CONTROL AND COORDINATION (Prashant Kirad).pdf

Control&
coordination
CLASS X - SCIENCE
CLASS X - SCIENCE

Coordination: working together of the various organs of an organism to
adjust various activities of life.
Control & coordination ensures:
Correct movement for each specific change (stimulus).
No wrong or unnecessary actions.
Coordination in Animals
Nervous System (Associated with Neurons)
Endocrine System (Associated with Hormones)
Coordination in Plants
Plant Movements
Plant Hormones
CONTROL & COORDINATION

COORDINATION IN ANIMALS:
Endocrine system
Nervous system
Central Peripheral
Hormones
Brain Spinal cord Cranial nerves Spinal nerves
Arise from the brain Arise from spinal cord
Fore - Brain
Mid - Brain
Hind- Brain

Receptors: Cells or groups of cells present in sense organs that detect stimuli and
convert them into nerve impulses.
Photoreceptors
Phonoreceptors Olfactoryreceptors
Location: Eye (retina)
Function: Detect light and
help in vision
Location: Inner ear
Function: Detect sound vibrations and help in hearing.
Location: Skin
Function: Detect temperature
changes (hot or cold).
Location: Nose
Function: Detect smells/odours.
Location: Tongue
Function: Detect taste
(sweet, sour, salty, bitter,
umami).
Stimulus (Stimuli) →Any change in the environment (internal or external) that
produces a response in an organism.Example: Light, sound, smell, touch, temperature.
Gustatoryreceptors
Thermoreceptors

Effectors: Parts of the body that respond to impulses sent by the nervous system,
converting them into actions. e.g. muscles and glands.
Response: The reaction of the organism to a stimulus. Example: Moving hand
away from a hot object.
STIMULUS :
RECEPTOR :
EFFECTOR :
RESPONSE :

Neurons are the basic,
structural and functional
units of the nervous system.
They are specialized cells that
transmit information in the form of
electrical impulses.
Functions of Neurons:
Receive signals from sensory organs
(eyes, ears, skin, etc.).
Process and interpret those signals.
Send responses to effectors
(muscles and glands) for action.
NEURON

PARTS OF NEURON
Present inside the cell
body of the neuron; it
controls the functioning
of the neuron and
contains the genetic
material (DNA).
The longest fibre extending from the cell body of a neuron; it
carries electrical impulses from the cell body to the axon terminal,
which passes the impulse to the next neuron’s dendrite.
Branch-like extensions from the cell body
of a neuron that receive information from
receptors or other neurons.
Also know as Cyton, The part
of a neuron containing the
nucleus; it processes
incoming information and
passes it towards the axon.
The end part of a neuron’s axon from
where chemicals are released to
transmit the impulse across the
synapse to the next neuron, muscle
cell, or gland cell.
Myelin Sheath
It is a fatty layer around the axon of
some neurons.
It acts as an insulating layer and
speeds up the transmission of nerve
impulses.

Synapse
The gap between the nerve ending of one neuron and the dendrite
of the next neuron.
Across this gap, the electrical impulse from the first neuron is
converted into a chemical signal, which crosses the gap and starts
a similar electrical impulse in the next neuron.
A nerve impulse is the electrical signal that travels along the neuron.
It is generated when a stimulus is detected by receptors and transmitted through neurons.
The impulse travels:
Dendrites → Cell body → Axon → Axon terminal → Synapse → Next neuron / muscle / gland.
This is how information is carried quickly from one part of the body to another.
Nerve Impulse

Stimulus detected by receptors
Chemical reaction at dendritic tip → Electrical impulse generated
Impulse travels through Dendrite → Cell Body → Axon → Axon Terminal
Electrical impulse triggers release of chemicals (neurotransmitters)
Chemicals cross synapse and start new electrical impulse in next cell
HOW NEURONS WORK

NEUROMUSCULAR JUNCTION
The point where a nerve ending meets a muscle, so
that the nerve’s message can make the muscle
contract.
Neurotransmitters are chemical messengers released from the axon
terminals of a neuron.
They help in transmitting the nerve impulse across the synapse (gap
between two neurons).
At the synapse, the electrical impulse is converted into a chemical signal
(neurotransmitter).
These chemicals quickly cross the gap and generate a new electrical
impulse in the next neuron, muscle cell, or gland cell.
NEUROTRANSMITTERS

TYPES OF NEURON
Connect sensory and motor
neurons within the brain
and spinal cord.
Carry messages from the
brain or spinal cord to
muscles or glands.
Carry messages from
sense organs to the
brain or spinal cord.
Sensory neurons Interneurons
Motor neurons

2016, 2018, 2024
Q. Identify the site where an electrical impulse is converted into a
chemical signal.
a) Axon
b) Dendrite
c) Synapse
d) Cell body

2024, 2023, 2021
Q. Which part of the neuron receives information from the axon of another
neuron?
a) Axon
b) Dendrite
c) Cyton
d) Synapse

2016, 2017, 2018, 2020, 2022, 2024
Q. What is a synapse? What is its function in the nervous system? Write
the functions of the following parts of a neuron:
a) Dendrites
b) Axon
c) Myelin sheath
Ans. Synapse: A junction between two neurons (or between a neuron and a muscle cell).
Function: It transmits information from one neuron to another through chemical messengers
called neurotransmitters. This ensures proper communication in the nervous system.
Functions of Neuron Parts:
a) Dendrites – Receive electrical impulses from other neurons and carry them towards the cell
body.
b) Axon – Conducts impulses away from the cell body to the next neuron, muscle, or gland.
c) Myelin sheath – A fatty layer around the axon that insulates it, prevents loss of impulse, and
helps in fast transmission of nerve impulses.

CBSE 2019
Diagram of neuron is shown. Label the parts A, B, C, and D.

2017, 2019, 2021, 2022, 2024
Q. (A)Differentiate between sensory, motor, and relay neurons (any two
points).
(B) Why is the neuron called the structural and functional unit of the
nervous system?
Sensory Neuron Motor Neuron Relay Neuron
Carries messages from receptors to the
central nervous system (CNS).
Carries messages from CNS to muscles or
glands (effectors).
Connects sensory neurons to motor
neurons within the CNS.
Example: From skin to spinal cord. Example: From spinal cord to hand muscle.
Example: In spinal cord between sensory
and motor pathways.
(b) because it is the basic cell that receives, processes, and transmits information through electrical and
chemical signals, enabling control and coordination in the body.

Q. Why can't electrical signals directly reach every cell in the body?
Ans. Electrical signals travel only through nervous tissue, and not all body
cells are connected to it, so they cannot reach every cell directly.

TYPES OF ACTIONS
Voluntary Action Involuntary Action Reflex Action
These actions can be controlled by
our own will.
These actions cannot be controlled by our
own will.
These actions cannot be controlled by
our own will.
Thinking is involved. Thinking is not involved. Thinking is not involved.
Brain is involved. Brain is involved. Spinal cord is involved.
Walking, Writing, Dancing, Jumping
Pumping of Blood, Peristaltic movements,
Contraction and relaxation of blood vessels
Withdrawal of hand when touching a hot
object.

2016, 2018, 2019, 2021, 2022
Q. Assertion and Reason
Assertion (A): Digestion is a voluntary action.
Reason (R): Voluntary actions are under conscious control.

REFLEX ACTION
A reflex action is a sudden, automatic, and involuntary response to a stimulus without
conscious thinking. Examples include jumping away from a bus, withdrawing the hand
from a flame, or mouth watering when hungry. It helps in quick protection from danger and
saves time by avoiding the slow thinking process.
Reflex arc :Pathway for reflex action connecting
sensory nerve to motor nerve.
It includes five main parts:
1.Stimulus – e.g. heat detected by skin receptors.
2.Sensory neuron – carries message to spinal cord.
3.Spinal cord – processes the message.
4.Motor neuron – carries command from spinal cord.
5.Effector (muscle) – contracts and withdraws the
hand.

Provides immediate and automatic response to
harmful stimuli.
Protects the body from injury (e.g., withdrawing
hand from hot object).
Saves time by avoiding delay of thinking in the
brain.
Helps in survival and safety by giving quick
reactions in emergencies.
Importance of Reflex Action

Q. How have reflex arcs evolved in animals? Why are they important?
Ans. Reflex arcs have evolved in animals to provide rapid and automatic
responses to harmful or sudden stimuli. This helps animals to protect
themselves quickly without waiting for the brain to process the
information.
Located mainly in the spinal cord, reflex arcs skip the brain’s detailed
processing.
This makes the reaction faster and more efficient.
They give animals a survival advantage by helping them escape
danger or prevent injury in emergency situations.

CBSE 2018, 2021, 2022
Explain reflex action with the help of a labelled diagram of reflex arc.
Mention the role of neurons in this mechanism.
Ans. Reflex Action: A reflex action is a sudden, automatic, and involuntary response to a stimulus.
It helps in protecting the body from harmful situations (e.g., withdrawing hand from a hot object).
Role of Neurons in Reflex Arc:
Sensory neurons: Carry messages from receptor to CNS
(spinal cord/brain).
Relay neurons: Connect sensory and motor neurons
inside CNS.
Motor neurons: Carry messages from CNS to effector
organs (muscles/glands).

2024, 2021, 2019
Q. Which of the following actions is an example of a reflex action?
a) Taking notes in class
b) Pulling hand away from a hot object
c) Eating food
d) Walking in a park

2024, 2023, 2020
Q. Reflex actions are controlled by:
a) Brain
b) Spinal cord
c) Cerebrum
d) Medulla

2023, 2021, 2019
Q. Which of the following correctly represents the path of a reflex arc?
a) Effector →Receptor →Brain →Motor neuron
b) Receptor →Sensory neuron →Brain →Motor neuron →Effector
c) Receptor →Sensory neuron →Spinal cord →Motor neuron →Effector
d) Receptor →Brain →Spinal cord →Muscle

2024
Q. Ravi accidentally touches a hot pan while cooking and immediately pulls his hand away.
This rapid response saves him from a severe burn.
1.What is the correct sequence of events when Ravi’s hand touches the hot pan
unconsciously?
2.Define a reflex action. Using a flowchart, illustrate each step of the reflex action Ravi
experienced when he touched the hot pan.
3.Explain why reflex arcs are considered more efficient for quick responses in such
situations.
Ans. 1. Sequence: Heat (Stimulus) → Receptor (Skin) → Sensory neuron → Spinal cord →
Motor neuron →Muscle (Effector) →Hand withdraws (Response).
2. Reflex Action: A sudden, automatic and involuntary response to a stimulus without brain
involvement. Flow: Stimulus →Receptor →Sensory neuron →Spinal cord →Motor neuron →
Effector →Response.
3. Efficiency of Reflex Arc: Reflex arcs skip brain processing, give faster responses, and
protect the body from harm.

The brain, inside the skull, is the main
coordinating centre of the body.
It is surrounded by three membranes
(meninges) with cerebrospinal fluid in
between, which cushions it from shocks.
BRAIN
Midbrain Hindbrain
PARTS OF BRAIN
Forebrain
Cerebrum
Thalamus
Hypothalamus
Cerebellum
Pons
Medulla

Corpus Callosum
The corpus callosum is a thick band of nerve fibres in the brain.
It connects the left and right hemispheres of the cerebrum.
Its main function is to allow communication between the two halves of the brain, so
that they can work together

Cerebrum
Controls intelligence, memory, learning, emotions, and
voluntary movements.
Thalamus
Acts as a relay station, directing sensory signals to the
cerebrum.
Hypothalamus
Regulates hunger, thirst, sleep, body temperature, and
emotions.
Controls the pituitary gland (involved in hormone secretion).
FORE BRAIN
The forebrain is the largest and most complex part of the brain, responsible for higher-
level functions such as thinking, perceiving, and controlling voluntary actions.

The midbrain is the middle part of the brain,
located between the forebrain and
hindbrain.
🌟Functions of the Midbrain:
Connects forebrain and hindbrain.
Controls certain involuntary actions.
Regulates reflex movements of eyes,
head, and neck in response to visual and
auditory stimuli.
Helps in processing sensory information
and keeps the body alert.
MID BRAIN

Cerebellum:
Controls balance, posture, and coordination of
body movements.
Pons
Helps in relaying signals between different
parts of the brain and controls breathing.
Medulla oblongata
Controls involuntary actions like heartbeat,
breathing, blood pressure, vomiting,
salivation.
HIND BRAIN
The hindbrain is the lower part of the brain, located at the back of the skull. It connects the
brain to the spinal cord.

PROTECTION OF BRAIN AND SPINAL CORD
Protection of the Brain:
The brain is protected by the bony skull (cranium).
It is covered by three membranes (meninges).
A fluid called cerebrospinal fluid (CSF) surrounds it,
which acts as a shock absorber and protects it from
injury.
Protection of Spinal Cord
The spinal cord is protected by the vertebral column
(backbone).
It is also covered by meninges.
Cerebrospinal fluid (CSF) around the spinal cord provides
cushioning and prevents damage.

2024, 2022, 2020
Q. Which part of the brain maintains posture and balance of the body?
a) Cerebrum
b) Cerebellum
c) Medulla
d) Hypothalamus

2024, 2023, 2021
Q. Which part of the brain controls voluntary actions like writing and
reading?
a) Medulla
b) Cerebellum
c) Cerebrum
d) Hypothalamus

2021 (Sample), 2022, 2023
Q. Case Study -
A 10-year-old child tries to ride a bicycle for the first time. Initially, he
struggles to maintain balance, but over time, he improves his coordination
and does not fall. This learning process is due to the role of a specific part of
the brain responsible for posture, balance, and muscle coordination.
1. Which part of the brain helps the child maintain balance?
a) Cerebrum
b) Medulla
c) Cerebellum
d) Hypothalamus

2021 (Sample), 2022, 2023
Q. Case Study -
2. What type of action is involved in learning to ride a bicycle?
a) Involuntary action
b) Reflex action
c) Voluntary action
d) Hormonal action
3. The cerebellum is a part of which major division of the brain?
a) Forebrain
b) Midbrain
c) Hindbrain
d) None of the above

2024, 2023, 2020
Q.(i) Which part of the brain is responsible for —
(1) Intelligence
(2) riding a bicycle
(3) vomiting
(4) controlling hunger
(ii) How is the brain and spinal cord protected against mechanical
injuries?

CBSE 2022 HOTS
What will happen if the cerebellum is damaged? State any two effects.
Ans. If the cerebellum is damaged:
The person will lose balance and posture.
Voluntary actions will lose precision and coordination.

Exocrine glands Endocrine glands
GLANDS
Glands are special organs in our body that make and release substances like hormones,
enzymes, sweat, or saliva.
Release hormones directly into the
blood.
Example: Pituitary gland, Thyroid
gland, Adrenal gland
Release their secretions through ducts
to a surface or organ.
Example: Sweat glands, Salivary
glands, Tear glands

GLANDS
Glands are special organs in our body that make and release substances like hormones,
enzymes, sweat, or saliva.
Exocrine Glands Endocrine Glands
Have ducts → pour secretions to a specific organ or surface. Ductless glands → release hormones directly into the blood.
Secrete substances like enzymes, saliva, sweat, mucus, etc. Secrete hormones only.
Act locally (limited effect where ducts open). Act on distant target organs/tissues through blood.
Examples: Salivary glands, Sweat glands, Tear glands.
Examples: Pituitary gland (growth hormone), Thyroid gland
(thyroxin), Adrenal gland (adrenaline), Pancreas (insulin),
Testis (testosterone), Ovary (oestrogen).

HORMONES
Chemical messengers secreted by endocrine glands, transported by blood to
target organs.
Provide control and coordination along with the nervous system.

Located just below the brain.
Secretes several hormones, including growth
hormone.
Growth hormone regulates the growth and
development of bones and muscles.
Located just below the hypothalamus in the brain.
The hypothalamus controls the pituitary gland by
secreting releasing and inhibiting hormones.
PITUITARY GLAND
Deficiency of growth hormone during childhood causes
dwarfism, resulting in short stature.
Excess growth hormone leads to gigantism, making the
person abnormally tall.

Attached to the windpipe in the body.
Produces thyroxine hormone (contains iodine).
Thyroxine controls the rate of metabolism of
carbohydrates, fats, and proteins.
Goitre – Swelling of the neck due to an enlarged thyroid
gland, usually caused by lack of iodine in the diet.
THYROID GLAND
Some Iodine rich sources:
Seaweed, Fish, shellfish, Table salts labeled “iodized”,
Dairy (milk, cheese, yogurt), Eggs, Beef liver, Chicken.

PARATHYROID GLAND
Four small glands embedded in the thyroid gland.
Secrete parathormone.
Parathormone regulates calcium and phosphate
levels in the blood.
THYMUS GLAND
Located in the lower part of the neck and upper
part of the chest.
Secretes thymus hormone, which helps in the
development of the body’s immune system.
Large in young children but shrinks after puberty.

Located just below the stomach.
Exocrine function: Secretes pancreatic juice
containing enzymes like trypsin and lipase for
digestion.
Endocrine function: Secretes hormones insulin and
glucagon.
Insulin – Lowers blood sugar level; controls sugar
metabolism.
Glucagon – Raises blood sugar level.
Deficiency of insulin causes diabetes, characterised by
high sugar level in blood and sugar present in urine.
Dual / Mixed / Heterocrine Gland)
PANCREAS

Two glands located on top of the kidneys.
Secrete adrenaline hormone.
Functions: Regulates heart rate, breathing rate,
blood pressure, and carbohydrate metabolism.
Secreted in small amounts normally, but in
large amounts during fear or excitement.
Large secretion prepares the body for action
(“fight or flight” response).
Known as the glands of emergency.
ADRENAL GLANDS
Q. Explain how adrenaline helps our body to face an
emergency situation.
Answer: Adrenaline is secreted by the adrenal glands
(above kidneys). It is directly released into the blood
during stress or fear.
It increases heartbeat → more oxygen to muscles.
Increases breathing rate → more oxygen intake.
Diverts blood from digestive system/skin → to
skeletal muscles.
Prepares body for “fight or flight” response.

Testes
Present only in males.
Produce the male sex hormone testosterone.
Also produce male gametes (sperms).
Testosterone controls the development of male sex
organs and male features such as deeper voice,
moustache, beard, and more body hair.
Changes caused by testosterone are associated with
male puberty, usually between 13–14 years of age.

Ovaries
Present only in females (ovaries)
Produce two hormones: Oestrogen and
Progesterone.
Oestrogen →controls development of female sex
organs, secondary sexual characters (soft skin,
feminine voice, mammary glands).
Progesterone →prepares uterus for implantation
& maintains pregnancy.
Changes due to oestrogen are associated with
puberty (10–12 years age).

Hormonal Imbalance: Excess or deficiency of
hormones harms the body. Example:
Insufficient insulin →Diabetes.
Excess insulin →May lead to coma.
Feedback Mechanism: Controls hormone
release timing and amount.
Example:
High blood sugar →pancreas secretes more
insulin.
As sugar level falls to normal →insulin
secretion automatically decreases.
FEEDBACK MECHANISM
Q. How is the timing and the amount of
release of insulin in the blood regulated?

Hormone Gland (Location) Function
Growth Hormone Pituitary gland (just below brain)
Regulates growth and development of bones and
muscles
Thyroxine
Thyroid gland (attached to windpipe in
neck)
Controls metabolism of carbohydrates, fats, and
proteins
Parathormone
Parathyroid glands (embedded in thyroid
gland)
Regulates calcium and phosphate levels in blood
Thymus Hormone Thymus gland (lower neck, upper chest) Helps in development of immune system
Insulin Pancreas (below stomach) Lowers blood sugar level
Glucagon Pancreas (below stomach) Raises blood sugar level
Adrenaline Adrenal glands (on top of kidneys)
Prepares body for emergency — increases
heartbeat, breathing rate, blood pressure
Testosterone Testes (in males)
Controls development of male sex organs and
secondary sexual characters
Oestrogen Ovaries (in females)
Controls development of female sex organs and
secondary sexual characters

2016, 2018, 2020, 2022, 2024
Q. Which hormone is responsible for maintaining the sugar level in the
blood?
a) Thyroxine
b) Adrenaline
c) Insulin
d) Estrogen

2015, 2017, 2019, 2023
Q. The master gland in the human body is:
a) Thyroid
b) Adrenal
c) Pituitary
d) Pancreas

2024, 2021
Q. Select out of the following a gland which does NOT occur as a pair in
the human body :
(a) Pituitary
(b) Ovary
(c) Testis
(d) Adrenal

2019, 2024
Q. A child grows abnormally tall. Which hormone might be responsible
for this?
a) Insulin
b) Growth hormone
c) Thyroxine
d) Testosterone

2016, 2019,2021
Q.Name the endocrine glands associated with the following functions and
the hormones they secrete:
1.Regulation of blood sugar level.
2.Growth and development of the body.
3.Fight or flight response
Ans.
1.Regulation of blood sugar level – Pancreas → Insulin, Glucagon
2.Growth and development of the body – Pituitary gland → Growth hormone (GH)
3.Fight or flight response – Adrenal gland → Adrenaline

2024, 2021, 2018
Q.Why is iodised salt important? Name the hormone and disease caused
by its deficiency.
Ans. Iodised salt is important because iodine is needed by the thyroid gland to secrete
the hormone thyroxine.
Hormone: Thyroxine
Disease due to deficiency: Goitre (enlargement of thyroid gland, swelling in neck)

CBSE 2023
A hormone ‘X’ is secreted in blood when a person is under scary situation.
(a) Identify the hormone ‘X’ and the gland that secretes it.
(b) Explain its role in dealing with scary or emergency situations.
Ans. (a) Hormone ‘X’ → Adrenaline
Secreted by → Adrenal glands (located above kidneys).
(b) Role in emergency (Fight or Flight response):
Increases heartbeat → more oxygen supply to muscles.
Increases breathing rate.
Diverts blood from digestive system/skin → to skeletal muscles.
Prepares body to face emergency by providing more energy and alertness.

CBSE 2024
Q. What is hypothyroidism? How can it be managed? What dietary
changes can help regulate TSH levels?
Ans. Hypothyroidism → A condition in which the thyroid gland does not produce enough
thyroxin hormone, usually due to iodine deficiency.
Effect → Causes a disease called Goitre, in which swelling occurs in the neck.
Management → Taking iodised salt in diet helps to regulate thyroxin (TSH levels) and
prevent goitre.

CBSE 2024, 2022, 2021
A 14-year-old girl was diagnosed with an enlarged thyroid gland. The
doctor told her she has goitre due to iodine deficiency. Her family was
advised to use iodised salt.
Questions:
1.Which hormone is deficient in this case?
2.Name the gland that secretes it.
3.Write one function of this hormone.
4.Name a dietary source that prevents this disorder.
Ans.
Hormone deficient: Thyroxine
Gland: Thyroid gland
One function: Regulates metabolism of carbohydrates, fats, and proteins
Dietary source: Iodised salt / Seafood

Q. Why is chemical communication better than electrical impulses as a
means of communication between cells in multicellular organisms?
Ans. Electrical impulses have a limited range → they can only pass through connected neurons, not
reach every cell of the body.
Also, neurons need a recovery time before transmitting the next impulse.
Chemical communication (through hormones) is better because:
Wider range → Hormones can travel through blood and reach all parts of the body.
Long-lasting effect → Chemical signals act for longer duration, unlike the short-lived electrical
impulses.
Target-specific → Hormones act only on specific target tissues or organs.

Both use chemical signals
(hormones) for control and
coordination.
In both, cells change shape to
bring about response.
Both help the organism adapt and
survive in changing environment.
Animals Plants
Have specialised tissues
(nerves, muscles) for
conduction of
information.
No specialised tissues
for conduction of
information.
Movement happens due
to change in shape of
muscle cells (caused by
special proteins).
Movement happens due
to change in amount of
water in cells
(swelling/shrinking).
Q. How is coordination in plants different from animals?

MOVEMENTS
NASTIC TROPIC
CONTROL AND COORDINATION IN PLANTS
Plants lack a nervous system and muscles.
They still respond to stimuli (e.g., touch-me-not folds leaves on touch).
Non-directional response to stimulus
Independent of growth
Directional growth towards/away from
stimulus
Dependent on growth

TROPIC MOVEMENT
Positive Tropism: When a plant part grows or moves towards the
stimulus, such as roots growing towards water or stems growing towards
light.
Negative Tropism: When a plant part grows or moves away from the
stimulus, like roots growing away from light.
Phototropism Geotropism Chemotropism
Hydrotropism
Thigmotropism

1. Phototropism:
The movement of a plant part in response to light is called
phototropism.
Positive Phototropism: The plant's stem grows toward light.
Negative Phototropism: The plant's roots grow away from light.
Germinated bean seeds kept in a flask facing light show shoots
bending towards light and roots bending away from light. When
the flask is turned, the new growth changes direction according to
light, but the old parts do not. This shows that shoots are
positively phototropic and roots are negatively phototropic.

2. Geotropism
Movement of a plant part in response to gravity.
Positive Geotropism: Plant part grows toward gravity (e.g., roots).
Negative Geotropism: Plant part grows against gravity (e.g., stem).
3. Chemotropism
Movement of a plant part in response to chemical stimulus.
Positive Chemotropism: Growth toward the chemical (e.g.,
pollen tube growing towards ovules).
Negative Chemotropism: Growth away from the chemical.

4. Hydrotropism
Movement of a plant part in response to water.
Positive Hydrotropism: Plant part moves towards water.
Negative Hydrotropism: Plant part moves away from water.
Tendrils are thin, thread-like structures
in climbing plants that help them
attach to a support. They are sensitive
to touch and show positive
thigmotropism, meaning they grow
towards the object they touch.
5. Thigmotropism

Non-directional movement in
response to touch. In the sensitive
plant (Mimosa pudica or chhui-
mui), touching the leaflets causes
them to fold and droop quickly.
Thigmonasty
Non-directional movement of flower petals in
response to light. Flowers open when the inner petal
surfaces grow more and close when the outer
surfaces grow more. e.g. Dandelion and Tulip (open in
light) and Moonflower or Evening Primrose (open in
dark/close in sun).
Photonasty
NASTIC MOVEMENT

Tropic movements Nastic movements
Unidirectional response to the stimulus Non-directional response to the stimulus
Growth dependent movements Growth independent movements
More or less permanent and
Irreversible
Temporary and reversible
Slow action Immediate action
TROPISM V/S NASTIC MOVEMENT
TROPISM V/S NASTIC MOVEMENT

2015, 2016, 2020, 2022
Q. Movement of sunflower towards light is an example of:
a) Geotropism
b) Chemotropism
c) Phototropism
d) Thigmotropism

2016, 2023,2024,2025
Q. Observe the given figures A and B. When chhui-mui (sensitive) plant is
touched, its leaves fold.
This is due to:
(A) Hormonal effect
(B) Thermal effect
(C) Change in amount of water in cells
(D) Electromagnetic effect

2016, 2023
Q. Assertion and Reason
Assertion (A): The leaves of Mimosa pudica droop when touched.
Reason (R): The movement in Mimosa is caused by unequal growth on both
sides of the leaf.

2024, 2021, 2018
Q. Raghav potted some germinated seeds in a pot. He put the pot in a
cardboard box that was opened from one side. He keeps the box in a way
that the open side of the box faces sunlight near his window. After 2-3 days,
he observes the shoot bends towards the light, as shown in the image.
Which type of tropism does he observe?
(a) Geotropism
(b) Phototropism
(c) Chemotropism
(d) Hydrotropism

CBSE 2019, 2021, 2024
Q. Name the type of movement shown in:
(a) Folding of Mimosa pudica leaves
(b) Opening of dandelion flowers in morning

TYPES OF HORMONES
PLANT HORMONES
Carried out by plant hormones (phytohormones).
Growth of a plant occurs in three stages:
1.Cell division – Formation of new cells by mitosis.
2.Cell enlargement – Increase in size of cells.
3.Cell differentiation (cell specialization) – Cells become specialized
for specific functions.
AUXIN
GIBBERELLINS
ABSCISIC ACID
CYTOKININS
ETHYLENE

Promote cell elongation in shoots.
Control phototropism (light) and geotropism
(gravity).
When light falls on one side, auxin moves to
shady side →cells grow longer →stem bends
towards light.
Help in fruit development.
1. AUXIN
2. GIBBERELLINS
Help in seed germination.
Promote flowering.
Promote fruit development.

Q. Why does a plant bend towards light? Explain the role of auxin in this process.
Ans. When light falls on a plant from one side, auxin hormone moves towards the shaded
side of the stem.
Auxin stimulates cell elongation.
As a result, cells on the shaded side grow longer than those on the lighted side.
This unequal growth causes the stem to bend towards light.

Promote cell division.
Found in high concentration in fruits and seeds (rapid
growth regions).
3. CYTOKININS
Inhibits growth (opposite of auxin/gibberellins).
Causes wilting of leaves.
Induces dormancy in seeds and buds.
Acts as a stress hormone (helps plant respond to stress - drought).
Closes stomata during water stress to reduce water loss.
4. ABSCISIC ACID (ABA)
Stimulates fruit ripening.
Promotes leaf fall and aging.
5. ETHYLENE

Hormone Location (Produced at) Function
Auxins Shoot tips
Promote cell elongation; control phototropism &
geotropism.
Gibberellins Stem regions Promote stem elongation; help in seed germination.
Cytokinins Fruits and seeds (rapid growth areas) Promote cell division.
Abscisic Acid (ABA) Various plant parts
Inhibits growth; causes wilting of leaves; acts as a
stress hormone.
Ethylene Fruits (ripening regions)
Stimulates fruit ripening; promotes leaf fall and
aging.

2016, 2018, 2020, 2023
Q. Which plant hormone is responsible for cell elongation?
a) Cytokinin
b) Abscisic acid
c) Auxin
d) Ethylene

2018, 2020, 2023
Q. Which plant hormone helps in the ripening of fruits?
a) Auxin
b) Gibberellin
c) Ethylene
d) Cytokinin

2015, 2019, 2022
Q. Which plant hormone helps in breaking seed dormancy and promotes
germination?
a) Cytokinin
b) Auxin
c) Abscisic acid
d) Gibberellin

2024, 2021
Q. Where are auxins produced? How do they help in phototropism?
Ans. Auxins are produced at the tips of stems and roots.
In phototropism, when light falls on one side of the plant, auxin moves to the shaded side of
the stem. This causes the cells on the shaded side to grow longer, making the stem bend
towards the light.

Brain? Checked. Hormones? Checked. Confidence? Double
checked. Bas ab tum ready ho Class 10 ko top karne ke liye!"
th

CONTROL AND COORDINATION (Prashant Kirad).pdf

CONTROL AND COORDINATION (Prashant Kirad).pdf

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