Which of the following is associated with decrease in cardiac output?
Explanation:
Decrease in cardiac output occurs mainly when parasympathetic neural signals to the heart prevail. The vagus nerve slows the heart rate (and reduces contraction strength), lowering cardiac output. In NCERT, the parasympathetic system reduces heart rate and thus CO. Sympathetic nerves increase heart rate and force of contraction, raising CO. Adrenal medullary hormones (adrenaline) also increase heart rate and strength, again increasing CO. The pneumotaxic centre primarily regulates breathing patterns, not directly cardiac output, so it does not cause a decrease in CO by itself. Therefore, option 2 is correct.
🧠 Did You Know?
Parasympathetic effects on the heart are mediated by muscarinic receptors that slow heart rate.
In Agave, the vegetative propagule is called a bulbil. A bulbil is a small bulb-like shoot that forms on the plant and can develop into a new plant when separated. This concept is described in NCERT under vegetative propagation, where bulbil formation is noted for certain plants like Agave. The other options are different structures: a rhizome is an underground stem; an offset is a small plant produced at the base of the parent (common in some aquatic or succulent plants); an eye is a bud or a part of a stem that can give rise to a new shoot. Thus bulbil is the correct term for Agave’s vegetative propagule.
🧠 Did You Know?
Some plants produce plantlets or bulbils that can detach and grow elsewhere, aiding rapid propagation without seeds.
💡 NCERT Memory Line:
Bulbil is a type of vegetative propagule mentioned in NCERT to describe a bulb-like shoot that forms on the plant.
