One system called nervous system functions by the conduction of nerve impulses like the conduction of an electric current.
What is Nervous System ?
The system that controls and coordinates all the activities of various body parts in response to external and internal stimuli by the conduction of nerve impulses is called Nervous System.
Function of Nervous System
The major function of nervous system performs are below function of nervous system :
- Control : The main function of Nervous system controls all the functions of various body parts.
- Co-ordination : Every body activity involves many body parts. The activities of all the body parts are co-ordinated and integrated by this system.
- High faculties, such as, thinking, reasoning, memory emotions, etc. are controlled by this system.
- Reflexes : All the spontaneous, automatic, involuntary activities are controlled by the nervous system.
- It keeps us informed about the outside world by way of various sense organs and it is also the function of nervous system.
- It keeps us informed about the internal environment of the body.
- The function of nervous system is also to control and co-ordinate voluntary muscular activities.
- Regulates involuntary activities such as beating of heart and breathing.
It was all about function of nervous system. All above 8 points are the most important function of nervous system.
NEURON – The unit of Nervous system
Structure of neuron ( Unit of Nervous System )
Structurally a neuron consists of three parts :
(1) Cyton : The main part of neuron is cell body called Cyton or perikaryon. It is bounded from the outside by a simple cell membrane. Its cytoplasm is called neuroplasm.
(c) Axon : From the cyton arises always one very long process called axon. It may be from few millimetres to one metre in length.
Classification of neurons ( Unit of Nervous System )
According to their functions, the neurons ( unit of nervous system ) are categorized into three types :
(a) Sensory (Afferent) neurons
(b) Motor (Efferent) neurons
(c) Association (Connector) neurons.
(a) Sensory (Afferent) neurons : These neurons ( unit of nervous system ) carry sensory impulses from the sense to the central nervous system. organs
(b) Motor (Efferent) neurons : These neurons transmit impulses from the central A nervous system to the effectors i.e. muscles or glands.
(c) Association (Connector) neurons : These neurons ( unit of nervous system ) are present in the central nervous system (brain and spinal cord) and connect sensory neurons to motor neurons.
Nerve fibres in Nervous System
An axon of a neuron covered by one or two sheaths is called nerve fibre. The nerve fibre small (microscopic) upto one metre be very may in length. Depending upon the sheaths covering the axon of neuron here called neuraxis.
(b) Non-myelinated nerve fibre
(a) Myelinated nerve fibres : In these nerve fibres the axon of neuron is surrounded by two sheaths. The inner sheath is called myelin sheath and the outer sheath is called neurilemma. The medullary sheath is not continuous showing constrictions called nodes of Ranvier.
Functions of the myelin sheath :
- To increase the speed of nerve impulse conduction.
- To insulate the axon, i.e., prevents mixing of impulses in the adjacent fibres.
(b) Non-myelinated nerve fibres : In these nerve fibres the axon of neuron is covered by only one sheath called neurilemma. Myelin sheath is absent.
What are the two types of Nervous System ?
Division of Nervous System is into two major parts. Those two types of Nervous System are :-
It includes all those nerves, nerve fibres, ganglia (aggregates of cell bodies of neuron) that carry impulses from viscera to CNS which controls involuntary actions of smooth muscles, cardiac muscles and glands.
CENTRAL NERVOUS SYSTEM ( CNS )
- Spinal cord
Position, Protection and Meninges The human brain is highly developed. It is largest amongst all the animals. In an average it approximately weighs about 1350 g.
These are Piamater (innermost, very thin, tough and highly vascular membrane), Arachnoid (thin delicate middle layer and non-vascular) and Duramater (outermost, thick, non-vascular, tough fibrous membrane), from inner to outerside.
So here is its function…
Functions of CSF :
- It serves as shock absorbing medium. It protects the brain and the rest of CNS against jerk and jolts.
- It maintains constant pressure in and around the brain.
Structure of Brain
Human brain is a whitish, bilaterally symmetrical structure. It is divisible into three regions :
It is differentiated into three parts :
(a) Olfactory lobes
(a) Olfactory lobes : The olfactory lobes of human brain are a pair of poorly developed, club-shaped, widely separated bodies. They are visible from the ventral surface only. The olfactory lobes are concerned with the sense of smell.
Functions of Cerebrum :
- It is the seat of memory, will power, emotions, experiences, intelligence, reasoning, learning, invent and plan.
- It initiates and controls the movements of striped muscles.
- It controls the conscious sensations and all voluntary actions.
- (iv) It perceives the sensory impulses, such as, pain, touch, taste, smell, hearing and sight.
- What is called subconscious or uncon- scious mind is also located in the cerebrum. Many past experiences are covered up by more recent impressions which dominate conscious activity. Past experiences may be recalled in dreams or when hypnotized or when skilfully questioned.
(c) Diencephalon : It is a small rhomboidal lobe. It is completely covered superiorly by large cerebrum but visible from the inferior surface as a small area.
Functions of Diencephalon : Diencephalon of human brain controls many body functions, such as :
- Hypothalamus temperature, control of pituitary gland and blood pressure. controls body
- Thalamus acts as a relay centre for pain pressure impulses to cerebrum.
Mid-brain of humans is significantly small, thick stalk, about 2 cm long. It connects the fore-brain with cerebellum and pons of hind brain.
Functions of Mid-brain:
- It connects the hind brain with fore brain and conveys impulses.
- It controls the sight and auditory impulses (hearing).
It is the posterior, small part of the brain. It is differentiated into three parts :
(a) Pons varolii
(c) Medulla oblongata.
(a) Pons varolii : It is centrally located below cerebellum.
It carries impulses from medulla oblongata to fore-brain. It also carries impulses from one hemisphere of the cerebellum to other and coordinates muscular movements on both sides.(b) Cerebellum : It is the largest part of hind-brain. It is present below the cerebrum and above the medulla oblongata, behind the pons.
It helps to maintain the balance or equilibrium during movements and it controls and coordinates muscular activity (balance of the body).
(c) Medulla oblongata : It is about 2.5 cm long that extends from pons to spinal cord. It is almost triangular in shape. It is also hollow from inside.
It controls the involuntary activities of internal organs like beating of heart, movement of breathing, sneezing, swallowing, vomiting, coughing, hiccupping and peristaltic movement of alimentary canal.
The Spinal Cord
The spinal cord is a long, unsegmented, cord like structure extending from medulla oblongata of brain through the neural canal of the vertebral column to the lumbar region.
Walls of vertebrae, meninges and CSF protect the spinal cord. Like-brain, spinal cord is also made-up of grey matter and white matter.
Functions of Spinal Cord:
The spinal cord performs two important functions:
- The spinal cord tracts serve as two-way conduction paths between peripheral nerves and the brain. Ascending tracts conduct sensory impulses up the cord to the brain while descending tracts conduct motor impulses down the cord from the brain.
- The spinal cord functions as reflex centre which controls all the spinal reflexes.
- It controls reflexes below neck.
PERIPHERAL NERVOUS SYSTEM ( PNS )
All the whitish, thread-like nerves, which connect the various body parts with the central nervous system, collectively constitute the peripheral nervous system. It is divided into two :
- Somatic Nervous System
- Autonomic Nervous System
Somatic nervous system
It consists of Cranial and Spinal nerves.
Cranial nerves : Those nerves which arise from the brain are called cranial nerves. There are 12 pairs of cranial nerves.
- Cervical spinal nerves in the neck – 8 pairs
- Thoracic spinal nerves in thorax – 12 pairs
- Lumbar spinal ne -5 pairs rves in abdomen
- Sacral spinal nerves in hip region 5 pairs
- Coccygeal spinal nerves in tail region -1 pair
All spinal nerves are mixed nerves.
Autonomic nervous system (ANS)
That part of the nervous system which controls all the involuntary activities of various body parts is called autonomic nervous system. It is divided in two parts :
Emotions and Autonomic Nervous System:
Autonomic nervous system is strongly influenced by emotions, such as, sorrow, happiness, anger, fear, sexual stimulation, etc.
Conclusion or Summary of the Nervous System
- What is Nervous System ?
- Function of Nervous System.
- Unit of Nervous System.
- Structure of Nervous System.
- What are the two types of Nervous System ?
- Their functions etc.