Control and coordination

CHAPTER - 7
CONTROL AND COORDINATION

1a) Stimuli :-
The changes in the environment to which living
organisms respond are called stimuli.
Eg :- heat, cold, sound, smell, taste, touch, pressure,
gravity, water etc.
Living organisms respond to stimuli in the form of body
movements.
b) Coordination :-
For a proper response to a stimulus many organs in
body should work together. The working together of
various organs in an organism to produce a proper
response to a stimulus is called coordination.
i) In animals control and co ordination is done by the
nervous system and endocrine system.
the
ii) In plants control and co ordination is done by chemical
substances called plant hormones or phytohormones.

2) Coordination in animals :-
In animals control and co ordination is done by the nervous system
and endocrine system.
The nervous system consists of the brain, spinal cord and nerves.
Receptors :- are the sense organs which receive the stimuli anda)
pass the message to the brain or spinal cord through the
nerves.
Eg :- Photoreceptors in the eyes to detect light.
Phonoreceptors in the ears to detect sound.
Olfactory receptors in the nose to detect smell.
Gustatory receptors in the tongue to detect taste.
Tangoreceptors in the skin to detect touch.
b) Effectors :- are the muscles and glands which respond
sensory
to the
information from the brain and spinal cord through the motor nerves.
c) Sensory nerves :- are nerves which carry information from the
receptors (sense organs) to the brain and spinal cord.
d) Motor nerves :- are nerves which carry information from the brain
and spinal cord to the effectors (muscles and glands).

3) Human nervous system :-
a) Parts of the nervous system :-
The human nervous system consists of the Central Nervous System
and Peripheral Nervous System.
i) The central nervous system :- consists of the brain, and spinal
cord.
ii) The peripheral nervous system:- consists of cranial nerves
arising from the brain and spinal nerves arising from the spinal cord.

b) Nerve cell (Neuron) :-
Neuron is the structural and functional unit of the nervous system. It
has a cell body called cyton containing a nucleus and cytoplasm. It has
several branched structures called dendrites. It has a long nerve fibre
called axon which is covered by a protective covering called Myelin
sheath. The junction between two neurons is called synapse.
Messages pass through the nerve cell in the form of chemical and
electrical signals called nerve impulse. The dendrites receive the
information and starts a chemical reaction which produce electrical
impulse which passes through the axon.

 Myelin sheath is made by specialized cells called glia. In the brain, the glia
that make the sheath are called oligodendrocytes, and in the peripheral
nervous system, they are known as Schwann cells.
 The brain contains at least ten times more glia than neurons. Glia perform
many jobs. Researchers have known for a while that glia transport nutrients to
neurons, clean up brain debris, digest parts of dead neurons, and help hold
neurons in place.
 Purkinje cells are a special type of neuron found in the cerebellum. These
cells have highly developed dendritic trees which allow them to receive
thousands of signals.
 Nodes of Ranvier are the spaces between the myelin coating on the neuron's
axon. Much like the plastic coating on a wire needs to be clear to connect to
an appliance and supply power, there must be breaks in the myelin to conduct
electricity in neurons.
 Electricity travels quickly through the axon wrapped in myelin. At the nodes of
Ranvier, electricity can be conducted within the cell's environment, and the
electrical signal will be propagated down the axon.
 At the nodes of Ranvier the cell membrane, or boundary of the cell is
exposed. This part of the membrane has proteins, called channel proteins,
which allow ions to enter and exit the cell. They're like doors for the cell,
letting specific people in and out.

This whole process is largely controlled by sodium and potassium ions.
Below is a diagram of the sodium and potassium ion channels in neurons.
These channels are in the membrane at the nodes of Ranvier.
https://www.youtube.com/watch?v=oa6rvUJlg7o

Types of Neurons
In terms of function, scientists classify neurons into three broad types: sensory,
motor, and interneurons.
1. Sensory neurons
Sensory neurons help you:
•taste
•smell
•hear
•see
•feel things around you
 Sensory neurons are triggered by physical and chemical inputs from your
environment.
 Sound, touch, heat, and light are physical inputs.
 Smell and taste are chemical inputs.
For example, stepping on hot sand activates sensory neurons in the soles of
your feet. Those neurons send a message to your brain, which makes you
aware of the heat.

2. Motor neurons
• Motor neurons play a role in movement, including voluntary and involuntary
movements.
• These neurons allow the brain and spinal cord to communicate with
muscles, organs, and glands all over the body.
• There are two types of motor neurons: lower and upper.
 Lower motor neurons carry signals from the spinal cord to the smooth
muscles and the skeletal muscles.
 Upper motor neurons carry signals between your brain and spinal cord.
For instance, When you eat, lower motor neurons in your spinal cord send
signals to the smooth muscles in your esophagus, stomach, and intestines.
These muscles contract, which allows food to move through your digestive
tract.

3. Inter-neurons/Relay Neuron
• Interneurons are neural intermediaries found in your brain and spinal
cord. They’re the most common type of neuron.
• They pass signals from sensory neurons and other interneurons to motor
neurons and other inter-neurons. Often, they form complex circuits that
help you to react to external stimuli.
For instance, when you touch something hot, sensory neurons in your
fingertips send a signal to interneurons in your spinal cord. Some
interneurons pass the signal on to motor neurons in your hand, which allows
you to move your hand away. Other interneurons send a signal to the pain
center in your brain, and you experience pain.

Structure of neuron (Nerve cell)

Transmission of messages through neurons

Nervous System
Voluntary Nervous SystemAutonomic Nervous System
Peripheral Nervous System
Central Nervous System
Consisting Brain & Spinal Cord
Consisting all nerves of the body like
Cranial Nerve, Spinal Nerve, Visceral
Nerves etc.
Which is under the control of brainWhich operates automatically or
involuntarily

CENTRAL NERVOUS SYSTEM
BRAIN
SPINAL CORD

c) Brain :-
The brain is the main coordinating centre in the human body. It is
protected by the cranium. It is covered by three membranes called
meninges filled with a fluid called cerebrospinal fluid which protects
the brain from shocks.
The brain has three main parts. They are fore brain, mid brain and
hind brain.
i) Fore brain :- consists of the cerebrum and olfactory lobes. It is the
thinking part of the brain and controls voluntary actions. It controls
touch, smell, hearing, taste, sight, mental activities like thinking,
learning, memory, emotions etc.
ii) Mid brain :- controls involuntary actions and reflex movements of
head, neck, eyes etc.
iii) Hind brain :- consists of cerebellum, pons and medulla.
Cerebellum :- controls body movements, balance and posture.
Pons :- controls respiration.
Medulla :- controls heart beat, blood pressure, swallowing, coughing,
sneezing, vomitting etc.

Various functions of the Brain
 Receives information carrying nerve impulse from all the sensory organs of the
body.
 Responds to the impulse brought in by sensory organs by sending its own
instructions through motor nerve to the muscles and glands causing them to
function.
 It correlates the various stimuli from different sense organs and produces the most
appropriate and intelligent response.
 It coordinates the body activities so that the mechanisms and chemical reactions of
the body work together efficiently.
 It stores information so that behavior can be modified according to the past
experience.

d) Spinal cord :-
The spinal cord starts from the brain and extends
through the vertebral column.
nerves.
It has 31 pairs of spinal
It is concerned with spinal reflex actions and the
conduction of nerve impulses to and from the brain.

Peripheral Nervous System
Autonomic Nervous System Voluntary Nervous System

4a) Reflex action :-
Reflex action is a sudden, unconcious and involuntary
response of the effectors to a stimulus.
Eg :- We suddenly withdraw our hand if we suddenly
touch a hot object.
In this reflex action, the nerves in the skin (receptor)
detects the heat and passes the message through the
sensory nerves to the spinal cord. Then the information
passes through the motor nerves to the muscles (effector)
of the hand and we withdraw our hand.

b) Reflex arc :-
The pathway of a reflex action is called reflex arc. In a
reflex arc the stimulus is received by the receptors (sense
organs) and it passes through the sensory nerves to the
spinal cord. From the spinal cord the information passes
through the motor
for the response.
nerves to the effectors (muscles/glands)
Stimulus
Response
Motor nerves
Effectors
(Muscles/Glands)
Spinal cord
Sensory nerves
Receptors
(Sense organ)

Autonomic Nervous System
 Auto means- ‘Self’ and nomos means ‘governing’, so this
system is self governing nervous system.
 Part of Peripheral Nervous system.
 Controls the activities of the internal organs of our body
automatically even without our thinking about them.
 Controls the specific process like breathing, heart beat,
digestion, sweating etc. that maintain or life and keep us
alive.
 Its nerves are attached to the smooth muscles of the
various organs of the human body like head, heart, blood
vessels, alimentary canal, lungs, kidney, urinary bladder,
glands and skin etc.

Voluntary Nervous System
 Voluntary means- ‘acting of one's own free will’, so this
system is under the control of the person.
 Part of Peripheral Nervous system.
 Actions like thinking and which are performed by us
knowingly are called voluntary actions.
 This system helps us to take voluntary actions which are
under the conscious control of the brain.
 Ex- Writing a letter, Dancing, Kicking a ball etc.

ENDOCRINE GLANDS IN HUMAN BEINGS

Endocrine glands in Human Beings
The endocrine glands also help in control and coordination. The endocrine
glands produce chemical substances which help to control and coordinate
various activities in the body.
The endocrine glands in our body are :- pineal, hypothalamus, pituitary,
thyroid, parathyroid, thymus, adrenal, pancreas, testes and ovary.
Examples of coordination by endocrine glands :-
I.) The pineal gland is a small, pea-shaped gland in the brain.
Its function isn't fully understood. Researchers do know that it produces and
regulates some hormones, including melatonin. Melatonin is best known for the
role it plays in regulating sleep patterns.
II) The hypothalamus is a small region of the brain. It's located at the base of the
brain, near the pituitary gland. Hypothalamus plays a crucial role in many important
functions, including: releasing hormones, regulating body temperature, maintaining
daily physiological cycles, controlling appetite, managing of sexual behaviour,
regulating emotional responses. The hormones produced in the hypothalamus
are corticotrophin-releasing hormone, dopamine, growth hormone-releasing
hormone, somatostatin, gonadotrophin-releasing hormone and thyrotropin-releasing
hormone, Oxytocin, Vasopressin.
iii) The pituitary gland produce growth hormones. Deficiency of this hormone in
childhood causes dwarfism. Excess of this hormone causes tall growth.

iv) Iodine is needed by the thyroid gland to produce the hormone thyroxin.
Thyroxin controls the metabolism of carbohydrates, fats and proteins and helps
in proper growth. If the diet is deficient in iodine it causes goitre,
It makes two hormones that are secreted into the blood: thyroxine (T4) and
triiodothyronine (T3). These hormones are necessary for all the cells in your body
to work normally.
 The hypothalamus produces TSH Releasing Hormone (TRH) that signals the
pituitary to tell the thyroid gland to produce more or less of T3 and T4 by either
increasing or decreasing the release of a hormone called thyroid stimulating
hormone (TSH).
 Too much T3 and T4 in your body (hyperthyroidism, and too little T3 and
T4 in your body (hypothyroidism):
 Hypothyroidism:- Wait gain
 Hyperthyroidism:- Weight loss
v) Parathyroid glands are four small glands of the endocrine system which
regulate the calcium in our bodies by Parathyroid Hormone( PTH). Parathyroid
glands are located in the neck behind the thyroid where they continuously monitor
and regulate blood calcium levels.

VII) The Pancreas produces the hormone insulin which controls the blood sugar
level. Increase in blood sugar level causes diabetes. A diabetic patient has to
take insulin injections to control his blood sugar level.
Vi.) The thymus gland is a small organ behind the breastbone that plays an
important function both in the immune system and endocrine system. Though the
thymus begins to atrophy (decay) during puberty, its effect in "training"
T lymphocytes to fight infections and even cancer lasts for a lifetime.
The thymus gland produces several hormones including:
 thymopoietin and thymulin, which are hormones that assist in the process
where T cells differentiate into different types
 thymosin, which accentuates the immune response as well as stimulating
pituitary hormones such as growth hormone
 thymic humoral factor, which acts similarly to thymosin, but increases the
immune response to viruses in particular
 serves as two glands in one: A digestive exocrine gland and A hormone-
producing endocrine gland.
A) As an exocrine gland, the pancreas excretes enzymes to break down the
proteins, lipids, carbohydrates, and nucleic acids in food.
B) Functioning as an endocrine gland, the pancreas secretes the hormones
insulin and glucagon to control blood sugar levels throughout the day.

 Epinephrine (Adrenaline) and Norepinephrine (Noradrenaline)
 When we are frightened or angry, the Adrenal glands produce more Adrenalin
(Ephinephrin) hormone which is sent through the blood to the heart, rib muscles
and diaphragm. This increases breathing rate to supply more oxygen to the muscles
to prepare the body to either run away or fight with the enemy.
VIII) The adrenal glands (also known as suprarenal glands) are endocrine glands that
produce a variety of hormones including adrenaline and the steroids aldosterone and
cortisol. They are found above the kidneys.
 Adrenal glands produce hormones that help regulate your metabolism, immune
system, blood pressure, response to stress and other essential functions.
 Cortisol: control the body’s use of fats, proteins and carbohydrates; suppresses
inflammation; regulates blood pressure; increases blood sugar; and can also decrease
bone formation.
Also controls the sleep/wake cycle. It is released during times of stress to help your
body get an energy boost and better handle an emergency situation.
 Aldosterone:plays a central role in regulating blood pressure and certain
electrolytes (sodium and potassium). Also helps regulate the blood pH by controlling
the levels of electrolytes in the blood.
 DHEA and Androgenic Steroids: are weak male hormones. They are precursor
hormones that are converted in the ovaries into female hormones (estrogens) and
in the testes into male hormones (androgens).

IX ) The testes in males produces the hormone testosterone which controls the production
of male gamete, sperms and changes during puberty.
X) The ovary in females produces the hormone oestrogen which controls the
development of female sex organs and female features like feminine voice, soft
skin, mammary glands etc. It also produces progesterone hormone which
controls the uterus changes during menstrual cycle and it also helps in the
maintenance of pregnancy. Ovary also make the female gamete called Ova.

5) Coordination in plants :-
In plants control and coordination is done by chemical
substances called plant hormones or phytohormones.
There are five main types of plant hormones. They are
Auxins, Gibberillins, Cytokinins, Abscisic acid and
Ethylene.
i) Auxins :- help in cell division, cell elongation and growth.
ii) Gibberillins :- help in growth of stem and branches.
iii) Cytokinins:- help in cell division, formation of fruits
seeds.
and
iv) Abscisic acid :- inhibits growth and affects wilting of
leaves.
v) Ethylene :- helps in flowering and ripening of fruits.
Dormancy:- A resting, inactive condition in which metabolism
almost stops.

6) Movements in plants :-
Movements in plants are of two main types. They are :-Tropic
movements and Nastic movements.
a) Tropic movements :- are directional movements towards or
away from the stimulus and it depends on growth. They are of
different types like Phototropism, Geotropism, Chemotropism,
Hydrotropism, Thigmotropism, etc.
i) Phototropism :- is movement of plants in response to light. If it is
towards light, it is called positive phototropism. Eg:- Bending of
shoot towards light. If it is away from light, it is called negative
phototropism. Eg:- Bending of root away from light.
ii)Geotropism :- is the movement of plants in response to gravity.
If it is towards gravity it is called positive geotropism. Eg:-
Downward growth of roots. If it is away from gravity it is called
negative geotropism. Eg:- Upward growth of shoot.
iii) Chemotropism :- is movement of plant in response to chemical
stimuli. Eg:- Growth of pollen tube towards the ovule.
iv) Hydrotropism :- is the movement of plants in response to water.
V) Thigmotropism :- is the movement of plants parts in response to the
touch of the object. Eg. Climbing parts of the plants such as tendrils grow
towards of an support and wind around it.

Usefulness of Tropic Movements
1. Positive Geotropic/Positive Hydrotropic
2. Negative Geotropic/ Positive Phototropic
These movements help the plants to obtain water and nutrients from soil and
light from the sun, which are necessary for their growth and survival.

b) Nastic movements :- are non directional movements which
are neither towards or away from the stimulus and it does not
depend on growth.
Note: All tropisms are growth movements but all nasties/nastic
movements are not growth movements.
Eg. Folding up of the leaves a sensitive plant on touching is not a
growth movement but the opening and closing of petals of flowers
by the action of sunlight is a growth movement.
Thigmonasty:- Non-directional movement of a plant part in response to
the touch pf an object. Here stimulus is “Touch”.
Eg :- If we touch the leaves of touch me not plant/ Mimosa pudica, its leaves
fold up and droops down immediately due to the change in the amount of
water in the leaves.
Note:- Folding of leaves of a sensitive plant is not a case of tropism like
Thigmotropism. In this case directional movement of leaves does not depend
on the direction of stimulus (touch).

Eg :- If we touch the leaves of touch me not plant, its leaves fold up
and droops down immediately due to the change in the amount of
water in the leaves. Depending upon the amount of water in the
leaves, it swells or shrinks.

Sensitive plant has pad like swellings called ‘pulvini’ at the base of each leaf. Pulvini contain a
lot of water in their cells. Due to internal water pressure called Turgor Pressure in them, all the
pulvini are very firm and hold the leaves above them upright. Pulvini has also lare intracellular
spaces between their cells.
The folding of the leaves of a sensitive plant on touching is due to to sudden loss of water from
pad like swellings called Pulvini present at the base of all the leaves of the sensitive plant which
make the pulvini lose their firmness causing the leaves of droop and fall.
When the leaves of sensitive plant are touched with a finger, then a n electrical impulse is
generated which travels through ordinary cells. This electrical impulse acts on a plant hormone.
The plant hormone makes the water migrate from the cells of one half of a pulvinus to the
intracellular spaces in the other half of pulvinus. This loss of water from half of pulvinus cause
the pulvinus to lose its firmness making the leaf to fold. Depending upon the amount of water in
the leaves, it swells or shrinks.

PHOTONASTY:- The Non-directional movement of a plant part (usually
petals of flowers) in response to light. Here stimulus is ‘Light’
Note:- The opening of closing of flowers in response to light are growth movements.
Petals open when their inner surfaces grow more than their outer surfaces.
On the other hand, petals close when their outer surfaces grow more than their inner
surfaces.

Control and coordination

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