CBSE Guide and CBSE Notes: Class 10 Control and Coordination - Important Definitions and Study Materials

 

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:
https://www.cbsencertsolution.com - flow diagram for Reflex Arc
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.
CBSE Guide NCERT Solution - Diagram of Human 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.
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