Introduction
- The quick information-processing network of our body is the nervous system.
- It enables organisms to sense changes, interpret them, and coordinate appropriate actions.
- The brain, spinal cord, neurons, receptor cells, and synapses are all parts of this system.
The Nervous System =
Central Nervous System (CNS)
+
Peripheral Nervous System (PNS)
+
Peripheral Nervous System (PNS)
Example
Central Nervous System and Peripheral Nervous System
- The brain and spinal cord make up the Central Nervous System (CNS). It controls our body.
- The CNS and other parts of the body are linked by multiple branches of nerves, known as the Peripheral Nervous System.
- Body sends signals that travel through the Peripheral Nervous System and reach the CNS.
- The brain receives a signal, interprets it, and then sends a response to the relevant body part.
- The body sends a signal to the brain by the spinal cord in the form of an impulse, and the brain sends to the body as response.
What are Neurons?
- Neurons are the fundamental component of the nervous system.
- Neurons carry the impulses from the body to the CNS and from the CNS to the body, which is known as neurotransmission.
Structure:
- A cell body, dendrites, dendron, axon, and axon terminals together constitute a neuron.
- The cell body has the nucleus and other organelles.
- Dendrites include a tiny, branch-like structure.
- A layer of fat surrounds the dendron and axon, and is known as the myelin sheath.
- At the end of a neuron, axon terminals are present.
Mechanism of a neuron:
- An electrical impulse is taken by the branch-like dendrites.
- From the dendrites, it is passed on to the dendron and the axon.
- Both of these are long so that the neurotransmission is quicker.
- The myelin sheath allows an impulse to travel more rapidly as it can jump between gaps to speed up this transmission.
- The axon ends in axon terminals that transfer the impulses to the relevant surrounding neurons.
Synapse
- A neuron passes on information to the next neuron so that it reaches either the CNS or the body.
- There is a tiny gap between two neurons, known as a synapse.
- At the synapse, there is an axon terminal of one neuron and dendrites of another.
- In a neuron, a signal runs in the form of an electrical impulse.
- The electrical impulse triggers the chemical messengers to release.
- From the axon terminal, the signal is sent in the form of chemical messengers.
- The chemical messengers cover the tiny gap and reach the dendrites of the next neuron and generate an electrical impulse.
Types of Neurons
- On the basis of their functions, neurons are classified into three types: Sensory Neurons, Relay Neurons, and Motor Neurons.
Need help with Nervous System?
Our tutors explain it step by step, matched to your exam board.
Book a Consultation →Types of Nerves
- Nerves, based on their functions, are of three types:
- Sensory Nerves are made up of a collection of axons from sensory neurons and send signals to the CNS.
- Axons from motor neurons constitute Motor Nerves. Their signal follows the same pathways.
- Mixed Nerves have both sensory and motor fibers, thus serve both functions.
Receptor Cells and Reaction to stimulus
- Our body can detect any internal or external change, which is known as a stimulus.
- Sense organs in our body have cells that identify various kinds of changes. These cells are receptor cells.
- When receptor cells detect a stimulus, they generate impulses.
- From the sense organs, these impulses are usually carried to the brain by the nerves.
- After processing the information received, the brain sends impulses to the relevant part of the body.
- This causes an action, known as a response.
- For example, we see an apple with our eyes. The receptor cells detect a stimulus, produce an impulse, and sensory neurons take it to the brain. It processes, makes decision and transmits a signal to the muscles (effector) that carry out the response by picking up the apple.
Reflex Arc
- Our body has a system that saves it from a harmful stimulus.
- When a sudden, harmful change comes into contact with our body, we tend to take quick action to protect ourselves.
- For example, withdrawal of the hand immediately when it touches a hot pan.
- This quick and involuntary response to a stimulus is a reflex action.
- The neural pathway that is followed for reflex action to complete is called the Reflex Arc.
The Reflex Arc Pathway:
FAQS
Two main parts of the nervous system include the Central Nervous System and the Peripheral Nervous System.
A stimulus is a change inside the body or in the surroundings, interpreted by receptor cells.
A synapse is the gap between neurons where impulses cross via chemical messengers called neurotransmitters.
The nerve pathway followed for the rapid and automatic response to a harmful stimulus is called the reflex arc.
No, reflex action and the reflex arc are not the same. Reflex action is the sudden and involuntary response to a stimulus, whereas the reflex arc is the pathway.
Sensory neurons take signals from the body to the Central Nervous System. However, motor neurons transmit signals from the CNS to the muscles and glands to respond.
