DELHI PUBLIC SCHOOL JAMNAGAR

Chapter Notes
Grade: X Subject: Biology
Topic: Chapter 7 (Control and coordination) Date: 07.10.2023

INTRODUCTION
• 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: Withdrawal of hand on touching a hot object.

Top Definitions
1) Stimulus: Any change in environment or within that bring about the reaction eg: Touching a
hot plate.
2) Response: The reaction of our body to these changes. eg. Withdrawal of our hand
3) Receptors: Specialized structures at the ends of the nerve fibres that collect/ receives
the information to be conducted by the nerves, and are located in the sense organs.
4) Gustatory receptors: Receptors present in tongue and capable of detecting taste.
5) Olfactory receptors: Receptors present in nose and capable of detecting smell.
6) Synapse: A specialized junction (gap) between two neurons, across which nerve impulse
passes.
7) Neuromuscular junction: The neuromuscular junction is a synaptic connection between the
terminal end of a motor nerve and a muscle.
8) Nerve impulse: An electrochemical signal that travels through a neuron in response to a
stimulus.
9) Effectors: A muscle or gland, or organ capable of responding to a stimulus, especially a
nerve impulse.
10) Sensory neuron: A neuron that conducts impulses from a receptor organ to the central
nervous system.
11) Motor neuron: A neuron that conducts impulses from the central nervous system to muscle
or gland (effectors).
12) Relay neuron: A neuron which connects sensory neurons with motor neurons in neural
pathways.

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:
(a) To receive the information from environment
(b) To receive the information from various body parts. (Stimuli for Response)
(c) To act accordingly through muscles and glands
 • The nervous system is composed of specialized tissues; called nervous tissue.
• The nerve cell or neuron is the functional unit of the nervous system.
• It is the nervous system which is mainly responsible for control and coordination in
complex animals.

Neuron: It is the structural and functional unit of nervous system. Neuron is a highly
specialized cell which is responsible for transmission of nerve impulses.

The neuron consists of the following parts:

(a) Dendrite: Acquires information.
(b) Cell body: Acquired information travels as an electrical impulse.
(c) Axon: Longest fibre on the cell body is called axon. It transmits electrical impulse
from cell body to dendrite of next neuron.

Note: Myelin Sheath: There is an insulator cover around the axon. This is called myelin
sheath. The myelin sheath insulates the axon against nerve impulses from the surroundings.

Types of Neuron
(a) Sensory neuron: These neurons receive signals from a sense organ.
(b) Motor neuron: These neurons send signals to a muscle or a glands (effecters)
(c) Association neuron (Relay neuron): These neurons relay the signals between sensory neuron
and motor neuron.

Mechanism of transmission of impulse (functioning of Neuron)

(i) The information from the receptors is acquired at the end of the dendritic tip of the
nerve cell as a chemical reaction that creates an electrical impulse.
(ii) The impulse travels from the dendrite to the cell body and then at the end of the axon.
(iii) Chemicals are released at the end of the axon by the effect of electrical impulse.
(iv) These chemicals (neurotransmitters) cross the synapse and start a similar electrical
impulse in the dendrite of the next neuron.
(v) Synapse 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.
(vi)The similar synapse finally allows delivery of such impulses from the neuron to the other
cells, such as muscle cells or gland.
Types of receptors and their functions

S.NO. NAME OF SENSE ORGAN NAME OF RECEPTOR FUNCTIONS

1 Ear Phono receptors Hearing and Balance of
the body
2 Eyes Photo receptors Sight
3 Skin Thermo receptors and Heat or cold and Touch
Thigmo receptors
4 Nose Olfactory receptors Smell detection
5 Tongue Gustatory receptors Taste detection

Nervous System in Humans

• The nervous system in humans can be divided into two main parts (a) the central
nervous system (b) and the peripheral nervous system.
• The peripheral nervous system can be further divided into the somatic nervous system
and the autonomous nervous system.

Central Nervous System

• The central nervous system is composed of the brain and the spinal cord.
• The brain controls all the functions in the human body.
• The spinal cord works as the relay channel for signals between the brain and the
peripheral nervous system.
Peripheral Nervous System
• The peripheral nervous system is composed of the cranial nerves and spinal nerve
• The spinal nerves come out of the spinal cord and go to the organs which are below the
head region
• Cranial nerves emerge from brain.
Autonomous Nervous System
• The autonomous nervous system is composed of a chain of nerve ganglion which runs
along the spinal cord.
• It controls all the involuntary actions in the human body.
• The autonomous nervous system can be divided into two parts: Sympathetic and Para
sympathetic
Human Brain
• Human brain is a highly complex organ; which is mainly composed of the nervous tissue.
• The brain is covered by a three- layered system of membranes; called meninges.
• Cerebrospinal fluid is filled between the meninges.
• The CSF provides cushion to the brain against mechanical shocks. Furthermore, the
brain is housed inside the skull for optimum protection.
• The human brain can be divided into three regions: forebrain, midbrain and hindbrain.
• Parts of Human Brain
(a) Forebrain: It is composed of the cerebrum.
(b) Midbrain
(c) Hindbrain: It is composed of the cerebellum, pons and medulla oblongata.

Cerebrum
• The cerebrum is the largest part in the human brain.
• It is divided into two hemispheres; called cerebral hemispheres.
• Functions of cerebrum
(a)The cerebrum controls the voluntary motor actions.
(b) It is the site of sensory perceptions; like tactile and auditory perceptions.
(c) It is the site of learning and memory.
(d) Main thinking and largest part of the brain.
(e) It has 3 main areas-
• Sensory area- to receive impulses from sense organs via Receptors
• Motor area- control voluntary movements
• Association areas- Reasoning, learning & intelligence.

Hypothalamus
• The hypothalamus lies at the base of the cerebrum
• It controls sleep and wake cycle (circadian rhythm) of the body.
• It also controls the urges for eating and drinking.

Mid brain
• Controls involuntary actions.

Cerebellum
• Cerebellum lies below the cerebrum and at the back of the whole structure
• It coordinates the precision of voluntary actions
• MAINTAINING THE POSTURE AND BALANCE OF THE BODY.
• When you are riding your bicycle; the perfect coordination between your
Pedaling and steering control is achieved by the cerebellum, WALKING IN
STRAIGHT LINE AND PICKIMG UP PENCIL.

Medulla
• It lies at the base of the brain and continues into the spinal cord.
• Medulla controls various involuntary functions; like blood pressure, salivation and
vomiting etc
Protection of the brain & the spinal cord
• Bony outer covering: skull OR BONY BOX for the brain and vertebral column/ BACK
BONE for the spinal cord.
• Cerebrospinal fluid present in between the three membranes provides shock absorption.

How does nervous tissue cause action? / How animal muscles move?
• When the nerve impulse reaches the muscle, muscle fibre moves.
• They move by changing shape so that they shorten.
• Muscle cell have special contractile proteins that both change their shape and
arrangement in the cell in response to nervous electrical impulses

Reflex Action
• Reflex action is a special case of involuntary movement in voluntary organs. When a
voluntary organ is in the vicinity of a sudden danger, it is immediately pulled away from
the danger to save itself.
• Reflex action: A reflex action is an sudden and quick involuntary reaction to a
stimulus that protects the body from potentially dangerous situations like touching
something hot.
• For example; when your hand touches a very hot electric iron, you move away your
hand in a jerk. All of this happens in flash and your hand is saved from the imminent
injury. This is an example of reflex action.

Reflex Arc
• Reflex arc: It is a shortest pathway for an impulse to travel from the receptor organ via
central nervous system to the effector
• The path through which nerves signals; involved in a reflex action; travel is called the
reflex arc.
• The following flow chart shows the flow of signal in a reflex arc.
 Receptor ⇨ Sensory Neuron ⇨ Relay
neuron ⇨ Motor neuron ⇨ Effector
(Muscle / Gland)
• The receptor is the organ which comes in the danger zone.
• The sensory neurons pick signals from the receptor and send them to the relay
neuron.
• The relay neuron is present in the spinal cord.
• The spinal cord sends signals to the effector via the motor neuron.
• The effector comes in action moves the receptor away from the danger.
• The reflex arc passes at the level of the spinal cord and the signals involved in
reflex action do not travel up to the brain. This is important because sending signals
to the brain would involve more time.
• Although every action is ultimately controlled by the brain, the reflex action is
mainly controlled at the level of spinal cord.

Endocrine System
• The endocrine system is composed of several endocrine glands.
• A ductless gland that secretes hormones directly into the bloodstream.
• A ductless gland is called endocrine gland.
• Hormones are produced in the endocrine glands.
• Hormones- (i) are chemical messenger secreted by endocrine glands
(ii) Are secreted in small amounts & may act in nearby places or distant places.
• The secretion of an endocrine gland that is transmitted by blood to specific tissues in
the body.
• Hormone is mainly composed of protein. Hormones assist the nervous system
in control and coordination.
 • Nerves do not reach to every nook and corner of the body and hence hormones
are needed to affect control and coordination in those parts. Moreover, unlike
nervous control; hormonal control is somewhat slower.

Difference between nervous and endocrine system

Nervous system Endocrine system

Mode of communication Electrical impulses Chemical compounds

Speed of communication Very quick Slow

Can reach Only cells connected by All cells of the body

nervous system

Continuity Cannot continuously Can act steadily and

transmit impulses persistently

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.
• A feedback mechanism tends to accelerate or inhibit the hormonal secretion.
• E.g., Feedback mechanism to control the sugar level in blood is as follows
 No. GLAND HORMONES Location FUNCTION TARGET
1. Hypothalamus i) Releasing Brain Regulates secretion of SITE
Pituitary
hormones (RH) pituitary hormones. gland
ii) Inhibiting
hormones
2. Pituitary Growth hormone Brain Controls growth- dwarfism & Most
Gland (GH) gigantism. tissues
3. Thyroid Gland Thyroxin Neck / Controls carbohydrate, protein Body
throat and fat metabolism tissues
4. Adrenal Gland i) Adrenaline Above Prepares the body to deal with Body
ii) Noradrenaline kidney Emergency situations tissues

5. Pancreas Insulin Below Regulates blood glucose levels Tissues

stomach
Deficiency causes Diabetes
6. Testis Testosterone Lower Develops male reproductive Male body
abdominal organs & accessory sexual tissues
region characters. Influence male
sexual behavior.

7. Ovary i) Estrogen Lower Develops female reproductive Female

abdominal organs, accessory sexual body
tissues
region characters & female
secondary behavior.
ii) Progesterone Supports pregnancy,
stimulates milk secretion.

Note: Deficiency of growth hormone causes dwarfism and over secretion causes gigantism.

How body react in stressed situations?

• In case of flight or fight reaction to an emergency situation, Adrenal glands release
adrenaline into blood
• which acts on heart and other tissues
• And causes faster heart beat so that more oxygen is supplied to muscles
• And there is reduced blood supply to digestive system and skin
• Diversion of blood to skeletal muscles to increase in breathing rate.

Why Iodized 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, Iodized salt which is necessary for proper working of thyroid gland.
• Its deficiency causes a disease called goiter (Swollen neck).
 Diabetes
• Disease in which blood sugar (glucose) level increase.
• Cause: Due to the deficiency of insulin hormone secreted by pancreas that is
responsible to control blood sugar levels.
• Treatment: Injections of insulin hormone.

Coordination in Plants
• Plants do not have a nervous system. They use chemical means for control and
coordination.
• Plant hormones (Phyto hormones) are responsible for various kinds of movements in
plants.
• Movements in plants can be divided into two main types
(i) Independent of growth (nastic movement)
(ii) Dependent on growth (tropic movement)

Independent of growth
• Immediate response to stimulus.
• 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.
E.g., Drooping of leaves of ‘Touch-me-not’ plant on touching it.

Dependent on growth
• These movements are tropic movements i.e., directional movements in response to
stimulus.
• E.g. 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.

Tropic Movement
• Tropic movements happen as a result of growth of a plant part in a particular
direction.
• The directional movements shown by plants in response to environmental factors.
• The movements which are in a particular direction in relation to the stimulus are called
tropic movements.
• There are five types of tropic movements
• Geotropic (b) Phototropic ( c) Hydrotropic (d) Thigmotropic (e) Chemotropism

Geotropic Movement
• The growth in a plant part in response to the gravity is called geotropic movement.
• The directional movements shown by plants in response to gravity.
• Roots usually show positive geotropic movement, i.e. they grow in the direction of the
gravity. Stems usually show negative geotropic movement.
Phototropic Movement
• The growth in a plant part in response to light is called phototropic movement.
• The movement of a plant towards or away from light.
• Stems show positive phototropic movement, while roots show negative phototropic
movement.
• If a plant is kept in a container in which no sunlight reaches and a hole in the container
allows some sunlight; the stem finally grows in the direction of the sunlight.
• Auxin is the shade loving hormone. It will diffuses to the shady part and cause stem cell
elongation, leading to differential growth.
• This happens because of a higher rate of growth (due to stem cell elongation in shady
part of plant) in the part of stem which is away from the sunlight
• As a result, the stem bends towards the light.
• The heightened rate of cell division is attained by increased secretion of the plant
hormone auxin in the part which is away from sunlight
Hydrotropic Movement
• When roots grow in the soil, they usually grow towards the nearest source of water.
• This shows a positive hydrotropic movement.
• The movement of a plant either towards or away from water.

Thigmotropic Movement:
• The growth in a plant part in response to touch is called thigmotropic movement.
• Such movements are seen in tendrils of climbers.
• The tendril grows in a way so as it can coil around a support.
• The differential rate of cell division in different parts of the tendril happens due to
action of auxin.

Chemotropism
• Movement or growth of an organism or part of an organism in response to a
chemical stimulus.
• Pollen tubes growth show chemotropism by growing towards the ovules.
Nastic Movement
• The movements which do not depend on the direction from the stimulus acts are called
nastic movement.
• For example; when someone touches the leaves of mimosa, the leaves droop.
• The drooping is independent of the direction from which the leaves are touched
• Such movements usually happen because of changing water balance in the cells.
• When leaves of mimosa are touched, the cells in the leaves lose water and become
flaccid; resulting in drooping of leaves.

Plant Hormones
• These are the chemicals synthesized in plants which help in regulating plant growth.
• Are chemical compounds which help to coordinate growth, development and responses to
the environment?
• They are of two types (a) Growth promoters (b) growth inhibiters
• Auxin, gibberellins and cytokinin promote growth in plant parts.
• Abscisic acid and Ethylene inhibit growth in a particular plant part.

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