Nervous System is part of Biology. Below are notes on 10 sub-topics, followed by practice MCQs from State PSC and UPSC papers.

Central Nervous System (CNS): Brain – Structure, Divisions (Forebrain, Midbrain, Hindbrain), and Functions

  • Brain Overview:
    • Electroencephalogram (EEG): Monitors electrical activity of the brain.
    • Responsible for thinking, regulating heartbeat, and balancing the body.
    • Brain tissue itself lacks pain receptors.
    • Paralysis is often linked to disorders of the brain.
  • Brain Divisions & Functions:
    • 1. Forebrain (Prosencephalon): The largest part of the human brain.
      • Cerebrum: Controls voluntary actions, thinking, memory power, speech, intelligence, reasoning, and processing sensory information.
      • Thalamus: Acts as a major relay station for sensory and motor signals to the cerebral cortex.
      • Hypothalamus: Regulates body temperature, hunger, thirst, sleep, and various emotional responses. Connects the nervous system to the endocrine system via the pituitary gland.
      • Diencephalon: Part of the forebrain; the retina is an outgrowth of the diencephalon.
      • Limbic System: (e.g., Amygdala, Hippocampus) Considered the emotional brain; involved in emotions, motivation, and memory formation.
    • 2. Midbrain (Mesencephalon): Connects the forebrain to the hindbrain.
      • Involved in reflexes, eye movements, and processing auditory and visual information.
    • 3. Hindbrain (Rhombencephalon):
      • Cerebellum: Known as the "little brain." Primarily responsible for maintaining body posture, equilibrium, balance, and the precision of voluntary actions (e.g., walking in a straight line, riding a bicycle).
      • Pons: Relays signals between the cerebrum and cerebellum; also involved in sleep and respiration.
      • Medulla Oblongata: Controls involuntary vital functions such as heartbeat, breathing, blood pressure, digestion, swallowing, sneezing, and coughing.

Central Nervous System (CNS): Spinal Cord – Structure, Functions, and Reflex Arc

  • The spinal cord extends from the medulla oblongata (at the foramen magnum) down to the first or second lumbar vertebra (L1/L2).
  • It is protected by the vertebral column, meninges (dura mater, arachnoid mater, pia mater), and cerebrospinal fluid (CSF).
  • Internally, the spinal cord consists of Hshaped grey matter (containing neuron cell bodies, dendrites, unmyelinated axons, interneurons) surrounded by white matter (myelinated axons forming ascending and descending tracts).
  • Grey matter features dorsal horns (receiving sensory input) and ventral horns (containing motor neuron cell bodies).
  • Functions of the Spinal Cord:
    • Conduction Pathway: Transmits sensory (afferent/ascending tracts) impulses from the periphery to the brain and motor (efferent/descending tracts) impulses from the brain to effector organs.
    • Reflex Center: Serves as the primary center for most reflex actions, enabling rapid, involuntary responses without immediate conscious brain processing.
  • Reflex Arc: The neural pathway that mediates a reflex action; it is an involuntary, rapid, and stereotyped response to a stimulus.
  • Sequence of a Reflex Arc: Receptor: Detects the stimulus (e.g., 1. pain, stretch). Sensory Neuron (Afferent Neuron): 2. Transmits the sensory impulse from the receptor towards the Central Nervous System (spinal cord). Relay Neuron (Interneuron): Located 3. within the grey matter of the spinal cord, it synapses with the sensory neuron and transmits the impulse to the motor neuron. (May be absent in monosynaptic reflexes). Motor Neuron (Efferent Neuron): 4. Transmits the motor impulse from the spinal cord to the effector organ. Effector: A muscle or gland that car5. ries out the response (e.g., muscle contraction for withdrawal, gland secretion).
  • Reflex actions are crucial for quick responses, with the spinal cord bypassing the brain for the immediate execution of the action.

Common Disorders of the Nervous System (e.g., Alzheimer's, Parkinson's, Epilepsy)

  • Alzheimer's Disease: Neurodegenerative disorder affecting the brain.
  • Characterized by progressive memory loss, cognitive decline, and behavioral changes.
  • Pathology involves abnormal protein deposits: Extracellular amyloid plaques (betaamyloid protein) and intracellular neurofibrillary tangles (tau protein).
  • Exact cause is multifactorial (genetic, lifestyle, environmental factors); not primarily caused by interaction of Al, Cu, Ag, or Sn with internal organs.
  • Parkinson's Disease: Chronic, progressive neurodegenerative disorder affecting the brain.
  • Primarily involves the loss of dopamine-producing neurons in the substantia nigra.
  • Characterized by motor symptoms: tremors, rigidity, bradykinesia (slowness of movement), and postural instability.
  • Pathology includes the presence of Lewy bodies, which are abnormal protein aggregates (alpha-synuclein).
  • Epilepsy: Neurological disorder characterized by recurrent, unprovoked seizures.
  • Seizures result from abnormal, excessive, or synchronized electrical activity in the brain.
  • Causes can be genetic, structural (e.g., brain injury, tumor, stroke), infectious, metabolic, immune, or unknown (idiopathic).

Generation and Conduction of Nerve Impulse (Action Potential)

  • Nerve impulse (Action Potential) is a rapid, transient change in the electrical potential across a neuron's membrane, enabling signal transmission.
  • Resting Membrane Potential (RMP):
    • Neuron at rest is polarized (-70mV inside, + outside).
    • Maintained by the Na+/K+ pump (actively transports 3 Na+ out, 2 K+ in) and higher permeability of the membrane to K+ ions than Na+ ions at rest.
  • Threshold Stimulus: Minimum stimulus required to open voltage-gated Na+ channels and initiate an Action Potential.
  • Depolarization (Rising Phase):
    • Voltage-gated Sodium (Na+) channels open rapidly.
    • Sodium (Na+) ions rush into the cell (influx), driven by concentration and electrical gradients.
    • Membrane potential rapidly becomes positive (up to +30mV to +40mV).
    • Follows an "All-or-None" principle: an AP either fires completely or not at all.
  • Repolarization (Falling Phase):
    • Voltage-gated Sodium (Na+) channels inactivate.
    • Voltage-gated Potassium (K+) channels open slowly.
    • Potassium (K+) ions rush out of the cell (efflux).
    • Membrane potential returns to a negative value.
  • Hyperpolarization (Undershoot): Brief period where K+ channels close slowly, causing the membrane potential to become slightly more negative than RMP before returning to resting state.
  • Refractory Period: Time during which a new action potential cannot be generated (absolute refractory) or requires a stronger than usual stimulus (relative refractory). Ensures unidirectional impulse propagation.
  • Conduction of Nerve Impulse:
    • Unmyelinated axons: Continuous conduction, slower.
    • Myelinated axons: Saltatory conduction (impulse jumps from Node of Ranvier to Node of Ranvier), much faster due to myelin sheath insulation.
  • Key elements for transferring electrical signals: Sodium (Na+) and Potassium (K+) ions are essential for the generation and conduction of nerve impulses in the human body by moving across the neuronal membrane through specific channels.

Neuron: Structure, Types, and Function

  • Neurons (nerve cells) are the structural and functional units of the nervous system, specialized for receiving and conducting electrochemical impulses.
  • A neuron consists of three main parts:
    • Cell Body (Soma/Perikaryon): Contains nucleus and organelles; site of protein synthesis.
    • Dendrites: Short, branched processes receiving incoming signals.
    • Axon: Long, single process transmitting impulses away from the cell body.
  • Axon Structure:
    • Myelin Sheath: Insulating lipid layer around axons, formed by glial cells.
    • Schwann cells: Form myelin in the Peripheral Nervous System (PNS).
    • Oligodendrocytes: Form myelin in the Central Nervous System (CNS).
    • Nodes of Ranvier: Gaps in the myelin sheath, facilitating faster impulse conduction (saltatory conduction).
    • Axon Terminal: End of axon, releases neurotransmitters at synapses.
  • A Nerve is a bundle of many axons (nerve fibers) located outside the CNS.
  • Components of a nerve include axons, their myelin sheaths (formed by Schwann cells in PNS), and surrounding connective tissues (e.g., endoneurium, perineurium, epineurium).
  • Smooth muscles are effector tissues and are not a part of the nerve structure itself.

Organization of the Nervous System (CNS, PNS)

  • Nervous System is broadly organized into the Central Nervous System (CNS) and the Peripheral Nervous System (PNS).
  • CNS (Central Nervous System): Consists of the brain and spinal cord.
  • PNS (Peripheral Nervous System): Comprises all the nerves extending from the CNS to the rest of the body.
  • CNS Function: Serves as the primary integration and control center of the nervous system. It processes sensory information (input nerves) and initiates motor commands (output nerves).
  • Integration Point: Input (afferent) and output (efferent) nerves meet and interact within the Central Nervous System (CNS) for processing and response generation.

Peripheral Nervous System (PNS): Somatic Nervous System (Cranial and Spinal Nerves)

  • Peripheral Nervous System (PNS): Connects Central Nervous System (CNS) to rest of the body.
  • Somatic Nervous System (SNS): A subdivision of PNS, responsible for voluntary control of skeletal muscles and transmitting sensory information. Comprises cranial and spinal nerves.
  • Cranial Nerves: There are 12 pairs of cranial nerves in humans and mammals. They originate from the brain/brainstem and innervate primarily the head and neck, with some extending to the trunk. Can be sensory, motor, or mixed.
  • Spinal Nerves: There are 31 pairs of spinal nerves in humans. They emerge from the spinal cord and innervate the trunk and limbs. All spinal nerves are mixed nerves (contain both sensory and motor fibers).
  • The 31 pairs of spinal nerves are categorized as: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal pair.

Reflex Actions: Components and Types

  • Reflex Action: Involuntary, rapid, automatic response to a stimulus.
  • Purpose: Body protection, homeostasis.
  • Control: Primarily spinal cord (spinal reflexes); some brainstem (cranial reflexes). Higher brain centers not involved in initiation.
  • Reflex Arc: Neural pathway of a reflex action.
  • Components of Reflex Arc (sequential order): Receptor: Detects stimulus, converts to 1. impulse. Sensory Neuron (Afferent): Transmits 2. impulse from receptor to CNS. Integration Center (CNS): Spinal cord 3. (often via interneuron) processes impulse. Motor Neuron (Efferent): Transmits 4. impulse from CNS to effector. Effector: Muscle or gland performs the 5. response.
  • Examples of Reflex Actions: Salivation, withdrawal reflex (e.g., hand from hot object), knee-jerk, blinking, coughing.
  • Actions NOT considered simple reflex actions: Voluntary movement of hand. Breathing and heart-pumping are involuntary but complex physiological regulations, not simple reflex arcs.

Sensory Receptors: Classification and Overview

  • The minimum distance of clear vision (near point) for a normal healthy human eye is 25 cm.
  • The image formed on the retina by the eye lens is real, inverted, and diminished (smaller than the object).
  • The retina contains two types of photoreceptor cells: rods and cones.
  • Rods are responsible for scotopic (dim light) vision and peripheral vision, containing the visual pigment Rhodopsin.
  • Cones are responsible for photopic (bright light) vision, color vision, and central vision.
  • 'Adaptation' of eyes in the dark, known as dark adaptation, is primarily due to the repletion (regeneration) of Rhodopsin pigment in the rod cells, increasing their sensitivity to dim light.

Synapse and Synaptic Transmission

  • Synapse: Microscopic gap between two neurons.
  • Chemicals, specifically neurotransmitters, cross the synapse.
  • Neurotransmitters are released from the nerve endings (axon terminals/synaptic knobs) of the presynaptic neuron.

15. Endocrine System

Practice MCQs: Nervous System

Central Nervous System (CNS): Brain – Structure, Divisions (Forebrain, Midbrain, Hindbrain), and Functions

  1. Electroencephalogram (EEG) is used in monitoring

    Asked in: BPSC Prelims Exam 64th

    1. heart
    2. liver
    3. pancreas
    4. brain
    Show answer

    Answer: D. brain

  2. On an average, Urea excreted by a healthy adult human per day is (a) 2 - 2.5 gm (b) 10 - 15 mg (c) 150 - 200 mg (d) 25 - 30 gm

    Asked in: HOMOEOPATHIC MEDICAL OFFICER 2 2023

    1. 2 - 2.5 gm
    2. 10 - 15 mg
    3. 150 - 200 mg
    4. 25 - 30 gm
    Show answer

    Answer: D. 25 - 30 gm

    This question is about human physiology and the excretion of nitrogenous waste products. Urea is the primary nitrogenous waste product excreted by humans.

  3. The nitrogenous waste-uric acid is excreted out by and Lizards both

    Asked in: Lower Subordinate Service Examination 2021

    1. Human
    2. Birds
    3. Lizards
    4. Birds and Lizards both
    Show answer

    Answer: D. Birds and Lizards both

    This question tests knowledge of comparative animal physiology and excretion mechanisms, specifically focusing on the form of nitrogenous waste excreted by different animals. Electroencephalogram (EEG) is a neurophysiological measurement technique that records the electrical activity of the brain, particularly from the cerebral cortex.

  4. Body temperature is regulated by

    Asked in: BPSC Prelims Exam 64th

    1. thalamus
    2. hypothalamus
    3. cerebellum
    4. medulla
    Show answer

    Answer: B. hypothalamus

    BPSC Prelims Exam-65th The hypothalamus, located in the brain, acts as the body's thermostat, regulating body temperature through mechanisms like sweating, shivering, and vasodilation/vasoconstriction.

  5. In a human brain memory power is found in

    Asked in: CGPSC Prelims Exam 2013

    1. Medulla oblongata
    2. Cerebrum
    3. Brain cavity
    4. Cerebellum
    Show answer

    Answer: B. Cerebrum

    The Cerebrum is the largest part of the brain and is responsible for higher-level functions including memory, learning, thinking, and voluntary movements.

  6. Which part of the brain maintains posture and equilibrium of the body ?

    Asked in: HPPSC HPAS Prelims 2018

    1. Fore-brain
    2. Mid-brain
    3. Hind-brain
    4. Spinal cord
    Show answer

    Answer: C. Hind-brain

    - The hindbrain consists of the pons, medulla oblongata, and cerebellum. - The cerebellum, located at the back of the brain below the cerebrum, is a major part of the hindbrain responsible for coordinating voluntary movements such as posture, balance, coordination, and speech, resulting in smooth and balanced muscular activity. It constantly receives information from the sensory systems, the spinal cord, and other parts of the brain and uses this to regulate posture, coordination, and balance. - The forebrain (cerebrum and diencephalon) is primarily involved in higher cognitive functions, voluntary movement initiation, and sensory processing. - The midbrain is involved in relaying sensory and motor information and certain reflexes. - The spinal cord relays signals and is involved in simple reflexes, but the primary control center for overall posture and equilibrium maintenance is in the brain, especially the cerebellum.

  7. मǔस्तष्क का कौन सा भाग शरीर के आसन और संतुलन को बनाए रखता है ?

    Asked in: HPPSC HPAS Prelims 2018

    1. अग्र-मlÖतष्क
    2. मध्य-मlÖतष्क
    3. पश्च-मlÖतष्क
    4. रीढ़ की हल्डि् ल्डिी
    Show answer

    Answer: C. पश्च-मlÖतष्क

    पश्च-मlÖतष्क में पोंस (Pons), मेल्डिु लिा ऑबलिोंगटा (Medulla Oblongata) और अनुमlÖतष्क (Cerebellum) शाlमलि होते हैं। अनुमlÖतष्क ही विह प्रमुख संरचना है जो Öविैlच्छक गlतयों के समन्विय, मुद्रा, संतुलिन और समन्विय को lनयंlत्रत करती है, lजससे शरीर की गlत सुचारू और संतुlलित होती है।

  8. EEG is used to measure the functioning of :

    Asked in: OPSC CS Prelims 2019

    1. Heart
    2. Brain
    3. Skeletal muscle
    4. All of these
    Show answer

    Answer: B. Brain

    EEG stands for Electroencephalogram. It is a test that measures electrical activity in the brain using small metal discs (electrodes) attached to the scalp. The recording of these electrical signals is used to diagnose and monitor neurological conditions like epilepsy, sleep disorders, and brain damage.

  9. The retina is outgrowth of the

    Asked in: RPSC RAS Prelims 2013

    1. mesencephalon
    2. diencephalon
    3. telencephalon
    4. pons varoli
    Show answer

    Answer: B. diencephalon

    The retina is an embryological outgrowth of the diencephalon, specifically forming from the optic cups which evaginate from the lateral aspects of the developing forebrain (proencephalon), which later differentiates into the telencephalon and diencephalon.

  10. The temperature in human body is controlled by A) Hypothalamus B) Skin C) Cerebellum D) Muscles

    Asked in: TSPSC Group 1 Prelims 2023

    1. Hypothalamus
    2. Skin
    3. Cerebellum
    4. Muscles
    Show answer

    Answer: A. Hypothalamus

    The hypothalamus, located in the brain, acts as the body's thermostat. It monitors body temperature and activates mechanisms (like sweating to cool down or shivering to generate heat) to maintain it within a narrow, healthy range (thermoregulation).

Central Nervous System (CNS): Spinal Cord – Structure, Functions, and Reflex Arc

  1. Reflex arcs are evolved in animals for quick and efficient responses. Which one of the following sequences correctly represents a reflex arc?

    Asked in: UPSC CDS 1 2023

    1. Receptor—Sensory neuron—Relay neuron in spinal cord—Brain—Motor neuron—Effector
    2. Receptor—Sensory neuron—Brain—Relay neuron in spinal cord—Motor neuron—Effector
    3. Receptor—Motor neuron—Relay neuron in spinal cord—Sensory neuron—Effector
    4. Receptor—Motor neuron—Brain—Sensory neuron—Effector
    Show answer

    Answer: A. Receptor—Sensory neuron—Relay neuron in spinal cord—Brain—Motor neuron—Effector

    The fundamental components of a reflex arc are Receptor, Sensory neuron, Integration center (often involving interneurons in the spinal cord), Motor neuron, and Effector. The speed of reflex action is due to the short pathway, often bypassing higher brain centers for the rapid motor command.

  2. Reflex action is the function of:

    Asked in: APPSC Draughtman 2008

    1. Cerebellum
    2. Spinal Card
    3. Medulla
    4. Nurves
    Show answer

    Answer: B. Spinal Card

    The spinal cord is the main center for processing many types of reflex actions, allowing for quick, involuntary responses without direct involvement of the higher brain centers like the cerebrum.

Common Disorders of the Nervous System (e.g., Alzheimer's, Parkinson's, Epilepsy)

  1. A person is unable to read a newspaper without his glasses. He is most probably suffering from

    Asked in: UPSC NDA 2 2016

    1. myopia
    2. presbyopia
    3. astigmatism
    4. hypermetropia
    Show answer

    Answer: D. hypermetropia

    Hypermetropia is a refractive error where the eye focuses images behind the retina, making near objects appear blurry. Presbyopia is an age-related loss of the eye's ability to focus on near objects. Both conditions require convex lenses (reading glasses) to correct near vision.

  2. Which organ of human body does the disease Alzheimer affect

    Asked in: RPSC RAS Prelims 2003

    1. The ear
    2. Brain
    3. Eye
    4. Stomach
    Show answer

    Answer: B. Brain

    The disease typically begins in the hippocampus, a part of the brain crucial for memory, and progressively damages other areas of the brain, impairing thinking, memory, and behaviour.

  3. Alzheimer's desease is caused by

    Asked in: WBCS Main Paper 4 2022

    1. interaction of Al with internal organs of the body.
    2. interaction of Cu with internal organs of the body.
    3. interaction of Ag with internal organs of the body.
    4. interaction of Sn with internal organs of the body.
    Show answer

    Answer: A. interaction of Al with internal organs of the body.

    While the options present specific metal interactions, the association with Aluminum was one of the earlier, though now largely disputed, hypotheses regarding environmental factors in Alzheimer's disease. Current scientific consensus primarily points to the accumulation of amyloid plaques and tau tangles in the brain.

  4. Out of the following which is not the characteristics of 'concrete-operation stage" given by Jean Piaget ?

    Asked in: Sr. Teacher Gr II (Sanskrit Edu.) Exam 2018 1 2018

    1. Reversibility of thought
    2. Conservation
    3. Use of serial ordering and part-whole concepts
    4. Emergence of symbolic function
    Show answer

    Answer: D. Emergence of symbolic function

    The emergence of symbolic function is a characteristic of Piaget's preoperational stage, not the concrete-operational stage. Characteristics of the concrete-operational stage include reversibility, serial ordering, and part-whole concepts.

  5. To measure intelligence of children, who prepared first intelligence scale ?

    Asked in: Sr. Teacher Gr II (Sanskrit Edu.) Exam 2018 1 2018

    1. J.M. Cattell
    2. Alfred Binet
    3. Stenberrg
    4. Weshtler
    Show answer

    Answer: B. Alfred Binet

    Alfred Binet developed the first intelligence scale for children.

  6. Out of the following which is not the 'content dimension' as given by Guilford 'Structure of Intellect' model ?

    Asked in: Sr. Teacher Gr II (Sanskrit Edu.) Exam 2018 1 2018

    1. (1) Figural
    2. (2) Cognition
    3. (3) Symbolic
    4. (4) Verbal
    Show answer

    Answer: B. (2) Cognition

    In Guilford's Structure of Intellect model, Cognition is classified as an 'operation' dimension, while Figural, Symbolic, and Semantic (Verbal often falls under Symbolic or Semantic) are 'content' dimensions.

Generation and Conduction of Nerve Impulse (Action Potential)

  1. Which one of the following elements is needed in the human body to transfer electrical signals by nerve cells ?

    Asked in: UPSC NDA 1 2018

    1. Lithium
    2. Sodium
    3. Rubidium
    4. Caesium
    Show answer

    Answer: B. Sodium

    Nerve impulses, or action potentials, are electrical signals that travel along nerve cells. This process involves the rapid movement of ions, particularly sodium (Na⁺) and potassium (K⁺), across the nerve cell membrane through specific ion channels. The differential concentrations of these ions across the membrane create an electrochemical gradient, which, when disturbed, generates the electrical signal. Sodium ions play a critical role in the depolarization phase of the action potential.

  2. The transfer of electrical signals by nerve cells in human body is enabled by

    Asked in: UPSC NDA 2 2022

    1. sodium
    2. potassium
    3. iron
    4. sodium and potassium
    Show answer

    Answer: D. sodium and potassium

    Nerve impulses (action potentials) are electrical signals that travel along the axon of a neuron. These signals are generated by the movement of ions, primarily sodium (Na+) and potassium (K+), across the cell membrane. Voltage-gated ion channels specific for Na+ and K+ open and close in sequence, causing rapid changes in the membrane potential.

Neuron: Structure, Types, and Function

  1. The cells associated with receiving and conducting impulses are:

    Asked in: UPSC Geoscientist 2021

    1. Neuron
    2. Plasma cells
    3. Adipocytes
    4. Macrophages
    Show answer

    Answer: A. Neuron

    Neurons are the specialized cells responsible for communication via impulses in the nervous system.

  2. Which one of the following is not a part of nerves ?

    Asked in: UPSC NDA 1 2015

    1. Axons
    2. Connective tissues
    3. Schwann cells
    4. Smooth muscles
    Show answer

    Answer: D. Smooth muscles

    Axons are the main projections of nerve cells that transmit signals. Schwann cells (a type of glial cell) form the myelin sheath around axons in the peripheral nervous system. Connective tissues (epineurium, perineurium, endoneurium) form the outer layers and internal support structure of nerves. Smooth muscles are a type of muscle tissue found in organs and blood vessels; they are not structural components of a nerve. While nerves innervate smooth muscles (control their function), the muscle tissue itself is not part of the nerve structure.

  3. The father of Intelligence test construction is

    Asked in: Sr. Teacher Gr.II Comp. Exam 2016 1 2016

    1. Francis Galton
    2. Alfred Binet
    3. Lavator
    4. William Stern
    Show answer

    Answer: B. Alfred Binet

    Alfred Binet's pioneering work laid the foundation for the field of psychometrics and the development of standardized intelligence tests.

Organization of the Nervous System (CNS, PNS)

  1. Input and output nerves meet at

    Asked in: BPSC Prelims Exam 69th

    1. liver
    2. central nervous system
    3. heart
    4. None of the above
    Show answer

    Answer: B. central nervous system

    - Input nerves (sensory) carry signals towards the CNS. - Output nerves (motor) carry signals away from the CNS. - The CNS (brain and spinal cord) is where these signals are processed and meet functionally.

  2. Ques #:96 Kohler's experiment on chimpanzee demonstrated 1) Learning through insight 2) Learning through S-R association 3) Learning through observation 4) Learning through imitation

    Asked in: Sr. Teacher GR II 2011

    1. 1 and 2
    2. 1, 2 and 3
    3. 1, 2, 3 and 4
    4. 1 and 4
    Show answer

    Answer: A. 1 and 2

    Kohler's experiments are a foundational study in Gestalt psychology, emphasizing the concept of "insight" in learning – a sudden understanding of a problem's solution. This contrasts with behaviorist theories that focus on S-R associations.

  3. Which group is not concerned with the solar system A) Planetary system B) Asteroids C) Nervous system D) Comets

    Asked in: ASSISTANT AUDIT OFFICER 2017 18 2017

    1. Planetary system
    2. Asteroids
    3. Nervous system
    4. Comets
    Show answer

    Answer: C. Nervous system

    The nervous system is a biological system and is unrelated to the solar system.

Peripheral Nervous System (PNS): Somatic Nervous System (Cranial and Spinal Nerves)

  1. There are how many pairs of cranial nerves in human ?

    Asked in: MPPSC CS Prelims 2020

    1. 8
    2. 12
    3. 25
    4. 31
    Show answer

    Answer: B. 12

    The 12 pairs of cranial nerves are designated by Roman numerals (I-XII) and have specific names and functions (e.g., Olfactory, Optic, Vagus).

  2. Cranial nerve in mammals are

    Asked in: WBPSC CS Prelims 2015

    1. 10 pairs
    2. 10
    3. 12 pairs
    4. 12
    Show answer

    Answer: C. 12 pairs

    The twelve pairs of cranial nerves are Olfactory (I), Optic (II), Oculomotor (III), Trochlear (IV), Trigeminal (V), Abducens (VI), Facial (VII), Vestibulocochlear (VIII), Glossopharyngeal (IX), Vagus (X), Accessory (XI), and Hypoglossal (XII).

  3. The number of spinal nerves in human body are

    Asked in: WBPSC CS Prelims 2019

    1. 12 pairs
    2. 31 pairs
    3. 31
    4. 12
    Show answer

    Answer: B. 31 pairs

    Humans typically have 31 pairs of spinal nerves emerging from the spinal cord.

Reflex Actions: Components and Types

  1. Which of the following is not a reflex action ?

    Asked in: HPPSC HPAS Prelims 2018

    1. Breathing
    2. Heart-pumping
    3. Salivation
    4. Movement of hand
    Show answer

    Answer: D. Movement of hand

    - Reflex actions are involuntary, rapid responses to stimuli mediated by the nervous system, often without conscious thought. Examples include withdrawal from pain or heat, blinking, salivation, knee- jerk reflex. - Salivation is a classic reflex action triggered by stimuli like the sight, smell, or taste of food. - Heart-pumping and breathing are vital physiological processes that are primarily involuntary and regulated by the autonomic nervous system through complex reflexive mechanisms responding to internal cues (like blood pressure or CO2 levels). - "Movement of hand" can refer to a voluntary action (like picking up an object) or an involuntary reflex action (like withdrawing the hand from a hot surface). Since voluntary movement of the hand is possible and common, it is not exclusively a reflex action. Compared to the other options which describe primarily involuntary/reflexively controlled physiological processes, voluntary "Movement of hand" is clearly not a reflex action.

  2. Ǔनम्नͧलͨखत में से कौन एक प्रǓतवतर्त ͩक्रया (reflex action) नहीं है ?

    Asked in: HPPSC HPAS Prelims 2018

    1. श्वास
    2. हाटर्त पंप
    3. लिार
    4. हाथ का lहलिना
    Show answer

    Answer: D. हाथ का lहलिना

    प्रlतवितर्त lक्रयाएँ (Reflex actions) मlÖतष्क के सचेत lनयंत्रण के lबना होने विालिी अनैlच्छक, तीव्र प्रlतlक्रयाएँ होती हैं, जो अक्सर रीढ़ की हल्डि् ल्डिी द्वारा lनयंlत्रत होती हैं। श्वास, हृदय का पंप करना और लिार आना शरीर के अनैlच्छक कायर्त हैं जो अlधकांशतः प्रlतवितर्त चाप (reflex arcs) और Öविायत्ति तंlत्रका तंत्र द्वारा lनयंlत्रत होते हैं। हाथ का lहलिना आमतौर पर मlÖतष्क के सेरेब्रलि कॉटर्मेक्स से शुरू होने विालिी एक Öविैlच्छक lक्रया होती है।

  3. Which one of the following depicts the correct circuit of a reflex arc?

    Asked in: UPSC NDA 2 2018

    1. Effector—sensory neuron—spinal cord— motor neuron—receptor
    2. Receptor—sensory neuron—spinal cord— motor neuron—effector
    3. Receptor—sensory neuron—brain—motor neuron—effector
    4. Sensory neuron—receptor—brain—effector— motor neuron
    Show answer

    Answer: B. Receptor—sensory neuron—spinal cord— motor neuron—effector

    - A reflex arc is the neural pathway that mediates a reflex action. - The receptor detects the stimulus. - The sensory (afferent) neuron transmits the impulse from the receptor towards the central nervous system (CNS). - The integration center (in simple reflexes, often the spinal cord) processes the signal. - The motor (efferent) neuron transmits the impulse from the CNS to the effector. - The effector (muscle or gland) carries out the response.

  4. Which of the following is the correct sequence of the components in a reflex arc ? - (1) Muscle $\rightarrow$ Motor neuron $\rightarrow$ Receptor $\rightarrow$ Sensory neuron $ \rightarrow$ Spinal cord - (2) Muscle $\rightarrow$ Sensory neuron $\rightarrow$ Spinal cord $\rightarrow$ Motor neuron $\rightarrow$ Receptor - (3) Receptor $\rightarrow$ Sensory neuron $\rightarrow$ Spinal cord $\rightarrow$ Motor neuron $\rightarrow$ Muscle - (4) Receptor $\rightarrow$ Motor neuron $\rightarrow$ Spinal cord $\rightarrow$ Sensory neuron $\rightarrow$ Muscle

    Asked in: School Lecturer (School Edu.) 2018 2 2018

    1. Muscle $\rightarrow$ Motor neuron $\rightar‐ row$ Receptor $\rightarrow$ Sensory neuron $ \rightarrow$ Spinal cord
    2. Muscle $\rightarrow$ Sensory neuron $\righ‐ tarrow$ Spinal cord $\rightarrow$ Motor neuron $\rightarrow$ Receptor
    3. Receptor $\rightarrow$ Sensory neuron $\righ‐ tarrow$ Spinal cord $\rightarrow$ Motor neuron $\rightarrow$ Muscle
    4. Receptor $\rightarrow$ Motor neuron $\righ‐ tarrow$ Spinal cord $\rightarrow$ Sensory neuron $\rightarrow$ Muscle
    Show answer

    Answer: C. Receptor $\rightarrow$ Sensory neuron $\righ‐ tarrow$ Spinal cord $\rightarrow$ Motor neuron $\rightarrow$ Muscle

    The reflex arc allows for rapid, involuntary responses to stimuli, bypassing conscious processing in the brain for quicker reactions.

Sensory Receptors: Classification and Overview

  1. The minimum distance of clear vision for a normal healthy eye of human being is supposed to be

    Asked in: UPPCS Prelims 2016

    1. 50cm
    2. 10cm
    3. 15 cm
    4. 25 cm
    Show answer

    Answer: D. 25 cm

    For a normal healthy human eye, the minimum distance at which objects can be seen clearly without strain is called the near point of distinct vision. This distance is conventionally taken to be 25 centimeters.

  2. Image formed on retina is :

    Asked in: UPPCS Prelims 1995

    1. Equal to object but invented
    2. Smaller than object but straight
    3. Smaller than object but inverted
    4. EquaL to object but straight
    Show answer

    Answer: C. Smaller than object but inverted

    A converging lens forms a real and inverted image when the object is placed outside its focal length, which is the case for vision of distant or nearby objects onto the retina. The image formed on the retina is also reduced in size compared to the actual object.

  3. 'Adaptation' of eyes in dark due to

    Asked in: WBCS Main Paper 4 2019

    1. depletion of vision pigment in rods
    2. depletion of vision pigment in cones
    3. repletion of vision pigment in rods
    4. repletion of vision pigment in cones
    Show answer

    Answer: C. repletion of vision pigment in rods

    Rods are photoreceptor cells in the retina responsible for vision in low light levels (scotopic vision). Rhodopsin is the light-sensitive pigment in rods. In bright light, rhodopsin is bleached (broken down), making rods less sensitive. Moving to darkness allows rhodopsin to regenerate, increasing the

Synapse and Synaptic Transmission

  1. In human beings, certain chemicals which cross the synapse between nerve cells are released from

    Asked in: UPSC CAPF 2020

    1. cell body of nerve cell
    2. nucleus of nerve cell
    3. nerve endings of nerve cell
    4. axon of nerve cell
    Show answer

    Answer: C. nerve endings of nerve cell

    The synapse is the junction between two nerve cells. When an action potential reaches the axon terminal, it triggers the release of neurotransmitters stored in vesicles into the synaptic cleft, where they bind to receptors on the postsynaptic neuron.

  2. The gap between two neurons is called a

    Asked in: WBCS Main Paper 4 2021 · Combined (Group C) Exam 2023

    1. dendrite
    2. synapse
    3. axon
    4. impulse
    Show answer

    Answer: B. synapse

    Neurons, the nerve cells, communicate with each other by transmitting signals. This transmission occurs across a specialized junction between two neurons called a synapse. The synapse includes the presynaptic terminal of one neuron, the synaptic cleft (the gap), and the postsynaptic membrane of the next neuron.