Nokea
Which type of cells make up the myelin sheaths?
- A. Glial cells.
- B. Dendrites.
- C. Melanocytes.
- D. Squamous cells.
Correct Answer: A
Rationale: The correct answer is A: Glial cells. Glial cells are responsible for producing the myelin sheaths that surround and insulate nerve cells in the central and peripheral nervous systems. Schwann cells in the peripheral nervous system and oligodendrocytes in the central nervous system are types of glial cells that form the myelin sheaths. Choice B, dendrites, are not involved in forming myelin sheaths; they are extensions of neurons that receive signals. Choice C, melanocytes, are cells responsible for producing melanin, not myelin. Choice D, squamous cells, are flat epithelial cells found in various tissues but are not involved in myelin sheath formation.
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Which structure of the nervous system carries an action potential in the direction of a synapse?
- A. Cell body
- B. Axon
- C. Neuron
- D. Myelin
Correct Answer: B
Rationale: The correct answer is the axon. The axon is the elongated, threadlike part of a neuron that carries nerve impulses away from the cell body towards other neurons or target cells, such as muscles or glands, in the direction of a synapse. Action potentials travel along the axon as electrical signals to communicate with neighboring cells. The cell body (choice A) contains the nucleus and organelles but does not transmit action potentials. Neuron (choice C) is a broad term that includes the entire nerve cell, not a specific structure. Myelin (choice D) is a fatty substance that surrounds and insulates axons, aiding in the conduction of nerve impulses, but it does not directly carry the action potential towards a synapse.
When animals eat, insulin is released from the pancreas, stimulating glucose uptake by the liver. When glucose levels drop, the pancreas reduces insulin release. This is an example of which mechanism for maintaining homeostasis?
- A. Negative feedback.
- B. Positive feedback.
- C. Stress response.
- D. Parasympathetic regulation.
Correct Answer: A
Rationale: This mechanism is an example of negative feedback. Negative feedback systems work to counteract changes in the body and maintain a stable internal environment (homeostasis). In this case, the release of insulin in response to high glucose levels is followed by a reduction in insulin release when glucose levels drop. This response helps regulate glucose levels and return them to a normal range, demonstrating the characteristic of negative feedback where the body's response opposes the initial stimulus to maintain equilibrium. Positive feedback would amplify the initial change rather than counteract it, so it is not the correct choice. Stress response and parasympathetic regulation are not directly involved in this glucose regulation process, making them incorrect choices.
How does water affect the temperature of a living thing?
- A. Water increases temperature.
- B. Water keeps temperature stable.
- C. Water decreases temperature.
- D. Water does not affect temperature.
Correct Answer: B
Rationale: Water has a high specific heat capacity, which means it can absorb and release a large amount of heat energy without causing a significant change in temperature. This property allows water to help regulate the temperature of living things by buffering against sudden temperature changes in the environment. Overall, water helps to maintain a stable temperature within living organisms, which is crucial for their survival and physiological processes. Choices A, C, and D are incorrect because water's high specific heat capacity enables it to stabilize temperatures rather than increasing, decreasing, or having no effect on them.
Which of the following is an example of a tissue?
- A. chloroplasts
- B. liver
- C. mammal
- D. hamstring
Correct Answer: B
Rationale: The correct answer is 'B: liver.' The liver is an example of a tissue. Tissues are groups of cells that work together to perform specific functions in the body. The liver is made up of different types of cells that work together to carry out various essential functions, such as detoxification, metabolism, and storage of nutrients. Option A (chloroplasts) refers to organelles, not tissues. Option D (hamstring) is a muscle, not a tissue. Option C (mammal) represents a higher level of organization than tissues, as it refers to a classification of organisms, not a specific tissue type.
What are groups of cells that perform the same function called?
- A. tissues
- B. plastids
- C. organs
- D. molecules
Correct Answer: A
Rationale: Groups of cells that perform the same function are called tissues. Tissues are composed of a group of similar cells working together to carry out specific functions within an organism. Each type of tissue has a specialized structure that enables it to perform its specific role effectively. Plastids are cell organelles found in plants responsible for functions like photosynthesis and storage, not groups of cells. Organs are composed of different types of tissues working together. Molecules are made up of atoms and are not groups of cells.