Class 10 Biology – Chapter 5: Nervous System

Board: Federal Board (FBISE)

Section I: Multiple Choice Questions

Q1. Reaction to any stimulus is called:

A) Receptor
B) Impulse
C) Response
D) Effector

Correct Answer: C) Response

Q2. The unit of structure and function in the nervous system is:

A) Neuron
B) Muscle cell
C) Nephron
D) Cardiac cell

Correct Answer: A) Neuron

Q3. Thyroid gland has the ability to store:

A) Iodine
B) Chlorine
C) Fluorine
D) Zinc

Correct Answer: A) Iodine

Q4. Endocrine glands pour their secretion directly into:

A) Lymph
B) Blood
C) Organs
D) Muscles

Correct Answer: B) Blood

Q5. Islets of Langerhans are parts of the:

A) Thyroid gland
B) Adrenal gland
C) Pancreas
D) Gonads

Correct Answer: C) Pancreas

Q6. Nerve impulse is best described as:

A) Chemical
B) Electrical
C) Osmotic
D) Electrochemical

Correct Answer: D) Electrochemical

Q7. When a person is frightened, which substance increases the blood sugar level?

A) Adrenaline
B) Amylase
C) Glycogen
D) Insulin

Correct Answer: A) Adrenaline

Q8. Which part of the brain detects temperature changes in the blood?

A) Cerebellum
B) Cerebral hemispheres
C) Hypothalamus
D) Medulla

Correct Answer: C) Hypothalamus

Q9. The question and its options are missing from the supplied text.

Q10. In contrast to nerve impulse, the response produced by hormones takes longer because:

A) Hormones are specific in their action.
B) Hormones are transported through the bloodstream.
C) Hormones are produced in small amounts.
D) The molecules of hormones are small in size.

Correct Answer: B) Hormones are transported through the bloodstream.

Q11. Once released, neurotransmitter molecules typically produce signals in postsynaptic neurons by:

A) Entering the postsynaptic neuron
B) Attaching to vesicles
C) Binding to presynaptic receptors
D) Binding to postsynaptic receptors

Correct Answer: D) Binding to postsynaptic receptors

Q12. The parts of the brain represented by I and II are:

(Note: I points to the cerebellum and II points to the pons.)

A) Cerebellum / Pons
B) Cerebrum / Pons
C) Cerebellum / Medulla oblongata
D) Cerebrum / Medulla oblongata

Correct Answer: A) Cerebellum / Pons

Q13. The components of this reflex arc are:

(Note: Based on standard reflex arc numbering: 1 = Receptor, 2 = Sensory neuron, 3 = Interneuron, 4 = Motor neuron, 5 = Effector.)

A) Receptor / Sensory neuron / Motor neuron / Interneuron / Effector
B) Sensory neuron / Motor neuron / Interneuron / Receptor / Effector
C) Receptor / Effector / Sensory neuron / Interneuron / Motor neuron
D) Receptor / Sensory neuron / Interneuron / Motor neuron / Effector

Correct Answer: D) Receptor / Sensory neuron / Interneuron / Motor neuron / Effector

Q14. Four characteristics of a specific hormone are listed below:

i. Increased rate and intensity of heartbeat.
ii. Increased blood pressure.
iii. Decreased blood flow to skin and alimentary canal.
iv. Increased blood flow to limbs.

Q15. Which is this hormone?

A) Adrenaline
B) Glucagon
C) Insulin
D) Testosterone

Correct Answer: A) Adrenaline

Section II: Short Answer Questions

Q1. What is the nervous system?

Answer:

The nervous system is an organ system containing a network of specialized cells called neurons. These cells coordinate body actions and transmit signals between different parts of the body to respond to internal and external stimuli.

It consists of two main parts:

1. Central Nervous System (CNS).

2. Peripheral Nervous System (PNS).

Q2. What is the role of the nervous system?

Answer:

The main functions of the nervous system are:

1. Sensory Perception: Detects changes (stimuli) in the internal and external environment.

2. Integration: Processes, interprets, and analyzes sensory information to formulate appropriate decisions.

3. Motor Response: Controls body activities by sending signals to effectors (muscles and glands).

Q3. Differentiate between the central nervous system and peripheral nervous system.

Answer:

Q4. Name the parts of the human brain.

Answer:

The human brain is divided into three main regions:

1. Forebrain: Consists of the cerebrum, thalamus, and hypothalamus.

2. Midbrain: Connects the forebrain to the hindbrain and acts as a relay centre for visual and auditory information.

3. Hindbrain: Consists of the cerebellum, pons, and medulla oblongata.

Q5. Write two functions of the cerebellum.

Answer:

1. Body Equilibrium: Controls and coordinates precise muscle movements to maintain balance and posture.

2. Motor Coordination: Facilitates smooth and accurate voluntary movement patterns, such as walking and typing.

Q6. How are the brain and spinal cord protected?

Answer:

The central nervous system (CNS), consisting of the brain and spinal cord, is protected by three layers of defence:

1. Bony Covering: The brain is protected by the skull (cranium), while the spinal cord is protected by the vertebral column.

2. Meninges: Three protective membrane layers (dura mater, arachnoid mater, and pia mater) enclose both the brain and spinal cord.

3. Cerebrospinal Fluid (CSF): Fluid present around the CNS cushions it against mechanical shocks.

Q7. Describe the peripheral nervous system.

Answer:

The Peripheral Nervous System (PNS) comprises all nerves extending outside the brain and spinal cord.

• Cranial Nerves: 12 pairs originating directly from the brain.

• Spinal Nerves: 31 pairs originating from the spinal cord.

Functional Divisions:

• Somatic Nervous System: Controls voluntary muscle movements.

• Autonomic Nervous System: Controls involuntary visceral functions. It is divided into the sympathetic and parasympathetic systems.

Q8. What are the types of neurons? What are their functions?

Answer:

1. Sensory Neurons: Transmit nerve impulses from sensory receptors to the CNS.

2. Interneurons (Intermediate Neurons): Located entirely within the CNS; they process, analyze, and integrate sensory information.

3. Motor Neurons: Carry motor commands away from the CNS to effectors (muscles and glands).

Q9. Define stimulus with examples.

Answer:

Definition: A stimulus is any detectable change in the internal or external environment that produces a physiological or behavioural response in an organism.

Examples: Heat, light intensity, sound, pressure, pain, and changes in chemical concentration.

Q10. Define and sketch a synapse.

Answer:

Definition: A synapse is a microscopic junction between the axon terminal of one neuron (presynaptic cell) and the dendrite or cell body of an adjacent neuron (postsynaptic cell). Nerve impulses pass across this junction through chemical signals.

Labeled Diagram: Draw and label the structure of a synapse.

Q11. How does an impulse cross a synapse?

Answer:

1. Arrival of Impulse: An electrical impulse reaches the axon terminal of the presynaptic neuron.

2. Release of Neurotransmitter: Vesicles fuse with the presynaptic membrane and release neurotransmitters into the synaptic cleft.

3. Diffusion and Binding: Neurotransmitters diffuse across the cleft and bind to specific receptor sites on the postsynaptic membrane.

4. Signal Generation: Binding triggers an electrical change (impulse) in the receiving postsynaptic neuron.

Q12. What action or change do neurotransmitters transmit to the target cell?

Answer:

Neurotransmitters can produce either of the following effects:

• Excitatory Action: Depolarizes the target cell membrane, triggering a new nerve impulse or contraction.

• Inhibitory Action: Hyperpolarizes the target cell, preventing the generation of an impulse or reducing its activity.

Q13. What happens to neurotransmitters after they deliver their message?

Answer:

After binding to postsynaptic receptors, neurotransmitters are rapidly removed from the synaptic cleft through the following processes:

1. Enzymatic Degradation: They are broken down by specific enzymes. For example, acetylcholinesterase breaks down acetylcholine.

2. Reuptake: They are transported back into the presynaptic neuron for recycling.

3. Diffusion: They move away from the synaptic gap through diffusion.

Q14. How many different types of neurotransmitters are there?

Answer:

There are over 100 known neurotransmitters in the human nervous system. They are broadly classified into:

1. Small Molecule Transmitters: Acetylcholine and monoamines such as dopamine, serotonin, adrenaline (epinephrine), and noradrenaline.

2. Amino Acids: Glutamate, GABA (gamma-aminobutyric acid), and glycine.

3. Neuropeptides: Endorphins, substance P, and enkephalins.

Q15. What is a reflex action?

Answer:

A reflex action is an immediate, automatic, involuntary response to a specific stimulus without prior conscious thought. It is controlled primarily by the spinal cord.

Example: Withdrawing a hand instantly upon touching a hot object.

Q16. Name the endocrine glands of humans.

Answer:

The major human endocrine glands are:

1. Pituitary Gland.

2. Thyroid Gland.

3. Parathyroid Glands.

4. Adrenal Glands.

5. Pancreas (Islets of Langerhans).

6. Gonads (testes in males and ovaries in females).

7. Pineal Gland and Thymus Gland.

Q17. Name the hormones secreted by each endocrine gland.

Answer:

Q18. Differentiate between the following:

(a) Cerebrum and Cerebellum

(b) Sensory and Motor Neuron

(c) Voluntary and Involuntary Action

(d) Nerve Impulse and Hormonal Transmission

(e) Endocrine Glands and Exocrine Glands

Section III: Extensive Answer Questions

Q1. Describe the nervous system and its role in humans.

Introduction

The human nervous system is an intricate regulatory network designed for rapid coordination and communication within the body. It enables humans to perceive external stimuli, integrate information, and execute appropriate responses.

Structural Organization

1. Central Nervous System (CNS)

• Brain: The main coordination centre, responsible for processing sensory data, cognitive thoughts, memory, and voluntary control.

• Spinal Cord: Acts as a pathway for signal transmission between the brain and peripheral nerves. It also serves as the main centre for spinal reflex actions.

2. Peripheral Nervous System (PNS)

• Somatic Nervous System: Relays signals to skeletal muscles and controls voluntary movements.

• Autonomic Nervous System: Controls involuntary organs, including cardiac muscles, smooth muscles, and glands.

It operates through two divisions:

• Sympathetic Division: Prepares the body for the “fight or flight” response during stress.

• Parasympathetic Division: Controls “rest and digest” activities under normal conditions.

Core Roles in Humans

• Homeostasis Maintenance: Continuously monitors internal variables, such as temperature and arterial pressure, and regulates physiological responses.

• Sensory Processing: Transforms external energy, such as light and sound, into neural signals for conscious perception.

• Higher Cognitive Functions: Governs learning, memory, emotions, and decision-making processes.

Q2. Draw a vertical section of the human brain and label it. Write the functions of each part.

Diagram: Vertical Section (Sagittal Section) of Human Brain

Draw a vertical section of the human brain and label its major parts.

Functions of Key Brain Parts

1. Forebrain

• Cerebrum: Coordinates voluntary actions, sensory perception, intelligence, speech, and memory storage.

• Thalamus: Acts as a relay station for sensory pathways heading towards the cerebrum.

• Hypothalamus: Regulates body temperature, hunger, thirst, and sleep. It also controls pituitary gland secretions.

2. Midbrain

• Relays sensory information from the eyes and ears to the forebrain.

• Controls visual and auditory reflexes.

3. Hindbrain

• Cerebellum: Coordinates precise skeletal muscle movements and maintains posture and balance.

• Pons: Assists the medulla in regulating breathing rates and serves as a pathway between the cerebrum and cerebellum.

• Medulla Oblongata: Controls vital involuntary functions such as heart rate, breathing, blood pressure, and swallowing.

Q3. Draw and label a cross-section of the human spinal cord and write its structure and function.

Diagram: Cross-Section of Spinal Cord

Draw and label a cross-section of the human spinal cord.

Structure of Spinal Cord

• Grey Matter: The inner, butterfly-shaped region made of cell bodies, unmyelinated interneurons, and neuroglia. It contains dorsal horns (sensory input) and ventral horns (motor output).

• White Matter: The outer region composed of myelinated axon bundles forming ascending (sensory) and descending (motor) tracts.

• Central Canal: Runs through the centre of the grey matter and contains cerebrospinal fluid (CSF).

Functions of Spinal Cord

1. Conduction Pathway: Connects peripheral nerves to the brain for sensory input and motor output.

2. Reflex Centre: Serves as the primary centre for processing simple spinal reflex actions independently of conscious brain control.

Q4. Outline the types of neurons with diagrams.

Classification and Structure

Draw and label the three types of neurons: sensory neuron, interneuron, and motor neuron.

1. Sensory Neurons

• Structure: A single long dendrite leads towards the cell body, with a short axon extending towards the CNS.

• Role: Conduct impulses from sensory organs to the CNS.

2. Interneurons

• Structure: Have highly branched dendrites and multiple short processes. They are found entirely inside the CNS.

• Role: Interpret sensory inputs and help initiate motor outputs.

3. Motor Neurons

• Structure: Have multiple short dendrites attached to the cell body and a long, often myelinated axon extending away from the CNS.

• Role: Transmit motor instructions from the CNS to muscles or glands.

Q5. Explain that nerve impulses are electrical and travel across a neuron.

Electrochemical Nature of Nerve Impulse

A nerve impulse is a wave of electrochemical change passing rapidly along the neuron’s membrane. It operates through the selective movement of ions (Na⁺ and K⁺) across the axonal membrane.

1. Resting Membrane Potential (RMP)

• When a neuron is at rest (not conducting impulses), the inside of the cell membrane is negatively charged relative to the outside (approximately −70 mV).

• This potential is maintained partly by the sodium-potassium pump, which pumps 3 Na⁺ ions out of the cell and 2 K⁺ ions into the cell.

2. Action Potential (Depolarization)

• When a threshold stimulus is received, voltage-gated Na⁺ channels open, allowing sodium ions (Na⁺) to enter the axon rapidly.

• The interior becomes positively charged relative to the outside (approximately +30 mV).

3. Propagation of Wave

– This localized electrical change causes adjacent voltage-gated channels to open, propagating the action potential along the length of the axon.

4. Repolarization

– Immediately after the impulse passes, K⁺ channels open and potassium ions leave the cell, helping restore the negative internal resting potential.

Q6. What are neurotransmitters?

Answer:

Definition

Neurotransmitters are specialized chemical messengers produced by neurons and stored within synaptic vesicles at axon terminals.

Mechanism of Action

1. When an action potential arrives at an axon terminal, presynaptic vesicles release neurotransmitters into the synaptic cleft through exocytosis.

2. Neurotransmitters diffuse across the gap (approximately 20 nm) and bind to specific receptors on the postsynaptic membrane.

3. Binding opens ion channels or activates other cellular pathways, changing the postsynaptic membrane potential and either triggering or inhibiting a new signal.

Common Examples and Roles

• Acetylcholine (ACh): Stimulates skeletal muscle contractions.

• Adrenaline (Epinephrine): Increases heart rate and changes blood flow during stress responses.

• Dopamine: Involved in motor control, motivation, and reward pathways.

• Serotonin: Regulates mood, sleep, and appetite.

Q7. Explain reflex action with a diagram.

Description

A reflex action is an immediate, automatic, involuntary response to a stimulus. The neural pathway that controls this response is called a reflex arc.

Step-by-Step Mechanism

1. Receptor: Detects a stimulus, such as heat on the skin, and converts it into a nerve impulse.

2. Sensory Neuron: Transmits the impulse through the dorsal root into the spinal cord.

3. Interneuron: Processes the signal in the grey matter of the spinal cord and transfers the command to the motor neuron.

4. Motor Neuron: Carries the impulse out of the spinal cord through the ventral root.

5. Effector: The target muscle contracts, quickly removing the body part from danger.

Diagram: Draw and label the reflex arc, showing the receptor, sensory neuron, interneuron, motor neuron, and effector.

Q8. Identify the major endocrine hormones with their functions.

Answer:

Notes by Sir Dilawar
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