Control and Coordination

• Living organisms respond and react to various stimuli like heat, light, cold, touch, pressure etc. Plants and animals both respond to stimuli but in different manner.Example : withdrawl of hand on touching a hot object.

Control and Coordination in Animals

• It is brought about in all animals with the help of two main systems.

a) Nervous System
b) Endocrine System
Nervous System

• Functions

i) To receive the information from environment.

ii) To receive the information from various body parts. (Stimuli Response).

iii) To act accordingly through muscles and glands.


• Any change in environment or within that bring about the reaction e.g. : touching a hot plate.


• The reaction of our body to these changes. eg. withdrawal of our hand.

• How do we detect that we are touching a hot object?


Are specialised tips of some nerve cells that detect the information
from the environment.\n\n

Receptors are Sense Organs

• Inner Ear

• Photo receptors Eyes

• Skin

• Olfactory Receptor (Nose)

• Gustatory Receptor (Tongue)


Structural and functional unit of nervous system.

• Neuron (3 main parts)

• Dendrite (Information is acquired)

• Cell body and Axon(Information travels as an electrical impulse).

• Synapse(Part where electrical signal is converted into chemical message for onward transmission to next neuron by release of neurotransmitters)

• Synapse : The point of contact between the terminal branches of axon of one neuron with the dendrite of another neuron is called synapse.

Reflex Action

• A quick, sudden, immediate response of the body to the certain stimuli that involves Spinal cord. eg. (not brain) withdrawal of hand, knee jerk etc.

• Reflex arc : The pathway through which impulses pass is called reflex arc.


• Responses are of three main types

1. Voluntary : Controlled by fore brain eg. Talking, Writing.

2. Involuntary : Controlled by mid and hind brain eg. Heart beat, vomiting, regulation of heartbeat.

3. Reflex action : Controlled by spinal cord eg. Withdrawl of hand on touching a hot object.

Human Nervous System

a) Central Nervous System

• Brain – Fore Brain,Mid Brain,Hind Brain.

• Spinal Cord.

b) Peripheral Nervous System

• Cranial Nerves – Arise from the brain.

• Spinal Nerves – Arise from Spinal Card.

c) Autonomic Nervous System.

• Sympathetic Nervous System

• Para Sympathetic Nervous System

Human Brain

• Human brain has three major parts or regions.

a) Forebrain

b) Mid Brain

c) Hind Brain

• For Brain :

Most complex/specialized part of the brain is CEREBRUM.

• Functions :

1. Thinking part of the brain.

2. Control the voluntary actions.

3. Store information (Memory).

4. Centre associated with HUNGER.

5. Receives sensory impulses from various body parts and integrates it.

• Mid Brain :

• HYPOTHALAMUS : Chemical co-ordination.

• PITUITARY GLAND : Secretes hormones.

• Hind Brain :


i) Controls posture and balance

ii) Control precision of voluntary actions

MEDULLA Controls involuntary actions eg. blood pressure, salivation, vomiting

• PONS Involuntary action, regulation of respiration


• Brain : Brain is protected by a fluid filled balloon which acts as shock absorber and enclosed in cranium (Brain Box).

• Spinal Cord : Spinal Cord is enclosed in Vertebral column.

Coordination between Nervous and Muscular Tissue

• Information [collected by Nervous tissue] (Sensory Nerve)-Central Nervous System[CNS]-

Information Processed by [CNS] – Decesion made [by CNS] – Passed to muscles – Muscles+

• [Change in shape and arrangement of proteins] – Contraction [Muscle cell] – Muscle shorten – Action

Coordination in Plants

• Movement in Plants
a) Movement dependent on growth

• Tropic movements [directional movements in response to stimulus]

(i) Phototropism – Movement towards light.

(ii) Geotropism – Movement towards gravity.

(iii) Chemotropism – Movement towards Chemicals/growth of pollen tube towards avule.

(iv) Hydrotropism – Movement towards /water.

b) Movement independent of growth [immediate response to stimulus] eg. dropping of leaves of Touch-me-not plant on touching it.

Plant hormones

Are chemical compounds which help to coordinate growth, development and responses to the environment.

a) Auxin : [Synthesized at shoot tip].

Function : – Helps in growth.

Phototropism : more growth of cells towards light.

b) Gibberellin : Helps in the growth of the stem.

c) Cytokinins : Promotes cell division.

d) Abscisic acid : Inhibits growth, cause witting of leaves.(Stress hormone)

Hormones in Animals

• Hormones : These are the chemical messengers secreted in very small amounts by specialised tissues called ductless glands. They act on target tissues/organs usually away from their source.

• Endocrine System helps in control and coordination through chemical compounds called HORMONES.

• For glands function see table in NCERT.

Iodised Salt Is Necessary Because

• Iodine mineral is essential part of thyronine hormone so it is important that we must consume iodised salt as in turn it is essential for thyroid gland as it controls carbohydrate, proteins and fat metabolism for best balance of growth deficiency of iodine might cause disease called goitre.


• Cause : It is due to deficiency of Insulin hormone secreted by Pancreas that is responsible to lower/control the blood sugar levels.

• Treatment : Patients have to internally administer injections of insulin hormone which helps in regulating blood-sugar level.

Feedback Mechanism makes sure that hormones should be secreted in precise quantities and at right time, which is regulated by feedback mechanism.

Important Questions

1.  Name the largest part of the hind-brain.

Ans. Cerebellum.

2. Name the system which facilitates the communication between the central nervous system and the other body parts of the body.

Ans. Peripheral nervous system.

3. State the role played by ovaries in a human female.

Ans. Ovaries produce mature ova which in turn produces a female sex hormone called estrogen. Estrogen is essential for development of secondary sex organs in female as well as secondary sexual characters like high pitch voice, development of mammary glands.

4. Name the longest cell present in the human body.

Ans. Neuron is the longest cell present in human body.

5. Name the gland and the hormone secreted by the gland, which are associated with following problems :

(i) a girl has grown extremely tall.

(ii) a woman has a swollen neck.

Ans. (i) Pituitary gland – Growth hormone.

(ii) Thyroid gland – Thyroxine hormone.

6. Trace the sequence of events through a reflex arc which occur when a bright light is focussed on your eyes.

Ans. Light – Eye – Sensory neuron – Central nervous system – Motor neuron – Effector muscle – Eye lids close.

7. “As the blood sugar level in our body falls insulin secretion is reduced.” Justify this statement in the reference of feedback mechanism that regulates the timing and amount of hormone released.

Ans. Insulin is a hormone that regulates our blood sugar level by converting it into glycogen which can be stored.

Hence, if there is more levels of sugar in blood then more insulin is produced and if the sugar level is less than insulin production is also reduced.

This is because of feedback mechanism where the blood sugar itself acts as a feedback for more or reduced insulin synthesis.

8. What is synapse ? In a neuron cell how is an electrical impulse created and what is the role of synapse in this context ?

Ans. Synapse is the gap/junction between two successive neurons.

All information from the environment is detected by the specialized tips of some nerve cells present in tissues and organs. These are called receptors. They are located in our sense organs like nose, tongue, skin, eye and inner ear.

Sensory receptors are of different types. Photoreceptors, phonoreceptors, olfactoreceptors, gustatoreceptors, thermoreceptors and so on. They detect light, sound, smell, taste, heat and cold respectively.

The above mentioned receptors initiate electrical impulses to be picked up by sensory nerves. This impulse travels from the dendrite to the cell body, and then along the axon to its end. Axon ending of one neuron are placed close to dendrites of the next neuron. This junction is called synapse or gap. As soon as the impulse reaches the end of neuron it sets off release of some chemical (Neurotransmitters). These chemicals cross the gap or synapse and start a similar electrical impulse in dendrite of next neuron. Finally, the impulse reaches a muscle or a gland.

9. If you happen to touch a hot object what would be your response ? With the help of well labelled diagram explain how this response happen.

Ans. If we happen to touch a hot object unknowingly, then our hand will be retraced back away from it. This happens as it is a never mediated, automatic, involuntary and a spontaneous response acting without consulting the will. Such a response is referred as a reflex action. The pathway taken by a stimulus to travel from receptor organ to effector organ is known as reflex arc.

10. Name the two components of central nervous system. How are they protected ? Name the component which is considered as highest coordinating centre of the body. Describe its three regions.

Ans. Brain and spinal cord are the two components of central nervous system.

Human brain is protected by a bony skull, also called as cranium. Internal to the skull it is covered from outside by three membranes called menings. In between the meninges there is a fluid called as cerebrospinal fluid. Bneath the membranes brain is subdivided into three major parts namely fore-brain, midbrain and hind brain.

Brain is considered as highest coordinating centre of the body.

Its three regions are given below :

(a) Fore-brain is the main thinking part of the brain. It has different regions or areas such as :

(i) Sensory area – It receives sensory impulses from various receptors.

(ii) Auditory area – It is concerned with hearing.

(iii) Gustatory area – It is concerned with taste.

(iv) Olfactory area –  Ii is concerned with smell.

(v)  Optic area – It is concerned with sight.

(vi) Association area – This area interprets various sensory informations and makes decision how to respond.

(vii) Motor area – Decisions made by association area is passed on to this area which control the movement of voluntary muscles.

(b) Midbrain comprises of four lobes. So it is also known as copra quadrigemina. Actions of involuntary muscles are controlled by the mid-brain and hind-brain.

(c) Hind-brain compirses of cerebellum, pons varolii and medulla oblongata. Cerebellum is the second largest part of brain that coordinated muscular activity of the body as well as maintaining body equilibrium or posture. Pons connects cerebellum and medulla oblongata and functions as a relay cenre among different parts of brain. It possesses pneumotaxix area of respiratory centre. Medulla oblongata lies bellow cerebellum and continues behind spinal cord. Involuntary actions like blood pressure, salivation and vomiting are controlld by the medulla in the hind-brain.

11. With the help of suitable example explain the terms phototropism, geotropism and chemotropism.

Ans. (i) The stimulus oriented movement of plant or plant part is called tropism. The direction of movement is related to the direction of stimulus. These movements are always growth oriented movements. They are of different types namely phototropism( Growth movement in response to light), hydrotropism ( water), geotropism (force of gravity), thigmotorpism (contact) and chemotropism (chemical).

(ii) Phototropism is a directional growth movement which occours in response to unidirectional exposure to light. The region of photoreception is shoot apex where auxin is produced. Auxin moves from illuminated region to the shaded region. This causes more growth on the dark side of stem causing it to bend towards the source of light. Movement of shoot towards light is called phototropism.

(iii) Roots are positively geotropic and negatively phototropic. Shoots are positively phototropic and negatively geotropic. Growth of pollen tube inside the style, ovary and ovule in response to the chemicals produced by them is an example of chemotropism.

12. (a) Define hormone. Write four characterstics of hormones in humans.

(b) Name the disorder caused by the following situation :

(i) Under secretion of growth hormone.

(ii) Over secretion of growth hormone.

(iii) Under secretion of insulin.

(iv) Deficiency of iodine.

Ans. (a) Hormones are chemical informational molecules that are required in minutes quantities and are directly poured in the blood stream. They act on a specific organ called target organ. So their site of production varies from site of action.

Their characteristics are :

(i) They are poured into blood stream.

(ii) Are generally proteinaceous or steroid.

(iii) Their secretion is regulated by feedback mechanism.

(iv) Their site of action and secretion is different.

(b) (i) Dwarfism

(ii) Gigantism

(iii) Diabetes

(iv) Goitre.

13. What is the significance of peripheral nervous system ? Name the components of this nervous system.

Ans. Peripheral nervous system comprises of nerves that directly arise from central nervous system connecting different parts of the body for voluntary control of the brain. It consists of cranial nerves and spinal nerves.

14. How do muscle cells respond to electrical impulses ?

Ans. Muscle cells have special proteins that change their shape and arrangement in the cell in response to electrical impulse. This leads to the excitation of the excitation of the muscle cells which then spreads over the whole muscle fibre. thereby causing it to shorten or contract.

15. List two primary functions of testosterone.

Ans. Testosterone is a male hormone that

(i) stimulates the development of male secondary sex organs at puberty.

(ii) also helps in development of male secondary sexual character like beard, moustache, deep voice and growth of bones.