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CLASS Xth SCIENCE
CHAPTER 07
CONTROL AND COORDINATION
Coordination- The working together of various organs of the body of an organism in a proper
manner to produce appropriate reaction to a stimulus is called coordination.
Stimulus- The changes in the environment to which an organism responds and reacts is called
Stimulus
Control & coordination in animals- takes place by
(i) Nervous system &
(ii) Endocrine system
Nervous system
Stimulus ĺ Receptor organ ĺ Sensory nerve ĺ Brain/Spinal cord
Response ← Effector organ ← Motor nerve
Endocrine system
Stimulus ĺ Endocrine organ ĺ Secrete hormone ĺ Hormone in blood
Response ← Target organ
Parts of the Nervous system – (i) Brain (ii) Spinal cord (iii) Nerves (Neurons)
A Neuron is the structural & functional unit of Nervous system
Parts of a neuron- (i) Dendrites (ii) Cell body (iii) Axon
Synapse- Space/junction between two adjacent nerves is called Synapse.
Passing of information takes place –(i) By Electric impulse (inside the neuron) and
(ii) In the form of chemicals (At synapse)
Reflex action- Spontaneous, involuntary and automatic response to a stimulus to protect us
from harmful situations. Eg. On touching a hot object unknowingly we instantly withdraw our
hand.
Reflex arc- The pathway of the reflex action is called Reflex arc.
Stimulus ĺ Receptor organ ĺ Sensory nerve ĺ Spinal cord ĺĺEffector organĺ Response
Nervous system- (1) Central Nervous system (CNS) (2) Peripheral Nervous system
(PNS)
(i) Brain (i) Autonomic Nervous system
(ii) Spinal cord (ii) Voluntary Nervous system
Brain (i) Centre of coordination of all activities (ii) Thinking is involved (iii) Complex
process
Parts of brain
Fore brain Mid brain Hind brain
(i) Cerebrum
(ii) Thalamus
(iii) Hypothallamus
----------
(i) Cerebellum
(ii) Pons
(iii) Medulla oblongata
Fore brain
Cerebrum- (i) Main thinking and largest part of the brain.
(ii) It has 3 main areas-
a. Sensory area- to receive impulses from sense organs via
Receptors
b. Motor area- control voluntary movements.
c. Association areas- Reasoning, learning & intelligence.
Thalamus – It relays sensory information to the Cerebrum
Hypothallamus- It forms the link between Nervous system & Endocrine system
Mid brain- It connects Fore brain and Hind brain. Controls reflex of eyes & ears
Hind brain- Connects the Fore brain & Hind brain
Cerebellum – Controls & coordinates muscular movements, maintaining body posture and
equilibrium.
Pons- Acts as a bridge between brain & spinal cord
Medulla oblongata- Controls involuntary actions like blood pressure, salivation, vomiting, etc.
Spinal cord- Cylindrical or tubular structure extending downwards from the Medulla
oblongata.
Protection of the brain & the spinal cord-
(i) Bony outer covering: skull for the brain & vertebral column for the spinal cord.
(ii) Cerebrospinal fluid present in between the three membranes.
Action caused by Nervous tissue
Information ĺ Nervous tissue ĺ Brain Muscles ĺ Causes action
Path or action-
Nerve impulse ĺ Muscle cell ĺ Changes shape due to special proteins
Action caused ← Shorter form of muscles ← Change shape & arrangement of cell
Chemical communication by hormones- (advantages)
(i) Electrical impulses have their limitations because they reach only those cells connected
to the nervous tissue.
(ii) Also the nerve cells cannot generate & transmit impulses continuously.
(iii)Electrical communication is slower.
Hormones- (i) are chemical messengers secreted by endocrine glands
(ii) Are secreted in small amounts & may act in nearby places or distant places.
(iii) Do not take part in the reaction & are destroyed immediately
Hormones are secreted by- Endocrine glands & Exocrine glands
S. No. Endocrine glands Exocrine glands
1. Ducts absent Ducts present
2. Secrete hormones Secrete enzymes
3. Secreted in blood Secreted in ducts of glands
4. Situated away from the site of action Situated near the site of action
Coordination in plants- Only chemical coordination is present in plants.
Tropic movements- The movements of plants in the direction of stimulus (positive) or away from it (negative) are called tropic movements. E.g. Phototropism, Geotropism.
Chemotropism.
Nastic movements -The movements of plants independent of stimuli are called nastic movements. E.g.- Touch me not plant leaves close when touched.
Plant hormones (Phytohormones)
Examples- 1. Auxins- Help in growth of root & shoot tips.
2. Gibberellins- Help in vegetative growth
3. Cytokinins- Promote cell division
4. Abscissic acid - Inhibits growth & causes wilting (falling) of leaves
Important diagrams-
1. Structure of neuron (nerve cell)2.Reflex arc 3.Human brain4.Endocrine glands .
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