Control and Coordination

Control and Coordination

• Life Processes:
  • Involve nutrition, respiration, transport, and excretion.
  • Movement is a sign of life.
• Types of Movements:
  • Growth-Related:
    • Plants grow and move, like seedlings pushing through soil.
  • Non-Growth-Related:
    • Examples: Cats running, children playing, buffaloes chewing cud.
• Response to Environment:
  • Movements respond to environmental changes.
  • Example: A cat runs when it sees a mouse.
  • Purpose: Use environmental changes to their advantage (e.g., plants grow towards sunlight).
• Controlled Movement:
  • Movements are carefully controlled.
  • Depends on the event triggering the movement.
  • Example: Whispering in class vs. shouting.
• Control and Coordination Systems:
  • Needed for detecting events and making the correct response.
  • Use specialized tissues in multicellular organisms.

Animals – Nervous System

• Detection and Response:
  • Touching a hot object needs urgent detection and response.
  • Information is detected by nerve cell tips (receptors) in sense organs.
• Types of Receptors:
  • Gustatory Receptors: Detect taste.
  • Olfactory Receptors: Detect smell.
• Nerve Impulses:
  • Information triggers a chemical reaction, creating an electrical impulse.
  • Impulse travels from the dendrite to the cell body, then along the axon.
  • At the axon end, the impulse causes chemical release.
  • Chemicals cross the synapse, starting a new impulse in the next neuron.
• Nervous Tissue:
  • Made of an organized network of neurons.
  • Conducts information via electrical impulses.
  • Parts of a neuron:
    • Dendrite: Acquires information.
    • Axon: Transmits electrical impulses.
    • Synapse: Converts electrical impulse into a chemical signal.

What Happens in Reflex Actions?

• Reflex Actions:
  • Sudden actions in response to environmental changes.
  • Examples:
    • Jumping out of the way of a bus reflexly.
    • Pulling hand back from a flame reflexly.
    • Mouth watering when hungry reflexly.
  • These actions happen without conscious thought.
• Reflex Arc:
  • Definition: Simple connection between nerves detecting a signal (input) and nerves causing an action (output).
  • Process:
    • Detecting heat → Move muscles quickly.
    • Completed quickly without involving the brain.
  • Location: Connections are made in the spinal cord, where nerves from all over the body meet.
• Importance of Reflex Arcs:
  • Reflex actions are faster than thinking and responding.
  • Essential for urgent and dangerous situations, like touching a hot object.
  • Evolved as efficient ways to respond quickly even in animals with little or no complex thinking ability.
• Example of Reflex Arc in Action:
  • Touching a flame:
    • Nerves detect heat.
    • Signal sent through spinal cord.
    • Immediate response to move hand away from the flame.
  • Bright light focused on eyes:
    • Light detected by eyes.
    • Signal sent to the brain and spinal cord.
    • Reflex action to close or squint eyes quickly.

Summary

Reflex actions allow for quick responses to urgent situations without the need for conscious thought. This is achieved through a reflex arc, a simple and direct pathway for signals between sensory and motor nerves, primarily located in the spinal cord. Reflex arcs are essential for survival and efficiency, especially in situations where thinking would take too long.

Human Brain

• Role of Spinal Cord:
  • Not just for reflex actions.
  • Made of nerves supplying information to the brain.
  • Spinal cord and brain form the central nervous system (CNS).
• Functions of the Brain:
  • Main coordinating center of the body.
  • Allows thinking and voluntary actions (e.g., writing, talking, moving a chair).
  • Sends messages to muscles.
  • Communicates with the body through the peripheral nervous system (cranial and spinal nerves).
• Parts of the Brain:
  • Fore-Brain:
    • Main thinking part.
    • Receives sensory impulses (hearing, smell, sight).
    • Makes decisions and sends instructions to motor areas.
    • Contains hunger center for the sensation of feeling full.
  • Mid-Brain and Hind-Brain:
    • Control involuntary actions (e.g., heartbeat, breathing, digestion).
    • Medulla in the hind-brain controls blood pressure, salivation, vomiting.
    • Cerebellum:
      • Responsible for precision of voluntary actions.
      • Maintains posture and balance (e.g., walking, riding a bicycle).

Protection of the Brain

• Brain is protected by:
  • A bony box (skull).
  • A fluid-filled balloon inside the skull for shock absorption.
• Spinal cord is protected by:
  • Vertebral column (backbone).

How Nervous Tissue Causes Action

• Nervous Tissue Functions:
  • Collects and processes information.
  • Sends information and decisions to muscles.
  • Muscle tissue performs the final action.
• Muscle Movement:
  • Nerve impulses reach muscle fibers.
  • Muscle cells move by changing their shape (shorten).
  • Muscle cells have special proteins that change shape and arrangement in response to electrical impulses.
• Types of Muscles:
  • Voluntary Muscles: Controlled by thinking.
  • Involuntary Muscles: Not controlled by thinking.

Coordination in Plants

How Plants Respond to Stimuli

• No Nervous System or Muscles:
  • Unlike animals, plants lack nervous systems and muscles.
  • Plants still respond to stimuli like touch and light.

Types of Plant Movements

1. Immediate Response to Stimulus:
   • Example: Touch-me-not plant (Chhui-mui) folds its leaves when touched.
   • Mechanism:
     • No growth involved.
     • Movement happens at a point different from the touch.
     • Uses electrical-chemical signals to convey information from cell to cell.
     • Cells change shape by altering their water content, causing swelling or shrinking.
2. Movement Due to Growth:
   • Example: Pea plant tendrils climb by wrapping around supports.
   • Mechanism:
     • Tendrils are sensitive to touch.
     • The part of the tendril in contact with an object grows slower than the part away from the object.
     • This differential growth causes the tendril to curl around the object.
     • Directional growth appears as movement over time.

Tropic Movements

• Phototropism: Shoots grow towards light, roots grow away from light.
• Geotropism: Roots grow downwards, shoots grow upwards.
• Hydrotropism: Growth towards water.
• Chemotropism: Growth towards chemicals (e.g., pollen tubes growing towards ovules).

Chemical Coordination

• Electrical Impulses:
  • Fast but limited to connected cells.
  • Cells need time to reset after transmitting impulses.
• Chemical Communication:
  • Slower but can reach all cells.
  • Uses hormones to transmit information.

Plant Hormones

1. Auxins:
   • Promote cell elongation.
   • Help shoots bend towards light by concentrating on the shady side.
2. Gibberellins:
   • Promote stem growth.
3. Cytokinins:
   • Promote cell division.
   • Found in high concentrations in fruits and seeds.
4. Abscisic Acid:
   • Inhibits growth.
   • Causes wilting of leaves.

Hormones in Animals

Chemical Signals in Animals

• Chemical Transmission:
  • Animals use hormones for transmitting information.
  • Example: When a squirrel faces danger, its body prepares for “fight or flight”.

Adrenaline and the Endocrine System

• Adrenaline:
  • Secreted by adrenal glands.
  • Prepares the body for action (fighting or running away).
  • Effects:
    • Heart beats faster.
    • More oxygen to muscles.
    • Blood flow to digestive system and skin is reduced.
    • Blood diverted to skeletal muscles.
    • Breathing rate increases.
• Endocrine System:
  • Hormones are part of this system, helping in control and coordination.

Importance of Hormones

• Thyroxin and Iodine:
  • Thyroxin is produced by the thyroid gland.
  • Regulates metabolism of carbohydrates, proteins, and fats.
  • Requires iodine, found in iodised salt.
  • Deficiency of iodine can cause goitre (swollen neck).
• Growth Hormone:
  • Secreted by the pituitary gland.
  • Regulates growth and development.
  • Deficiency in childhood can lead to dwarfism.
• Puberty Hormones:
  • Testosterone in males.
  • Oestrogen in females.
  • Cause physical changes during puberty.
• Insulin and Diabetes:
  • Produced by the pancreas.
  • Regulates blood sugar levels.
  • Insulin deficiency causes diabetes, treated with insulin injections.

Hormone Regulation

• Feedback Mechanisms:
  • Hormone secretion is controlled by feedback loops.
  • Example: Insulin production increases when blood sugar rises and decreases when sugar levels fall.

Do You Know?

• Hypothalamus and Hormones:
  • The hypothalamus controls the release of many hormones.
  • Example: When growth hormone levels are low, the hypothalamus releases a growth hormone-releasing factor.
  • This factor stimulates the pituitary gland to release growth hormone.

Key Points

• Hypothalamus plays a crucial role in hormone regulation.
• It stimulates the pituitary gland to release growth hormone when needed.
• Endocrine glands secrete hormones, each with a specific role in the body.

Examples

• Hypothalamus: Releases factors to control other glands.
• Pituitary Gland: Releases growth hormone.
• Growth Hormone: Promotes growth and development.

Summary

• The hypothalamus helps regulate hormone levels.
• Endocrine glands have specific functions and secrete hormones.
• Understanding the roles of these hormones helps in understanding body functions and growth.

Chapter Summary:

• Control and coordination are functions of the nervous system and hormones.
• Nervous system responses include reflex action, voluntary action, and involuntary action.
• The nervous system uses electrical impulses to send messages.
• The nervous system gets information from sense organs and acts through muscles.
• Chemical coordination happens in both plants and animals.
• Hormones produced in one part of an organism move to another part to have an effect.
• A feedback mechanism controls the action of hormones.