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Animals have a complex nervous system.

Animals have a complex nervous system. It receives and interprets the signals from the surroundings, and sends the messages to the brain. The structure of the nervous system depends upon the body plan of an organism e.g. animals that do not have a defined head or tail, they have web-like arrangements of nerve cells throughout the body. Animals with a defined head have the nervous system divided into three parts: the Central Nervous System, Peripheral Nervous System, and Autonomous Nervous System.

In all the vertebrates, the  central nervous system  comprises the brain and the spinal cord. The brain contains centres that process the signals received, regulate the homeostasis, and control emotions and intelligence. The spinal cord helps in the transfer of information to and from the brain. Explore more about  Nervous System

The nervous system consists of different parts performing different functions, listed below are the functions of various parts.

The brain consists of the following parts performing the following functions:

It consists of 12 pairs of cranial nerves which are connected to the brain having particular functions. The following are the nerves and their respective functions:

This system is segregated into parasympathetic and sympathetic nervous systems which have contrasting effects on the same organ set. The parasympathetic nervous system is linked with a relaxed condition such as the contraction of the pupils, slowing of the heart rate, energy for food digestion etc. The sympathetic nervous system is necessary during a crisis and is linked with “fight or flight reaction”. Increased rate of breathing, pupil dilation, Increase in the heart rate, Increased rate of salivation and perspiration etc.

A neuron is the structural and functional unit of a nervous system. It has the capacity to receive and dispatch electrochemical signals. They have three basic parts:

This is the main part of the neuron and consists of a nucleus, mitochondria, endoplasmic reticulum, and ribosomes. If the cell body dies, the neuron does not survive.

An axon or a nerve cell is a long cylindrical structure that conducts nerve impulses away from the cell body. It is covered with a thin layer of insulated electrical wire known as myelin. Myelinated neurons are found in the peripheral nervous system, while non-myelinated neurons are found in the brain and the spinal cord.

These are located on either side of the neuron. These are small branch-like projections used to connect with the adjacent neuron. Also read:  Neuron 

When several axon fibres are bundled together they form a nerve. Nerves are of three types:

When the direction of impulse is from the receptor to the brain or spinal cord, the nerve fibres are called sensory. For eg., nerves in the eyes, nerves, and ears.

When the impulse is directed from the brain or spinal cord to the gland or muscle, it is known as a motor neuron.

A mixed nerve contains both the sensory and the motor nerves. For eg., spinal nerves Also refer:  Nerves

The  human brain  receives signals from the sense organs and transmits them back to the nerves. The brain is placed in the skull which contains the cerebrospinal fluid to protect the brain from any mechanical shocks. It is divided into three regions:

It receives the impulses from the receptors. It has specific areas to analyze the different signals like hearing, smelling, etc. The process of thinking also takes place here. The incoming signals are interpreted and transmitted to the respective regions.

Our body performs various voluntary and involuntary functions. Voluntary actions like running and pushing are under human control. Involuntary actions such as blinking, breathing are automatic, and not under human control.

The hindbrain contains the medulla and the cerebellum. These control breathing, salivation, blood pressure, etc. Also refer:  Brain diseases

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