Frog - control and coordination system - class-XI

The withdrawal of a leg in response to a stimulus in a brain-crushed frog is a classic example of a simple reflex, which is mediated by the spinal cord and does not require higher brain centers.

The ophthalmic branch of the trigeminal nerve is a sensory nerve in frogs that carries sensory information from the snout and head region. Cutting it results in a loss of sensation in those areas.

The process of growth and development is regulated by thyroxine hormone which is produced by thyroid gland. Iodine is required for thyroxine production. Thus insufficient production of thyroxine in the tadpoles leads to the incomplete development.

Frogs, like all amphibians, possess 10 pairs of cranial nerves that emerge from the brain.

The process of growth and development is regulated by thyroxine hormone which is produced by thyroid gland. Iodine is required for thyroxine production. That is why retarded growth is seen in tadpoles living in iodine deficient water. 

In an insect or an amphibian, the process of transformation from an immature form to an adult form in two or more distinct stages is known as metamorphosis. For the metamorphosis of tadpoles, thyroid hormone along with the essential constituent iodine is necessary.

Autonomous neural system controls and coordinates the involuntary activities of various organs. It regulates involuntary activities of the body i.e., activities that are not under the will power of the animal, e.g. swallowing of food, pupillary reflex, peristalsis of the intestine, etc.

The sympathetic nervous system is responsible for the 'fight or flight' response, which includes increasing the heart rate (heart beat).

The hindbrain in frog consists of the 'cerebellum' and 'medulla oblongata'. So, the correct answer is 'Both (a) and (b)'.

There are ten pairs of cranial nerves arising from the brain. The brain is enclosed in a bony structure called brain box. The brain is divided into fore-brain mid-brain and hind-brain. Forebrain includes olfactory lobes, paired cerebral hemispheres, and unpaired diencephalon. The midbrain is characterized by a pair of optic lobes. Hind-brain consists of cerebellum and medulla oblongata. The ventricle opens into a sac-like conus arteriosus on the ventral side of heart.

Ear acts as a hearing as well as balancing organ. RBCs are nucleated and contain red coloured pigment namely haemoglobin.

In frog, the medulla oblongata passes out through foramen magnum and continues into spinal cord. Frogs are ureotelic.