Question and Answer Study Material
SECTION A: BASIC CONCEPTS
Q1. What are stimuli? Give examples. Answer: The senses that evoke responses in organisms are called stimuli. Examples include:
- External stimuli: taste, touch, light, sound
- Internal stimuli: hunger, thirst
Q2. What are receptors? Answer: Receptors are specialized cells in the sense organs and other parts of the body that receive stimuli and generate suitable impulses.
Q3. Name the major parts of the nervous system. Answer: The major parts of the nervous system are:
- Brain
- Spinal cord
- Nerves
SECTION B: NEURON STRUCTURE AND FUNCTION
Q4. What is a neuron? Describe its structure. Answer: A neuron or nerve cell is the basic structural unit of the nervous system. Its main parts are:
- Cell body: Contains cytoplasm and nucleus
- Dendrite: Branches of dendron that receive impulses from adjacent neurons
- Dendron: Short filament from cell body that carries impulses from dendrites to cell body
- Axon: Longest filament from cell body that carries impulses from cell body to outside
- Axonite: Branches of axon that carry impulses to synaptic knob
- Synaptic knob: Tip of axonite that secretes neurotransmitters
Q5. What is myelin sheath? State its functions. Answer: Myelin sheath is a membrane containing lipid that repeatedly encircles the axons of most neurons.
Functions of myelin sheath:
- Provide nutrients and oxygen to the axon
- Accelerate impulses
- Act as an electric insulator
- Protect the axon from external shocks
Q6. Differentiate between white matter and grey matter. Answer:
- White matter: Part of brain and spinal cord where myelinated nerve cells are present in abundance. Has shiny white color due to myelin sheath.
- Grey matter: Part of brain and spinal cord where non-myelinated nerve cells are present.
Q7. Compare Schwann cells and Oligodendrocytes. Answer:
- Schwann cells: Form myelin sheath in nerves by encircling the axon repeatedly
- Oligodendrocytes: Form myelin sheath in brain and spinal cord by covering different axons simultaneously or different parts of same axon repeatedly
SECTION C: IMPULSE GENERATION AND TRANSMISSION
Q8. How are nerve impulses generated and transmitted? Answer:
- Normally, the outer surface of neuron's plasma membrane is positively charged and inner surface is negatively charged due to ion distribution
- When stimulated, ion distribution changes - inner surface becomes positive, outer becomes negative
- This charge difference stimulates adjacent parts causing similar changes
- As this process proceeds, impulses get transmitted as electric charges
- Nerve impulses are messages transmitted through neurons
Q9. What is a synapse? Explain its structure and function. Answer: Synapse is the junction between two neurons or between a neuron and a muscle/glandular cell.
Structure: Contains synaptic knob, synaptic cleft, and receiving dendrite/cell
Function:
- When electric impulses reach synaptic knob, neurotransmitters are secreted into synaptic cleft
- Neurotransmitters stimulate adjacent dendrite/cell generating new electric impulses
- Helps regulate speed and direction of impulses
- Examples of neurotransmitters: Acetylcholine, Dopamine
SECTION D: TYPES OF NEURONS AND NERVES
Q10. Classify neurons based on direction of impulse. Answer:
- Sensory neurons: Carry impulses to brain and spinal cord
- Motor neurons: Carry impulses from brain and spinal cord to various body parts
Q11. Classify nerves based on their functions. Answer:
- Sensory nerve: Formed of sensory nerve fibers; carries impulses from body parts to brain and spinal cord
- Motor nerve: Formed of motor nerve fibers; carries impulses from brain and spinal cord to body parts
- Mixed nerve: Formed of both sensory and motor nerve fibers; carries impulses to and from brain and spinal cord
SECTION E: NERVOUS SYSTEM DIVISIONS
Q12. What are the two main divisions of the nervous system? Answer:
- Central Nervous System (CNS): Brain and Spinal cord
- Peripheral Nervous System (PNS): Cranial nerves (12 pairs) and Spinal nerves (31 pairs)
SECTION F: BRAIN STRUCTURE AND FUNCTION
Q13. How is the brain protected and nourished? Answer: Protection:
- Protected inside skull
- Covered by meninges (three-layered membrane)
- Cerebrospinal fluid fills inner membranes and brain ventricles
Nourishment:
- Cerebrospinal fluid provides nutrients and oxygen
- Regulates pressure inside brain
- Protects from injuries
Q14. Describe the parts of brain and their functions. Answer:
Cerebrum (largest part):
- Center of thought, intelligence, memory, imagination
- Evokes sensations, controls voluntary movements
- Outer grey part: Cortex; Inner white part: Medulla
Cerebellum (second largest):
- Coordinates muscular activities
- Maintains body equilibrium
Thalamus:
- Acts as relay station of impulses to/from cerebrum
- Analyzes impulses and sends important ones to cerebrum
Hypothalamus:
- Maintains homeostasis
Medulla oblongata:
- Controls involuntary actions (heartbeat, breathing)
SECTION G: SPINAL CORD
Q15. Describe the structure and functions of spinal cord. Answer: Structure:
- Continuation of medulla oblongata
- Protected inside vertebral column
- Covered by meninges
- Central canal filled with cerebrospinal fluid
- White matter outside, grey matter inside
Functions:
- Transmits impulses between body parts and brain
- Coordinates repeated movements (walking, running)
- Center for spinal reflexes
Q16. How are spinal nerves formed? Answer: 31 pairs of spinal nerves arise from spinal cord. Each spinal nerve is formed by joining of:
- Dorsal root: Carries sensory impulses to spinal cord
- Ventral root: Carries motor impulses from spinal cord
SECTION H: REFLEX ACTION
Q17. What is reflex action? Explain with pathway. Answer: Reflex actions are accidental and involuntary responses towards stimuli that happen without conscious control.
Reflex Arc Pathway:
- Stimulus → 2. Receptor (generates impulses) → 3. Sensory neuron (carries impulses to spinal cord) → 4. Interneuron (connects sensory and motor neurons, generates quick responses) → 5. Motor neuron (carries information to muscles) → 6. Related muscle (produces response)
Q18. Differentiate between spinal reflexes and cerebral reflexes. Answer:
- Spinal reflexes: Controlled by spinal cord (e.g., withdrawing hand from hot object)
- Cerebral reflexes: Controlled by cerebrum (e.g., blinking when light suddenly falls on eyes)
SECTION I: AUTONOMOUS NERVOUS SYSTEM
Q19. What is autonomous nervous system? Name its divisions. Answer: Autonomous nervous system controls activities beyond conscious level. It's part of peripheral nervous system.
Divisions:
- Sympathetic system: Active during emergency situations
- Parasympathetic system: Returns body to normal state after emergency
Q20. Compare sympathetic and parasympathetic systems. Answer:
Sympathetic System (Emergency Response):
- Pupil dilates
- Production of saliva decreases
- Trachea expands
- Heart beat increases
- Gastric activities slow down
- Glycogen is converted to glucose
- Peristalsis in the intestine slows down
- Urinary bladder regains normal state
- Production of hormone increases
Parasympathetic System (Normal State):
- Pupil contracts
- Production of saliva increases
- Trachea contracts
- Heart beat becomes normal
- Gastric activities become normal
- Glucose is converted to glycogen
- Peristalsis in the intestine becomes normal
- Urinary bladder contracts
- Production of hormone decreases
SECTION J: NERVOUS SYSTEM DISORDERS
Q21. Describe common nervous system diseases. Answer:
Alzheimer's Disease:
- Symptoms: Loss of memory, inability to recognize people, inability to do routine work
- Cause: Accumulation of insoluble protein in neural tissues, neuron destruction
Parkinson's Disease:
- Symptoms: Loss of body balance, irregular muscle movement, body shivering, profuse salivation
- Cause: Destruction of specialized ganglions, reduced dopamine production
Epilepsy:
- Symptoms: Continuous muscular contraction, frothy mouth discharge, teeth clenching, unconsciousness
- Cause: Continuous and irregular flow of electric charges in brain
SECTION K: APPLICATION QUESTIONS
Q22. Why is it important to wear helmets while riding two-wheelers? Answer: The brain is the control center of all life activities. Even minor damage can cause serious problems. Helmets protect the skull and brain from injuries during accidents, preventing potential nervous system damage.
Q23. How does alcohol affect reflex action? Answer: Alcohol accelerates the action of GABA (gamma amino butyric acid), a neurotransmitter in the brain. Higher doses retard brain action, weakening reflex action and preventing proper decision-making at the right time.
Q24. What precautions should be taken while helping accident victims? Answer:
- Don't lift people quickly by holding arms or legs
- Be careful about spinal cord injuries
- Avoid moving the person unnecessarily to prevent further spinal cord damage
- Provide proper first aid following standard procedures
SECTION L: DIAGRAM-BASED QUESTIONS
Q25. Draw and label the structure of a neuron. Answer: [Students should draw a neuron showing cell body with nucleus and cytoplasm, dendrites, dendron, axon with myelin sheath, axonites, and synaptic knobs]
Q26. Draw the reflex arc pathway. Answer: [Students should draw the pathway: Stimulus → Receptor → Sensory neuron → Spinal cord (interneuron) → Motor neuron → Muscle response]
SECTION M: ANALYTICAL QUESTIONS
Q27. A thorn pierces the foot and the leg is withdrawn. Answer the following: a) What are the stimulus and response?
- Stimulus: Thorn piercing the foot
- Response: Leg withdrawal
b) Was the leg withdrawn after sensing pain? Identify the type of action.
- No, the leg was withdrawn before sensing pain
- This is a reflex action (spinal reflex)
Q28. Why doesn't the spinal cord extend to the full length of vertebral column in adults? Answer: In newborns, the spinal cord extends to the tip of vertebral column. In adults, it's seen only up to the middle because the spinal cord doesn't grow in proportion to the vertebral column's growth.
Important Points to Remember:
- Nervous system has two main parts: CNS and PNS
- Neuron is the basic structural unit of nervous system
- Myelin sheath provides protection and accelerates impulses
- Synapses help in impulse transmission between neurons
- Brain has five main parts with specific functions
- Reflex actions are involuntary and protective
- Autonomous nervous system controls unconscious activities
- Proper care is needed to maintain nervous system health
Study Tip: Practice drawing diagrams of neuron structure, brain parts, and reflex arc. Understanding the pathway of nerve impulses is crucial for answering application questions.