known as the bicuspid valve. The mitral valve prevents blood from flowing back into the left atrium during ventricular contraction. The tricuspid valve is located between the right atrium and right ventricle, the pulmonary valve is between the right ventricle and the pulmonary artery, and the aortic valve is situated between the left ventricle and the aorta. Therefore, choices A, B, and D are incorrect as they are not related to preventing blood from entering the left atrium during ventricular contraction.
How are the motor pathways of the ANS arranged?
- A. Single neuron from CNS to target organ
- B. Two neurons, a pre-ganglionic and post-ganglionic neuron
- C. Multiple neurons from CNS to target organ
- D. Single neuron from CNS to peripheral ganglia
Correct Answer: B
Rationale: The correct answer is B. The motor pathways of the autonomic nervous system (ANS) are organized with two neurons: a pre-ganglionic neuron that transmits the signal from the central nervous system (CNS) to a ganglion, and a post-ganglionic neuron that conveys the signal from the ganglion to the target organ. This dual-neuron pathway enables the integration and modulation of signals before reaching the target organ, allowing for a more sophisticated and adaptable control system. Choice A is incorrect as it describes a single neuron pathway, which is not characteristic of ANS motor pathways. Choice C is incorrect as it suggests multiple neurons from the CNS to the target organ, which is not the typical arrangement. Choice D is incorrect as it describes a single neuron pathway from the CNS to peripheral ganglia, which does not account for the ganglionic transmission in ANS motor pathways.