Control and Coordination
Understanding how living organisms control and coordinate their activities through nervous system and hormones
Introduction to Control and Coordination
In the previous chapter, we studied life processes involved in maintenance functions. We associated movement with life, but not all movements are connected with growth. Animals show movements not connected with growth, like a cat running or children playing. These movements are responses to environmental changes and are carefully controlled.
Key Concepts
- Living organisms respond to changes in their environment
- Responses must be appropriate and controlled
- Control and coordination are essential for survival
- Multicellular organisms use specialized tissues for control and coordination
Animals use nervous and muscular tissues for control and coordination, while plants use different mechanisms involving hormones and growth responses.
Learning Outcomes
After studying this chapter, students will be able to:
- Explain the structure and function of neurons
- Differentiate between reflex actions, voluntary actions, and involuntary actions
- Describe the human brain and its various parts
- Explain how plants coordinate and respond to stimuli
- Identify major animal hormones and their functions
- Compare nervous and hormonal coordination
Period-Wise Teaching Plan
This chapter is designed to be covered over 8 periods, each lasting 45 minutes. Below is the detailed period-wise plan:
Topics: Need for control and coordination, differences between animal and plant coordination systems.
Activities: Discussion on daily life examples of coordination, video presentation on reflex actions.
Topics: Structure of neuron, nerve impulse transmission, synapses.
Activities: Activity 6.1 - Testing taste with blocked nose, diagram drawing of neuron structure.
Topics: Reflex actions, reflex arc, voluntary and involuntary actions.
Activities: Testing knee-jerk reflex, diagram of reflex arc, discussion on reflex actions.
Topics: Parts of brain and their functions, central and peripheral nervous system.
Activities: Activity 6.3 - Identifying endocrine glands, brain model examination.
Topics: Immediate responses to stimuli, movement in sensitive plant, nastic movements.
Activities: Observing sensitive plant (Mimosa pudica), video on plant movements.
Topics: Tropic movements, plant hormones, phototropism and geotropism.
Activities: Activity 6.2 - Phototropism experiment, observing tropic movements.
Topics: Endocrine system, major hormones and their functions, feedback mechanisms.
Activities: Activity 6.4 - Completing hormone table, case studies on hormonal disorders.
Topics: Revision of all concepts, important questions, doubt clearing.
Activities: Chapter quiz, group discussion, Q&A session.
Teaching Methodology
The teaching approach for this chapter should be a blend of:
- Interactive lectures with multimedia presentations
- Hands-on activities and experiments
- Group discussions and collaborative learning
- Visual aids like charts, models, and diagrams
- Case studies on hormonal disorders
- Regular assessment through quizzes and assignments
Nervous System
In animals, control and coordination are provided by nervous and muscular tissues. The nervous system uses electrical impulses to transmit messages rapidly across the body.
Structure of Neuron
The basic unit of the nervous system is the neuron (nerve cell). Neurons are specialized cells that transmit electrical impulses from one part of the body to another.
- Dendrites: Receive information from receptors or other neurons
- Cell body: Contains nucleus and cytoplasm
- Axon: Long fiber that conducts impulses away from the cell body
- Nerve endings: Terminal points that connect to other neurons or effectors
Nerve Impulse Transmission
Information acquired at the dendritic tip sets off a chemical reaction that creates an electrical impulse. This impulse travels from the dendrite to the cell body, and then along the axon to its end.
Synapse: The gap between two neurons where chemicals (neurotransmitters) are released to transmit the impulse to the next neuron.
Reflex Actions
Reflex actions are sudden, automatic responses to stimuli that do not involve conscious thought. They are designed to protect the body from harm.
Reflex Arc
The pathway followed by a nerve impulse during a reflex action is called a reflex arc. It involves:
- Receptor (detects stimulus)
- Sensory neuron (carries impulse to spinal cord)
- Interneuron (in spinal cord)
- Motor neuron (carries impulse to effector)
- Effector (muscle or gland that responds)
Activities & Experiments
Test how blocking the nose affects taste perception to demonstrate the connection between smell and taste.
Test knee-jerk reflex and pupillary reflex to demonstrate involuntary responses.
Human Brain
The brain is the main coordinating center of the body. It receives information from all parts of the body and integrates it to generate appropriate responses.
Central Nervous System
The brain and spinal cord constitute the central nervous system (CNS). The peripheral nervous system consists of nerves that connect the CNS to all parts of the body.
Parts of the Brain
- Fore-brain:
- Cerebrum: Thinking, reasoning, memory, voluntary actions
- Thalamus: Relay station for sensory impulses
- Hypothalamus: Controls hunger, thirst, emotions, body temperature
- Mid-brain: Controls reflex movements of head, neck and trunk in response to visual and auditory stimuli
- Hind-brain:
- Cerebellum: Coordinates voluntary movements, maintains posture and balance
- Pons: Relays messages between different brain parts
- Medulla oblongata: Controls involuntary actions like heartbeat, breathing, blood pressure
Protection of Nervous Tissue
The brain is protected by:
- Skull: Bony structure that encloses the brain
- Meninges: Three protective membranes
- Cerebrospinal fluid: Cushions the brain against shocks
The spinal cord is protected by the vertebral column (backbone).
Did You Know?
The human brain contains about 86 billion neurons and trillions of connections (synapses). It is one of the most complex structures known to exist!
Coordination in Plants
Plants lack a nervous system and muscles, but they can still respond to stimuli. Plants show two types of movements:
Types of Plant Movements
- Growth-independent movements: Quick movements not involving growth (e.e., sensitive plant)
- Growth-dependent movements: Slow directional movements caused by growth (e.g., phototropism)
Immediate Responses to Stimuli
Plants like the sensitive plant (Mimosa pudica) respond quickly to touch by folding their leaves. This movement is caused by changes in water pressure in specific cells, not by growth.
Tropic Movements (Tropisms)
Tropisms are directional growth responses in plants. The direction of growth is determined by the direction of the stimulus.
| Type of Tropism | Stimulus | Response | Example |
|---|---|---|---|
| Phototropism | Light | Shoots grow toward light; roots grow away from light | Sunflower following the sun |
| Geotropism | Gravity | Roots grow downward; shoots grow upward | Roots growing downward in soil |
| Hydrotropism | Water | Roots grow toward water | Roots growing toward water source |
| Chemotropism | Chemicals | Growth in response to chemicals | Pollen tubes growing toward ovules |
| Thigmotropism | Touch | Growth in response to touch | Tendrils coiling around support |
Activities & Experiments
Demonstrate how plant shoots bend toward light by growing bean seedlings in a controlled light environment.
Observe how roots always grow downward and shoots upward regardless of how seeds are oriented.
Hormones in Animals
Animals use chemical coordination through hormones in addition to nervous coordination. Hormones are chemical messengers secreted by endocrine glands directly into the bloodstream.
Endocrine System
The endocrine system consists of glands that secrete hormones directly into the bloodstream. Hormones regulate various body functions including growth, metabolism, and reproduction.
Major Endocrine Glands and Hormones
| Endocrine Gland | Hormone(s) | Functions | Disorders |
|---|---|---|---|
| Pituitary | Growth hormone, TSH, FSH, LH | Regulates growth, controls other endocrine glands | Dwarfism, Gigantism |
| Thyroid | Thyroxine | Regulates metabolism | Goiter, Cretinism |
| Pancreas | Insulin, Glucagon | Regulates blood sugar level | Diabetes mellitus |
| Adrenal | Adrenaline | Prepares body for emergency situations | Addison's disease |
| Testes | Testosterone | Development of male sex organs, secondary sexual characteristics | Hypogonadism |
| Ovaries | Estrogen, Progesterone | Development of female sex organs, menstrual cycle | Menstrual disorders |
Feedback Mechanisms
Hormone secretion is regulated by feedback mechanisms to maintain homeostasis. For example:
- When blood sugar rises, pancreas secretes insulin
- Insulin helps cells absorb glucose, lowering blood sugar
- When blood sugar drops, insulin secretion decreases
Fight or Flight Response
Adrenaline (epinephrine) is released during emergency situations. It prepares the body for "fight or flight" by:
- Increasing heart rate and breathing rate
- Diverting blood to muscles
- Increasing blood pressure
- Boosting energy supplies
Activities & Experiments
Identify endocrine glands on diagrams and models, and discuss their functions.
Complete a table of hormones, their glands, and functions to reinforce learning.
Teaching Resources
Key Terms
- Neuron: Basic unit of nervous system
- Synapse: Junction between two neurons
- Reflex action: Automatic response to stimulus
- Reflex arc: Pathway of reflex action
- CNS: Central nervous system (brain and spinal cord)
- PNS: Peripheral nervous system (nerves)
- Hormone: Chemical messenger
- Tropism: Directional growth response in plants
- Phototropism: Growth response to light
- Geotropism: Growth response to gravity
- Endocrine gland: Ductless gland that secretes hormones
Assessment Questions
Chapter Review Questions
- What is the difference between a reflex action and walking?
- What happens at the synapse between two neurons?
- Which part of the brain maintains posture and equilibrium of the body?
- How do we detect the smell of an agarbatti (incense stick)?
- What is the role of the brain in reflex action?
- What are plant hormones?
- How is the movement of leaves of the sensitive plant different from the movement of a shoot towards light?
- Give an example of a plant hormone that promotes growth.
- How do auxins promote the growth of a tendril around a support?
- How does chemical coordination take place in animals?
- Why is the use of iodised salt advisable?
- How does our body respond when adrenaline is secreted into the blood?
- Why are some patients of diabetes treated by giving injections of insulin?
Additional Resources
- Interactive 3D model of human brain and nervous system
- Video demonstration of reflex actions
- Time-lapse videos of plant tropisms
- Virtual lab on endocrine system
- Case studies on hormonal disorders
- Printable diagrams for labeling practice
