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Control and Coordination in Animals: Nervous system
and endocrine system
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Receptors: Receptors are the specialized tips of the nerve fibers that collect the information to be
conducted by the nerves
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These are classified as follows :
● Phono-receptors: These are present in the inner ear
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● Photo-receptors: These are present in the eye
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● Thermo-receptors: These are present in skin
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These receptors are also known as thermoreceptors
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Functions: These receptors receive smell
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Functions: These help in taste detection
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The nerve cell or neuron is the functional unit of the nervous system
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Functions of the nervous system:
● Nervous system receives information from the environment
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● To act according to muscles and glands
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NEURON AS STRUCTURAL AND FUNCTIONAL UNIT OF NEURAL SYSTEM
● A neuron is composed of three major parts: cell body, dendrites and axon
● The cell body contains cytoplasm with typical cell organelles and certain granular
bodies called Nissl’s granules
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● The axon is a long fibre,
the distal end of which is
branched
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● The axons transmit nerve
impulses away from the
cell body to a synapse or
to a neuro-muscular
junction
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● The myelinated nerve
fibers are enveloped with
Schwann cells, which form
a myelin sheath around
the axon
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● Myelinated nerve fibres
are found in spinal and cranial nerves
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The human neural system is divided into two parts : (i) the central neural system (CNS) (ii) the peripheral
neural system (PNS) The CNS includes the brain and the spinal cord
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The nerve fibres of the PNS are of two types :
(a) afferent fibres: nerve fibres transmit impulses from tissues/organs to the CNS
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The PNS is divided into two divisions:
a
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the autonomic neural system: it transmits impulses from the CNS to the involuntary organs and
smooth muscles of the body
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Reflex Action: Reflex action is a special case of involuntary movement involuntary organs
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For example, when your hand touches a very hot electric iron, you move away your hand in a jerk
Reflex Arc: The path through which nerves signals, involved in a reflex action, travel is called the reflex arc
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Receptor → Sensory neuron → Relay neuron → Motor neuron → Effector (muscle)
a
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b
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The relay
neuron is present in the spinal cord
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The spinal cord sends signals to the effector via the motor neuron
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The effector comes in action, moves the receptor away from the danger
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This is important because sending signals to the brain would involve more
time
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Human Brain: The brain is covered by a three-layered system of membranes, called meninges
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The CSF providers cushion the brain against mechanical
shocks
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Some main structures of the human brain are explained below :
Cerebrum: The cerebrum is the largest part in the human brains
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Functions of cerebrum
● It is the site of sensory perceptions, like tactile and auditory perceptions
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Hypothalamus: It controls sleep and wake cycle (circadian rhythm) of the body
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Cerebellum: It coordinates the motor functions, It controls posture and balance
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The medulla controls various involuntary
functions, like heatr beat respiration, etc
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Pons: It relays impulses between the lower cerebellum and spinal cord, and higher parts of the brain like the cerebrum
and midbrain, also regulates respiration
Spinal cord: Spinal cord controls the reflex actions and conducts messages between different parts of the body and

brain
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When a
muscle receives a nerve
signal, a series of events is
triggered in the muscle
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Calcium ions enter the
muscle cells
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It results in actin and
myosin filaments sliding
towards each other and that
is how a muscle contracts
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Contraction in a muscle
brings movement in the
related organ
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Co-ordination in Plants: Unlike animals, plants do not have a nervous system
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Many plant hormones are responsible for various kinds of movements in plants
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Tropic movement
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Tropic Movement: The movements which are in a particular direction in relation to the stimulus are called tropic
movements
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There are four types
of tropic movements
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Roots
usually show positive geotropic movement, i
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they grow in the direction of the gravity
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(ii) Phototropic Movement: The growth in a plant part in response to light is called phototropic movement
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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
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As a result, the stem bends towards the light
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(iii) Hydrotropic Movement: When roots grow in the soil, they usually grow towards the nearest source of water
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(iv) Thigmotropism Movement: The growth in a plant part in response to touch is called thigmotropism movement
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The tendril grows in a way so as it can coil around a support
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2
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For example, when someone touches the leaves of mimosa, the leaves droop
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Such movements usually happen because of changing water
balance in the cells
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Plant hormones: Plant hormones are chemical which help to co-ordinate growth, development and responses to the
environment
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Function: Helps in growth
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● Gibberellin: Helps in the growth of the stem
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● Abscisic acid: Inhibits growth, cause wilting of leaves
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● A ductless gland is called endocrine gland
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● Hormone is mainly composed of protein
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But unlike nervous control, hormonal control is somewhat slower
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Thyroid stimulating hormone
(TSH)
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TSH stimulates the functioning of the thyroid
gland
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Thyroid
Gland

Neck

Thyroxine

Controls general metabolism and growth in
the body
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Pancreas

Near stomach

Insulin

Controls blood sugar level

Testis (male)

In Scrotum

Testosterone

Sperm production, development of secondary
sexual characters during puberty
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Iodised salt is necessary because: Iodine mineral is essential part of thyronine hormone so it is important that we must
consume iodised salt as in turn it is essential for thyroid gland as it controls carbohydrate, proteins and fat metabolism
for best balance of growth deficiency of iodine might cause disease called goitre
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Treatment : Patients have to internally administer injections of insulin hormone which helps in regulating blood-sugar
level
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Feedback mechanism: A type of self-regulating mechanism in which the level of one substance in body influences the
level of another

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