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7. Control and Coordination

Chapter 7. Control and Coordination 

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All living organisms respond to various stimuli like heat, light, cold, touch, pressure etc.
Example : Withdrawal of hand on touching a hot object.

Control and Coordination in Animals:
It is brought about in all animals with the help of two main systems
(a) Nervous System
(b) Endocrine System

Functions of Nervous System
(i) To receive the information from environment
(ii) To receive the information from various body parts.
(Stimuli → Response)
(iii) To act accordingly through muscles and glands. 

1. Stimulus : Any change in environment to which the organisms respond is called stimulus. E.g., touching a hot plate.
2. Response : The reaction of our body to a stimulus. E.g. withdrawal of our hand on touching hot plate.
3. Receptors : Are specialised tips of some nerve cells that detect the information from the environment.

Type of Receptors :

(i) Photo receptor : for vision (Eye) 

(ii) Phono receptor : for hearing (Ear)

(iii) Gustatory receptor : for taste (Tounge) 

(iv) Olfactory receptor : for smelling (Nose) 

(v) Thermo receptor : for for feeling heat (skin) 

These receptors are usually located in our sense organs, such as the inner ear, the nose, the tongue, and so
on.

Nervous Tissue: nervous tissue is made up of an organised network of nerve cells or neurons, and is specialised for conducting information via electrical impulses from one part of the body to another.

Nervous cell (neuron) : The unit of nervous tissue is called nevous cell or neuron. 

Structure of neuron:

 

Functions of nervous cell or neuron:

Nervous cell or neuron is specialised for conducting information via electrical impulses from one part of the body to another.

The parts of nervous cells: 

(i) Dendrite : Where informations are acquaired at the end of the dendritic tips of a nerve cell. 

(ii) From Dendrite to cytoplsm : Here the the impulse travels from the dendrite to the cell body, and then along the axon to its end.

(iii) Axon : At the end of the axon, the electrical impulse sets off the release of some chemicals. These chemicals cross the gap, or synapse, and start a similar electrical impulse in a dendrite of the next neuron.

Propagation of informations through nerves : 

All informations to our brain that delivers the informations that are acquaired at one end of dendritics of the nerve cell and sets off a chemical reaction that creates an electrical impulse. This impulse travels from the dendrite to the cell body, and then along the axon to its end. At the end of the axon, the electrical impulse sets off the release of some chemicals. These chemicals cross the gap, or synapse, and start a similar
electrical impulse in a dendrite of the next neuron.Such informations are transmitted from one place to another place of the body.

Synapse: The space between two neurons is called synapse. 

 

7. Control and Coordination

प्रतिवर्ती क्रिया :

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किसी उद्दीपन के प्रति, मस्तिष्क के हस्तक्षेप के बिना, अचानक अनुक्रिया, प्रतिवर्ती क्रिया कहलाती है | 

ये क्रियाएँ स्वत: होने वाली क्रियाएँ है जो जीव की इच्छा के बिना ही होती है | 

उदाहरण:

(i) किसी गर्म वस्तु को छूने से जलने पर तुरंत हाथ हटा लेना | 

(ii) खाना देखकर मुँह में पानी का आ जाना 

(iii) सुई चुभाने पर हाथ का हट जाना आदि | 

प्रतिवर्ती क्रियाओं का नियंत्रण: सभी प्रतिवर्ती क्रियाएँ मेरुरज्जू के द्वारा नियंत्रित होती है |

 ऐच्छिक क्रियाएँ: वे सभी क्रियाएँ जिस पर हमारा नियंत्रण होता है, ऐच्छिक क्रियाएँ कहलाती हैं | 

जैसे- बोलना, चलना, लिखना आदि | 

ऐच्छिक क्रियाओं का नियंत्रण: ऐच्छिक क्रियाएँ हमारी इच्छा और सोंचने से होती है इसलिए इसका नियंत्रण हमारे सोचने वाला भाग अग्र-मस्तिष्क के द्वारा होता है | 

अनैच्छिक क्रियाएँ : वे सभी क्रियाएँ जो स्वत: होती रहती है जिनपर हमारा कोई नियंत्रण नहीं होता है | अनैच्छिक क्रियाएँ कहलाती है | 

जैसे: ह्रदय का धड़कना, साँस का लेना, भोजन का पचना आदि | 

अनैच्छिक क्रियाओं का नियंत्रण: अनैच्छिक क्रियाएँ मध्य-मस्तिष्क व पश्च-मस्तिष्क के द्वारा नियंत्रित होती हैं | 

प्रतिवर्ती चाप : प्रतिवर्ती क्रियाओं के आगम संकेतों पता लगाने और निर्गम क्रियाओं के करने के लिए संवेदी तंत्रिका कोशिका और प्रेरित तंत्रिका कोशिका मेरूरज्जु के साथ मिलकर एक पथ का निर्माण करती है जिसे  प्रतिवर्ती चाप कहते है | 

जन्तुओं में प्रतिवर्ती चाप एक दक्ष प्रणाली अथवा जंतुओं में प्रतिवर्ती चाप की उपयोगिता : 

अधिकतर जंतुओं में प्रतिवर्ती चाप इसलिए विकसित हुआ है क्योंकि इनके मस्तिष्क के सोचने का प्रक्रम बहुत तेज नहीं है। वास्तव में अधिकांश जंतुओं में सोचने के लिए आवश्यक जटिल न्यूराॅन जाल या तो अल्प है या अनुपस्थित होता है। अतः यह स्पष्ट है कि वास्तविक विचार प्रक्रम की अनुपस्थिति में प्रतिवर्ती चाप का दक्ष कार्य प्रणाली के रूप में विकास हुआ है। यद्यपि जटिल न्यूराॅन जाल के अस्तित्व में आने के बाद भी प्रतिवर्ती चाप तुरंत अनुक्रिया के लिए एक अधिक दक्ष प्रणाली के रूप में कार्य करता है।

अर्थात जन्तुओं में सोंचने की शक्ति बहुत कम या क्षीण होती है जिससें वे तुरन्त अनुक्रिया कर अपना बचाव नही कर सकते है। अतः इस कमी को पुरा करने के लिए अधिकतर जन्तुओं में प्रतिवर्ती चाप एक दक्ष प्रणाली के रूप में कार्य करता है।

Human Brain: The human brain is a very large part of the nervous system, which is made up of nerve cells. Along with the spinal cord, it forms the central nervous system.

Spinal Cord: The spinal cord is a cylindrical bundle of nerve fibres. It passes through the vertebral column (spine) from the brain towards the coccyx. It connects all parts of the body with the nervous system and, along with the brain, forms the central nervous system.

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Functions:

(i) They receive information from all parts of the body and integrate it.

(ii) They send messages to the muscles.

(iii) The brain allows us to think and enables us to perform actions based on our thoughts.

(iv) All reflex actions are controlled by the spinal cord.

(v) All voluntary and involuntary activities are controlled by the brain.

Cranium: The cranium is the part of the human skull that protects the brain. The brain is located inside the cranium.

Meninges: The meninges are a protective covering made up of three thin membranes that protect the human brain from internal injuries. A fluid is present within these layers, which is called Cerebrospinal Fluid (CSF). It extends from the brain to the spinal cord.

CSF (Cerebrospinal Fluid): It is a fluid found between the layers of the meninges. It protects the brain from internal injuries and helps protect the brain and spinal cord from mechanical shocks.

Parts of the Brain and Their Functions:

The Parts of Brain and Their Functions:

1. Forebrain: It is the main thinking part of the brain. It contains areas that receive sensory impulses from different receptors. It has specialised areas for hearing, seeing and smelling. It controls the movement of voluntary muscles. It also contains a centre associated with hunger.

2. Midbrain: It is involved in controlling various involuntary activities and reflex responses of the body.

3. Hindbrain: It also controls involuntary activities. Various involuntary activities such as blood pressure, salivation and vomiting are controlled by the medulla located in the hindbrain.

The hindbrain consists of three main centres:

(i) Cerebellum: It coordinates and refines voluntary movements and controls the posture and balance of the body. For example, walking in a straight line, riding a bicycle and picking up a pencil.

(ii) Pons: It plays an important role in regulating and controlling the process of respiration.

(iii) Medulla Oblongata:  It controls various involuntary activities such as blood pressure, salivation and vomiting.

Nervous System:

Parts of the Nervous System:

7. Control and Coordination

Control and Coordination in Plants

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Control and coordination in plants are carried out by plant hormones, which are also called phytohormones. Different plant hormones help in coordinating growth, development and responses to the environment. They help plants respond appropriately to different stimuli such as light, gravity, water and touch.

Plants show two different types of movements-

(1)  Growth-independent movements - These movements do not depend on the growth of the plant. Such movements usually occur rapidly in response to a stimulus. For example, the folding or shrinking of the leaves of the touch-me-not plant (Mimosa pudica) when touched.

(2)  Growth-dependent movements -  These are the movements in plants that occur due to the growth of different parts of the plant body. Such movements are generally slow because they are associated with growth. Examples include the movement of tendrils, movement of a plant towards light and movement of roots towards water.

(1) Growth-independent Movement 

Movement in the Touch-me-not Plant - When we touch the touch-me-not plant (Mimosa pudica), it responds to the stimulus by showing movement in its leaves. The leaves fold or droop as a result of the touch. This movement is not related to growth because it occurs rapidly and does not involve the growth of the plant.

Immediate Response of Plants to a Stimulus - 

Plants also use electrochemical means to transmit information about touch from one cell to another. However, unlike animals, plants do not have any specialised tissues such as nerves for conducting information throughout the body. Plant cells also do not have specialised proteins like those found in animal muscle cells for producing movement. Instead, plant cells can change their shape by changing the amount of water inside them. As a result, the cells may swell or shrink, causing changes in the shape and position of different plant parts. This mechanism helps the touch-me-not plant show a rapid response when touched.

(2) Growth-dependent Movement 

(a) Movement of Tendrils -

Tendrils are thin, thread-like structures that help climbing plants to obtain support. When a tendril comes in contact with a support, the side away from the support grows faster than the side in contact with the support. This unequal growth causes the tendril to coil around the support. Thus, the movement of tendrils is a growth-dependent movement.

(b) Tropisms

   (i) Phototropism

Phototropism is the growth movement of a plant part in response to light. The shoot of a plant generally grows towards light and therefore shows positive phototropism, while roots generally grow away from light.

   (ii) Geotropism (Gravitropism)

Geotropism or gravitropism is the growth movement of a plant part in response to gravity. Roots generally grow towards gravity and show positive geotropism, whereas shoots generally grow away from gravity and show negative geotropism.

   (iii) Chemotropism

Chemotropism is the growth movement of a plant part in response to a chemical stimulus. For example, the growth of the pollen tube towards the ovule during fertilisation is an example of chemotropism.

   (iv) Hydrotropism

Hydrotropism is the growth movement of a plant part in response to water or moisture. Plant roots generally grow towards a source of water and therefore show positive hydrotropism. This helps plants obtain water necessary for their growth and survival.

7. Control and Coordination

Control of the Time and Amount of Hormone Secretion

The time and amount of hormone secretion are controlled by a feedback mechanism. For example, if the blood sugar level increases, the cells of the pancreas detect it and, in response, secrete more insulin. When the blood sugar level decreases, the secretion of insulin also decreases.

Hormones

Hormones are chemical substances that perform the functions of control and coordination in animals and plants.

Formation of Hormones in Animals

In animals, hormones are produced by endocrine glands.

In humans and animals, glands are of two types:

1. Endocrine Glands
2. Exocrine Glands

(1) Endocrine Glands

The glands that do not have ducts are called endocrine glands. They release hormones directly into the blood.

Examples: Pineal gland, Pituitary gland, Thyroid gland, Parathyroid glands, Thymus gland, Adrenal glands, Pancreas, Ovaries and Testes.

(2) Exocrine Glands

The glands whose secretions are released through ducts are called exocrine glands.

Examples: Lacrimal glands, Salivary glands and Sweat glands.

Human Endocrine Glands, Hormones and Their Functions

1. Pituitary Gland

Hormones: Growth hormone, TSH, FSH, LH, ACTH, etc.

Functions:

• Growth hormone promotes the growth of bones and other body tissues.
• TSH stimulates the thyroid gland to produce thyroid hormones.
• FSH and LH help in the development and functioning of reproductive organs.
• The pituitary gland controls the activities of several other endocrine glands, so it is often called the master gland.

2. Thyroid Gland

Hormones: Thyroxine (T4) and Triiodothyronine (T3)

Functions:

• Regulates the metabolism of the body.
• Helps in the growth and development of the body.
• Supports the normal functioning of many organs.

3. Parathyroid Glands

Hormone: Parathyroid hormone (PTH)

Functions:

• Maintains the calcium level in the blood.
• Helps in the proper functioning of bones and muscles.

4. Adrenal Glands

Hormones: Adrenaline, Cortisol, Aldosterone, etc.

Functions:

• Adrenaline prepares the body to deal with emergency situations and is known as the “fight or flight” hormone.
• Cortisol helps the body respond to stress and regulates metabolism.
• Aldosterone helps maintain salt and water balance in the body.

5. Pancreas

Hormones: Insulin and Glucagon

Functions:

• Insulin lowers the blood glucose level.
• Glucagon increases the blood glucose level.
• Together, they help maintain the normal blood sugar level.

6. Pineal Gland

Hormone: Melatonin

Function:

• Regulates the sleep-wake cycle and biological rhythms of the body.

7. Thymus Gland

Hormone: Thymosin

Functions:

• Helps in the development and maturation of T-lymphocytes (T-cells).
• Supports the immune system.

8. Ovaries

Hormones: Estrogen and Progesterone

Functions:

• Estrogen helps in the development of female secondary sexual characteristics.
• It also helps in the development of female reproductive organs.
• Progesterone helps regulate the menstrual cycle and prepares the uterus for pregnancy.

9. Testes

Hormone: Testosterone

Functions:

• Helps in the development of male secondary sexual characteristics.
• Promotes the development of male reproductive organs.
• Helps in the production of sperms.

Phytohormones or Plant Hormones

The chemical substances that perform the functions of control and coordination in plants are called phytohormones or plant hormones.

There are five main types of plant hormones:

1. Auxins

• Auxins promote cell growth and cell differentiation in plants.
• Auxins promote the growth of fruits.
• They increase the length of cells.

2. Gibberellins

• Gibberellins promote cell growth and cell differentiation in plants.
• They promote the growth of fruits and stems.

3. Cytokinins

• Cytokinins promote cell division in plants.
• They help in the growth and development of plant tissues.

4. Abscisic Acid (ABA)

• It inhibits or regulates the growth of plants.
• It helps control water loss in plants.
• It can promote protein synthesis and is involved in plant stress responses.

5. Ethylene

• Ethylene promotes fruit ripening.
• It can increase the number of female flowers in some plants.
• It helps regulate stem growth and development.

7. Control and Coordination