CONTROL AND COORDINATION – REVISION NOTES
1. Meaning of Control and Coordination
-
Control: Regulation of body activities.
-
Coordination: Proper timing and integration of body functions.
-
In multicellular organisms, control and coordination are achieved by:
-
Nervous system
-
Hormonal (chemical) system
-
2. Nervous System in Animals
Functions
-
Receives information from environment
-
Processes information
-
Produces appropriate response through muscles or glands
Neuron (Nerve Cell)
Parts and Functions
-
Dendrite – receives stimulus
-
Cell body – processes information
-
Axon – transmits electrical impulse
-
Synapse – gap between neurons where chemical transmission occurs
Important Point
-
Information travels as electrical impulse, but crosses synapse as chemical signal.
3. Reflex Action
Definition
-
A quick, automatic and involuntary response to a stimulus.
Reflex Arc Pathway
Stimulus → Receptor → Sensory neuron → Spinal cord → Motor neuron → Effector
Significance
-
Protects body from harm
-
Does not involve conscious thinking
-
Formed in spinal cord, not brain
4. Human Brain
Parts and Functions
Brain Part | Function |
Forebrain | Thinking, memory, sensory interpretation |
Midbrain | Controls involuntary actions |
Hindbrain | Balance, posture, involuntary actions |
Hindbrain includes
-
Cerebellum – posture & balance
-
Medulla – heartbeat, breathing, salivation
Protection of Nervous Tissue
-
Brain protected by skull
-
Spinal cord protected by vertebral column
-
Cerebrospinal fluid acts as shock absorber
5. Coordination in Plants
Types of Movements
-
Growth-independent movement
-
Example: Touch-me-not (Mimosa) leaf folding
-
-
Growth-dependent movement
-
Example: Shoot bending towards light
-
Tropic Movements
Directional growth responses to stimuli
|
Tropism |
Stimulus |
Example |
|
Phototropism |
Light |
Shoot bends towards
light |
|
Geotropism |
Gravity |
Roots grow
downwards |
|
Hydrotropism |
Water |
Roots grow towards
water |
|
Chemotropism |
Chemicals |
Pollen
tube growth |
6. Plant Hormones (Phytohormones)
|
Hormone |
Function |
|
Auxin |
Cell elongation,
phototropism |
|
Gibberellins |
Stem
growth |
|
Cytokinins |
Cell division |
|
Abscisic acid |
Inhibits
growth, wilting |
Key Point
-
Plant hormones are synthesized at one place and act at another.
7. Hormones in Animals
Endocrine System
-
Ductless glands
-
Hormones released directly into blood
-
Action is slow but long-lasting
Important Hormones and Functions
|
Hormone |
Gland |
Function |
|
Growth hormone |
Pituitary |
Body growth |
|
Thyroxine |
Thyroid |
Metabolism |
|
Insulin |
Pancreas |
Controls blood
sugar |
|
Adrenaline |
Adrenal |
Fight or
flight |
|
Testosterone |
Testes |
Male secondary
characters |
|
Estrogen / Progesterone |
Ovaries |
Female
secondary characters |
Adrenaline – Fight or Flight Hormone
-
Increases heartbeat
-
Increases breathing rate
-
Diverts blood to muscles
-
Prepares body for emergency
8. Feedback Mechanism
-
Maintains hormone balance
-
Example:
-
High blood sugar → more insulin
-
Normal blood sugar → insulin reduced
-
9. Key Differences for Exams
Reflex Action vs Voluntary Action
Reflex Action
Voluntary Action
Automatic
Conscious
Spinal cord
Brain
Very fast
Comparatively slow
Nervous Control vs Hormonal Control
|
|---|
10. One-Line Exam Points
-
Synapse converts electrical signal to chemical signal.
-
Cerebellum maintains posture and balance.
-
Auxin accumulates on shady side of shoot.
-
Iodine deficiency causes goitre.
-
Insulin deficiency causes diabetes.