Nervous system – Ncert class 10 Science givesa complete guide to the nervous system. And its complete up of the brain, spinal cord, and peripheral nerve fibres. At the macroscopic level, nerves are easily see as bundles of axons somatodendrically and myelinate axons in associate tracts called fascicles which are surround by the unmyelinate sheath called the perineurium. In spite of its structure, we don’t know much about this fascinate organ.
This article will discuss different aspects of the nervous system like motor function or memory in various body regions like cerebellum, spinal cord or cortex. These are taught in ncert class 10 science syllabus
1.The structure of the nervous system
The nervous system is a very complex structure and we do not know much about it. This is due to its complexity and slow rate of development during pregnancy, and gestation period. It takes nine months for this complex network of neurons to develop.
Nervous tissue consists of millions of neurons which are organise in a specific manner, they send and receive impulses called nerve impulses. Each nerve cell is link to other nerve cells by means of dendrites or axon, and also take end-feet situated on the dendrite or axon membrane. The organisation within the brain is hierarchical, sub-divisions take remain describe in frontal lobe, parietal lobe etc. There are also higher divisions called spinal cord segments.
The central nervous system is divided into
(i) the primate brain
(ii) the human brain,
(iii) the spinal cord, and
(iv) hypo-spinal tract.
There are two types of neurons in the spinal cord: motor neurons which control muscle movement and sensory neurons which detect physical changes in the body such as pain. Spinal nerves arise from peripheral nerves that innervate specific organs or tissues by means of myelination. Motor neurons project through tracts called tracts to interneurons and cell bodies, where it mix with inhibitory impulse and communicate to muscles through synapses. At the same time, the synaptic transmission of impulses between the motor neuron and interneuron is block, thus preventing unwanted movements.
The medulla oblongata contains smooth muscles that regulate respiration and heart rate. The brainstem controls spinal reflexes such as vomiting and sneezing. The cerebellum is responsible for balance and equilibrium. The cortex and subcortical nuclei are involve in emotions, memory, perception etc. The pineal gland keeps time while the thalamus provides sensory information to parts of the brain.
The motor system is compose of two types of neurons: motor neurons which control muscle movement and sensory neurons which detect physical changes in the body such as pain. Motor neurons project through tracts called tracts to interneurons cell bodies, where it mix with inhibitory impulse and communicate to muscles through synapses. At the same time, synaptic transmission of impulses between the motor neuron and interneuron is block, thus preventing unwanted movements.
3.Peripheral nerve fibres
Nerve fibres (axons) constitute bundles called plexus which form nerves surround internal organs or tissues for innervation: these are known as peripheral nerve fibers.
In the body, nerves usually arise from spinal neurons, whereas cranial nerves arise from interneurons.
4.Parts of the nervous system & affect on various aspects of body
The brain is responsible for higher functions such as thinking, learning (memory), reasoning and feeling emotion. The spinal cord is longer and is responsible for reflex and movements that are produce without conscious thought and intention: it continues to control posture and movement as well as body chemistry. Many other systems exist in the human body which are closely connect with the nervous system. These include:
5.Different types of neurons and functions
Functional classification of Neurotransmitters:
(i) Firstly excitatory neurons (ii) Secondly inhibitory neurons (iii)Lastly mixed neurons.
The results of synapses are either excitatory or inhibitory impulses. And also neuron not generate an impulse if the result is inhibit: impulses which result in no change in behaviour are consider mix
6.Types of neurons and their functions
Each neuron consists of a cell body, dendrites, axon, and end-feet situated on the dendrite or axon membrane.
In the cell body can found nuclei, mitochondria, and other organelles. The dendrites carry action potentials and neurotransmitters to synapses. The axon has a higher conduction velocity than the dendrite. And thus it is also responsible for carrying impulses with high conduction velocities. An axon, which originates from nerve fibre. Also bends towards the target region where it will follow the bundle of dendrophe or myelinatedfibres in association tracts called fascicles. Each fascicle has many end-feet around its circumference, some of which have synaptic contacts between them; they are called terminal branch. The dendrites and axons cross the synapse in a series of electrical impulses or spikes.
The end of the axon, called synaptic knobs and spines, it cover with the plasma membrane called synaptic membrane, which limits the diffuse of gass and ions. When the action potential reaches the synaptic knob it causes mechanical changes within the plasma membrane such as ionic currents, due to which secondary dendrites can form. Secondary dendrites consist of dendritic spines coated with myelin sheaths, terminating in synaptic knobs. One set of these knobs will travel along the fibre to discharge action potentials onto neighbouring neurons.
A nerve is compose of two types of axon and dendrites. And the axon consists of an originating cell body, dendritic tree, and terminal branches. And also the name “axon” is derive from the Greek word meaning “axis”. The typical length of the axon in a nerve is around 10–100 µm for peripheral nerves and about 1 mm for cranial nerves neurons have a special name specific to their anatomy. And also guide, Conduit or Sensory neuron etc.
8.Cells and tissues
The transmission of impulses is complete by the cells and tissues in the body including:
(i) Cells or tissues that act as receptors for stimuli or sensory information (ii) Cells and tissues that act as transmitters by means of which nerve impulses are conduct (iii) And also cells or tissues that aid in the conduction of nerve impulses, such as myelin sheaths, Schwann cells etc..
Nerve impulses and their conduction velocity
A nerve impulse is a nerve cell’s response to a stimulus. And they conduct along the axon at a conduction velocity of up to 150 metres per second.
10.Neurons and their functions
Neurons are of two types:
(i) Excitatory neurons
(ii) Inhibitory neurons.
In the central nervous system, nerve impulses that originate in sensory neurons terminate on special types of neurons called inhibitory interneurons, which in turn excite other neurons. The synapses between inhibit and excitatory nerve fibres are known as synapses of reciprocal inhibition. At these synapses, the release neurotransmitter results in lower the firing threshold of the adjacent neuron and thus inhibit its firing. At the same time, an action potential can release by an adjacent cell resulting in excitation.
The nervous system is complete up of the brain and spinal cord. Neurotransmitters are chemicals that cross cell membranes, causing excitation or inhibition of target cells.The main difference between neurons such as motor neurons is that they have dendrites. And it communicate through the gap junctions, and release action potentials. Infinity Learn provides the best ncert class 10 science solutions.
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