Nokea
Which of these diseases does NOT require the introduction of foreign nucleic acid?
- A. kuru
- B. polio
- C. rabies
- D. St. Louis encephalitis
Correct Answer: A
Rationale: The correct answer is A (kuru) because kuru is a prion disease caused by misfolded proteins, not foreign nucleic acid. Polio, rabies, and St. Louis encephalitis are caused by viruses, which contain foreign nucleic acid. Prions do not contain nucleic acid and replicate by inducing misfolding of normal cellular proteins. Therefore, kuru does not require the introduction of foreign nucleic acid for its transmission and development.
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With an action potential, depolarization of the axomembrane is recorded as the gates open, allowing ________ to flow into the axon.
- A. potassium ions
- B. H+ ions
- C. sodium ions
- D. all of the above
Correct Answer: C
Rationale: During the depolarization phase of an action potential, voltage-gated sodium channels open, allowing sodium ions to flow into the axon. This influx of positively charged ions causes the membrane potential to become more positive, leading to the rapid rise in voltage observed during an action potential. Sodium ion influx is essential for initiating and propagating nerve impulses.
Nerve impulses are carried to another part of the body by a neuron's (nerve cell):
- A. dendrites
- B. axon
- C. neuron cell body
- D. synapse
Correct Answer: B
Rationale: The axon is the part of a neuron responsible for carrying nerve impulses away from the cell body to other neurons, muscles, or glands. It is a long, slender projection that conducts electrical signals, known as action potentials, to the axon terminals. At the terminals, the signal triggers the release of neurotransmitters into the synapse, facilitating communication with the next neuron or target cell. The axon is essential for transmitting information across the nervous system.
Like the brain, the spinal cord is surrounded by bone, meninges, and ________.
- A. cerebrospinal fluid
- B. white matter
- C. gray matter
- D. water
Correct Answer: A
Rationale: The spinal cord, like the brain, is protected by bone (vertebrae), meninges, and cerebrospinal fluid (CSF). CSF provides cushioning, nutrients, and waste removal for the central nervous system. White matter and gray matter are components of the spinal cord's internal structure, while water is not a specific protective element. Therefore, cerebrospinal fluid is the correct answer.
Which of the following is not a side effect of dopamine agonists?
- A. Drowsiness
- B. Nausea
- C. Impulse control disorder
- D. Livedo reticularis
Correct Answer: D
Rationale: Livedo reticularis is not a side effect of dopamine agonists. Common side effects include drowsiness, nausea, and impulse control disorders.
Which one of the following is the correct sequence of events that follows a threshold potential: 1. the membrane becomes depolarized 2. sodium channels open and sodium ions diffuse inward 3. the membrane becomes repolarized 4. potassium channels open and potassium ions diffuse outward while sodium is actively transported out of the cell
- A. 3,2,4,1
- B. 2,1,4,3
- C. 2,1,3,4
- D. 1,2,4,3
Correct Answer: B
Rationale: The correct sequence is: sodium channels open and sodium ions diffuse inward (2), the membrane becomes depolarized (1), potassium channels open and potassium ions diffuse outward while sodium is actively transported out of the cell (4), and the membrane becomes repolarized (3). Thus, B is the correct answer.