Explain the nervous system of frog.

NERVOUS SYSTEM OF FROG:

The set of organs which control and coordinate all the activities of the body is called the nervous system. It is composed of two parts: the central nervous system and the peripheral nervous system.

Central Nervous System:

It includes the brain and the spinal cord.

Brain:

The brain is protected in the brain case or cranium, which is the major portion of the skull. Brain has three parts which are called fore brain, mid brain and hind brain.

Fore Brain:

The most anterior region comprises the olfactory lobes. Immediately behind the olfactory lobes, there are two large outgrowths called the cerebral hemispheres.

Functions:

Olfactory lobes are associated with the sense of smell and transfer of olfactory sensation to the cerebral hemispheres which are the seats of intelligence and memory. The diencephalon receives a variety ofmessages from the internal and external environment of the body and also controls the secretions of hormones from the pituitary gland.

Mid Brain:

Behind the cerebral hemispheres are located two prominent outgrowths called the optic lobes. The part between the optic lobes and hemispheres is known as the diencephalon. On the dorsal surface of the diencephalon is present a pineal body while on its ventral surface the pituitary gland is attached.

Function:

This part is associated with the eyes and vision.

Hind Brain:

 The last part of the brain consists of the cerebellum and the medulla oblongata.

Function:

 This part controls and coordinates body movements and maintains balance of the body. The medulla also controls respiration. circulation and digestion.

Spinal Cord:

 The spinal cord starts from the posterior end of the medulla oblongata like a thick thread. It passes from the skull through a hole and enters the . canal of the vertebral column. The vertebral column protects the spinal cord. Brain and spinal cord are not solid. They have a system of canals. which is filled with a fluid

Function:

 The spinal cord controls the movement of the trunk area and many other functions independently. 

PERIPHERAL NERVOUS SYSTEM:

Peripheral nervous system consists of nerves, which connect the central nervous system with various parts of the body. They are of two types:

(1) Cranial Nervous: Nerves originating from brain are called cranial nerves. In frog. there are ten pairs of cranial nerves. 

(2) Spinal Nerves: Nerves originating from spinal cord are called spinal nerves. There are nine or ten pairs of spinal nerves. Nerves are of following types: 

 
i. Sensory Nerves: These nerves take messages from sensory organs to central nervous system. 

 
ii. Motor Nerves: These nerves take messages from central nervous system to glands and muscles. 

 
Mixed Nerves: They carry out both the above mentioned functions. Spinal nerves are all mixed nerves while cranial nerves are of all three types: 

Besides these nerves, some special nerves are present in the head and trunk region called the autonomic nerves. which work automatically. They control the internal organs of the body such as heart, lungs, stomach, smooth muscles of the intestine, vessels and glands.