Class 10 Science Chapter 6 Control and Coordination in Living Organisms

Class 10 Science Chapter 6 Control and Coordination in Living Organisms

Nervous System in Animals

1. Introduction to the Nervous System:

• In animals, control and coordination are achieved through the nervous system and muscular tissue.
• The nervous system detects information from the environment and coordinates responses through electrical impulses.

1. Detection of Stimuli:

• Information from the environment is detected by receptors located at the tips of nerve cells.
• Sense Organs: Receptors are found in sense organs like the eyes, nose, tongue, and skin.
  • Gustatory receptors: Detect taste.
  • Olfactory receptors: Detect smell.

1. Transmission of Electrical Impulses:

• When a receptor detects a stimulus, it generates a chemical reaction that creates an electrical impulse.
• The impulse travels through the neuron from the dendrite to the axon and reaches the synapse.
• At the synapse, the electrical impulse is converted into a chemical signal and transmitted to the next neuron or to muscle cells.

1. Structure of a Neuron:

• A neuron is made up of three main parts:
  • Dendrites: Receive information from the environment.
  • Axon: Transmits the electrical impulse.
  • Synapse: Where the impulse is transmitted to the next neuron or muscle.

1. Network of Nerve Cells:

• The nervous system consists of an organized network of nerve cells, or neurons, specialized for conducting electrical impulses.
• This network allows rapid communication between different parts of the body, enabling quick responses to stimuli.

Reflex Actions

1. What are Reflex Actions?:

• Reflex actions are automatic, quick responses to stimuli that do not involve conscious thought.
• These actions are designed to protect the body from danger (e.g., pulling your hand away from a hot object).

1. Reflex Arc:

• Reflex actions occur through a pathway called the reflex arc.
• The reflex arc involves the following sequence:
  1. Receptor detects the stimulus (e.g., touching a hot object).
  2. The signal is transmitted via sensory neurons to the spinal cord.
  3. Motor neurons send a response signal to the muscles.
  4. The muscles react, causing a quick movement (e.g., pulling the hand away).

1. Importance of Reflex Actions:

• Reflex actions bypass the brain for faster responses to dangerous stimuli.
• The brain processes the information later, but the body responds immediately through the spinal cord, ensuring quick protection.

1. Examples of Reflex Actions:

• Pulling hand away from a hot object.
• Knee-jerk reaction when the knee is tapped.
• Blinking when something suddenly approaches the eyes.

1. Evolutionary Importance:

• Reflex arcs are essential for survival as they provide a quick response to harmful situations.
• Even animals with simple nervous systems rely heavily on reflex actions for protection.

The Human Brain

1. Introduction:

• The brain is the central coordinating organ of the body, responsible for processing information and controlling various functions.
• It is part of the central nervous system (CNS), which also includes the spinal cord.

1. Main Parts of the Brain:

• The brain has three major regions: Forebrain, Midbrain, and Hindbrain. a. Forebrain:
• The forebrain is the main thinking part of the brain.
• It processes sensory information (sight, smell, hearing, taste).
• It contains areas responsible for reasoning, emotions, decision-making, and memory.
• It controls voluntary movements (e.g., moving arms, legs). b. Midbrain:
• The midbrain coordinates some reflex movements, particularly those involving the eyes and ears. c. Hindbrain:
• The hindbrain controls essential involuntary functions such as breathing, heartbeat, and blood pressure.
• It includes:
  • Medulla: Controls involuntary actions like breathing, heart rate, and blood pressure.
  • Cerebellum: Coordinates balance and posture, and ensures precision in voluntary movements (e.g., walking, riding a bicycle).

1. Protection of the Brain:

• The brain is protected by a bony skull called the cranium.
• It is surrounded by cerebrospinal fluid, which acts as a cushion to absorb shocks and protect the brain from injury.

1. Voluntary and Involuntary Actions:

• Voluntary actions: Controlled by the forebrain (e.g., talking, walking, writing).
• Involuntary actions: Controlled by the medulla and include activities like breathing, digestion, and heartbeat, which occur without conscious control.

1. Coordination of Complex Activities:

• Different regions of the brain work together to process sensory input and decide appropriate responses.
• For example, the forebrain may receive visual information, the midbrain may coordinate eye movements, and the hindbrain maintains balance during the movement.

Protection of the Brain and Spinal Cord

1. Importance of Protection:

• The brain and spinal cord are delicate and vital organs, responsible for controlling various bodily functions and transmitting signals.
• Proper protection is essential to prevent damage to these organs, which could lead to serious health issues or loss of functions.

1. Protection of the Brain:

• The brain is protected by three main structures:
  1. Cranium (Skull): A bony structure that encases the brain, providing a hard outer layer to protect it from physical injury.
  2. Meninges: Three layers of membranes (dura mater, arachnoid mater, pia mater) that cover the brain and provide additional cushioning.
  3. Cerebrospinal Fluid (CSF): A fluid that fills the space between the meninges and the brain. It acts as a shock absorber, preventing the brain from hitting the skull during sudden movements.

1. Protection of the Spinal Cord:

• The spinal cord is protected by the vertebral column (backbone).
• The spinal cord runs through a hollow canal within the vertebral column, which shields it from injury.
• Like the brain, the spinal cord is also surrounded by cerebrospinal fluid and meninges, providing additional protection.

1. Role of the Vertebral Column:

• The vertebral column is a series of bones (vertebrae) that form the backbone.
• It provides structural support to the body and protects the spinal cord, which connects the brain to the rest of the body.

Nervous Tissue and Its Role in Causing Action

1. Function of Nervous Tissue:

• Nervous tissue is responsible for collecting information, processing it, and transmitting it throughout the body.
• It controls various actions and responses, including voluntary and involuntary movements.

1. How Does Nervous Tissue Cause Action?:

• When a nerve impulse reaches a muscle, it triggers movement.
• Muscle cells respond to the electrical impulses from the nervous tissue by changing their shape.

1. Muscle Contraction:

• Muscle cells contain special proteins that rearrange themselves when they receive a nervous impulse.
• This rearrangement of proteins causes the muscle cells to shorten, leading to muscle contraction.
• Muscle contraction is the basis of all body movements, from simple actions like blinking to complex actions like running.

1. Types of Muscles:

• There are two main types of muscles:
  1. Voluntary Muscles: Muscles that we can control consciously (e.g., arm and leg muscles used for walking, writing).
  2. Involuntary Muscles: Muscles that function without conscious control (e.g., muscles involved in digestion, heart beating).

1. Role of Neurons:

• Neurons, the cells of the nervous system, transmit electrical impulses to muscles.
• The sequence of events involves:
  1. Receptors detecting a stimulus.
  2. Transmission of the signal through sensory neurons.
  3. Processing the signal in the brain or spinal cord.
  4. Sending a response signal through motor neurons to the muscles.
  5. Muscle contraction to perform the action.

Coordination in Plants

1. Introduction:

• Unlike animals, plants do not have a nervous system or muscles to coordinate their activities.
• However, plants respond to stimuli like light, gravity, and touch using different mechanisms.

1. Types of Movements in Plants:

• Plants show two types of movements:
  1. Movement due to External Stimuli (Nastic Movements): These are quick movements not dependent on growth, such as the folding of leaves in the ‘touch-me-not’ plant.
  2. Movement due to Growth (Tropic Movements): These are slower, growth-dependent movements, like roots growing towards the ground (geotropism) or shoots bending towards light (phototropism).

1. Immediate Response to Stimulus:

• Some plants, like the touch-me-not (Mimosa), show rapid movement in response to stimuli.
• When the plant is touched, its leaves fold, but this movement does not involve growth.
• The movement occurs due to changes in the amount of water in certain plant cells, causing them to swell or shrink, which results in the folding of the leaves.

1. Movement Due to Growth:

• Tropic movements involve the growth of plant parts in response to external stimuli. There are several types:
  • Phototropism: Movement towards light. For example, plant shoots grow towards light to maximize photosynthesis.
  • Geotropism: Movement in response to gravity. Roots grow downward (positive geotropism), while shoots grow upward (negative geotropism).
  • Hydrotropism: Movement in response to water. Roots grow towards moisture.
  • Chemotropism: Movement in response to chemicals, such as the growth of pollen tubes towards ovules during fertilization.

1. Mechanism of Growth Movement:

• The direction of plant growth is regulated by plant hormones like auxins.
• Auxins accumulate on the side of the plant that is away from light, causing the cells on that side to grow longer, making the plant bend towards the light.

Hormones in Animals

1. Introduction to Hormones:

• Hormones are chemical messengers that regulate various processes in animals, including growth, metabolism, and reproduction.
• Hormones are produced by endocrine glands and released directly into the bloodstream.

1. Role of Hormones:

• Hormones help maintain balance and coordinate various activities in the body.
• Unlike nervous signals, which act rapidly and are short-lived, hormonal signals act more slowly but have long-lasting effects.

1. Adrenaline – The Fight or Flight Hormone:

• Adrenaline is secreted by the adrenal glands when the body is under stress or in danger.
• It prepares the body for “fight or flight” by:
  • Increasing the heart rate.
  • Diverting blood to muscles and away from the digestive system.
  • Increasing the breathing rate to provide more oxygen.
• These changes enable the body to react quickly in dangerous situations.

1. Thyroxin – Metabolism Regulator:

• Thyroxin is secreted by the thyroid gland.
• It regulates the body’s metabolism by controlling the rate at which carbohydrates, proteins, and fats are processed.
• Iodine is required for the production of thyroxin; a deficiency of iodine can cause goitre (swelling of the neck due to thyroid gland enlargement).

1. Insulin – Blood Sugar Regulator:

• Insulin is secreted by the pancreas.
• It helps regulate blood sugar levels by facilitating the uptake of glucose by cells.
• A lack of insulin or improper insulin function can lead to diabetes, where blood sugar levels rise, causing various health issues.

1. Growth Hormone:

• Growth hormone is secreted by the pituitary gland.
• It regulates the growth and development of the body, especially during childhood and adolescence.
• A deficiency in growth hormone during childhood can lead to dwarfism, while an excess can cause gigantism.

1. Sex Hormones:

• Testosterone (in males) and oestrogen (in females) are responsible for the changes that occur during puberty.
• These hormones regulate reproductive functions and secondary sexual characteristics, such as facial hair growth in males and breast development in females.

1. Feedback Mechanism:

• Hormone secretion is controlled by a feedback mechanism.
• For example, if blood sugar levels rise, the pancreas secretes more insulin. As sugar levels drop, insulin production decreases.
• This ensures that hormones are produced in precise amounts based on the body’s needs.

How Does Chemical Coordination Take Place in Animals?

1. Introduction to Chemical Coordination:

• Chemical coordination in animals is regulated by hormones, which act as chemical messengers.
• Hormones are produced by endocrine glands and travel through the bloodstream to target organs or tissues, where they initiate specific biological responses.

1. Endocrine Glands:

• The endocrine system consists of glands that secrete hormones directly into the bloodstream.
• Major endocrine glands include:
  • Pituitary gland: Known as the “master gland,” it controls other endocrine glands and regulates growth through the secretion of growth hormone.
  • Thyroid gland: Produces thyroxin, which controls metabolism.
  • Adrenal glands: Secrete adrenaline, which prepares the body for stress or danger.
  • Pancreas: Produces insulin to regulate blood sugar levels.
  • Testes (in males) and Ovaries (in females): Secrete sex hormones like testosterone and oestrogen, regulating reproduction and sexual development.

1. Hormones as Chemical Messengers:

• Hormones are produced in one part of the body and travel through the blood to other parts where they exert their effects.
• Each hormone has specific target organs or cells that respond to the hormone’s signal.

1. Role of Hormones in Chemical Coordination:

• Hormones help in the regulation of various body functions, including:
  • Growth: Growth hormone regulates body growth during childhood.
  • Metabolism: Thyroxin controls the rate at which food is metabolized to produce energy.
  • Reproduction: Testosterone and oestrogen regulate reproductive processes and secondary sexual characteristics.
  • Stress Response: Adrenaline prepares the body to react quickly to dangerous or stressful situations by increasing heart rate, breathing, and blood flow to muscles.
  • Blood Sugar Regulation: Insulin controls blood sugar levels by promoting the uptake of glucose into cells.

1. Feedback Mechanisms in Hormonal Control:

• Hormonal balance in the body is maintained by feedback mechanisms.
• Example: The pancreas releases insulin when blood sugar levels rise. As blood sugar levels decrease, insulin secretion is reduced.
• This feedback mechanism ensures that hormones are secreted in precise amounts based on the body’s needs.

1. Importance of Hormonal Coordination:

• Hormonal coordination ensures the proper functioning of various processes in the body.
• It plays a key role in maintaining homeostasis, or internal stability, despite changes in the external environment.

Here are the notes for the next topic in Chapter 6, “Control and Coordination”:

What You Have Learned – Summary of Control and Coordination

1. Control and Coordination in Living Organisms:

• Nervous system and hormones are responsible for control and coordination in animals.
• In plants, coordination occurs through chemical signals and growth-related movements.

1. Nervous System:

• The nervous system uses electrical impulses to transmit information between different parts of the body.
• The system includes the brain, spinal cord, and a network of nerves.
• Voluntary actions: Actions controlled consciously (e.g., walking, talking).
• Involuntary actions: Actions that happen without conscious control (e.g., heart beating, breathing).
• Reflex actions: Quick, automatic responses to stimuli (e.g., pulling hand away from a hot object).

1. Neurons and Synapses:

• Neurons are specialized cells that transmit nerve impulses.
• Synapses are junctions between two neurons where impulses are chemically transmitted.

1. Brain Function:

• The brain is divided into three main regions:
  • Forebrain: Controls thinking, memory, and voluntary actions.
  • Midbrain: Coordinates reflex actions involving eyes and ears.
  • Hindbrain: Controls involuntary actions like breathing and heart rate, and helps maintain balance and posture.

1. Hormonal Coordination:

• Hormones are chemical messengers secreted by endocrine glands.
• Hormones regulate growth, metabolism, reproduction, and other vital functions.
• Hormonal coordination is slower but has longer-lasting effects compared to nervous coordination.
• Examples of hormones:
  • Adrenaline: Prepares the body for stress or danger.
  • Insulin: Regulates blood sugar levels.
  • Thyroxin: Controls metabolism.

1. Feedback Mechanism:

• Hormone secretion is regulated by feedback mechanisms, ensuring that hormones are produced in appropriate amounts.
• Example: When blood sugar levels rise, the pancreas secretes insulin to bring them back to normal.

1. Coordination in Plants:

• Plants do not have a nervous system or muscles, but they respond to stimuli through tropic movements (e.g., phototropism, geotropism).
• Plant hormones, such as auxins and gibberellins, regulate growth and development.

1. Importance of Coordination:

• Coordination in living organisms ensures that different parts of the body work together efficiently in response to internal and external changes.
• It is essential for survival, allowing organisms to adapt to their environment and maintain homeostasis.

Home

NotesJobs