plzzz give notes of chapter 7 ncert class 10
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THE NERVOUS SYSTEM
Neuron
Neuron is the structural and functional unit of the nervous system.
Central nervous system
The central nervous system (CNS) is made up of the brain and the spinal cord. Functions of different parts of the brain are:
Peripheral nervous system
The nerves given out by the brain and the spinal cord form the peripheral nervous system (PNS).
There are 12 cranial nerves and 31 spinal nerves in humans.
Somatic nervous system
It forms a part of the PNS.
The nerves of PNS that control the voluntary actions of the body form the somatic nervous system.
Autonomic nervous system
All the nerves of the PNS that control the involuntary actions in the body form the autonomic nervous system.
Two divisions of autonomic nervous system are: sympathetic and parasympathetic nervous system.
The sympathetic nervous system prepares the body for intense physical activity and is often referred to as the fight-or-flight response, while the parasympathetic nervous system has almost the exact opposite effect and relaxes the body and inhibits or slows many high energy functions.
Reflex action
Reflex action is a sudden, involuntary reaction of the body in response to stimuli.
Reflex arc
It is the path followed by electrical impulse during a reflex action.
The impulse travels from the receptor organ to the spinal cord/brain. It is processed there and the information is brought back to the concerned muscle to carry out the action.
Protection of CNS
The brain is protected by 3 main layers –
The bony skull (cranium)
The cerebrospinal fluid
The meninges (Dura mater, Arachnoid and Pia mater).
Plant Hormones and Movements
Plant hormones
Control and coordination in plants are carried out by hormones.
Growth independent movements
The movements which are not growth related are called nastic movements. These movements occur in response to environmental stimuli but the direction of response is not dependent on the direction of the stimulus.
Examples:
Phototropic movement (light dependent)
Geotropic movement (gravity dependent)
Chemotropic movement (chemical dependent)
Hydrotropic movement (water dependent)
Thigmotropic movement (touch dependent)
Geotropism
Movement of plant parts in response to earth’s gravitational force is known as geotropism/gravitropism.
Towards gravity – positive geotropism
Away from gravity – negative geotropism
Root grows towards gravity and shoot grows away from gravity
Phototropism
Movement of plant parts in response to light is known as phototropism.
Towards light – positive phototropism
Away from light – negative phototropism
Stems move towards light and roots move away from light
To know more about Phototropism, visit here.
Hydrotropism
Movement of plant parts in response to water or moisture.
Towards water – positive hydrotropism
Away from water – negative hydrotropism
Again, root movement in search of water is positive hydrotropism
Chemotropism
Movement of plant parts in response to chemical stimuli is known as chemotropism.
Towards chemical – positive chemotropism
Away from chemical – negative chemotropism
The growth of pollen tube towards the ovule is positive chemotropism
Thigmotropism
Movement of plant parts in response to touch is called as thigmotropism.
Towards touch – Positive thigmotropism
Away from touch – negative thigmotropism
Movement of tendrils around the support is positive thigmotropism
The Endocrine System
Exocrine glands
Exocrine glands are glands that discharge secretions by means of ducts, which open onto an epithelial surface.
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