The '9+2' arrangement of microtubules is characteristic of: MCQ with Answer and Explanation

The '9+2' arrangement of microtubules is characteristic of:
A. Cilia and flagella
B. Intermediate filaments
C. Mitotic spindle fibers
D. Centrioles and basal bodies
Answer: Option A
Solution (By JKSSB Mock Tests)
The '9+2' arrangement refers to nine doublets of microtubules surrounding a central pair, which is the classic axoneme structure of motile cilia and flagella. Centrioles and basal bodies possess a '9+0' arrangement (nine triplets, no central pair). Mitotic spindle fibers are single microtubules, and intermediate filaments lack a tubular microtubule structure entirely.

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Question #1
In the human brain, the 'limbic system' is primarily associated with:
A. Processing of visual and auditory information
B. Coordination of voluntary motor movements
C. Regulation of emotions, memory, and motivation
D. Regulation of heart rate and breathing

Correct Answer: Option C


Explanation:
The limbic system is a complex set of structures in the medial temporal lobe, including the hippocampus, amygdala, and hypothalamus. It is often called the 'emotional brain' and is primarily responsible for processing emotions (fear, anger, pleasure), forming and retrieving memories, and regulating motivation and homeostatic drives (hunger, thirst). The medulla regulates heart rate, the cerebellum coordinates movement, and the occipital/temporal lobes process sensory information.

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Question #2
Which of the following statements about the lymphatic system is correct?
A. The thymus is a secondary lymphoid organ.
B. It circulates blood throughout the body.
C. Lymph nodes produce red blood cells.
D. It returns interstitial fluid to the bloodstream.

Correct Answer: Option D


Explanation:
The lymphatic system drains excess tissue fluid (lymph) back to the venous blood. Blood circulation is the cardiovascular system; lymph nodes filter lymph; thymus is a primary lymphoid organ.

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Correct Answer: Option D


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