CANTROL AND CO-ORDINATION

Introduction

→ All the living organisms respond and react to changes in the

environment around them.

→ The changes in the environment to which the organisms respond

and react are called stimuli such as light, heat, cold, sound, smell, touch
etc.

→ Both plants and animals respond to s muli but in a different

manner.

Systems for Control and Coordination in Animals

→ Control and Coordina on in animals is done with the help of two

main systems:

(i) Nervous system

(ii) Endocrine system

Nervous System
→ Control and coordina on are provided by nervous and muscular
tissues.

→ Nervous ssue is made up of an organized network of nerve cells or

neurons which is specialized for conducting information via electrical
impulses from one part of the body to another.

Receptors

→ These are specialized ps of some nerve cells that detect the

information from the environment. `These are located in our sense
organs.

(i) Ear: It acts as phonoreceptors (receiving sound). It helps in hearing

and maintaining the balance of body.

(ii) Eyes: It acts as photoreceptors (receiving light). It helps in seeing

(iii) Skin: It acts as thermoreceptors (feels temperature). It helps in

feeling heat or cold and touch.
(iv) Nose: It acts as olfactory receptors (sense of smell). It helps in the
detection of the smell.

(v) Tongue: It acts as Gustatory receptors (sense of test). It helps in the

detection of taste.

Neuron

It is the structural and functional unit of nervous system

Functioning of Neuron

→ The informa on from receptors is acquired at the end of the

dendritic tip of a nerve cell as chemical reaction that creates an
electrical impulse.

→ This impulse travels from the dendrite to the cell body and then at
the end of the axon.

→ Chemicals are released at the end of the axon by the effect of

electrical impulse.
→ These chemicals cross the gap (synapse) and start a similar electrical
impulse in a dendrite of the next neuron.

→ The similar synapse finally allows delivery of such impulses from

neurons to other cells, such as muscles cells or gland.

Parts of Neuron

(i) Dendrite: It acquires information.

(ii) Cell body: The information acquired by it travels as an electrical

impulse.

(iii) Axon: It is the longest fibre on the cell body is called axon. It
transmits electrical impulse from cell body to dendrite of next neuron.
Synapse: It is the gap between the nerve ending of one neuron and
dendrite of the other neuron. Here, electrical signal is converted into
chemical signal for onward transmission.

Reflex Action

→ Reflex ac on is quick, sudden and immediate response of the body

to a stimulus.

Example: Knee jerk, withdrawal of hand on touching hot object.

→ S mulus: It is observable or detectable change in the external or

internal environment to which an organism reacts.

→ Reflex arc: The pathway through which nerve impulses pass during
reflex action is called reflex arc.
→ Response: It is the final reac on a er the reflex action.

Three types of responses:

(i) Voluntary: Controlled by fore brain. Example: talking, writing.

(ii) Involuntary: Controlled by mid and hind brain. Example: heart beat,
vomiting, respiration.

(iii) Reflex action: Controlled by spinal cord. Example: withdrawal of

hand on touching a hot object.

Need for Reflex Actions

→ In some situa ons such as touching a hot object, pinching etc. we

need to act quickly, otherwise our body would be harmed. Here
response is generated from spinal cord instead of brain. In this way,
time for taking action is reduced which save us from injury.

Human Nervous System

→ Human nervous system consists of two parts, Central nervous

system (CNS) and Peripheral nervous system (PNS).

→ Central nervous system consists of Brain and Spinal Cord.

→ Peripheral nervous system consists of Cranial Nerves which arise

from the brain and Spinal Nerves which arise from the Spinal cord.

Human Brain

→ Brain is the main coordina ng centre of the body. It has three major
parts:

(i) Fore-brain

(ii) Mid-brain

(iii) Hind-brain
Fore-brain

→ It is the most complex or specialised part of the brain. It consists of

cerebrum.

→ Func ons of Fore-brain:

(i) Thinking part of the brain.

(ii) Control the voluntary actions.

(iii)Store information (Memory).

(iv) Receives sensory impulses from various parts of the body and
integrate it.

(v) Centre associated with hunger.

Mid-brain

→ Controls involuntary ac ons such as change in pupil size and reflex

movements of head, neck and trunk.
Hind-brain

It has three parts:

(i) Cerebellum : Controls posture and balance. Precision of voluntary

actions. Example: picking pen.

(ii) Medulla : Controls involuntary actions. Example: blood pressure,

salivation, vomiting.

(iii) Pons : Involuntary actions, regulation of respiration.

Protection of Brain and Spinal Cord

→ Protec on of Brain: Brain is protected by a fluid filled balloon which

acts as shock absorber and is enclosed in cranium (skull or brain box).

→ Protec on of Spinal Cord: Spinal cord is enclosed in vertebral

column.

Coordination between Nervous and Muscular Tissue

→ For taking place the voluntary ac ons, the brain has to send
messages to muscles.

→ The communica on between the central nervous system and the

other parts of the body is facilitated by the peripheral nervous system
consisting of cranial nerves arising from the brain and spinal nerves
arising from the spinal cord.

→ The brain thus allows us to think and take ac ons based on that
thinking. This is accomplished through a complex design, with different
parts of the brain responsible for integrating different inputs and
outputs.

Limitations of Electric communication/Nervous system

(i) Electric impulse will reach only to those cells that are connected by
nervous tissue.

(ii) After generation and transmission of an electrical impulse, the cell

takes some time to reset its mechanism before transmitting another
impulse. So cells cannot continually create and transmit impulse.
(iii) Plants do not have any nervous system.

Chemical communication

→ It helps in overcoming the limita ons of electric communica on.

Coordination in Plants

→ There are three types of movements in plants.

(i) Independent of growth

(ii) Dependent on growth

Independent of growth

→ Independent growth has immediate response to the s mulus.

• Plants use electrical-chemical means to convey information from cell
to cell.

• For movement to happen, cells change their shape by changing the

amount of water in them, resulting in swelling or shrinking of cells.

Example: Drooping of leaves of ‘Touch-me-not’ plant on touching it.

Dependent on growth

→ These movements are tropic movements i.e., direc onal movements

in response to stimulus.

• Tendrils: The part of tendril away from the object grows more rapidly
as compared to the part near the object. This causes circulating of
tendril around the object.

• Phototropism: Movement towards light.

• Geotropism: Movement towards/away from gravity.

• Chemotropism: Growth of pollen tube towards ovule.

• Hydrotropism : Movement towards water.

Plant Hormones

→ These are chemical compounds which help to coordinate growth,

development and responses to the environment.

→ Main plant hormones are:

• Auxin: This hormones synthesized at shoot tip. It helps the cells to

grow longer and involved in phototropism (response towards light).

• Gibberellin : It helps in the growth of the stem.

• Cytokinins: It promotes cell division. This is present in greater

concentration in fruits and seeds

• Abscisic Acid: It inhibits growth. It also cause wilting of leaves and also
known as stress hormone.
Hormones in Animals

→ Hormones are the chemical substances which coordinate the

activities of living organisms and also their growth.

• Endocrine glands : These glands secrete their product (hormone) into

the blood and the main organ for releasing the hormones.

• The list of endocrine gland with the hormones names and their
functions are given below:

(i) Thyroxine: This hormone is secreted by Thyroid. The Thyroid is

located in Neck/Throat region. It regulates the metabolism of
carbohydrates, fats and proteins.

(ii) Growth hormones: This is secreted by Pituitary (master gland). This

gland is located in Mid-brain. It regulates growth and development.

(iii) Adrenaline: This hormone is secreted by Adrenal. The adrenal gland

is located above both kidneys. It regulates blood pressure (increasing),
heart beat, carbohydrate metabolism (during emergency).
(iv) Insulin: This hormone is secreted by Pancreas. The pancreas is
located below stomach. It reduces and regulates blood sugar level.

(v) Sex hormones:

(a) Testosteron in males: This hormone is secreted by testis. The testis

is located in genital area. Its changes associated with puberty (Sexual
maturity).

(b) Estrogen in females: This hormone is secreted by Ovaries. The

ovaries are located in lower abdomen area. Its changes associated with
puberty (Sexual maturity).

Importance of iodine

Iodised salt is necessary because iodine mineral is essential part of

thyroxine hormone secreted by thyroid gland. Thyroxine regulates
metabolism of carbohydrates, fats and proteins. So, we must consume
iodised salt which is necessary for proper working of thyroid gland. It’s
deficiency causes a disease called goiter (Swollen neck).

Diabetes
Diabetes is a disease in which blood sugar level increases.

Cause of Diabetes

The disease is caused due to the deficiency of insulin hormone secreted

by pancreas that is responsible to control blood sugar levels.

Treatment of Diabetes

Injections of insulin hormone can help in the treatment of diabetes.

Feedback Mechanism

→ The excess or deficiency of hormones has a harmful effect on our

body. Feedback mechanism makes sure that hormones should be
secreted in precise quantity and at right time.

Example: Feedback mechanism to control the sugar level in blood is as

follows: