Whenever a person gets injury on his foot. He feels pain and his hand immediately reaches the injured site. Who informed the brain about injury? Who asked the hand to reach the site? In fact, there is an organ system in our body which carries messages from one part of the body to another and coordinates body functions. This system is called nervous system.
Human nervous system consists of central nervous system (CNS) and peripheral nervous system (PNS). The CNS consist on brain and spinal cord. While PNS consists of a network of nerves which connect the CNS to all parts of the body.
The nervous system oversees directing, supervising and controlling all the functions and activities of our organs and our organism in general.
Functions
The nervous system has the function of relationship, since, as the word indicates, it relates the functions and stimuli of the different parts of the body through this central system.
Structure
To study the nervous system, we can divide human body into two parts anatomically: the central nervous system (CNS) and the peripheral nervous system (SNP).
The Central Nervous System
The central nervous system (CNS) is made up of the brain and spinal cord. The encephalon is made up of:
- The brain: organ that controls voluntary actions. It is related to learning, memory and emotions.
- The cerebellum: coordinates the movements, reflexes and balance of the body.
- The medulla oblongata: directs the activities of the internal organs such as, for example, breathing, heartbeat and body temperature.
- The spinal cord connects to the brain and extends along the body through the inside of the spine.
The peripheral nervous system
The peripheral nervous system (SNP) encompasses all the nerves that leave the central nervous system to the whole body. It is constituted by nerves and nerve ganglia grouped in:
- Somatic nervous system (SNS): includes 3 types of nerves: sensory nerves, motor nerves and mixed nerves.
- Vegetative or autonomic nervous system (SNA): includes the sympathetic nervous system and the parasympathetic nervous system.
Read More: Peripheral Nervous System
Nervous system and Neurons
The cells of our nervous system are called neurons and exist only in this place.
Neurons receive stimuli from all parts of our body and, in turn, send the answers so that organs and other physical capacities function properly.
Neuron of Nerve Cell
Neuron or nerve cell is the basic structural and functional unit of the nervous system, I.e., brain, spinal cord and nerves are made up of neurons. Neurons carry messages in the form of Electra-chemical waves called nerve impulses.
The part of a neuron which contains nucleus and most of the cytoplasm is called cell body. The fine projections of the cell body which receive messages are called dendrites. A long projection of the cell body which conducts messages away from the cell body is called axon. Terminal ends of the axons transmit the messages to the next cells.
Interesting information: impulses may travel as fast as 150 meter per second or as slow as 0.2 meter per second.
Nerve
A nerve is an enclosed, cable-like bundle of axons present side by side in a common sheath. Nerve conveys messages carried by the individual neurons from one body part to another.
Types of Neurons
On the basis of their functions, neurons are of three types, I.e. Sensory Neurons, Motor Neurons and inter-neurons. Sensory neurons carry nerves impulses from sense organ (ears, eyes, skin, tongue, nose, etc.) to the central nervous system. Motor neurons carry nerve impulses from central nervous system to effects (muscles and glands), I.e., the parts which respond. Inter-neurons are present in central nervous system (brain and spinal cord). they from a link between sensory and motor Neurons.
Making model of a neuron
Material required
A small plastic ball, small pieces of thin wires, rope or string, a plastic cup, gum stick, needles, etc.
Procedure
- Attach small pieces of wires of different places around the plastic ball using gum stick or insulation tape.
- Attach one end of the long string or rope with the ball in the central region as shown in figure.
- Make a hole in the wall of plastic cup and tie the second end of long string with the plastic cup through the hole in its wall.
- Place the plastic ball and the cup as apart as possible on a table.
- The plastic ball will represent the cell body, pieces of wires will represent dendrites and long string will represent the axon in this model.
- Plastic cup will represent body organ with muscles or a gland.
Mini exercise
Make the diagram of a neuron or nerve cell and label its different parts.