Control and Coordination

 Visible movements in living organisms are often associated with life.

Movements can be a response to changes in the organism's environment.

Living organisms use movement to their advantage by adapting to environmental changes.

Movement in response to the environment is carefully controlled.

Different changes in the environment evoke specific movements in response.

Controlled movement is connected to the recognition of various events in the environment.

Living organisms rely on systems that provide control and coordination.

Specialized tissues are responsible for providing control and coordination in multicellular organisms.

6.1 ANIMALS – NERVOUS SYSTEM

Parts of a neuron:

(i) Information is acquired at the specialized tips of nerve cells called receptors, located in sense organs such as the inner ear, nose, tongue, etc.

(ii) Information travels as an electrical impulse from the dendrite to the cell body and then along the axon.

(iii) The electrical impulse is converted into a chemical signal at the end of the axon, where chemicals are released and cross the synapse to initiate a similar electrical impulse in the dendrite of the next neuron.

The difference in taste when the nose is blocked:

When the nose is blocked, the sense of smell is affected, which can impact the perception of taste.

The ability to detect certain flavors and aromas is reduced because the sense of smell contributes significantly to our perception of taste.

Taste and smell are closely linked, and when the sense of smell is compromised, it can affect how we perceive the taste of food.

A similar situation during a cold:

During a cold, the nasal passages are congested or blocked, affecting the sense of smell.

As a result, the perception of taste may be altered, and food may seem less flavorful or bland.

The sense of taste relies on the combination of taste buds on the tongue and the sense of smell to create the perception of flavors.

When the sense of smell is compromised due to a cold, it can affect the overall taste experience.

6.1.1 What Happens in Reflex Actions?

Reflex refers to a sudden action or response to a stimulus in the environment, which occurs without conscious thought or feeling in control.

Control and coordination in reflex actions are achieved through reflex arcs.

Reflex arcs allow for a rapid response without the need for conscious thinking.

In reflex arcs, the sensory nerves that detect a stimulus (input) are connected to motor nerves that control muscles (output) in a simple and direct manner.

Reflex arcs are commonly formed in the spinal cord, where sensory and motor nerves meet before the information is also sent to the brain.

Reflex arcs evolved as efficient ways of functioning in animals, particularly those without complex thinking processes.

Even with the existence of complex neuron networks for thinking, reflex arcs remain more efficient for quick responses to stimuli.

6.1.2 Human Brain

The spinal cord is not solely responsible for reflex actions. It is made up of nerves that supply information for thinking and coordination.

The brain, along with the spinal cord, forms the central nervous system, which receives information from all parts of the body and integrates it.

Voluntary actions, such as writing, talking, and moving objects, involve the brain sending messages to muscles.

The peripheral nervous system, consisting of cranial nerves and spinal nerves, facilitates communication between the central nervous system and the rest of the body.

The brain is responsible for thinking and decision-making, with different regions specialized for receiving sensory impulses and interpreting them.

The fore-brain is the main thinking part of the brain, with separate areas for different senses and association areas for interpreting sensory information.

Decision-making in response to sensory information involves passing information to the motor areas that control voluntary muscle movement.

Certain sensations, like feeling full, are controlled by specific centers in the fore-brain.

 Involuntary actions, such as salivation, heartbeats, and digestion, are controlled by the mid-brain and hind-brain.

The medulla in the hindbrain controls involuntary actions like blood pressure, salivation, and vomiting.

The cerebellum, a part of the hindbrain, is responsible for precision in voluntary actions, posture, and balance.

Without these automatic and involuntary actions, daily activities would require conscious thinking and control.

6.1.3 How are these Tissues protected?

The brain, being a delicate organ involved in crucial activities, is protected by the body's design.

The brain is situated inside a bony box, which is the skull, providing physical protection against external forces.

Inside the skull, the brain is surrounded by cerebrospinal fluid, which acts as a cushion and shock absorber, further protecting the brain from impacts.

The vertebral column, also known as the backbone, runs down the middle of the back and protects the spinal cord.

The spinal cord is a vital part of the central nervous system, and its protection by the vertebral column is essential for its proper functioning and prevention of damage.

The combination of the skull and vertebral column creates a protective structure for the brain and spinal cord, safeguarding them from potential injuries.

6.1.4 How does the Nervous Tissue cause Action?

Muscle tissue plays a crucial role in executing movements in response to nervous signals.

When a nerve impulse reaches a muscle, the muscle fibers undergo a change in shape, resulting in muscle movement.

Muscle cells possess special proteins that can change their shape and arrangement within the cell in response to nervous electrical impulses.

These proteins, when rearranged, cause the muscle cells to shorten, leading to muscle contraction.

Voluntary muscles are under conscious control and can be moved or contracted at will.

Involuntary muscles, also known as smooth muscles, are not under conscious control and perform involuntary actions such as the contraction of the heart, digestion, or movement of internal organs.

The mechanism of muscle contraction and the regulation of voluntary and involuntary muscles may differ based on the specific arrangement and control of the proteins involved.

Overall, the distinction between voluntary and involuntary muscles lies in their control and regulation rather than the fundamental mechanism of muscle cell movement.

6.2 COORDINATION IN PLANTS

Plants lack a nervous system and muscles, yet they are capable of responding to stimuli.

Plants exhibit two different types of movements: growth-dependent movement and growth-independent movement.

Growth-dependent movement refers to the directional movement of plant parts, such as the roots growing downward and the stems growing upward. This movement is a result of the plant's growth in response to environmental cues.

Growth-independent movement is observed in plants like the sensitive plant (chi-mui) of the Mimosa family. When its leaves are touched, they fold up and droop rapidly. This movement does not involve growth but is a quick response to external stimuli.

The movement in sensitive plants is facilitated by changes in turgor pressure, which is the pressure exerted by the cell contents against the cell wall. Touch triggers the release of certain chemicals, leading to the loss of turgor pressure in specific cells, causing the folding and drooping of the leaves.

Overall, plants have evolved different mechanisms to respond to stimuli and exhibit movement, utilizing growth-dependent and growth-independent strategies. These responses allow plants to adapt to their environment and optimize their survival and reproduction.

6.2.1 Immediate Response to Stimulus

In plants like the sensitive plant, movement occurs in response to touch without involving growth.

The plant detects the touch through specialized cells called mechanoreceptors, which are present in the leaves and other sensitive parts of the plant.

When the mechanoreceptors are stimulated by touch, they initiate an electrical-chemical signaling process within the plant.

Unlike animals, plants do not have specialized nervous tissue for information conduction. However, they use electrical signals and chemical messengers to communicate the touch response from cell to cell.

The movement in plants is achieved through changes in cell shape. Instead of using specialized proteins like animal muscle cells, plant cells alter their shape by regulating the amount of water present in them.

By changing the water content, plant cells can swell or shrink, leading to changes in cell shape and consequent movement in response to touch or other stimuli.

This movement through changes in cell shape allows plants to respond to their environment and exhibit various types of tropic movements, such as phototropism (response to light) or gravitropism (response to gravity).

6.2.2 Movement Due to Growth

Some plants exhibit movement through tropic responses, which can be either towards or away from stimuli.

Tendrils in plants like the pea plant respond to touch by exhibiting circulatory movement. The part of the tendril in contact with an object grows less rapidly than the rest, causing the tendril to circle around and cling to the support.

Plants show tropic movements in response to environmental triggers such as light (phototropism) and gravity (geotropism). Shoots exhibit positive phototropism by bending toward light, while roots exhibit negative phototropism by bending away from light.

Other types of tropic movements in plants include hydrotropism (response to water) and chemotropism (response to chemicals). An example of chemotropism is the growth of pollen tubes towards ovules during reproduction.

Information communication in multicellular organisms involves both electrical impulses and chemical communication.

Electrical impulses are rapid but limited to cells connected by nervous tissue, while chemical communication can reach all cells in the body.

Multicellular organisms use chemical compounds, such as hormones, for control and coordination. Hormones diffuse to the target cells and bind to specific receptors to transmit signals.

Plant hormones, such as auxins, gibberellins, cytokinins, and abscisic acid, regulate various aspects of plant growth, development, and responses to the environment.

Auxins promote the elongation of cells and play a role in phototropism. Gibberellins also contribute to stem growth. Cytokinins stimulate cell division, while abscisic acid inhibits growth and can cause leaf wilting.

6.3 HORMONES IN ANIMALS

Animals use hormones as chemical means of information transmission in their bodies.

In response to a scary situation, animals like squirrels release adrenaline, a hormone secreted from the adrenal glands, into the bloodstream.

Adrenaline acts on target organs or specific tissues, such as the heart, to increase heart rate and oxygen supply to muscles. It also diverts blood away from the digestive system and skin to skeletal muscles and increases breathing rate.

Animal hormones, including adrenaline, are part of the endocrine system, which plays a role in control and coordination in the body.

Animal hormones do not play a direct role in directional growth like plant hormones. However, they contribute to growth and development in specific places within the body.

Hormones like thyroxin, produced by the thyroid gland, regulate metabolism and growth.

Growth hormone, secreted by the pituitary gland, regulates overall growth and development. A deficiency of growth hormones can lead to dwarfism.

Puberty-related changes in appearance are caused by the secretion of testosterone in males and estrogen in females.

Insulin, produced by the pancreas, regulates blood sugar levels. Insufficient insulin secretion leads to diabetes.

Hormone secretion is regulated by feedback mechanisms, where the timing and amount of hormone released are adjusted based on the body's needs. For example, increased blood sugar levels trigger the pancreas to produce more insulin, while decreased levels reduce insulin secretion.

INTEXT QUESTIONS

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1. What is the difference between a reflex action and walking?

Ans: The main difference between a reflex action and walking is that a reflex action is an involuntary and automatic response to a specific stimulus while walking is a voluntary and coordinated movement involving multiple muscles and joints. Reflex actions are quick, stereotypical responses that do not require conscious thought, such as pulling your hand away from a hot surface. Walking, on the other hand, is a complex motor activity that involves a series of coordinated muscle contractions and balance adjustments.

2. What happens at the synapse between two neurons?

Ans: At the synapse between two neurons, information is transmitted from one neuron to another. When an action potential (electrical signal) reaches the end of a presynaptic neuron, it triggers the release of neurotransmitter molecules into the synapse. These neurotransmitters diffuse across the synapse and bind to specific receptors on the postsynaptic neuron. This binding process generates a new electrical signal in the postsynaptic neuron, allowing the transmission of information between neurons.

3. Which part of the brain maintains posture and equilibrium of the body?

Ans: The part of the brain that maintains posture and equilibrium of the body is the cerebellum. The cerebellum is located at the back of the brain, below the cerebrum. It receives sensory information from various sources, such as the inner ear, muscles, and joints, and integrates this information to coordinate muscle activity and maintain balance and posture. It plays a crucial role in smooth and coordinated movements.

4. How do we detect the smell of an agarbatti (incense stick)?

Ans: The sense of smell is detected through specialized sensory cells called olfactory receptors located in the nose. When we smell an agarbatti (incense stick), the molecules released from the agarbatti enter the nasal passages and bind to the olfactory receptors. These receptors then generate electrical signals that are transmitted to the brain through the olfactory nerve. The brain processes these signals and interprets them as a specific smell.

5. What is the role of the brain in reflex action?

Ans: The brain plays a vital role in reflex actions by coordinating and modulating the responses. While reflex actions are typically controlled by the spinal cord and lower brain centers, the brain can exert control and influence over these actions. It can modify or suppress reflexes based on the context and the individual's intention. The brain also receives sensory information related to the reflex action, allowing for perception and conscious awareness of the action. Additionally, higher brain regions can initiate voluntary movements that may override or modify reflex actions.

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1. What are plant hormones?

Ans: Plant hormones, also known as phytohormones, are chemical substances produced by plants that regulate various physiological processes. These hormones play crucial roles in plant growth, development, and responses to environmental stimuli. They are synthesized in specific plant tissues and then transported to target cells or organs, where they elicit specific biological responses.

2. How is the movement of leaves of the sensitive plant different from the

movement of a shoot towards light?

Ans: The movement of leaves in the sensitive plant (Mimosa pudica) is a response to touch and is known as thigmonasty. When the leaves are touched, they rapidly fold up and droop. This movement is not dependent on growth and happens due to changes in turgor pressure within the cells of the leaflets. In contrast, the movement of a shoot toward the light, known as phototropism, is a growth-dependent response. In phototropism, the shoot grows towards a light source by elongating cells on the shaded side and bending towards the light. The movement of the sensitive plant is reversible and immediate, while phototropism is a slower and more persistent response.

3. Give an example of a plant hormone that promotes growth.

Ans: One example of a plant hormone that promotes growth is gibberellin. Gibberellins are involved in regulating stem elongation, promoting cell division and elongation, and influencing seed germination and flowering. They are responsible for stimulating growth in stems and leaves and are often used in horticulture to induce elongation in certain plants.

4. How do auxins promote the growth of a tendril around a support?

Ans: Auxins promote the growth of a tendril around support through a process called differential growth. When a tendril comes into contact with a support, auxin accumulation occurs on the side of the tendril away from the support. This leads to higher cell elongation and growth on that side, causing the tendril to curve and wrap around the support. Auxins promote cell elongation by increasing the plasticity of the cell wall, allowing for expansion and growth in response to directional cues.

5. Design an experiment to demonstrate hydrotropism.

Ans: Experiment to demonstrate hydrotropism:

Materials needed:

Several small potted plants (e.g., bean plants)

Two containers filled with water

Plastic wrap or aluminum foil

Rubber bands

Procedure:

Take the small potted plants and divide them into two groups.

Cover the bottom half of one group's pots with plastic wrap or aluminum foil, securing it with rubber bands.

Leave the other group's pots uncovered.

Fill both containers with water.

Place the pots from both groups on top of the containers, ensuring that the bottom half of the covered pots does not come into contact with the water.

Observe the growth of the plants over several days.

The group of plants with the covered pots should exhibit hydrotropic growth, with their roots growing towards the water source to seek moisture.

The group of plants with the uncovered pots will show normal root growth without hydrotropic bending.

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1. How does chemical coordination take place in animals?

Ans: Chemical coordination in animals takes place through the endocrine system, which involves the secretion of hormones by various glands. Hormones are chemical messengers that are produced in specific glands or tissues, released into the bloodstream, and transported to target cells or organs. They bind to specific receptors on target cells, initiating a cascade of biochemical reactions that regulate various physiological processes. Hormones help coordinate growth, development, metabolism, reproduction, and responses to stress and stimuli in animals.

2. Why is the use of iodized salt advisable?

Ans: The use of iodized salt is advisable because iodine is essential for the synthesis of thyroid hormones. The thyroid gland requires iodine to produce hormones such as thyroxine (T4) and triiodothyronine (T3). These hormones play a crucial role in regulating the body's metabolism, including carbohydrate, protein, and fat metabolism. Iodine deficiency can lead to thyroid disorders, such as goiter, hypothyroidism, or cretinism. By consuming iodized salt, which is salt fortified with iodine, individuals can ensure an adequate intake of iodine, supporting proper thyroid function and overall health.

3. How does our body respond when adrenaline is secreted into the blood?

Ans: When adrenaline (epinephrine) is secreted into the blood, it elicits the "fight-or-flight" response in the body. Adrenaline is released by the adrenal glands in response to stressful or threatening situations. Here's how the body responds to adrenaline:

Increased heart rate: Adrenaline acts on the heart, causing it to beat faster and more forcefully, which increases blood flow and oxygen delivery to the muscles.

Dilation of airways: Adrenaline relaxes the smooth muscles in the airways, leading to bronchodilation and increased airflow to the lungs.

Increased blood pressure: Adrenaline causes constriction of blood vessels in certain areas, redirecting blood flow to vital organs and skeletal muscles, thereby increasing blood pressure.

Increased blood glucose levels: Adrenaline stimulates the liver to convert glycogen (stored glucose) into glucose, releasing it into the bloodstream. This provides a quick source of energy for the body's response to the perceived threat.

Heightened mental alertness and focus: Adrenaline enhances mental alertness and attention, preparing the individual to respond quickly and effectively to the situation.

These physiological changes collectively prepare the body to either confront the threat or flee from it, ensuring survival in potentially dangerous situations.

4. Why are some patients with diabetes treated by giving injections of insulin?

Ans: Some patients with diabetes are treated by giving injections of insulin because their bodies either do not produce enough insulin or are unable to use it effectively. Insulin is a hormone produced by the beta cells of the pancreas, and it plays a crucial role in regulating blood sugar levels. Here's why insulin injections are used:

Type 1 diabetes: In individuals with type 1 diabetes, the immune system mistakenly attacks and destroys the beta cells in the pancreas, leading to a lack of insulin production. As a result, these individuals require insulin injections to compensate for the deficiency and regulate their blood sugar levels.

Type 2 diabetes: In type 2 diabetes, the body's cells become resistant to the effects of insulin, or there is insufficient insulin production. Initially, lifestyle changes, such as diet and exercise, may be recommended. However, as the disease progresses, oral medications and eventually insulin injections may be necessary to manage blood sugar levels effectively.

Insulin injections help lower blood glucose levels by facilitating the uptake of glucose from the bloodstream into cells, particularly muscle and fat cells. By providing external insulin, patients can regulate their blood sugar levels and prevent complications associated with uncontrolled diabetes. The dosage and timing of insulin injections are typically tailored to each individual's specific needs.

EXERCISES

1. Which of the following is a plant hormone?

(a) Insulin

(b) Thyroxin

(c) estrogen

(d) Cytokinin.

Ans: (d) Cytokinin is a plant hormone. Insulin, thyroxin, and estrogen are hormones found in animals, not plants.

2. The gap between two neurons is called an

(a) dendrite.

(b) synapse.

(c) axon.

(d) impulse.

Ans: (b) Synapse is the correct answer. The synapse is the junction or gap between two neurons where they communicate with each other by transmitting chemical or electrical signals.

3. The brain is responsible for

(a) thinking.

(b) regulating the heartbeat.

(c) balancing the body.

(d) all of the above

Ans: (d) "All of the above" is the correct answer. The brain is responsible for various functions, including thinking, regulating the heartbeat, and maintaining balance in the body. It controls numerous other processes such as sensory perception, motor coordination, memory, and decision-making.

4. What is the function of receptors in our body? Think of situations where receptors do not work properly. What problems are likely to arise?

Ans: Receptors in our body detect and respond to various stimuli from the internal and external environment. Their function is to convert these stimuli into electrical signals that can be transmitted to the nervous system for processing and appropriate response. Receptors play a crucial role in our sensory perception, allowing us to sense touch, temperature, pain, taste, smell, and perceive our surroundings.

When receptors do not work properly, it can lead to sensory impairments or disorders. For example:

Loss of vision or blindness can occur if the receptors in the eyes (rods and cones) are affected.

Hearing loss or deafness can result from dysfunction of the auditory receptors in the ears.

Loss of taste or inability to perceive certain tastes can arise from malfunctioning taste receptors.

Numbness or reduced sensitivity to touch or pain can occur if receptors in the skin or nerves are damaged.

5. Draw the structure of a neuron and explain its function.

Ans: A neuron consists of three main parts: the cell body (soma), dendrites, and an axon. The cell body contains the nucleus and other organelles responsible for cellular functions. Dendrites are branch-like extensions that receive signals from other neurons or sensory receptors. The axon is a long, slender extension that carries electrical impulses away from the cell body to transmit signals to other neurons or target cells.

The function of a neuron is to transmit electrical signals, known as nerve impulses or action potentials. Dendrites receive incoming signals, which are then integrated into the cell body. If the received signals are strong enough, an action potential is generated in the axon. This electrical signal travels along the axon, often over long distances, to the axon terminals, where it can stimulate the release of chemical neurotransmitters. These neurotransmitters then transmit the signal to the next neuron or target cell, such as a muscle or gland.

6. How does phototropism occur in plants?

Ans: Phototropism in plants occurs in response to light. The growth of plant parts, such as shoots, towards a light source is known as positive phototropism. It is controlled by the plant hormone auxin. When light is detected by specialized receptors in plant cells called photoreceptors, auxin accumulates on the shaded side of the plant. This causes the cells on the shaded side to elongate, resulting in the bending of the plant toward the light source.

7. Which signals will get disrupted in case of a spinal cord injury?

Ans: In case of a spinal cord injury, the signals that get disrupted are those transmitted through the spinal cord. The spinal cord serves as a pathway for nerve impulses traveling between the brain and the rest of the body. Depending on the location and severity of the injury, various signals can be affected, leading to loss of sensation, paralysis, or impaired motor control in the parts of the body below the injury site.

8. How does chemical coordination occur in plants?

Ans: In plants, chemical coordination occurs through the action of plant hormones. These hormones are chemical messengers that regulate various physiological processes, including growth, development, and responses to environmental stimuli. They are produced in specific parts of the plant and transported to target tissues where they elicit specific responses. The different types of plant hormones, such as auxins, gibberellins, cytokinins, abscisic acid, and ethylene, interact and coordinate the growth and development of plant organs, the opening and closing of stomata, fruit ripening, and other important functions.

9. What is the need for a system of control and coordination in an organism?

Ans:In plants, chemical coordination occurs through the action of plant hormones. These hormones are chemical messengers that regulate various physiological processes, including growth, development, and responses to environmental stimuli. They are produced in specific parts of the plant and transported to target tissues where they elicit specific responses. The different types of plant hormones, such as auxins, gibberellins, cytokinins, abscisic acid, and ethylene, interact and coordinate the growth and development of plant organs, the opening and closing of stomata, fruit ripening, and other important functions.

10. How are involuntary actions and reflex actions different from each other?

Ans: Involuntary actions: These are automatic actions that occur without conscious control or awareness. They are essential for the normal functioning of various body systems. Examples include the beating of the heart, digestion, and regulation of breathing. Involuntary actions are regulated by the autonomic nervous system.

Reflex actions: Reflex actions are rapid, involuntary responses to specific stimuli. They are protective and occur in response to potential harm or danger. Reflex actions are generally mediated by the spinal cord and involve a specific neural pathway called a reflex arc. Examples include the withdrawal of a hand upon touching a hot object or the knee-jerk reflex. Reflex actions bypass conscious processing in the brain and provide quick, automatic responses.

11. Compare and contrast nervous and hormonal mechanisms for control and coordination in animals.

Ans: Nervous mechanism: The nervous system uses electrical impulses to transmit signals rapidly over short distances. Nerve cells, or neurons, are the main components of the nervous system. The nervous system allows for rapid and precise responses to stimuli and coordinates complex behaviors. It enables sensory perception, motor control, and integration of information. Nervous coordination is fast-acting but relatively short-lived.

Hormonal mechanism: The endocrine system utilizes chemical messengers called hormones to regulate and coordinate various physiological processes. Hormones are secreted by endocrine glands and transported through the bloodstream to target tissues. They act more slowly than nervous impulses but can have widespread and long-lasting effects on the body. Hormonal coordination is involved in growth, development, metabolism, reproduction, and maintaining homeostasis.

Both mechanisms work together in a coordinated manner to ensure proper control and coordination in animals, with the nervous system providing rapid responses and the endocrine system regulating long-term processes.

12. What is the difference between the manner in which movement takes place in a sensitive plant and the movement in our legs?

Ans: Sensitive plant movement:

The sensitive plant exhibits a rapid movement known as thigmonasty or seismonasty. When the plant is touched or stimulated, the leaflets of its compound leaves rapidly fold inward and droop. This response is a defensive mechanism to protect the plant from potential harm or to deter herbivores. The movement in the sensitive plant is triggered by touch or mechanical stimulation and involves changes in turgor pressure within cells.

Leg movement:

The movement in our legs is controlled by the skeletal muscular system, coordinated by the nervous system. It involves the contraction and relaxation of muscles, allowing us to walk, run, jump, and perform various voluntary movements. Leg movements are under conscious control and are initiated by signals from the brain through the spinal cord and peripheral nerves. The contraction of muscles and the movement of bones enable us to change positions, navigate the environment, and perform complex motor tasks.

MIND MAP