Nokea
Which of the following neurotransmitters slows down the activity of neurons to prevent overexcitation?
- A. Acetylcholine
- B. Dopamine
- C. GABA
- D. Serotonin
Correct Answer: C
Rationale: The correct answer is C: GABA (gamma-aminobutyric acid). GABA is an inhibitory neurotransmitter that slows down neuronal activity, helping to prevent overexcitation in the brain. It counterbalances the effects of excitatory neurotransmitters like glutamate, playing a crucial role in maintaining the balance of neuronal activity in the brain. Acetylcholine (Choice A) is primarily an excitatory neurotransmitter involved in muscle movement and cognitive functions. Dopamine (Choice B) plays a role in reward-motivated behavior and motor control. Serotonin (Choice D) is involved in regulating mood, appetite, and sleep but is not primarily responsible for slowing down neuronal activity to prevent overexcitation.
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What is the breakdown product of creatine phosphate, an energy source used for short bursts of muscle activity?
- A. Glucose
- B. Lactic acid
- C. Carbon dioxide
- D. Creatine
Correct Answer: B
Rationale: Creatine phosphate is utilized as an immediate energy source for short bursts of muscle activity. When it breaks down, it yields lactic acid as a byproduct. Lactic acid accumulation during intense exercise can lead to muscle fatigue and soreness. Therefore, the correct answer is lactic acid. The other choices are incorrect: Glucose is a different energy source derived from carbohydrates; Carbon dioxide is a waste product of cellular respiration, not specifically from creatine phosphate breakdown; Creatine is the precursor compound to creatine phosphate and is not the breakdown product.
What potential consequences can chromosomal nondisjunction have on offspring?
- A. Down syndrome, caused by an extra copy of chromosome 21.
- B. Turner syndrome, characterized by the absence of one X chromosome in females.
- C. Klinefelter syndrome, featuring one or more extra X chromosomes in males.
- D. All of the above.
Correct Answer: D
Rationale: - Chromosomal nondisjunction is the failure of homologous chromosomes or sister chromatids to separate properly during cell division, leading to an abnormal number of chromosomes in the resulting cells.
- Down syndrome is caused by an extra copy of chromosome 21, resulting from nondisjunction during meiosis. Individuals with Down syndrome have three copies of chromosome 21 instead of the usual two.
- Turner syndrome is characterized by the absence of one X chromosome in females, leading to a variety of physical and developmental features.
- Klinefelter syndrome features one or more extra X chromosomes in males, typically resulting in infertility and other physical characteristics.
Therefore, chromosomal nondisjunction can lead to various genetic disorders such as Down syndrome, Turner syndrome, and Klinefelter syndrome, making option D the correct answer.
What is the term for the pressure exerted by blood against the walls of blood vessels?
- A. Heart rate
- B. Blood pressure
- C. Cardiac output
- D. Stroke volume
Correct Answer: B
Rationale: Blood pressure is the term for the pressure exerted by blood against the walls of blood vessels. It is measured in millimeters of mercury (mmHg) and consists of two numbers: systolic pressure (the top number) and diastolic pressure (the bottom number). Heart rate (A) is the number of times the heart beats per minute, cardiac output (C) is the volume of blood pumped by the heart per minute, and stroke volume (D) is the volume of blood pumped by the heart in one contraction. Understanding blood pressure is crucial in assessing cardiovascular health and the risk of various conditions like hypertension.
Which factor affects the gravitational potential energy of an object the most?
- A. The mass of the object
- B. The distance from the ground
- C. The gravitational force
- D. The shape of the object
Correct Answer: B
Rationale: Gravitational potential energy is directly proportional to the height or distance from the ground. As the object is raised higher, its gravitational potential energy increases. While the mass of the object influences gravitational potential energy, the distance from the ground has a more significant impact on it. The gravitational force does not directly affect the gravitational potential energy; it is the force that causes the potential energy to change with height. The shape of the object also does not determine gravitational potential energy, as it is primarily determined by the object's position in a gravitational field.
Which of the following types of immunity is provided by the secretion of antibodies by B-cells?
- A. Cell-mediated
- B. Humoral
- C. Innate immunity
- D. Phagocytic
Correct Answer: B
Rationale: The correct answer is B: Humoral. Humoral immunity involves B-cells secreting antibodies to fight pathogens. In this type of immunity, antibodies circulate in the blood and other body fluids to neutralize pathogens and prevent infections. Cell-mediated immunity, on the other hand, involves the activation of T-cells to directly attack infected or abnormal cells, not the secretion of antibodies. Innate immunity refers to the nonspecific defense mechanisms the body has in place from birth, such as physical barriers and inflammatory responses. Phagocytic immunity is not a recognized type of immunity; phagocytosis is a mechanism used by cells like macrophages to engulf and digest pathogens, but it is not a specific form of immunity like humoral or cell-mediated immunity.