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SOMATOSENSORYSYSTEM

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Information pyramid

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Components of reflex arc

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Organization of neuronal pool

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divergence

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convergence

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Zones of facilitation

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epsp

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Interneuronal relations

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summation

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occlusion

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Reccurent inhibiton

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Receptors definition

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Classification according the energy

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Classification of receptors according to the

source of stimulus:

1. Telereceptors- eye, ear

2. Exteroreceptors- skin

3. Interoreceptors- inside body

4. Proprioreceptors

Classification according to the source

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General concepts of somstosensory system

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Somatic sensory system

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Receptor potential

The stimulus that produces a response in particular receptor is termedan adequate stimulus for that receptor. Many receptors are tunedto be

most sensitive to a narrow range of energy (for example, a particular

frequency of vibration or particular wavelength of light). The excitability

of the receptor is highest for an adequate stimulus.

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Relationship of amplitude receptor

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adaptation

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Adaptation of receptors

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Somatosensory receptors

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proprioceptors

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Major classes

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Cutaneous receptors

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Tactile receptors

1. Free nerve endings

2. Meissners corpuscle-an elongated encapsulated nerve ending of large

A myelinated fiber. Inside the capsulation many branching. In nonhairyskin (fingertips, lips). Sensitive to movement of objects and low

frequency vibrations.

3. Merkels discs- present with #2 in fingertips inside expanded tip tactile

receptors.Are often grouped together in receptor organ Iggo dome

receptor projecting upward against underside of epithelium. Slowlyadapting

4. Hair end-organ

5. Ruffinis end-organs- multibranched, encapsulated endings adapting

very slowly, signaling continuous deformation ( prolonged touch andpressure), located in deeper layers of the skin and deeper internal

tissues. Also found in joints capsules to signal the degree of joints

rotation.

6. Paccinian corpuscles- immediately beneath the skin and deep in fascial

tissues. Very rapidly adapting (vibration)

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Merkels discs

Iggo dome receptor

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Skin receptors

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Receptors in glabrous skin

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Ticle and itch

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Receptive field

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Temperature sensation

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There are six distinct Trp

channels in

thermoreceptors that

confer differenttemperature

sensitivities. As a rule,

different thermoreceptive

neurons express only

single type of channel.An exception appear to

be some cold receptors

that also express a

Trpv1, and are therefore

also sensitive to

increases in temperature

above 43oC.

Paradoxical feeling of

cold

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Spinal cord

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Dorsal column system

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Spinothalamic tract

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Spinothalamic pathway

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Dorsal column pathway

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Ascending tracts2

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Segmental organization of the spinal cord

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Dermatomes 1

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Purpose of pain

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Pain sensitivity

OC C

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NOCICEPTIVE

STIMULUS

INACTIVE ACTIVETISSUE TISSUE

KALIKREINS KALIKREINS

TISSUE KININOGENS KININES

POLARIZED DEPOLARIZED

FREE NERVE ENDINGS FREE NERVE ENDINGS

PAIN IMPULSES

> GENERATING OF PAIN IMPULSES AFTER A STIMULUS INJURING TISSUES