Nervous system of an animal is a complex structure, it mainly receives and detects signals from the surroundings and after detecting that signal, sends it to the brain. Nervous system structure can be detected by studying the body plan of the organism body. Example: The organism which are divided on the basis of head and tail, then in them they have a web like nerve cell which is spreaded throughout the body. Organisms who have a well defined head, then their nervous system is divided into three parts, they are: the Central Nervous System, Peripheral Nervous System, and Autonomous Nervous System.
Classification of Nervous System:
1. Central Nervous System– It consists of the brain and spinal cord. It’s location is in the head and continues along the back.
Brain: It is considered as the most important, largest and central part of the human nervous system. It controls all the functions of the nervous system, which help in getting messages and giving response to the human body. Human brain is covered by the skull, which provides protection from the frontal, lateral and dorsal side. The human brain is further divided into three major parts:
Forebrain: It is anterior most part of the brain consists of Cerebrum, Hypothalamus and Thalamus.
Midbrain: It is the smaller and central part of the human brain.
Hindbrain: It is the central region of the brain which is made up of Cerebellum, Medulla and Pons.
Spinal Cord: It is a cylindrical bunch of nerves, which is enclosed by spine. This spine connects all parts of the human body to the brain. It starts in continuation with the medulla and extends towards downward direction. It is covered by a bony cage called the vertebral column and surrounded by a membranous structure known as meninges.
2. Peripheral Nervous System– It consists of all the nerves continuing from the central nervous system to the entire body. It is the lateral most part of the human nervous system which helps in connecting different parts of the body with CNS.
Peripheral nervous system has two types of nerve fibers:
A. Afferent nerve fibers – These nerve fibers are responsible for transmission of messages from tissues and organs to the central nervous system.
B. Different nerve-fibers – These nerve fibers are responsible for sending messages from CNS to the corresponding peripheral organ.
C. Autonomous Nervous System– It is made up of both sympathetic and parasympathetic nerves.
Classification of Peripheral Nervous System:
Somatic Neural System (SNS): This neural system controls all the voluntary actions in the body by transmitting impulses from CNS to skeletal muscle cells.
Autonomic neural system (ANS): The autonomic neural system controls all the involuntary actions of the body like regulation of physiological functions (digestion, respiration, salivation, etc.).
3. Autonomous Nervous System– It is made up of both sympathetic and parasympathetic nerves.
Parts of Human Brain:
The human brain is made of the following parts and perform the given functions:
A. Cerebral Cortex – It controls the Voluntary movement, reasoning, language, perception.
B. Cerebellum – It helps in maintaining balance, movement and body posture. It further gets splitted into two hemispheres.
C. Hypothalamus – This part of the brain is responsible for the regulation of the temperature of the body, hunger centre, emotions, regulation of the circadian rhythms etc.
D. Medulla oblongata: It is also known as brain stem. It regulates functions like heart rate, breathing and blood pressure
E. Thalamus – It regulates the motor and sensory information and obtains the sensory information which further carries forward the information to the cerebral cortex.
F. Limbic system – It helps in maintaining the response to different emotions.
G. Basal Ganglia – It maintains the movements and balance and also has the caudate nucleus, globus pallidus, putamen, substantia nigra and subthalamic nucleus.
H. Midbrain – It controls various functions like hearing, vision, body movement, eye movement.
Parts of Nervous System:
Neurons are known as structural and functional units of the nervous system. It is of irregular shape and has the capability to conduct electrical signals. Neurons are further divided into different parts, which are discussed below:
A. Dendrite: It is the shortest fiber in the cell and extends out from the cell body of a neuron.
B. Axon: It is considered as the longest thread in the human body of a neuron and also covered by insulating and protective covering of sheath known as myelin sheath.
C. Cell body: It is made up of cytoplasm and nucleus.
D. Synapse: Gap present between adjacent pairs of neurons, through which nerve impulses pass is known as synapse.
E. Dendrites: They are present on either side of the neuron. They look like branch projections, which connect with the adjacent neuron.
Types of Nerves:
Combination of several axons are bundled together to form a nerve. Further nerves are divided into three types they are:
A. Sensory nerve: When nerve impulse travels through the receptor to the brain or spinal cord are called sensory nerve fibers. Example. nerves in the eyes, nerves, and ears.
B. Motor nerve: When the transmission impulse is from the brain or spinal cord to the gland or muscle, it is called a motor neuron.
C. Mixed neuron: A mixed nerve consists of both the sensory and the motor nerves. Example of a mixed neuron is spinal nerves.