Class X Science: Chapter 7, Control and Coordination
CBSE Notes | CBSE Guide | Important Terms &
Definitions
Geotropism
The upward and downward growth of shoots and
roots, respectively in response to the gravity of the earth is termed as
Geotropism. Example - roots are positively geotropic while shoots are
negatively geotropic.
Hydrotropism
The tendency of plants to grow towards water or
moisture is called hydrotropism. Example - roots are positively hydrotropism.
Phototropism
Phototropism is the growth movement of plants in
response to light. The shoots of a plant show positive phototropism and the
roots of a plant show negative phototropism. Example - the flower head of
sunflower is positively phototropic as it moves from east to west along with
sun.
Chemotropism
It is the tendency of growth towards some
chemical, e.g., growth of pollen tubes towards ovules and some organic
substances.
NERVOUS SYSTEM
(i) It is a system of conducting tissues that
receives stimulus and transmit it to other parts of the body forming network.
(ii) It is the most important for regulation,
control and coordination of body functions.
(iii) Comprises of neurons, nerves and nervous
organs.
(iv) Vertebrate nervous system consists of two
parts:
(A) Central Nervous System (CNS) including brain
and spinal cord.
(B) Peripheral Nervous System (PNS) including
cranial, spinal and visceral nerves
FUNCTIONS OF THE NERVOUS SYSTEM
(i) Regulates involuntary actions.
(ii) Controls and coordinates voluntary muscular
activities.
(iii) Keeps us inform about the outside world
through the sense organs.
(iv) Enables us to think, reason and remember.
(v) Controls all the reflex actions.
RECEPTOR
It is a cell or group of cells specialised to
detect a particular stimulus and to initiate the transmission of impulses via
the sensory nerves. There are five receptors or sense organs through which the
animals receive stimuli. These receptors are:
1. Photoreceptors for light (eyes),
2. Photoreceptors for sounds (ears),
3. Gustatory receptors for taste (tongue),
4. Olfactoreceptors for smell (nose),
5. Thigmo receptors for touch (skin).
The receptors pass information to the brain
through neurons.
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MECHANISM OF REFLEX ACTION
Reflex action involves the following steps:
(i) Receptor organ like skin perceive the
stimulus and activates a sensory nerve impulse.
(ii) Sensory organ carries message in the form
of sensory impulse to the spinal cord.
(iii) The spinal cord acts as modulator. The
neurons of spinal cord transmit the sensory nerve impulse to motor neuron.
(iv) Motor nerve conducts these impulses to the
effectors like leg muscles etc.
ADVANTAGES OF REFLEX ACTION
(A) It enables the body to give prompt and
appropriate responses to harmful stimuli and thus, protects our body.
(B) It minimises overloading of brain.
REFLEX ARC
It is the pathway taken by the nerves impulses
and responses in a reflex action. For example, impulses from receptor organs
like skin to the spinal cord and from the spinal cord to the effector organs
like muscles.
The reflex arc pathway can be shown in a flow
chart (Diagram) as below:
BRAIN
It is the highest coordinating centre in the
body. It is a part of the central nervous system and receives information from
various parts of the body and interprets them. There are 12 pairs of cranial
nerves which arise from the brain and spread throughout the head. The brain is
broadly divided into three regions: Fore-brain, Mid-brain and Hind-brain.
(A) Fore-brain
1. It is the main thinking part and the largest
region of the brain.
2. Includes prominent regions such as -
olfactory lobes, thalamus and hypothalamus.
3. Cerebrum is the dome - shaped roof of the brain. Different
areas of cerebrum have different functions, such as, sensory areas and motor
areas. There are specific regions of cerebrum for each kind of stimulus and
response. For example,
(a) Occipital lobe - region for site ie.,
visual reception.
(b) Temporal lobe - region for hearing
ie., auditory reception.
(c) Frontal lobe - region for speech,
facial muscle and higher mental activities.
(d) Parietal lobe - region for taste,
smell, touch and consciousness.
(e) Olfactory lobes - contain
Olfactoreceptors which are the organs of smell.
4. Thalamus is the major
coordinating center for sensory and motor signals, while Hypothalamus controls body
temperature, hunger, thirst etc.
(B) Mid-brain
1. Connects the fore-brain to hind-brain.
2. It controls reflex movements of the head,
neck and trunk.
(C) Hind-brain
1. Consists of three centres: Cerebellum, Pons
and Medulla Oblongeta.
2. Cerebellum lies at the roof of the hind-brain. It controls
the coordination of the body movements and posture.
3. Pons lie just above the Medulla and take part in
regulating respiration.
4. Medulla Oblongeta lies at the floor of the hind - brain and continues
into the spinal cord. It regulates swallowing, coughing, sneezing and vomiting.
FUNCTIONS OF BRAIN
1. Receives information carrying impulses from
all the sensory organs of the body.
2. Responds to the impulses by sending
instructions to the muscles and glands causing then to function accordingly.
3. Correlates various stimuli from different
sense organs and produces the most appropriate response.
4. Controls and coordinates all body activities.
5. Stores information so that behaviour can be
modified according to the past experience.
SPINAL CORD
1. It is the cylindrical structure and a part of
the CNS.
2. It begins in continuation with Medulla
oblongeta and extended downwards.
3. It is enclosed in a bony cage called
Vertebral Column. Coccyx is
the last bone of the Vertebral Column.
4. Thirty one pairs of Spinal Nerves arise from the spinal cord and spread throughout
the body.
5. It acts as a modular of reflex action.
Also Read: Class 10 Cbse Ncert Solution for all major subjects (Chapter Exercises
plus CBSE Notes and extra CBSE Hots for 10th NCERT textbooks)
TYPES OF PLANT HORMONES (PHYTOHORMONES)
1. Auxins, 2.
Gibberellins, 3. Cytokinins, and 4. Abscisic Acid (ABA).
Auxins
(a) Synthesised at the shoot-tip of the plant
body.
(b) Promotes cell elongation, root formation,
cell division, respiration and physiological processes like protein synthesis,
water uptake and proto-plasmic permeability.
(c) Play an important role in development of seedless
fruits.
Gibberellins
(a) Stimulate stem elongation, seed germination
and flowering.
(b) Maximum concentration of Gibberellins is
found in fruits and seeds.
Cytokinins
(a) Are produced in dividing cells throughout
the plant.
(b) In mature plants, Cytokinins are produced in
the root tips and are transported to shoot tip.
(c) Promote cell division, breaking of seeds,
buds and regulates flowing transport.
(d) Promote opening of stomata.
Abscisic Acid (ABA)
(a) It is a growth inhibitor which reverses the
growth.
(b) It causes dormancy of seeds, tubers and
bulbs.
(c) Promotes closing of stomata and is
responsible for the loss of RNA, proteins and chlorophyll.
Class 10 NCERT Science Chapter 7,
Control and Coordination - Related Posts
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