Class- X

                                                              Biology

                                                Control and coordination

Living organisms are able to detect changes in their environment and respond to them. This characteristic known as sensitivity is essential for survival of living organisms.

Sensitivity is a feature of single celled organisms as it is of flowering plants and animals, e.g. when amoeba detects a suitable food it moves to take it into a vacuole.

Changes that bring about responses are called stimuli, e.g. cat runs on seeing a mouse, we close or eyes when a bright light is focused on our eyes, we withdraw our hands when w touch a hot object. When we detect the change and respond to it with movement.

All the movements in response to the environment are carefully controlled.

Coordination is the working together of parts of the body as a whole, e.g. if you touch something hot, the muscles in your arm contract, so that your hand is quickly pulled away.

In animals internal communication, i.e. coordination involves both the nervous system and endocrine system (hormone producing system).to work together both endocrine and nervous system involves the following:

1.      Stimuli - any detectable change in the external or internal environment.

2.      Receptor- on organ that detects a specific stimulus.

3.      Coordination- system connects receptor to effectors.

4.      Effectors- an organ that produces a response as a result of stimulus detection.

In plants internal communication is via plant growth regulator substances.

             Plant hormones or phytohormones

The plants do not have a nervous system and sense organs like eyes, ears, or nose, etc., like the animals, but they can still sense things.

The plants coordinate their behavior against environmental changes by using hormones.

Plants have no nervous system, so plants use only hormones for coordination.

The plants respond to various stimuli very slowly by growing.

The function of control and coordination in plants is performed by the chemical substances called plant hormones.

Many different chemicals help to coordinate the growth of a plant. These chemicals are called plant hormones or phytohormones.

1.   They are produced in small amounts. Small amounts of these have profound effects on target cells.

2.   Plant hormones are very specific and unlike animal hormones are produced in the very organ where they have their effect.

3.   They synthesis and action of phythormones are greatly influenced by the external stimuli.

4.   Phytohormones regulate several functions in a plant like growth of roots, stems, leaves, flowering, seed germination, photoperiodism, geotropism, breaking of seed dormancy, ripening of fruits and opening and closing of stomata etc.

5.   They may promote or inhibit a process.

So far five types of phytohormones have been identified. Their names and major functions are given below--

Name of the plant hormones	Functions
Auxins	1.                           Stimulate growth of shoot and root tips. 2.                           Promote fruit growth and apical dominance 3.                           Suppress shedding of leaves and fruits
Gibberllins	1.                           Promote stem elongation 2.                           Stimulate flowering and fruit development. 3.                           Promote seed and bud germination
Cytokinins	1.          Stimulate cell division and growth 2.                           Promote seed germination 3.                           Delay ageing in plants.
Abscisic acid	1.                           Bring falling of leaves and fruits. 2.                           Maintain seed dormancy. 3.                           Inhibit growth.
Ethylene	1.                           Promote fruit ripening. 2.                           Along with ABA, stimulate abscission of leaves.

     

                      Movement in plants

Plants do not show locomotion and are rooted to one place. However, they do show movements in response to external stimuli and exhibits growth movements like bending, twisting, coiling and elongation etc. plant movements are caused by changes in the size of cells. These could be temporary or permanent.

Plant movement in response to external stimuli can be grouped into categories:

a.                           Tropic movement or tropism

b.                           Nastic movement

A.                          Tropic movement: A growth movement of a plant part in response to an external stimulus in which the direction stimulus determines the direction of response is called tropism. If the growth (or movement) of a plant part is towards the stimulus, it is called positive tropisms, and if the growth (or movement) of a plant part is away from the stimulus, then it is called negative tropism.

Tropisms are namely according to the stimulus. This will become

Stimulus	Types of tropism
Light	Phototropism
Gravity	Geotropism
Chemicals	Chemotropism
Water	Hydrotropism
Touch	Thigmotropism

Types of tropism:

i.                             Phototropisms: it is a response of plant to light. When a growing plant is illuminated by unidirectional light, the shoot bends towards the light. The shoots are said to be positively phototropic as they grow towards’ the light while roots are negatively, phototropic as they grow away, from light.

ii.                           Geotropism: It refers to the response induced by gravity. Roots of a plant grow downwards towards the gravity and show positive geotropism. Stem are said to be negatively geotropic as they grow away from gravity.

iii.                         Chemotropism: it is a response of a plant or a part of it to chemical, like the pollen tube is positively chemotropic as it moves towards the ovules due to chemicals produces over there.

iv.                          Hydrotropism- the movement of plant part in response to water is called hydrotropism. If the plant moves towards water, it is called positive hydrotropism. On the other hand if the plant part moves away from water then it is called negative hydrotropism.

v.                            Thigmotropism- the directional movement of plant part in response to the touch of an object is called thigmotropism.for e.g. the climbing parts of the plant such as tendrils grow any support which they happen to touch and wind around that support.so, tendrils of plant are positive thigmotropism.

B.                           Nastic movement: The movement of a plant part in response to an external stimulus in which the direction of response is not determination by the direction of stimulus is called nastic movement.

Types of nastic movement

 Photonasty : The movement of a plant part in response to light is called photonasty.

The opening and closing of petals of dandelion flowers in response to the intensity of light is an example of nastic movement.

Thigmonasty movement in touch me not plant, the leaflets are sensitive to touch’ the fold upwards in seconds on touching the plant. It is due to rapid loss of water from specialized cells at the base of leaflets. If the plant is left undisturbed in about 10 minutes the plant comes back to its original form.

Photoperiodism

Photoperiodism-it can be defined as a phenomenon or response of plants to the changing relative lengths of day and night called photoperiodiisam.

Photoperiod: it refers to the relative length of the day or the light period.

                         Control and coordination in animals-

         What are receptors?

A receptor is a cell (or a group of cells) in a sense organ which is sensitive to particular type of stimulus (or a particular type of change in the environment) such as light.

The common receptors are-

1.      Photo receptors detect light (eyes)

2.      Phanoreceptor detect sound (ear)

As the complexity in the animals increases the coordination of different parts of the body amongst themselves and with the external environment become necessary. All vertebrates have two systems

a.      Nervous system

b.      Endocrine system

Which not only control and coordinate various cellular activities but also help the animals to respond to the stimulus?

The nervous system is comparatively faster and localized in action while the endocrine system is slower and has a widespread action in the body. Both the systems interact and involved in the:

1.      Control and coordination of various functions in the body.

2.      Interaction between the environment and the body.

                          

  

                            Human nervous system     

Human nervous system consists of network or specialized cell called neuron.

A neuron is a structural function unit of nervous system.

Neurons vary in shape and size depending in their position and function but all neurons have a similar basic structure.

1.   An neuron posses three distinct regions:

a.   Cell body or cyton

b.   Dendrites

c.    Axon

Structure and functions of the parts of neuron have been explained in the given below:

Parts of the neuron	Structure and function
Cell body	The main part of the neuron consisting and nucleus.
Dendrites	Short, branched processes which receive nerve impulses and transmit the towards the cell body. They are grey in color and make up the grey matter of the brain and spinal cord.
Axon	Single, longer, unbranched processes which transmits impulses away from the cell body to the target cell. They are white in color and make up while matter of brain and spinal cord.
Myelin sheath	Made up of individual cells (Schwann cells) with abundant fatty material surrounding the axon, acts as an electrical insulator and speeds up the passage of impulses.
Nodes of ranvier	The gaps between the Schwann cells where the myeline sheath is absent.

                                                                                                                        

There are three types of neurons- sensory neurons, motor and interneuron depending on their action.

Sensory neurons: they carry nerves

Sensory neurons: They carry nerve impulses from peripheral tissues or receptor to central nervous system (CNS). They carry stimulus from receptors.    

 Receptors                        CNS  

Motor neurons: they take nerve impulses from CNS to peripheral tissue and organs, (called effectors). They carry message s from CNS to effectors.

            CNS                  Effectors  

Interneuron: also called association neurons, they are found completely within the CNS and make link between sensory and motor neurons.   

Nerve impulses-

Unlike the electrical impulses that are sent along the telephone lines, nerve impulses are caused by chemical changes in and around the nerves.

Nerve impulses travel rapidly in one direction, starting at the dendrites and finishing at the end of axon. 

Synapses-       

Minute gaps called synapse separate neuron from one another. Each synapse separates the end of the axon of one neuron from the dendrite of the next.

When nerve impulse arrives at the end of the axon they stimulate a production of a special chemical called neurotransmitter which diffuses across the synapse to the dendrites of the neighboring neurons.

Neuromuscular junction-

When the axon reaches the muscles, it splits into branches which make connection with the muscle fibers. The point where the two join is called the neuromuscular junction. There is a gap here, and the message gets across by means of a chemical substance just as it does between neuron at synapse. Synapse occurs between the swollen tips of terminals of the axon of one neuron and dendrites of cell body of another neuron. The tiny gap between the neuron is known as synaptic cleft. Impulses are also conducted at the point of contact between the terminals fibers of motor neurons and muscle fibers. Such a junction is a special type of synapse called a motor end plate. Each muscle fiber contains many nuclei lying in the cytoplasm just below the membrane, the sarcolemma. The sacroplasm contain numerous mitochondria. The bulk of the muscles fibers contain of a mass of parallel, fibrous, myofibrils the length of fiber.

                                                                                             

The reflex arc connects a sense organ with a muscle or a gland via the neuron as follows:

1.      The sense organ detects the stimulus in the form of energy such as sound, light or mechanical pressure.

2.      The stimulus is converted into an impulse which is transmitted to an effectors organ.

3.      When a impulse arrives at the effectors, the impulse cause an response for e.g.it may cause a muscle to contract or a gland to secrete.

The simplest form of response in the nervous system is called reflex action.

Reflex action can be defined as a rapid automatic short lived involuntary response to stimulus.

In a reflex action a particular stimulus creates a same automatic response every time.

                                  Spinal cord

·         It is a tubular or cylindrical structure extending downwards from.

·         The medulla oblongata

·         It is enclosed within the vertebral column and has diameter of that of the little finger.

·         It is surrounded by three membranes called meanings.

·         The distribution of grey and white matter is just the reverse

·         To what is represented in the brain. In the spinal cord, grey matter forms the center and the white matter is present in the periphery

·         In the center of spinal cord runs a narrow central canal containing the cerebrospinal fluid.

·         From the spinal cord arise 31 pairs of spinal nerves which are part of the peripheral nervous system.

                             Human brain

Human brain has three majors’ parts or regions

a.      Forebrain            b. Mid Brain           c. Hind Brain

Forebrain

Most complex/ specialized part of the brain is CEREBRUM

Functions:

1.      Thinking part of the brain

2.      Control the voluntary actions

3.      Store information (Memory)

4.      Center associated with HUNGER

5.      Receives sensory impulses from various body parts and integrates it.

Mid brain:

Hypothalamus: chemical coordination

Pituitary gland: secretes hormones

Hind brain:

1.         Cerebellum i) Controls posture and balance

                             ii) Control precision of voluntary actions

2.         Medulla   - controls involuntary actions

                            e.g.  Blood pressure, salivation, vomiting

3.         Pons   - involuntary  action, regulation of respiration

Cerebrum	Cerebellum
1.      Part of the fore brain. 2.      Largest part of brain covers most of the head region. 3.      Associated with memory, intelligence, and sensation like pain, touch etc and voluntary and involuntary muscle activities.	1.      Part of the hind brain. 2.      Comparatively very small part, present just above the back of the neck. 3.      Associated with voluntary muscular movement and maintenance of equilibrium.

Hormones in animals

Hormones: these are the chemical messengers secreted in very small amounts by specialized tissues called ductless glands. They act on target tissues/organs usually away from their source.

Endocrine system helps in control and coordination through chemical compound called hormones.

s.no.	hormone	Endocrine gland	Location	functions
1.	Thyroxine	Thyroid	Neck/ throat region	Regulation of metabolism of carbohydrates, fats and proteins.
2.	Growth hormone	Pituitary	Mid	Regulates growth and development.
3.	Adrenaline	Adrenal	Above both kidneys	Regulation(increasing)of blood pressure, heart beat, carbohydrate metabolism (during emergency)
4. Sex hormone	Testosterone in males Estrogen in females	Testes Ovaries	Genital / lower abdomen area	Estrogen- Changes associated with puberty (sexual maturity) Progesterone- To control uterus changes and maintenance of pregnancy
5.	Insulin	pancreas	Below stomach	Reduces and regulates blood sugar levels

Iodized salt is necessary because:

Iodine mineral is essential part of thyromine 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 fat metabolism for best balance of growth deficiency of iodine might cause disease called goiter.

Diabetes:

Cause: it is due to deficiency of insulin hormone secreted by pancreas that is responsible to lower/ control the blood sugar levels.

Treatment: patients have to internally administer injections of insulin hormone which helps in regulating blood- sugar level.