Different organs work together in an organism to carry out different functions, this is known as coordination. Proper control and coordination are necessary to carry out essential functions of life.
Coordination is mainly of two types:
1. Nervous coordination
2. Chemical coordination
The structural and functional unit of the nervous system.
Neuron (nerve cell) is the longest cell of the human body (up to 100 cm)
Neuron is made up of -
(i) Cell body
(ii) Cell processes (axon and dendron)
(i) Cell body: or Cyton or Soma or Perikaryon
(ii) Cell process:
(a) Axon:
Axon is the functional part of nerve cell, therefore the term "nerve fibre" usually refers to the axon.
Neuron
(b) Dendron:
Differences between Axon and Dendron
S.No. | Features | Axon | Dendron |
1 | Size | Long | Small |
2 | Number | Either absent or one | Either absent or one, mostly many |
3 | Diameter | Uniform | Non - Uniform |
4 | Branching | Generally unbranched | Branched |
5 | Terminal knobs (Telodendrin) | Present | Absent |
6 | Nissl's granule | Absent | Present |
7 | Myelin sheath | Present | Absent |
8 | The direction of nerve impulse | Away from cyton | Towards cyton |
Differences between medullated and non-medullated nerve fibre
S.No. | Features | Medullated nerve fibre | Non-medullated nerve fibre |
1 | Occurrence | White Matter | Grey Matter |
2 | Sheath | Two: inner medullary, outer neurilemma | Only neurilemma |
3 | Node of Ranvier | Present | Absent |
4 | Speed of nerve impulse | Faster | Slower |
Three Types of Neurons
Synapse
The junction between two adjacent neurons i.e. between the axon ending of one neuron and dendrites of the next.
Synapse between two Neurons
Nerve impulse
It is an electro-chemical information (signal) passing through neuron.
Neurotransmitters or Neurohormones
Chemical substances which either transmit or inhibit the message from one neuron to another.
Stimulatory Neurotransmitters | Inhibitory Neurotransmitters |
Stimulate impulse at synapse | Inhibit impulse at synapse |
Example: Acetyl choline (ACh) | Example: GABA (Gamma Amino Butyric Acid) |
Neuro-muscular Junction
Transmission of Nerve Impulse across Synapse
Receptors | Stimuli | Location |
Photoreceptors | light | eyes |
Phonoreceptors | sound | internal ear |
Olfactroreceptors | smell | nasal chamber |
Gustatoreceptors | taste | taste buds on tongue |
Tangoreceptors | touch | skin |
Thermoreceptos | temperature | skin |
Algesireceptors | pain | skin |
1. What is the nervous system in animals? |
2. How does the nervous system coordinate in animals? |
3. What is nervous coordination in animals? |
4. How do animals use nervous coordination to survive? |
5. What are some examples of nervous coordination in animals? |
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