Nokea
Which of the following is the main organ responsible for regulating sleep?
- A. Thalamus
- B. Hypothalamus
- C. Pituitary gland
- D. Pineal gland
Correct Answer: B
Rationale: The main organ responsible for regulating sleep is the hypothalamus. The hypothalamus plays a crucial role in controlling the body's circadian rhythm, which is the internal clock that regulates the sleep-wake cycle. It receives input from the eyes about light and darkness, aiding in determining when it's time to sleep or wake up. Additionally, the hypothalamus regulates the production of melatonin by the pineal gland, a hormone that helps control sleep patterns. While the thalamus relays sensory information to the brain, the pituitary gland is primarily responsible for hormone production and release, and the pineal gland produces melatonin under the control of the hypothalamus. Therefore, the hypothalamus is the correct choice as the main organ involved in sleep regulation.
You may also like to solve these questions
What happens to the potential energy of an object as it falls freely near the Earth's surface?
- A. Potential energy decreases
- B. Potential energy increases
- C. Potential energy remains constant
- D. Potential energy becomes zero
Correct Answer: A
Rationale: As an object falls freely near the Earth's surface, its potential energy decreases. This decrease occurs because the gravitational potential energy is being converted into kinetic energy as the object accelerates due to gravity. According to the law of conservation of energy, the total mechanical energy (the sum of potential and kinetic energy) remains constant in the absence of non-conservative forces like air resistance. Choice B ('Potential energy increases') is incorrect because the object's potential energy is being converted into kinetic energy, leading to a decrease. Choice C ('Potential energy remains constant') is incorrect as the conversion of potential energy to kinetic energy results in a decrease in potential energy. Choice D ('Potential energy becomes zero') is incorrect because potential energy is not reduced to zero but is transformed into kinetic energy as the object falls.
What protein complex controls the progression of mitosis through its activation and degradation?
- A. Ribosome
- B. Cyclin-dependent kinase (CDK)
- C. Centriole
- D. Microtubule
Correct Answer: B
Rationale: A) Ribosome: Ribosomes are cellular organelles responsible for protein synthesis and are not directly involved in controlling the progression of mitosis.
B) Cyclin-dependent kinase (CDK): CDKs are a family of protein kinases that regulate the cell cycle, including the progression of mitosis. CDK activity is controlled by cyclins, which bind to CDKs to activate them at specific points in the cell cycle. The activation and degradation of cyclins regulate the activity of CDKs, which in turn control the progression of mitosis.
C) Centriole: Centrioles are involved in organizing the microtubules of the mitotic spindle but do not directly control the progression of mitosis.
D) Microtubule: Microtubules are structural components of the cytoskeleton and are involved in various cellular processes, including mitosis, but they do not control
What is the significance of the nuclear envelope breaking down during mitosis?
- A. It allows the chromosomes to condense and become visible.
- B. It allows the spindle apparatus to form and attach to the chromosomes.
- C. It allows the sister chromatids to separate.
- D. It allows the nuclear material to be evenly distributed to the daughter cells.
Correct Answer: B
Rationale: A) The breakdown of the nuclear envelope does not directly cause the chromosomes to condense and become visible. Chromosome condensation is a separate process that occurs before mitosis begins.
B) The breakdown of the nuclear envelope is crucial for the formation of the spindle apparatus, a structure made of microtubules that helps separate the chromosomes during cell division. The spindle apparatus attaches to the chromosomes and helps move them to opposite poles of the cell.
C) The separation of sister chromatids occurs during anaphase, which is facilitated by the spindle apparatus. The breakdown of the nuclear envelope is not directly involved in this process.
D) The even distribution of nuclear material to daughter cells is achieved through the movement of chromosomes by the spindle apparatus, which is made possible by the breakdown of the nuclear envelope.
When ice melts, it undergoes a...
- A. Chemical change
- B. Physical change
- C. Nuclear change
- D. Radioactive decay
Correct Answer: B
Rationale: When ice melts, it undergoes a physical change, transitioning from a solid state to a liquid state. This change does not involve altering the chemical composition of the ice, making it a physical change rather than a chemical change, nuclear change, or radioactive decay. Choice A, 'Chemical change,' is incorrect because a chemical change involves a rearrangement of atoms resulting in new substances. Choice C, 'Nuclear change,' is incorrect as it refers to changes in the nucleus of an atom, not the phase transition of ice. Choice D, 'Radioactive decay,' is incorrect as it involves the spontaneous disintegration of an unstable atomic nucleus, which is not the process occurring when ice melts.
Which of the following is NOT a function of the muscular system?
- A. Movement
- B. Maintaining posture
- C. Generating heat
- D. Regulating blood sugar levels
Correct Answer: D
Rationale: The muscular system is responsible for movement, maintaining posture, and generating heat. Regulating blood sugar levels is not a function of the muscular system. This function is primarily carried out by the endocrine system, specifically the pancreas and its production of insulin and glucagon. Choices A, B, and C are all correct functions of the muscular system as they involve the contraction and relaxation of muscles to produce movement, support the body's structure, and generate heat as a byproduct of muscle activity.