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Questions and Answers

What are the major functions of the nervous system?

  • Support physical movement only
  • Control digestion and hormone production
  • Detect, analyze, and transmit information (correct)
  • Generate thoughts and emotions exclusively

    • Which component is NOT part of the central nervous system?

  • Spinal cord
  • Spinal nerves
  • Brain
  • Cranial nerves (correct)

    • What role do sensory receptors play in the sensory system?

  • Initiate muscle contractions directly
  • Release hormones into the bloodstream
  • Convert stimuli into nerve impulses (correct)
  • Store memories for future use

    • Which part of the nervous system is responsible for initiating motor activities?

    <p>Motor nervous system</p> Signup and view all the answers

    What are afferent nerve fibers responsible for?

    <p>Carrying impulses to the central nervous system</p> Signup and view all the answers

    External receptors are primarily located on which part of the body?

    <p>Body surface, mainly in the skin</p> Signup and view all the answers

    What does the intellectual nervous system provide the basis for?

    <p>Consciousness, memory, and behavior</p> Signup and view all the answers

    Which statement about sensory receptors is INCORRECT?

    <p>They function solely to relay information to the motor nervous system.</p> Signup and view all the answers

    What happens to the retinal receptors when heavy mechanical stimuli are applied to the eye?

    <p>They can produce flashes of light.</p> Signup and view all the answers

    What is the definition of excitability in receptors?

    <p>Ability to respond to their adequate stimuli.</p> Signup and view all the answers

    What type of potential changes occur in the receptors upon adequate stimulation?

    <p>Receptor Potential occurs, usually as depolarizations.</p> Signup and view all the answers

    Which type of receptors show hyperpolarization upon adequate stimulation?

    <p>Visual receptors (Rods &amp; Cones).</p> Signup and view all the answers

    Why are Pacinian corpuscles preferred for studying receptor potential?

    <p>They are easily stimulated and large in size.</p> Signup and view all the answers

    What changes occur in the nerve terminal of Pacinian corpuscles when pressure is applied?

    <p>Deformation of the nerve terminal opens Na+ channels.</p> Signup and view all the answers

    What defines phasic receptors?

    <p>They only respond to the beginning and end of stimulation.</p> Signup and view all the answers

    What is the maximal amplitude of receptor potential that can be achieved in these receptors?

    <p>100 mv.</p> Signup and view all the answers

    What is found inside the capsule of a Pacinian corpuscle?

    <p>Unmyelinated sensory nerve endings.</p> Signup and view all the answers

    What does modality discrimination refer to?

    <p>The ability to determine the type of sensation felt.</p> Signup and view all the answers

    According to Muller's law, what happens when a specific receptor is stimulated?

    <p>It produces a specific type of sensation aligned with its adequate stimulus.</p> Signup and view all the answers

    What principle extends Muller's law to explain the specific pathways for each sensation?

    <p>Labelled line principle</p> Signup and view all the answers

    Why do tonic receptors send continuous impulses to the CNS?

    <p>To inform about harmful stimuli.</p> Signup and view all the answers

    How does the central mechanism of modality discrimination function?

    <p>It depends on specific anatomical connections for sensations.</p> Signup and view all the answers

    What primarily distinguishes the function of tonic receptors from phasic receptors?

    <p>Tonic receptors maintain a constant discharge rate.</p> Signup and view all the answers

    What role does labelled line principle play in sensory processing?

    <p>It ensures each sensory modality travels through specific pathways.</p> Signup and view all the answers

    Which type of receptor is specifically stimulated by mechanical forms of energy?

    <p>Mechanoreceptors</p> Signup and view all the answers

    What unique characteristic do receptors exhibit according to Muller's law?

    <p>Each type is highly sensitive to only one type of stimulus.</p> Signup and view all the answers

    Which of the following receptors responds to temperature changes?

    <p>Thermal receptors</p> Signup and view all the answers

    Which type of receptor is responsible for detecting light waves?

    <p>Photorceptors</p> Signup and view all the answers

    What type of receptors are baroreceptors, and where are they found?

    <p>Mechanoreceptors in the aortic arch and carotid sinus</p> Signup and view all the answers

    What do nociceptors specifically respond to?

    <p>Injurious or painful stimuli</p> Signup and view all the answers

    Which type of receptor is involved in detecting changes in blood pressure?

    <p>Baroreceptors</p> Signup and view all the answers

    Which receptors are triggered by chemical stimuli in the carotid bodies?

    <p>Chemoreceptors</p> Signup and view all the answers

    What is the primary factor in intensity discrimination related to peripheral mechanisms?

    <p>Rate of impulse discharge from receptors</p> Signup and view all the answers

    How does the central mechanism affect intensity discrimination?

    <p>By increasing the number of afferents reaching the CNS</p> Signup and view all the answers

    What principle explains the sensation being referred to its original site in the body?

    <p>The law of projection</p> Signup and view all the answers

    What phenomenon occurs in amputees where they feel pain in a non-existing limb?

    <p>Phantom limb phenomenon</p> Signup and view all the answers

    What type of receptors are pain receptors classified as?

    <p>Free nerve endings</p> Signup and view all the answers

    Which type of pain receptor responds only to mechanical trauma?

    <p>Mechanical pain receptors</p> Signup and view all the answers

    What type of pain receptor responds to tissue damage from chemical agents?

    <p>Chemical pain receptors</p> Signup and view all the answers

    At what temperature do thermal pain receptors become activated?

    <p>Above 45°C</p> Signup and view all the answers

    Study Notes

    Nervous System Overview

    • The nervous system is responsible for detecting, analyzing, and transmitting information.
    • It's divided into the central nervous system (CNS) and the peripheral nervous system.
    • The CNS includes the brain and spinal cord.
    • The peripheral nervous system includes 12 pairs of cranial nerves and 31 pairs of spinal nerves.

    Sensory System Overview

    • The sensory nervous system detects internal and external changes and informs the CNS.
    • It consists of sensory receptors, afferent nerve fibers, and sensory centers in the brain and spinal cord.

    Sensory Receptors

    • Sensory receptors are specialized structures located at the peripheral terminations of afferent nerves.
    • They detect stimuli and convert them into nerve impulses.
    • Receptors are classified based on location (external or internal) and the nature of the stimulus they detect.

    External Receptors

    • Located on the body surface, primarily in the skin.
    • Respond to stimuli from the external environment.

    Internal Receptors

    • Found in deeper structures and viscera.
    • Respond to changes within the body.

    Receptor Classification by Stimuli

    • Mechanoreceptors: Respond to mechanical stimuli (touch, pressure, vibration, sound, stretch).
    • Chemoreceptors: Respond to chemical stimuli (taste, smell, blood gases).
    • Thermoreceptors: Respond to changes in temperature (cold and warm).
    • Pain receptors (nociceptors): Respond to injurious stimuli.
      • Can be further classified into:
        • Mechanical: Respond to mechanical trauma.
        • Chemical: Respond to chemical agents.
        • Thermal: Respond to extreme temperatures.
    • Photoreceptors: Respond to electromagnetic waves of light.

    Receptor Properties

    • Specificity: Receptors are highly sensitive to a specific type of stimuli called the adequate stimulus.
      • This principle is known as Muller's law.
    • Excitability: Receptors respond to their adequate stimuli.
      • Usually, this response involves depolarization through increased membrane permeability to sodium ions (Na+).
      • Visual receptors (rods and cones) show hyperpolarization upon stimulation.
      • The potential changes that occur in receptors during stimulation are called receptor potentials.
    • Rate of Discharge: The frequency of nerve impulses generated by a receptor is proportional to the intensity of the stimulus.
    • Adaptation: Receptors can become less responsive to a constant stimulus over time.

    Intensity Discrimination

    • The CNS determines stimulus intensity based on:
      • Rate of impulse discharge: A higher rate indicates a stronger stimulus.
      • Number of receptors activated: More receptors activated means a stronger stimulus.

    Locality Discrimination

    • The CNS identifies the location of a stimulus through:
      • Somatotopic map: Each area of the body is represented in a specific area of the cerebral cortex with dedicated neural pathways.
      • Law of projection: Although the sensory impulse arrives at the cerebral cortex, the sensation is perceived as originating from the site of stimulation in the body.
    • Phantom limb phenomenon: A severe pain is felt in a missing limb.
    • Phantom sensations: May occur after removal of other body parts (e.g., breast, teeth, eye).

    Pain Sensation

    • Pain is an unpleasant sensory and emotional experience associated with actual tissue damage.
    • Pain receptors (nociceptors) are free nerve endings.
    • They are specific to tissue damage, with subtypes that respond to different types of injuries (mechanical, chemical, thermal).

    Coding of Sensory Information

    • The CNS analyzes sensory information to determine:
      • Modality (type): Each type of sensory receptor is associated with a unique sensory modality (e.g., touch, pain, sight)
      • Intensity: Determined by the rate of impulse discharge and the number of receptors activated.
      • Locality: The location of the stimulus is identified based on the specific pathway it travels through.
    • Muller's law: Explains the principle of modality discrimination – a specific receptor type always produces the same sensory modality.
    • Labelled line principle: Each sensory modality has a dedicated anatomical pathway for transmitting information to the brain.
      • This ensures that the correct type of sensation is perceived.

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