Control and Coordination

Cheatsheet Content

1. Introduction to Control & Coordination Definition: The process by which living organisms maintain internal balance and respond appropriately to changes in their environment. Necessity: All living organisms, from simple to complex, need systems for control and coordination to survive and function efficiently. Types of Movement: Growth-dependent: Slow, directional movements (e.g., seedling growth). Growth-independent: Rapid movements not related to growth (e.g., touching a hot object, Mimosa plant closing leaves). 2. Animals - Nervous System Specialized tissues (nervous and muscular) provide control and coordination. 2.1. Neuron: Structural & Functional Unit Structure: Dendrite: Receives information, usually at its tip. Cell Body: Processes information. Axon: Transmits electrical impulse away from the cell body. Nerve Ending: Releases chemicals to transmit signal to next neuron or effector. Information Flow: Dendrite receives stimulus. Chemical reaction generates electrical impulse (nerve impulse). Impulse travels from dendrite $\rightarrow$ cell body $\rightarrow$ axon $\rightarrow$ axon end. At axon end, chemicals are released into the synaptic gap (synapse). Chemicals cross synapse and generate new electrical impulse in the next neuron's dendrite. Synapse: The microscopic gap between two neurons where information is transmitted chemically. 2.2. Reflex Actions Definition: Sudden, involuntary responses to stimuli, often without conscious thought, to protect the body. Reflex Arc: The neural pathway that mediates a reflex action. Components: Receptor $\rightarrow$ Sensory neuron $\rightarrow$ Spinal cord (relay neuron) $\rightarrow$ Motor neuron $\rightarrow$ Effector (muscle). Mechanism: Sensory receptors detect stimulus (e.g., heat). Sensory neuron transmits signal to the spinal cord. In the spinal cord, a relay neuron transmits the signal directly to a motor neuron. Motor neuron transmits signal to effector muscle, causing immediate action (e.g., pulling hand away). Information also reaches the brain, but the reflex action occurs before conscious processing. Importance: Provides quick responses in dangerous situations, especially vital for animals with less complex brains. 2.3. Human Brain Main Coordinating Centre: Concentrated network of neurons. Central Nervous System (CNS): Brain + Spinal Cord. Protection: Brain: Inside bony skull (cranium), surrounded by fluid-filled balloon for shock absorption. Spinal Cord: Protected by vertebral column (backbone). Major Parts: Fore-brain: Main thinking part. Receives sensory impulses (hearing, smell, sight). Has specialized areas for association, interpretation, and decision-making. Controls voluntary actions (e.g., writing, talking). Contains centers for hunger. Mid-brain: Controls some involuntary actions. Hind-brain: Cerebellum: Responsible for precision of voluntary actions, maintaining posture, and balance (e.g., riding a bicycle, walking straight). Medulla: Controls involuntary actions like blood pressure, salivation, vomiting, heartbeat, breathing. Pons: Involved in regulating respiration. 2.4. Nervous Tissue and Muscle Action Nerve impulses cause muscle cells to change shape (shorten) due to special proteins, leading to movement. 3. Plants - Coordination Plants lack a nervous system and muscles, coordinating through chemical means (hormones) and electrical-chemical signals. 3.1. Immediate Response to Stimulus (Growth-Independent) Example: Touch-me-not plant ( Mimosa pudica ) folds its leaves. Mechanism: Touch stimulus leads to electrical-chemical signal transmission from cell to cell. Cells change shape by altering their water content (swelling or shrinking), causing movement. 3.2. Movement Due to Growth (Tropic Movements) Definition: Directional growth movements in response to stimuli. Types of Tropism: Phototropism: Response to light. Shoots grow towards light (positive phototropism). Roots grow away from light (negative phototropism). Geotropism: Response to gravity. Roots grow downwards (positive geotropism). Shoots grow upwards (negative geotropism). Hydrotropism: Response to water (roots grow towards water). Chemotropism: Response to chemicals (e.g., pollen tube growth towards ovules). Thigmotropism: Response to touch (e.g., tendrils coiling around support). Tendrils grow faster on the side not in contact with the support, causing them to coil. 3.3. Plant Hormones (Phytohormones) Chemical compounds that coordinate growth, development, and responses. Auxins: Promote cell elongation in shoots. When light comes from one side, auxin diffuses to the shaded side, making cells grow longer and causing the shoot to bend towards light. Gibberellins: Promote stem growth. Cytokinins: Promote cell division, found in areas of rapid cell division (fruits, seeds). Abscisic Acid: Inhibits growth, causes wilting of leaves (stress hormone). 4. Hormones in Animals (Endocrine System) Chemical communication system for slower, widespread, and persistent effects. 4.1. Adrenaline (Fight or Flight Hormone) Secreted by: Adrenal glands. Action: Released directly into the blood, reaches target organs (e.g., heart). Effects: Heart beats faster $\rightarrow$ increased oxygen supply to muscles. Blood flow to digestive system and skin reduced $\rightarrow$ diverted to skeletal muscles. Breathing rate increases. Purpose: Prepares the body for immediate action in stressful situations (fight or flight response). 4.2. Other Important Hormones Hormone Endocrine Gland Functions Growth Hormone Pituitary gland Stimulates growth in all organs. Deficiency leads to dwarfism. Thyroxin Thyroid gland Regulates carbohydrate, protein, and fat metabolism. Requires iodine; deficiency causes goitre. Insulin Pancreas Regulates blood sugar levels. Deficiency causes diabetes. Testosterone Testes Development of male secondary sexual characteristics. Oestrogen Ovaries Development of female secondary sexual characteristics, regulates menstrual cycle. Releasing Hormones Hypothalamus Stimulates pituitary gland to release its hormones. 4.3. Feedback Mechanisms Regulate the timing and amount of hormone release. Example (Insulin): High blood sugar $\rightarrow$ pancreas produces insulin $\rightarrow$ blood sugar falls $\rightarrow$ insulin secretion reduced. 5. Comparison: Nervous vs. Hormonal Control Feature Nervous System Hormonal System Medium Electrical impulses via neurons Chemicals (hormones) via blood Speed Fast Slow Target Specific cells connected by neurons Widespread, all cells with receptors Duration Short-lived effects Longer-lasting effects Specificity Highly specific Less specific, broader effects