Coordination and Control - Biology Study Guide PDF

Coordination and Control 1. Introduction Coordination and control are essential processes in living organisms, allowing them to detect and respond to stimuli in their environment. These mechanisms ensure survival by maintaining homeostasis and enabling interaction with the environment. 2. Coordin...

Coordination and Control 1. Introduction Coordination and control are essential processes in living organisms, allowing them to detect and respond to stimuli in their environment. These mechanisms ensure survival by maintaining homeostasis and enabling interaction with the environment. 2. Coordination in Living Organisms Coordination involves the integration of functions and activities in the body to produce a cohesive response. It is achieved through two main systems: a. Nervous System ​ Components:​ ○​ Central Nervous System (CNS): Brain and spinal cord. ○​ Peripheral Nervous System (PNS): Nerves extending throughout the body. ​ Functions:​ ○​ Detects stimuli through sensory organs. ○​ Processes information in the brain and spinal cord. ○​ Sends responses to effectors (muscles and glands). ​ Key Terms:​ ○​ Neuron: The basic unit of the nervous system. ○​ Reflex Action: An automatic response to a stimulus (e.g., withdrawing a hand from a hot object). b. Endocrine System ​ Components: Glands that secrete hormones (e.g., pituitary, thyroid, pancreas).​ ​ Functions:​ ○​ Regulates long-term processes like growth, reproduction, and metabolism. ○​ Hormones travel through the blood to target organs. ​ Examples:​  ○​ Insulin regulates blood sugar levels. ○​ Adrenaline prepares the body for "fight or flight." 3. Control Mechanisms Control mechanisms maintain balance and ensure appropriate responses to stimuli. a. Homeostasis The process by which organisms maintain a stable internal environment. ​ Examples: ○​ Temperature regulation. ○​ Blood sugar level control. b. Feedback Mechanisms ​ Negative Feedback: Reverses a change to maintain balance (e.g., sweating to cool the body). ​ Positive Feedback: Enhances a change (e.g., blood clotting during injury). 4. Coordination in Plants Plants lack a nervous system but still respond to stimuli using: ​ Tropisms: Growth movements in response to stimuli (e.g., phototropism, gravitropism). ​ Plant Hormones: ○​ Auxins: Promote cell elongation. ○​ Cytokinins: Promote cell division. ○​ Gibberellins: Stimulate growth and seed germination. 5. Disorders of Coordination and Control ​ Parkinson's Disease: A nervous system disorder causing tremors and movement difficulties. ​ Diabetes Mellitus: Endocrine disorder due to insufficient insulin production or action. 6. Relationship Among the Receptor, CNS, and Effector All control systems include: ​ Receptors: Detect stimuli (changes in the environment). ​ Coordination Centers: Brain, spinal cord, or pancreas, which process information. ​ Effectors: Bring about responses, such as muscle contractions or hormone release. Flow of Information: Stimulus → Receptor → Coordinator → Effector → Response 7. Parts of a Neuron and Their Functions 1.​ Cell Body (Soma): ○​ Contains the nucleus and processes signals from dendrites. 2.​ Dendrites: ○​ Receive signals from other neurons or receptors. 3.​ Axon: ○​ Conducts electrical impulses away from the cell body. 4.​ Myelin Sheath: ○​ Insulates the axon and increases signal transmission speed. 5.​ Nodes of Ranvier: ○​ Gaps in the myelin sheath that speed up impulse transmission. 6.​ Axon Terminals: ○​ Release neurotransmitters to send signals across synapses. 7.​ Nucleus: ○​ Controls neuron function and protein production. 8.​ Synapse: ○​ Junction where neurons communicate via neurotransmitters. 9.​ Schwann Cells: ○​ Form myelin sheath in the Peripheral Nervous System (PNS). 10.​Cytoplasm: ○​ Supports organelles and metabolic activities. 8. Reflex Arc A reflex arc is the neural pathway involved in producing a reflex action—automatic, rapid responses to stimuli that protect the body from harm. Components of a Reflex Arc: 1.​ Stimulus: Triggers the reflex (e.g., a pinprick). 2.​ Receptor: Detects the stimulus (e.g., skin receptors). 3.​ Sensory Neuron: Transmits signal to CNS. 4.​ Interneuron (Relay Neuron): Processes information in the CNS. 5.​ Motor Neuron: Carries response signal to effector. 6.​ Effector: Performs the response (e.g., muscle contraction). Examples of Reflex Actions: ​ Withdrawal Reflex: Pulling hand away from a hot object. ​ Knee-Jerk Reflex: Sudden leg movement when tendon below the kneecap is tapped. ​ Pupil Reflex: Constriction of pupils in bright light. 9. Importance of Reflex Arcs ​ Protection: Quick responses to dangerous stimuli. ​ Efficiency: Faster than conscious actions. ​ Survival Mechanism: Helps maintain homeostasis (e.g., breathing, blinking). 10. Synapse and Signal Transmission A synapse is the junction between neurons or between a neuron and an effector cell (e.g., muscle or gland). It enables the transfer of signals. Structure of a Synapse: 1.​ Presynaptic Neuron: Sends the signal. 2.​ Synaptic Cleft: Gap between neurons. 3.​ Postsynaptic Neuron: Receives the signal. Transmission of an Impulse Across a Synapse: 1.​ Arrival of Action Potential at the axon terminal. 2.​ Calcium Ion Influx into the axon terminal. 3.​ Release of Neurotransmitters into the synaptic cleft. 4.​ Binding to Receptors on the postsynaptic neuron. 5.​ Generation of Postsynaptic Potential (Excitatory or Inhibitory). 6.​ Propagation or Inhibition of Signal.  7.​ Termination of Signal by enzymatic breakdown or reuptake. Key Points: ​ Synapses allow unidirectional signal transmission. ​ Chemical synapses use neurotransmitters, while electrical synapses use direct current flow. ​ Synaptic transmission is vital for learning, memory, and reflexes. 11. Summary ​ The nervous system provides fast responses, while the endocrine system regulates long-term functions. ​ Both systems work together to maintain homeostasis. ​ Reflex arcs allow rapid responses to stimuli without conscious control. ​ Synapses facilitate communication between neurons.