Questions
4–6 questions per exam
Difficulty
Medium
Importance
Core foundational topic — high frequency
Overview
Control and Coordination covers the intricate mechanisms through which multicellular organisms respond to internal and external stimuli. It is a cornerstone of the CBSE curriculum, bridging the gap between biological nervous signaling and complex chemical regulation via the endocrine system.
The Nervous System
The nervous system is divided into the Central Nervous System (CNS) and the Peripheral Nervous System (PNS), responsible for processing information and relaying signals. Neurons are the structural and functional units that propagate electrical impulses across synapses using neurotransmitters.
- CNS consists of the brain and spinal cord
- PNS comprises cranial and spinal nerves
- Dendrites receive signals while axons conduct impulses
- Synapse is the gap between two neurons
- Acetylcholine is a primary neurotransmitter
Reflex Action and Arc
Reflex actions are rapid, involuntary responses to stimuli that occur without conscious thought, functioning primarily to protect the organism from harm. The pathway taken by nerve impulses in a reflex action is known as the reflex arc, involving a sensory neuron, relay neuron, and motor neuron.
- Rapid response to avoid injury
- Involves spinal cord processing
- Sensory neuron -> Relay neuron -> Motor neuron
- Protective in nature
- Independent of the brain's higher centers
Hormones and Endocrine System
Hormones are chemical messengers secreted directly into the bloodstream by ductless glands to regulate various physiological processes. Unlike nervous responses, hormonal control is slower but provides sustained and systemic coordination throughout the body.
- Insulin regulates blood sugar levels
- Thyroxine controls metabolic rate
- Adrenaline prepares body for fight or flight
- Growth hormone stimulates tissue development
- Feedback mechanism controls secretion levels
Exam Tip
Always draw a labeled diagram of a neuron or the human endocrine system when asked, as it guarantees partial marks even if the description is concise.
Common Mistakes
- Confusing the order of components in a reflex arc pathway
- Failing to distinguish between endocrine glands (ductless) and exocrine glands
- Assuming hormones act as fast as electrical nerve impulses
More Revision Notes
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