Class 10 Science Chapter 6 Question Answers - Control and Coordination

Q1: Differentiate between tropic and nastic movements in plants.
Ans: Tropic Movements:

• There is directional growth of a plant or part of a plant in response to an external stimulus i.e., direction of stimulus controls direction of growth.
• The effect is more or less permanent.
• It is easily observed in stems and roots of plants.
• It occurs due to unequal growth on the two sides of a stem or root.
• For example, bending of root towards gravity and bending of shoot towards light.

Nastic Movements:

• The growth or movement is independent of the direction of stimulus.
• The effect is temporary and reversible.
• It occurs in specialised parts and organs of plants like leaves and petals of flowers.
• It usually involves alterations in cell volumes.
• For example, folding on leaflets of touch-me-not plant on touching them.

Q2: Mention one function for each of these hormones:
(a) Thyroxin
(b) Insulin
(c) Adrenaline
(d) Growth hormone
(e) Testosterone
Ans: (a) Thyroxin: It regulates carbohydrates, fat and protein metabolism.
(b) Insulin: It regulates blood sugar level.
(c) Adrenaline: It increases heart beat rate and supply of blood to various organs.
(d) Growth hormones: It regulates growth and development of an organism.
(e) Testosterone: It controls the bodily features, secondary sexual characters in males during puberty.

Q3: How does chemical coordination take place in animals?
Ans: Hormones secreted by the endocrine glands are directly poured into the blood stream as they are ductless glands. Blood carries these hormones to specific target tissue or organ where they act and trigger a particular biochemical or physiological activity in response to the stimulus received.

Q4: Why is the flow of signals in a synapse from axonal end of one neuron to dendritic end of another neuron but not the reverse?
Ans: The information received by the dendrites of neurons present at receptors is transferred in form of electrical impulse to the cell body, axon and the nerve endings at the ends of axon. At the axonal ends, chemicals are released between junction of two neurons called synapse. The chemical diffuses towards the dendrite of the next neuron where it generates an electrical impulse again. So, the electrical signals change to chemical signals and again to electrical signals for the next neuron.
Since the chemicals Eire released at the axonal ends and absent at dendrite end, the signal travels from axonal end to dendritic end of another neuron but not the reverse i.e., the flow of electrical impulse is unidirectional only.

Q5: Explain the process of neurotransmission in detail. Include the role of neurotransmitters, synapses, and the importance of this process in the human body.
Ans: Neurotransmission is the process by which nerve impulses are transmitted from one neuron to another or to target cells, such as muscle or gland cells. It plays a vital role in coordinating and controlling various activities in the human body. The key components involved in neurotransmission are neurotransmitters, synapses, and receptor cells.
Neurotransmitters are chemical messengers that are released from the axon terminals of a neuron into the synapse, which is the small gap between two neurons or between a neuron and a target cell. These neurotransmitters are stored in synaptic vesicles and are released when an action potential reaches the axon terminal.
The process of neurotransmission involves the following steps:

• Generation of an action potential: When a nerve impulse reaches the axon of a neuron, it generates an electrical signal called an action potential.
• Release of neurotransmitters: The action potential triggers the release of neurotransmitters from the synaptic vesicles into the synapse.
• Diffusion and binding: The neurotransmitters diffuse across the synapse and bind to specific receptors on the membrane of the target cell.
• Generation of a new action potential: The binding of neurotransmitters to receptors on the target cell's membrane leads to changes in the membrane potential, either depolarization or hyperpolarization. If the depolarization is strong enough to reach the threshold, it generates a new action potential in the target cell.
• Termination of the signal: The neurotransmitters are either broken down by enzymes in the synapse or taken back up by the presynaptic neuron for recycling.

Neurotransmission is essential for various bodily functions, including muscle contraction, perception of sensory stimuli, coordination of movements, and regulation of mood and emotions.

Q6: Describe the reflex arc and its significance in maintaining the body's safety and coordination.
Ans: The reflex arc is a neural pathway that mediates a reflex action. It involves a simple and rapid sequence of events in response to a specific stimulus, often without involving the brain's conscious processing.
The reflex arc consists of the following components:

• Receptor: The sensory organ or cell that detects the stimulus and converts it into a nerve impulse.
• Sensory neuron: Transmits the nerve impulse from the receptor to the spinal cord or brainstem.
• Interneuron (optional): In some reflex arcs, an interneuron located in the spinal cord or brainstem relays the impulse from the sensory neuron to the motor neuron.
• Motor neuron: Carries the nerve impulse from the spinal cord or brainstem to the effector organ (usually a muscle or gland).
• Effector: The muscle or gland that responds to the nerve impulse by producing a specific action.

Significance of the reflex arc:

The reflex arc serves as a protective mechanism that enables rapid responses to potential dangers, often without conscious thought. This is crucial for the body's safety and coordination in the following ways:

• Swift response: Reflex actions occur quickly, helping the body to react promptly to potential threats, such as withdrawing a hand from a hot object.
• Avoidance of injury: Reflexes help prevent injuries by causing immediate muscle contractions or other responses that can move the body away from harm.
• Maintaining posture and balance: Reflexes help in maintaining balance and posture, contributing to the body's overall coordination and stability.
• Diversion of excessive sensory input: In cases of overwhelming sensory input, reflexes can divert the excessive input away from higher brain centers, allowing the brain to focus on more critical tasks.

Q7: Explain the role of endocrine glands in the human body's control and coordination. Provide examples of hormones and their functions.
Ans: Endocrine glands are specialized organs that secrete hormones directly into the bloodstream. These hormones act as chemical messengers, regulating various physiological processes and maintaining coordination within the body. Endocrine glands play a crucial role in the control and coordination of bodily functions.
Examples of hormones and their functions:

Thyroxine (T4) and Triiodothyronine (T3): Produced by the thyroid gland, these hormones regulate metabolism, growth, and development. They influence energy production and consumption in cells throughout the body.

• Insulin: Produced by the pancreas, insulin helps regulate blood glucose levels by promoting the uptake of glucose into cells and its conversion to glycogen for storage.
• Adrenaline (Epinephrine): Secreted by the adrenal glands, adrenaline is responsible for the "fight or flight" response. It increases heart rate, dilates airways, and prepares the body for quick action in response to stress or danger.
• Growth Hormone (GH): Produced by the pituitary gland, GH stimulates growth and cell reproduction. It plays a crucial role in the development of bones and tissues.
• Testosterone and Estrogen: Produced by the testes and ovaries, respectively, these hormones are responsible for the development of secondary sexual characteristics and the regulation of the reproductive system.
• Melatonin: Produced by the pineal gland, melatonin helps regulate sleep-wake cycles (circadian rhythms) and is involved in maintaining the body's internal clock.
• Oxytocin: Produced by the hypothalamus and released by the pituitary gland, oxytocin plays a role in uterine contractions during childbirth and in promoting social bonding and emotional attachment.

The endocrine system's control and coordination are slower and more widespread compared to the nervous system. Hormones travel through the bloodstream, affecting various target cells and organs, ensuring the body's overall balance and proper functioning.

Q8: Differentiate between the central nervous system (CNS) and the peripheral nervous system (PNS). Explain the functions of each system in maintaining control and coordination.
Ans: Central Nervous System (CNS) and Peripheral Nervous System (PNS) are two integral components of the nervous system, each playing distinct roles in maintaining control and coordination within the human body.
Central Nervous System (CNS):

• The CNS consists of the brain and spinal cord.
• It acts as the control center, processing information, making decisions, and sending out commands.
• The brain is responsible for higher functions such as thinking, memory, emotion, and voluntary muscle movements.
• The spinal cord serves as a conduit for nerve impulses between the brain and the rest of the body, and it also controls reflex actions.
• The CNS integrates sensory input, processes it, and sends appropriate responses to effectors (muscles or glands) through the PNS.

Peripheral Nervous System (PNS):

• The PNS includes all the nerves outside the CNS, extending to the body's extremities.
• It is divided into the sensory (afferent) division and the motor (efferent) division.
• Sensory neurons transmit sensory information from receptors (such as the skin, eyes, and ears) to the CNS for processing.
• Motor neurons carry commands from the CNS to effectors, resulting in muscular contractions or glandular secretions.
• The motor division is further divided into the somatic nervous system (voluntary control over skeletal muscles) and the autonomic nervous system (involuntary control over smooth muscles, cardiac muscles, and glands).
• The autonomic nervous system is subdivided into the sympathetic and parasympathetic divisions, which regulate bodily functions in response to different situations, such as stress (sympathetic) and relaxation (parasympathetic).

In summary, the CNS is responsible for complex processing, decision-making, and conscious awareness, while the PNS serves as the communication network between the CNS and the rest of the body, ensuring coordinated responses to sensory input and maintaining bodily functions.

Q9: Compare and contrast the functions of the nervous system and the endocrine system in maintaining control and coordination within the human body. Provide specific examples of how each system contributes to the regulation of bodily functions.
Ans: The nervous system and the endocrine system are two distinct yet interconnected systems that work together to maintain control and coordination within the human body. While both systems play roles in transmitting information and regulating bodily functions, they differ in their modes of communication, speed of response, and target mechanisms.
Nervous System:

• Mode of Communication: The nervous system relies on electrical impulses and neurotransmitters to transmit signals rapidly along nerve cells.
• Speed of Response: Nervous system responses are rapid, allowing for immediate reactions to stimuli. For example, quickly removing a hand from a hot surface to avoid injury.
• Target Mechanism: The nervous system targets specific cells or groups of cells, such as muscles or glands, to elicit precise and localized responses.
• Example: In the "fight or flight" response, the sympathetic nervous system triggers the release of adrenaline, which prepares the body for quick action by increasing heart rate and dilating airways.

Endocrine System:

• Mode of Communication: The endocrine system uses hormones, chemical messengers released into the bloodstream, for communication between glands and target cells.
• Speed of Response: Endocrine system responses are slower compared to the nervous system due to the time required for hormones to travel through the bloodstream. These responses are better suited for long-term regulation.
• Target Mechanism: Hormones affect a wide range of target cells and organs throughout the body, coordinating processes such as growth, metabolism, and reproduction.
• Example: The thyroid gland releases thyroxine to regulate metabolism and energy production, ensuring a balance in the body's overall functions.

Interactions and Coordination:

• The nervous and endocrine systems often work in tandem to maintain homeostasis. For instance, the hypothalamus, a part of the brain, regulates the pituitary gland, which then controls various endocrine glands, demonstrating a close interplay between the two systems.
• In situations of stress, the sympathetic nervous system activates the "fight or flight" response, while the adrenal glands release hormones like adrenaline and cortisol to sustain the body's response over a more extended period.

In conclusion, the nervous system's rapid, localized responses complement the endocrine system's broader and more prolonged regulation of bodily functions. Together, these systems ensure effective control and coordination, adapting the body to its internal and external environment for optimal functioning.

Q10: Elaborate on the role of feedback mechanisms in maintaining homeostasis within the human body. Provide examples of negative feedback and positive feedback loops, explaining how they contribute to the regulation of physiological processes.
Ans: Feedback mechanisms play a crucial role in maintaining homeostasis, which refers to the body's ability to regulate internal conditions within a narrow range despite external changes. These mechanisms involve continuous monitoring and adjustment of various physiological processes to ensure stability and optimal functioning.
Negative Feedback:

Negative feedback is a regulatory mechanism where the body responds to a change in a variable by initiating processes that counteract or reverse the change. This helps maintain the internal environment within a desired range.
An example of negative feedback is the regulation of body temperature:

• When body temperature rises above the set point (e.g., due to hot weather or physical activity), thermoreceptors detect the change.
• The hypothalamus, a part of the brain, receives this information and sends signals to effectors, such as sweat glands and blood vessels.
• Sweat glands produce sweat, which evaporates and cools the body. Blood vessels dilate, allowing heat to dissipate through the skin.
• As a result, body temperature decreases, and the initial rise is counteracted. Once the temperature returns to the set point, the feedback loop is inhibited.

Positive Feedback:
Positive feedback is less common and occurs when a change in a variable triggers processes that amplify the change, moving the system away from the initial state. An example of positive feedback is the process of blood clotting:

• When a blood vessel is injured, platelets adhere to the site, releasing chemicals that attract more platelets.
• These platelets release substances that activate clotting factors, leading to the formation of a clot.
• As the clot forms, it releases even more clotting factors, further enhancing the clotting process.
• The cycle continues until a stable clot is formed, sealing the wound.

While positive feedback loops are not typically involved in maintaining constant internal conditions, they are crucial in certain processes, such as childbirth (contractions) and the immune response (amplifying the production of immune cells).
In summary, feedback mechanisms, particularly negative feedback, are essential for maintaining homeostasis by regulating various physiological parameters. Negative feedback ensures stability and prevents extreme fluctuations, while positive feedback plays a role in specific processes that require amplification or rapid responses. Together, these mechanisms enable the body to adapt and function optimally in changing environments.