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CONTROL AND COORDINATION

STIMULUS: any physical, chemical, or biological change

in the immediate environment of living organisms is
termed a stimulus.
Humans’ nervous system: -
1)Central nervous system {brain, spinal cord}
2)Peripheral nerves: {spinal-31 pairs and cranial
nerves-12 pairs}

Sensory organs perceive or sense stimuli

Eyes- sense light -photoreceptors
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Nose- sense smell – olfactory receptor.

Ears- sense sound – phono/ auditory receptor
Skin -sense temp- thermos cutaneous /receptor
Tongue- sense taste- gustatory receptor

- Receptor cells are only present in sensory organs.

- To receive stimuli.
- Send info to the CNS.
- 80% of what we taste is sensed by smell. Our taste
only perceives sweet, salty, bitter, and sour. In
case of cold, our mucus is so thick that the odor
from the molecules isn’t able to reach the recept-
ors. Thus, the food tastes bland.
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Info - Sensory receptors – Sensory Neuron- CNS –

Motor Neuron - effector

Neuron: -
1)basic and structural unit of the nervous system
2)Also known as nerve cell.

3)Longest cell of the body

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STRUCTURE OF NEURON
1. Dendrites [ receives the signal from receptors]

2. Cell body/ cyton [amplifies the electrical impulse]

Nissl granules: aid in the production and dispersal of

chemical substances such as proteins and peptides,

3. Axon [myelin sheath- insulating layer made of fats and proteins]

[nerve impulse travels throughout the axon until it reaches nerve
endings]

4. Nodes of Ranvier [the nodes of Ranvier allow the generation of a fast

electrical impulse along the axon. This rapid rate of conduction is called
saltatory conduction.

5.Axonal/nerve endings [ contains neurotransmitter(acetylcholine)

here electrical impulse gets changed to chemical impulse}

HOW DOES THE ELECTRICAL IMPULSE

TRAVEL THROUGH NEURON:
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Received by dendrites

Amplified by cell body

Travels through the axon to nerve endings.

Synapse: the gap between two adjacent neurons. Synapse acts like a
one-way valve because the chemical substance is present only on
one side of the gap.

- At the synapse, the axonal terminal comes in close proximity to

the dendron terminal of the next neuron. The Axon terminal is
expanded to form a presynaptic knob. On the other hand, the
dendrite terminal forms the post-synaptic depression. In
between the two lies a narrow fluid-filled space called synaptic
cleft. As the nerve impulses reach the presynaptic knob, the
synaptic vesicles get stimulated to release a chemical called
neurotransmitter in the synaptic cleft. The neurotransmitter
diffuses in the gap to come in contact with the chemoreceptor
sites in the post-synaptic membrane. In this way, nerve im-
pulses pass from one synapse to stimulate the dendron of the
other neuron.

Neuron transmitter: electrical impulse-chemical impulse -electrical

impulse
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PATHWAY :-
STIMULUS-RECEPTORS-DENDRITE OF THE SENSORY NEURON-SYNAPSE-
DENDRITES -VARIOUS NEURON- CNS -DENDRITE OF MOTOR NEURON-CELL
BODY-AXON-EFFECTOR CELLS

Three types of neurons: sensory neurons {take info from re-

ceptors to the cns}
2. motor neurons {take information from cns to effector
cells}
3. Relay neuron {coordinate between sensory and mo-
tor neurons}

NEUROMUSCULAR JUNCTION:
Neuron muscular junction: neuromuscular junction is
those synaptic junctions between neurons and the
muscle cells [motor neuron]
- Muscles cells change the shape and arrangement
in order to produce a respond to stimuli.
- They have a special protein (contractile protein –
myosin and actin) that changes the shape and ar-
rangement and thus giving it a shorter form.

Types of actions:
Voluntarily action- those actions that we carry out by
using our brain, Consciously
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Involuntary action – that action that is performed under

the unconscious direction of the brain.
e.g., breathing, beating of heart
Reflex action- sudden, fast, and unconscious actions.
e.g., salvation, blinking of eye
Involuntary:
Set of muscular movements that don’t require thinking.
Controlled by our brain but not by our conscious think-
ing.
Stimulus isn’t usually needed.
The speed of the response is slow but for a longer dura-
tion.
It only involves smooth muscles
Controlled by medulla
Reflex Action:
Spontaneous action in response to stimulus.
Stimulus are required.
Rapid automatic response to stimulus without the con-
scious involvement of the brain. controlled by the
spinal cord.
Very fast response but for a shorter duration.
Only a message is given to the brain.
Controlled by the spinal cord
It can occur in both glands and muscles
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REFLEX ARC -
The pathway taken by nerve impulses in a reflex action
is called reflex arc. Reflex arc allows rapid response.
Most effective for quick responses.
RECEPTORS- SENSORY NEURON-SPINAL CORD- RELAY
NEURON -MOTOR NEURONS-EFFECTOR
Advantage of reflex arc: - It is important for the survival
of animals.
- Enables the body to take quick action in harmful
stimuli thus protecting the body.
- Minimises the overloading of the brain.

Reflex arc for sneezing: - pollen or dust sensed by

receptors in the nose- sensory neurons- spinal
cord(CNS)-relay neuron-motor neurons-
effector(respiratory tissues)
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CNS: HUMAN BRAIN AND SPINAL CORD

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Human brain: -
Morphology: The brain is soft-whitish weighs 1.2 to 1.4
kg and occupies 98% of the total weight of the nervous
system. It has around 100 billion neurons.
1)The forebrain consists of the cerebrum, olfactory
lobes, diencephalon
- cerebrum {main thinking part, and voluntary ac-
tions/largest part of the human brain. Contains two
hemispheres connected by corpus callosum with 4
lobes–
Cerebral hemispheres – intelligence and voluntary ac-
tions.
Olfactory lobes – Each olfactory lobe consists of an in-
terior olfactory bulb and posterior narrow olfactory
stalk. These lobes receive impulses from olfactory re-
ceptors and thus act as centers of smell.
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Temporal lobe- senses auditory reception, emotion,

hearing, memory
Frontal – controls speech, facial and muscular activity,
intellectual activity also high mental activities.
Occipital – sense color/sight, visual reception.
Parietal- sense touch/pain/temperature/taste
Diencephalon – located in the inner side of the
cerebrum. the roof is called the epi-thalamus, the sides
are called the thalami and the base is called the hypo-
thalamus. The hypothalamus has centers for hunger,
thirst, fatigue, sleep, etc. It secretes neurohor-
mones.
Motor areas – instructs muscles to do various types of
jobs.

2)Midbrain: -
- controls reflex movements of the neck, head, and
trunk in response to visual and auditory stimuli.
--Also controls the reflex movements of the eye
muscles and changes in pupil size and shape of the eye
lens.
- has 2 fibre tracts called crura cerebri and two swell-
ing on each side called superior (centres of sight re-
flexes) and inferior colliculi (auditory reflexes).
The fibrous tracts connect the hind and forebrain. All
together known as corpora quadrigemina. They per-
form the function of conduction back and forth between
the cerebrum, cerebellum, medulla, and pons.
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3) The hindbrain – the cerebellum – posture and body

balance and enable us to make precise and accurate
movements also enable us to maintain equilibrium.
Medulla Oblongata: controlling involuntary actions
such as breathing, rate of heart, expansion, and con-
traction of blood vessels to regulate blood pressure.
Control centers for reflexes such as swallowing, cough-
ing, vomiting, etc.
Pons varolli: control breathing and sleep cycle.
- The brain is lodged in the brain box or cranium
which protects it. It is covered by membranes
called meninges these are the Pia meter (in-
nermost, thin, and vascular; arachnoid mem-
brane ( middle thin, and vascular) and dur-
ometer (thick, outermost, and fibrous), which
helps to protect it.
- The space between the membrane and the brain is
filled with a cerebrospinal fluid which protects
the brain from mechanical shock.
SPINAL CORD
An extension of the brain
Cylindrical
Length 37-35cm
Protected by a bony cage called the vertebral column.
It is surrounded by meninges
31 pairs of spinal nerves arise from it.
In case of a spinal cord injury, the signals coming from the receptors as well as the
signals sent to the effectors will be disrupted. As both of these signals meet in a
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bundle in the spinal cord, so, if there is any spinal cord injury then both of these sig-
nals will be disrupted.

- If an injury in the spinal cord will also affect the reflex arc as reflex
arcs are controlled by the spinal cord. So, in that case, our body
might not be able to function properly in dangerous or reflex situ-
ations.

Hormonal system
- Exocrine: secrete their products to ducts that carry
these products to other organs or outside the body.
Example: salivary glands.
-Endocrine glands: secrete their products directly into
the bloodstream
Example: pituitary and thyroid glands.

- Hormones are chemical messengers that are secreted directly into the blood, which car-
ries them to organs and tissues of the body to exert their functions
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THYROID GLANDS: -
- Largest endocrine glands located below the larynx
in the front portion of the neck.
- It secretes 3 hormones.
- It’s a bilobed gland.
- Secretion: - 1) thyroxine [T4]
2) triiodothyronine [T3][ inactive
form of thyroxine]
3) thyrocalcitonin
- T3 and T4 regulate metabolic rate, stimulate pro-
tein synthesis, and perform the development of
mental faculties. [ anxiety, restlessness]
- Regulates carbohydrates, proteins, and fats meta-
bolism in the body to provide the best balance for
growth.
- It also helps in regulating the body temperature.
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- Stimulate the rate of cellular oxidation and metabolism, maintaining basal metabolic
rate.
- Thyrocalcitonin: helps in reducing calcium and
phosphate levels from blood and increases absorp-
tion of calcium in the bone.
- Excess: Grave’s disease- Hypersecretion of thyroid hormones leading to loss of
weight, rapid heartbeat, and protrusion of the eyeball.
- Myxoedema- deficiency of thyroid hormones in adults. This leads to a puffy appear-
ance due to fat accumulation and low metabolic rate.
- Iodine is necessary for the gland to make thyroxine
hormone. In case iodine is deficient in our diet,
there is a possibility that we might suffer from
goiter.
- Target organs- body tissues for cellular oxidation.

PARATHYROID GLANDS: -
- The primary function of the four tiny parathyroid
glands is to secrete parathyroid hormone, which
controls the body’s calcium levels.
- The four parathyroid glands are located on the
thyroid’s backside.

ADRENAL GLANDS: -
- Known as gland of emergency / suprarenal glands.
- Two triangular-shaped glands called the adrenal
glands are found on top of each kidney. Occurs in
pairs.
- Each endocrine gland has two parts: the outer ad-
renal cortex and the inner adrenal medulla.
- ADRENAL CORTEX: - Secrets group of steroid hor-
mones
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- 1) mineral corticoids [ aldosterone: maintains wa-

ter and electrolyte balance and blood volume in
the body]
- 2) glucocorticoids [ cortisol: anti-inflammatory and
anti-allergic effects]
- 3) gonnadocorticoids [ stimulate the development
of secondary sexual characteristics both in males
and females]
ADRENAL MEDULLA: enables the organism to face
physical and emotional stress.
Adrenaline and noradrenaline:-
• Both the hormones together control, fear, anger, blood pressure, heartbeat,
respiration, and relaxation of smooth muscles.
- Target organs – body muscles and smooth muscles.
- Addison disease

Ques: -What happens in our body when a ferocious dog

chases us?
Ans: - In case of such an emergency, adrenal hormone
gets secreted which enables the body to get ready to
deal with such situations. The heart beats faster, result-
ing in a supply of more oxygen to our muscles. The
blood supply to the digestive system and skin is re-
duced due to the contraction of muscles around small
arteries in these organs. This diverts the blood to our
skeletal muscle. The breathing rate also increases be-
cause of the contractions of the diaphragm and the rib
muscles.

PITUITARY GLANDS: -
- Located just below the hypothalamus.
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- Smallest endocrine glands and is called “master

gland”
- Weighs 0.5 grams
- Secretes growth hormones, oxytocin, anti-diuretic
hormones, gonadotrophic hormones, LH hormones.
- Growth hormones: deficiency – dwarfism [ stunted
growth]
- Excess - Gigantism and Ac-
romegaly.

- Secretes follicle-stimulating hormone/thyroid stim-

ulating hormone/ growth hormone/ luteinizing hor-
mone
PANCREAS: - ]
- Functions as endo + exocrine glands. Thus, known
as the heterocrine gland.
- The balance of sugar and salt in our bodies is
maintained by synthesizing pancreatic hormones.
- As endocrine glands secrete glucagon and insulin.
- Insulin converts glucose to glycogen. It helps in
regulating blood sugar levels. If it is not secreted in
proper amounts, the sugar level in the blood rises
causing many harmful effects.
- Glucagon is an anti-insulin hormone. Helps to regu-
late your blood glucose levels. Glucagon increases
your blood sugar levels and prevents it from drop-
ping too low.
- Disease- diabetes mellitus; patients secrete sugar
in the urine, excessive urination, and thirst.
THYMUS: - the lower part of the neck and upper
parts of the chest
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HYPOTHALAMUS: - plays an important role in the

release of many hormones.
- The hypothalamus produces hormones that re-
lease or suppress other hormones across the body
enabling them to start and stop production.
- E.g., gonadotropin-releasing hormone (GnRH)
- For example: when the level of growth hormone is
low the hypothalamus secrets the growth hormone
releasing factor to stimulate the pituitary gland to
secrete growth hormones.
- Located near the base of the brain, above the pitu-
itary and below the thalamus.
- It’s regarded as the connection between the endo-
crine and nervous system.
- Secretes releasing hormone and secreting hor-
mone.
Testis and ovary: -
- Testis secretes testosterone. Deficiency causes de-
creased sexual drive, irritability, and depression.
- Testosterone controls the development and func-
tioning of accessory sex organs and secondary
sexual characters in males.
- Ovaries secrete estrogen and progesterone.
- Oestrogen helps to control the development of fe-
male secondary sexual character.
- Progesterone helps to control uterus changes dur-
ing menstrual cycle and helps in maintaining preg-
nancy. Thus known as pregnancy hormone.
- Prolactin(maternity hormone): production of milk
oxytocin : ejection of milk
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- Deficiency:- disturbed ovulation cycle

Innervated : supplied with nerves.

PLANT HOROMONES

- Plant shows two different types of movement one

dependent on growth e.g., directional growth of
seedling is caused by growth. [ tropic movement]
- The other independent of growth- when we touch
the leaves of the touch-me-not plant of the
mimosa family, they begin to fold up and droop in [
nastic movement]
- Plants also have electrical chemical means that
carry information from cell to cell.
- In animals, some cells must change shape for
movement to happen.
- But plant cells change shape by changing the
amount of water in them, resulting in swelling or
shrinking and therefore in changing shapes.
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- Responses of plants are slow / cannot be observed

immediately/controlled by photo hormones [phyto-
hormones].

- Growth movements that occur in the direction of

stimulus are known as tropic movements.
- In this, one response acts on the protoplasm from
one side.
- A tropic movement may be towards or away from
stimuli (positive and negative)
- phototropism: plant growth response to light
(roots are- negatively phototropic; shoot towards
light positively phototropic)
- geotropism: plant growth to gravity (roots – posit-
ive; shoot – negative geotropic)
- chemotropism: growth response to chemicals.
(Growth of pollen tube towards the ovule); roots
grow away from harmful acids
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- thigmotropism: touch response. (Positive – plants

such as peas) roots grow away from objects in the
soil.
- hydrotropism: response to water. (Roots are pos-
itively hydrotropic).

Nastic movements: - seismonasty (thigmonasty) Touch

me not plant
Nyctinasty: day-night changes
Photonasty: response to stimulus light
Dandelions opens and closes in the morning and even-
ing
Thermonasty: changes in plant parts caused by temp.
and are non-directional.
Flower of tulips and crocus opens at high temp.
- These movements are non-directional responses to
stimuli.
- These movements are independent of the direction
of the stimulus.
- These movements can be due to changes in turgor
or growth.
- E.g., the response of Mimosa pudica plant to touch.

- The plant is sensitive to touch because of pad-like

swellings called ‘pulvini’ at the base of each leaf.
- These pulvini have a lot of water pressure which
keeps them upright and tight.
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- But when we touch the plant the leaves, there is a

sudden loss of water and pressure. This causes
leave to droop in.

PHYTOHORMONES: -
- Growth Promotes – auxin, cytokinin, gibberellins.
- Growth inhibitors – abscisic acid and ethylene.
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AUXIN –
- Promote cell enlargement and cell differentiation.
- Promotes fruit growth.
- Auxin is synthesized and is secreted by meristem-
atic cells at the tips of stems.
- When a growing plant detects sunlight, a hormone
called auxin, is synthesized at the shoot to help the
cells to grow.
- When light is coming from one side of the plant,
auxin diffuses towards the shady side of the shoot.
- This concentration of auxin stimulates the cells to
grow longer on the side of the shoot which is away
from the light. Thus, the plant appears to bend to-
ward the light.
- it induces parthenocarpy. [seedless fruits]
- apical dominance
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Gibberellins: -
- Promotes cell enlargement and differentiation in
the presence of auxins.
- They promote fruit growth.
- Breaks seed and buds of dormancy.
- Elongation of shoots.
- promotes bolting, i.e. sudden elongation of internodes just before flowering in
rosette plants like cabbage and beet.
- Gibberellins delays senescence.

- It also induces maleness in certain plants like cannabis and Cucumis.

Cytokinin:
- Promote root growth.
- Promote cell division.
- Helps in breaking dormancy period.
- Formation of chloroplast.
- Delay aging in leaves.
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- Promote opening of stomata.

- Regulates phloem transport.
- Increase the shelf life of vegetables.
Abscisic Acid/ dormin : -
- Functions as a growth inhibitor hormone.
- Promotes dormancy in seeds and buds.
- Promotes wilting and falling of leaves and fruit fall.
[abscission of leaves}
- Helps in stomata closing to prevent loss of h2o.
ETHYLENE: -
- Promotes transverse growth.
- Senescence [ biological plant death or aging]
- Abscission of leaves and flowers
- Determining Flower Sex: Ethylene influences flower develop-
ment. In some plants, it promotes the production of female flowers
in male plants, contributing to reproductive success.
-
- Ripening of climatic fruits.
- Helps in breaking dormancy of buds seeds and
storage organs.
DORMANCY IN PLANTS: -
- In plants, dormancy is a period of arrested plant
growth.
- It’s a resting, inactive metabolic condition in plants
- For e.g., seeds are in dormant conditions before
they get favourable conditions to break the
dormancy and grow into a plant.
- Occurs due to abscisic acid.
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