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Physiology

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Central Nervous System

Question
18 out of 20
 

Massage and the application of linaments to painful areas in the body relieves pain due to-



A Stimulation of endogenous analgesic system

B Release of endorphins by the first order neurons in the brain stem

C Release of glutamate and substance P in the spinal cord

D Inhibition by large myelinated afferent fibres

Ans. D Inhibition by large myelinated afferent fibres

1. Pain:

Receptors: naked nerve ending (free nerve ending found in almost every tissues of the body.

&

Types of Pain

Nerve fiber involved in

Synaptic transmitors

transmission

1. Fast mild pain (first

Small diameter myelinated A Ii

Glutamate

or fast pain)

fibers; terminate primarily on

neurons in laminas I and V of

dorsal horn

2. Slow severe pain

Unmyelinated C-fiber; terminate

Substance –P

(slow or second pain)

primarily on neurons in laminas I

and II of dorsal hom

Tract Antolateral-spinothalamic tract

2. Gate system for Pain control:

a. "The synaptic junctions between the peripheral nociceptor fibers and the dorsal horn cells in the spinal cord are the sites of considerable plasticity. For this reason, the dorsal horn. has been called a gate, where pain impulse can be "Gated" - i.e. modified.

  1. For example: Stimulation of large diameter afferent fibers (i.e. AP fibers, touch receptors) from an area from which pain is being initiated reduces the pain. Collateral branches from the touch fibers (i.e. large diameter Ap-myelinated fibers) in the dorsal columns enter the substantiagelatinosa, and it has been postulated that impulses in these collaterals or interneurons on which they end inhibit transmission from the dorsal root pain fibers to the spinothalamic neurons.
  2. Mechanism:-Presynaptic inhibition at the endings of the primary afferent's that transmit pain impulses.
  3. "Stimulation of large type A β sensory fibers (i.e. Large myelinated A β-fibers) from the tactile receptors can depress the transmission of pain signals. This effect presumably result from local lateral inhibition (Presynaptic inhibition) in the spinal cord. It explains why rubbing the skin near painful area or application of liniments to painful area relieves the' pain" "Accupuncture, touching or shaking relieves pain in similar manner"
  4. "Stimulation with electrical vibrator at the site of pain also relieves pain".

Central Nervous System Flashcard List

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