SK Tuitions • Class 10 Science Biology
Coordination in Animals
Complete CBSE-style notes on receptors, nerve impulses, neurons, reflex action, nervous system, brain, spinal cord, endocrine system, hormones, differences, question answers, HOTS and interactive quiz.
1. Meaning of Coordination in Animals
Coordination means the proper control and regulation of different activities of the body so that the body can respond correctly to changes in the environment. In animals, coordination is mainly performed by two systems:
Nervous System
It gives quick, short-lived responses through electrical impulses carried by neurons.
Endocrine System
It gives slower but longer-lasting responses through chemical messengers called hormones.
2. Stimulus, Response and Receptors
A stimulus is any change in the environment that produces a reaction in an organism. A response is the reaction of the body to a stimulus. Receptors are specialised cells or nerve endings that detect stimuli.
| Receptor Type | Stimulus Detected | Sense Organ / Location | Example |
|---|---|---|---|
| Photoreceptors | Light | Eyes | Seeing objects |
| Phonoreceptors | Sound | Ears | Hearing a bell |
| Olfactory receptors | Smell | Nose | Smelling food |
| Gustatory receptors | Taste | Tongue | Tasting sweet or bitter food |
| Thermoreceptors | Temperature | Skin | Feeling hot or cold |
| Pain receptors | Painful stimulus | Skin and internal organs | Pricking of a pin |
How Receptors Generate an Impulse
- A stimulus is detected by a receptor.
- The receptor changes the stimulus into an electrical signal.
- This electrical signal is called a nerve impulse.
- The impulse travels through sensory neurons to the central nervous system.
- The brain or spinal cord processes the information and sends instructions to effectors.
3. Neuron: Structural and Functional Unit of Nervous System
A neuron or nerve cell is the basic unit of the nervous system. It receives, carries and transfers nerve impulses from one part of the body to another.
| Part of Neuron | Description | Function |
|---|---|---|
| Dendrites | Short, branched structures | Receive impulses from receptors or other neurons. |
| Cell body / Cyton | Main part containing nucleus and cytoplasm | Maintains the neuron and processes the impulse. |
| Axon | Long fibre-like extension | Carries impulse away from the cell body. |
| Myelin sheath | Fatty insulating covering around axon | Increases speed of impulse transmission. |
| Nerve ending / Axon terminal | Terminal branches of axon | Pass impulse to another neuron, muscle or gland. |
| Synapse | Small gap between two neurons | Allows transfer of message through chemicals called neurotransmitters. |
4. Types of Neurons
| Type of Neuron | Direction of Impulse | Function | Example |
|---|---|---|---|
| Sensory neuron | Receptor → CNS | Carries impulse from sense organs to brain or spinal cord. | Impulse from skin after touching a hot object. |
| Motor neuron | CNS → Effector | Carries instruction from brain or spinal cord to muscles or glands. | Message to hand muscles to pull away. |
| Relay neuron / Interneuron | Within CNS | Connects sensory neuron with motor neuron. | Present in spinal cord during reflex action. |
5. Reflex Action and Reflex Arc
A reflex action is a quick, automatic and involuntary response to a stimulus. It happens without conscious thinking and protects the body from harm.
Reflex Arc Pathway
Why Reflex Action is Important
- It gives a very fast response.
- It protects the body from injury.
- It does not wait for detailed brain analysis.
- It helps in survival by avoiding danger quickly.
6. Nervous System in Animals
The nervous system receives information, processes it and sends suitable instructions to muscles and glands.
| Division | Full Form / Meaning | Components | Main Function |
|---|---|---|---|
| CNS | Central Nervous System | Brain and spinal cord | Controls and coordinates body activities. |
| PNS | Peripheral Nervous System | Cranial nerves and spinal nerves | Connects CNS with different parts of the body. |
| ANS | Autonomic Nervous System | Sympathetic and parasympathetic nerves | Controls involuntary functions like heartbeat, digestion and breathing rate. |
7. Protection of Brain and Spinal Cord
Protection of Brain
- The brain is protected by the skull or cranium.
- It is covered by three protective membranes called meninges.
- Cerebrospinal fluid protects the brain from shocks and injuries.
Protection of Spinal Cord
- The spinal cord is protected by the vertebral column or backbone.
- It is also surrounded by meninges.
- Cerebrospinal fluid provides cushioning and protection.
8. Brain: Parts and Functions
The brain is the main control centre of the body. It receives information, interprets it, stores memory, controls voluntary actions and regulates many involuntary activities.
| Part of Brain | Location / Group | Main Functions |
|---|---|---|
| Cerebrum | Forebrain | Thinking, intelligence, memory, learning, emotions, voluntary actions and interpretation of sensory information. |
| Thalamus | Forebrain | Relay centre for sensory messages going to cerebrum. |
| Hypothalamus | Forebrain | Controls hunger, thirst, body temperature and links nervous system with endocrine system. |
| Midbrain | Between forebrain and hindbrain | Controls visual and auditory reflexes. |
| Cerebellum | Hindbrain | Maintains balance, posture and coordination of muscular activities. |
| Pons | Hindbrain | Helps in regulation of breathing and acts as a bridge between parts of brain. |
| Medulla oblongata | Hindbrain | Controls involuntary actions such as heartbeat, breathing, blood pressure, swallowing and vomiting. |
9. Role of Spinal Cord
- It acts as a pathway for nerve impulses between brain and body.
- It controls many reflex actions.
- It contains relay neurons involved in reflex arcs.
- It helps in quick protective responses before the brain becomes fully aware of the situation.
- It coordinates some simple repeated movements with the help of the nervous system.
10. Cerebral Reflex
A cerebral reflex is a reflex action in which the brain, especially the cerebrum or brain centres, is involved. It may be natural or learned through experience.
| Type | Control Centre | Example |
|---|---|---|
| Spinal reflex | Spinal cord | Withdrawal of hand from a hot object. |
| Cerebral reflex | Brain | Salivation on seeing tasty food, blinking due to sudden bright light, learned conditioned responses. |
11. Hormonal System in Animals
The hormonal system is also called the endocrine system. It consists of endocrine glands that secrete hormones directly into the blood. Hormones are chemical messengers that regulate growth, metabolism, reproduction, stress response and many other body functions.
| Endocrine Gland | Hormone | Main Function |
|---|---|---|
| Pituitary gland | Growth hormone | Controls growth of body. Also called master gland because it controls many other endocrine glands. |
| Thyroid gland | Thyroxine | Controls metabolism. Iodine is needed for making thyroxine. |
| Pancreas | Insulin | Regulates blood sugar level. |
| Adrenal gland | Adrenaline | Prepares body for emergency situations; increases heartbeat and breathing rate. |
| Testes | Testosterone | Controls male secondary sexual characters and sperm production. |
| Ovaries | Oestrogen and progesterone | Control female secondary sexual characters, menstrual cycle and pregnancy-related changes. |
12. What Links Nervous System and Hormonal System?
The hypothalamus links the nervous system and the endocrine system. It receives nerve signals from the brain and controls the pituitary gland by releasing special hormones. The pituitary gland then controls many other endocrine glands.
13. Definitions Chart
| Term | Definition |
|---|---|
| Coordination | Control and regulation of body activities to produce suitable responses. |
| Stimulus | A change in the environment that produces a response. |
| Response | The reaction of the body to a stimulus. |
| Receptor | A specialised cell or nerve ending that detects a stimulus. |
| Nerve impulse | An electrical signal travelling through a neuron. |
| Neuron | The structural and functional unit of the nervous system. |
| Synapse | A small gap between two neurons where impulse is transferred chemically. |
| Effector | A muscle or gland that produces a response. |
| Reflex action | A quick, automatic and involuntary response to a stimulus. |
| Reflex arc | The pathway followed by nerve impulses during reflex action. |
| CNS | Central nervous system consisting of brain and spinal cord. |
| PNS | Peripheral nervous system consisting of nerves outside CNS. |
| ANS | Autonomic nervous system controlling involuntary activities. |
| Hormone | A chemical messenger secreted by endocrine glands into blood. |
| Endocrine gland | A ductless gland that secretes hormones directly into blood. |
14. Difference Between Related Topics
Nervous System vs Hormonal System
| Basis | Nervous System | Hormonal System |
|---|---|---|
| Messenger | Electrical impulses and neurotransmitters | Hormones |
| Pathway | Neurons | Blood |
| Speed | Very fast | Slower |
| Effect | Short-lived | Long-lasting |
| Target | Specific muscles or glands | Target organs having suitable receptors |
Sensory Neuron vs Motor Neuron
| Basis | Sensory Neuron | Motor Neuron |
|---|---|---|
| Direction | Receptor to CNS | CNS to effector |
| Function | Carries sensory information | Carries motor instruction |
| Example | Impulse from skin to spinal cord | Instruction from spinal cord to hand muscles |
Voluntary Action vs Reflex Action
| Basis | Voluntary Action | Reflex Action |
|---|---|---|
| Control | Under conscious control | Automatic and involuntary |
| Speed | Comparatively slower | Very fast |
| Main centre | Brain | Mostly spinal cord |
| Example | Writing, walking intentionally | Withdrawal of hand from hot object |
Endocrine Gland vs Exocrine Gland
| Basis | Endocrine Gland | Exocrine Gland |
|---|---|---|
| Ducts | Ductless | Have ducts |
| Secretion | Hormones | Enzymes, sweat, saliva, etc. |
| Release | Directly into blood | Through ducts to target area |
| Example | Thyroid, pituitary, adrenal | Salivary gland, sweat gland |
15. Important Question Answers
Q1. What is coordination?
Answer: Coordination is the process by which different organs and systems of the body work together in a controlled manner to produce a proper response to a stimulus.
Q2. What are receptors?
Answer: Receptors are specialised cells or nerve endings that detect stimuli such as light, sound, smell, taste, temperature and pain, and convert them into nerve impulses.
Q3. How is a nerve impulse generated?
Answer: When a receptor detects a stimulus, changes occur in its membrane. This creates an electrical signal called a nerve impulse, which travels through neurons to the CNS.
Q4. What is a neuron?
Answer: A neuron is a nerve cell that receives, carries and transfers nerve impulses. It has dendrites, cell body, axon and nerve endings.
Q5. What is reflex action?
Answer: Reflex action is a quick, automatic and involuntary response to a stimulus. It protects the body from harm.
Q6. Define reflex arc.
Answer: Reflex arc is the pathway followed by nerve impulses during reflex action. It includes receptor, sensory neuron, spinal cord, motor neuron and effector.
Q7. Why is reflex action faster than voluntary action?
Answer: Reflex action is faster because the message is processed mainly in the spinal cord and does not wait for detailed analysis by the brain.
Q8. What are the main parts of the brain?
Answer: The main parts of the brain are forebrain, midbrain and hindbrain. Important structures include cerebrum, cerebellum, pons and medulla oblongata.
Q9. What is the function of cerebellum?
Answer: The cerebellum maintains balance, posture and coordination of muscular movements.
Q10. What is the role of medulla oblongata?
Answer: Medulla oblongata controls involuntary activities such as heartbeat, breathing, blood pressure, swallowing and vomiting.
Q11. How is the brain protected?
Answer: The brain is protected by the skull, meninges and cerebrospinal fluid. These structures protect it from shocks and injury.
Q12. What are hormones?
Answer: Hormones are chemical messengers secreted by endocrine glands directly into the blood. They regulate various body functions.
Q13. Why is pituitary gland called the master gland?
Answer: Pituitary gland is called the master gland because it secretes hormones that control the activity of several other endocrine glands.
Q14. What is the function of adrenaline?
Answer: Adrenaline prepares the body for emergency situations by increasing heartbeat, breathing rate, blood pressure and energy supply to muscles.
Q15. Which part links nervous and endocrine systems?
Answer: The hypothalamus links the nervous system and endocrine system by controlling the pituitary gland.
16. High Level Thinking Questions
Q1. Why do we withdraw our hand from a hot object before feeling pain clearly?
Answer: The withdrawal is controlled by a reflex arc through the spinal cord. The impulse reaches the spinal cord and immediately produces a motor response. The brain receives the pain message slightly later.
Q2. Why are both nervous and hormonal systems needed if both coordinate body functions?
Answer: The nervous system is needed for quick and short-term responses, while the hormonal system is needed for slower, long-term regulation such as growth, metabolism and reproduction.
Q3. A person with damage to cerebellum may not walk properly. Why?
Answer: The cerebellum coordinates muscular movement and maintains balance. If it is damaged, body posture and movement coordination are affected.
Q4. Why does adrenaline increase heartbeat during fear?
Answer: During fear, the body needs more oxygen and glucose for quick action. Adrenaline increases heartbeat and breathing rate so that more oxygen and energy reach muscles.
Q5. Why is the synapse important even though it is only a small gap?
Answer: The synapse allows one neuron to communicate with another neuron or effector using chemical messengers. Without synapses, impulses cannot be properly transferred across nerve pathways.
Q6. Why does iodine deficiency affect body metabolism?
Answer: Iodine is required to make thyroxine hormone. Thyroxine regulates metabolism. Deficiency of iodine reduces thyroxine production and can disturb metabolic activities.
Quick Revision Box
- Receptors detect stimuli and generate nerve impulses.
- Neuron is the structural and functional unit of nervous system.
- Sensory neurons carry impulses from receptors to CNS.
- Motor neurons carry instructions from CNS to effectors.
- Reflex action is fast, automatic and protective.
- Reflex arc usually involves receptor, sensory neuron, spinal cord, motor neuron and effector.
- CNS includes brain and spinal cord.
- PNS includes nerves outside CNS.
- ANS controls involuntary body functions.
- Cerebrum controls thinking, memory and voluntary actions.
- Cerebellum controls balance and posture.
- Medulla controls heartbeat, breathing and other involuntary actions.
- Hormones are chemical messengers secreted by endocrine glands.
- Hypothalamus links nervous system and endocrine system.
Interactive Quiz
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