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Class 10 Science Chapter 6 Control and Coordination notes

                                                                           Class 10 Chapter 7

                                                                       Control and Coordination

Living organisms respond to stimuli like cold, cough, light, heat, temperature, pressure etc.

For example When bright light is focused on our eyes or when we touch a hot object, we detect the change and respond to it with movement in order to protect ourselves.

And when we walk or we talk, all are just controlled and coordinated by our system. It is brought about in all animals with the help of two main systems –

(a) Nervous System

(b) Endocrine System

 Animals – Nervous System

The nervous system is a complex network of specialized cells, tissues, and organs that coordinates and controls the activities of an animal’s body. It plays a crucial role in receiving, interpreting, and responding to internal and external stimuli. The nervous system allows animals to perceive their environment, make decisions, and carry out appropriate responses.

Nerve Cells (Neurons) 

Neuron is the structural and functional unit of the nervous system.

When we touch a hot object, then touching a hot object is an urgent and dangerous situation for us. We need to detect it, and respond to it. All information from our environment is detected by the specialised tips of some nerve cells. These tips are receptors. Receptors are usually located in our sense organs, such as the inner ear, the nose, the tongue, and so on.

Phono receptors (Inner ears) – Hearing

Photoreceptors (Eyes) – Visual stimulus

Thermoreceptors (Skin) – Pain, touch, heat

Olfactory Receptors (Skin) – Smell detection

Gustatory Receptors (Tongue) – Taste detection

This information, acquired at the end of dendritic tip of a nerve cell, it 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.

Reflex Action – Some sudden action in response to something in the environment. These are some actions that we do without thinking about it, or without feeling in control of our reactions.

A reflex action is an involuntary and automatic response that occurs in response to a specific stimulus.

Reflex actions are controlled by the nervous system and involve a rapid transmission of nerve impulses along a neural pathway called a reflex arc.

Here’s how a typical reflex arc works:

  1. Stimulus: A stimulus, such as touching a hot surface or a sudden loud noise, activates sensory receptors in the body.
  2. Sensory neurons: The sensory receptors send nerve impulses through sensory neurons to the spinal cord. These neurons carry the sensory information from the point of stimulation to the central nervous system.
  3. Processing: In the spinal cord, sensory information is rapidly processed and analysed.
  4. Motor neurons: If the stimulus requires an immediate response, motor neurons are activated.
  5. Effector: The motor neurons transmit the nerve impulses from the central nervous system to the effectors, typically muscles or glands.
  6. Response: The effectors receive the nerve impulses and carry out the appropriate response. For example, if you accidentally touch a hot surface, the reflex action causes your hand to quickly retract before you even consciously register the pain.

Human Brain –

Thinking involves complex mechanisms and neural connections. These are concentrated in the brain, which is the main coordinating centre of the body.

The animal nervous system contains two primary components –

1. Central nervous system (CNS) – The CNS includes the brain and the spinal cord. It is the main control center of the body, responsible for processing and integrating information from the sensory organs and initiating appropriate responses. The brain is involved in various functions, such as thinking, memory, emotions, and motor control. The spinal cord serves as a pathway for transmitting signals between the brain and the rest of the body.

     2. Peripheral Nervous System (PNS): The PNS consists of nerves outside of the brain and spinal cord. It    connects the CNS to the rest of the body, including the muscles, glands, and sensory organs. Peripheral nervous system consisting of cranial nerves arising from the brain and spinal nerves arising from the spinal cord.

Parts of brain –

There are three major parts or regions –

(a) Fore – brain

(b) Mid – brain

(c) Hind – Brain

(a) Fore brain (Cerebrum) – Specialised for hearing, smell, sight and so on. The cerebrum is responsible for reasoning, logic, emotions, speech, memory, visual processing, recognition of auditory and taste stimuli, etc. There is separate areas of association where this sensory information is interpreted by putting it together with information from other receptors as well as with information that is already stored in the brain.

     (b) Hind brain – It consists three parts – (a) Pons (b) Medulla (c) cerebellum

      –  Cerebellum regulates and coordinates body movements, posture and balance.

       – Medulla Oblongata controls all involuntary movements like vomiting, sneezing, yawning, heartbeat, breathing, blood pressure, etc.

      –  Pons relays signals from the hindbrain to the forebrain. Connects cerebellum to cerebrum.

    (c) Mid brain – It helps to regulate movement and process auditory and visual information.

How are these Tissues protected? –

A delicate organ like the brain. Which is so important for a variety of activities. Needs to be carefully protected. for this, the body is designed so that the brain sits inside a bony box. Inside the box, the brain is contained in a fluid-filled balloon which provides further shock absorption.

How does the nervous tissue cause Action?

When the action or movement is to be performed, muscle tissue will do the final job of responding the information given by brain. This is done by muscle cell which have special proteins that change both their shape and their arrangement in the cell in response to nervous electrical impulses. When this happens. New arrangements of these proteins give the muscle cells a shorter form.

Coordination in plants  –

 –     Growth Independent Movements

The movements which are not growth-related are called nastic movements. These movements occur in response to environmental stimuli but the direction of response is not dependent on the direction of the stimulus.

  • The movement in the touch-me-not plant is thigmonastic movement (movement in response to touch). The plants use electrical–chemical means to convey this information from cell to cell. But unlike in animals, there is no specialised tissue in plants for the conduction of information. So plants cells changes shape by changing the amounts of water in them, resulting in swelling or shrinking, and therefore in changing shapes.

-Movements due to Growth

Movements due to growth refer to the changes in the position, shape, or size of an organism or its parts resulting from an increase in its size or the number of cells. These growth-induced movements are common in various living organisms, from plants to animals. Here are some examples of movements due to growth:

1. Phototropism

2. Gravitropism (Geotropism)

3. Hydrotropism

4. Chemotropism

 1. Phototropism: The bending or growth of plant parts (usually stems) towards a light source. This movement is caused by the differential growth of cells on the shaded and illuminated sides of the plant.

2. Gravitropism (Geotropism): The response of plant roots to gravity, growing downwards, and stems upwards. This enables roots to anchor the plant in the soil while stems reach toward the light source.

3. Hydrotropism – A hydrotropism is a plants growth towards water.

4. Chemotropism – The growth or movement of a plant or plant part in response to chemical stimulus.

Plant Hormones and Movements –

Control and coordination in plants are carried out by hormones.

Growth promoting hormones

1. Auxin – It promotes growth of plant.

It secretes at the shoot tip. When growing plants detect light, this hormone synthesizes at the shoot tip and helps the cell to grow longer. 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 light. Thus, the plant appears to bend towards light.

2. Gibberellins – It helps in the growth of the stem.

It secretes in the stem.

3. Cytokinins – It promotes cell division.

It secretes in the fruits and seeds. It is natural then that they are present in greater concentration in the areas of rapid cell division, such as fruits and seeds.

Growth inhibiting Hormones

1. Abscisic acid – This hormone inhibits growth.

It secretes in the leaves. It affects by wilting and yellowing of leaves.

2. Ethylene

Hormones in Animals (Endocrine System)

1. Adrenaline – This hormone secretes from the adrenal glands.

Adrenaline is secreted directly into the blood and carried to different parts of the body. The target organs or the specific tissues on which it acts include the heart. As a result, the heart beats faster, resulting in a supply of more oxygen to our muscles. The blood to the digestive system and skin is reduced due to the contraction of muscles around small arteries in these organs. This diverts the blood to our skeletal muscles. The breathing rate also increases because of the contractions of the diaphragm and the rib muscles. All these responses together enable the animal body to be ready to deal with the situation.

 2. Thyroxin – This hormone secretes from the thyroid gland.

Iodine is necessary for the thyroid gland to make thyroxin hormone. Thyroxin regulates carbohydrate, protein, and fat metabolism in the body so as to provide the best balance for growth. In case iodine is deficient in our diet, there is a possibility that a person may suffer from goiter.

3. Growth hormoneThis hormone secreted by the pituitary.

It regulates the growth and development of the body. If there is a deficiency of this hormone in childhood, it leads to dwarfism.

4. Testosterone – Mainly produces in testes of males.

Changes occur in male bodies at the time of puberty caused by this hormone.

5. Oestrogen and Progesterone – Produces in the ovaries of females.

Changes occur in female bodies at the time of puberty caused by this hormone.

6. Insulin – Produces in the pancreas.

The function of insulin hormone is to lower the blood sugar level. Insulin controls the metabolism of sugar. Deficiency of insulin causes diabetes. Diabetic patients are treated by giving injections of insulin.

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