NEET Practice Questions (MCQs) with Answers & Solutions

The hormone responsible for initiating rapid action in response to stress or fear, such as climbing down the stairs quickly during an earthquake, is adrenaline. Adrenaline, also known as epinephrine, is produced by the adrenal glands and plays a key role in the 'fight or flight' response by increasing heart rate, blood flow to muscles, and releasing glucose for immediate energy.

Matching the items from list-I with list-II correctly:
a) Adrenaline - Accelerates heart beat (2)
b) Hyperparathyroidism - Demineralisation (5)
c) Oxytocin - Child birth (4)
d) Hypothyroidism - Myxoedema (1)
e) Aldosterone - Salt-water balance (3)
Therefore, the correct matching option is (a - 2), (b - 5), (c - 4), (d - 1), (e - 3).

The parathyroid gland primarily functions to regulate calcium levels in the blood. It produces parathyroid hormone (PTH), which increases blood calcium levels by stimulating osteoclasts to break down bone and release calcium, enhancing calcium reabsorption in the kidneys, and increasing calcium absorption in the intestines. Thus, the correct answer is that the parathyroid gland increases blood Ca⁺² level.

Collar cells, also known as choanocytes, are specialized cells found in sponges (Phylum Porifera). These cells have a flagellum surrounded by a collar of microvilli and are responsible for creating water currents and capturing food particles.

The canal system is a characteristic feature of sponges (Phylum Porifera). This system consists of a network of channels and chambers through which water circulates, allowing sponges to filter feed and exchange gases.

In Porifera, the skeleton is made up of both spicules and spongin. Spicules are small, spike-like structures made of calcium carbonate or silica, while spongin is a fibrous protein. Together, they provide structural support to the sponge body.

Physalia, commonly known as the Portuguese man o' war, is a marine hydrozoan. It is not a single animal but a colonial organism made up of specialized individual animals (zooids) working together.

To match the items correctly, we need to associate the organisms with their phyla. Spongilla is a freshwater sponge that belongs to Porifera. Adamsia, also known as sea anemone, belongs to Cnidaria. Liver fluke is a parasitic flatworm that belongs to Platyhelminthes. Nereis is a type of polychaete worm that belongs to Annelida. Thus, the correct matching is: p - (i), q - (iv), r - (ii), s - (iii).