5. Literature recommended:

1. Lecture course.

2. Mistchenko V.P., Tkachenko E.V. Methodical instructions for medical students (short lecture course).-Poltava, 2005.-P. 15-16.

3. Mistchenko V.P., Tkachenko E.V. Methodical instructions on Normal Physiology on practical classes for dental and medical students.-Poltava, 2005.-P. 36-40.

4. Ganong W.F. Review of Medical Physiology.-21^st ed.-2003.-Section II.

5. Kapit W., Macey R.I., Meisami E. The Physiology Colouring Book: Harpers Collins Publishers, 1987.-P. 80.

6. Guyton – Ganong – Chatterjee. Concise Physiology /Ed. By Dr Raja Shahzad Gull: M.B.B.S., F.C.P.S., King Edward Medical College.-Lahore, 1998 (1^st Edition).-P.295-301.

7. Guyton A.C. Textbook of Medical Physiology.-NY, 1992.-P.606-618.

1. Materials for self-control:

A. Control questions:

1. Innervation segmentary character and its significance.

2. Spinal centers.

3. Spinal conductive tracts.

4. Spinal reflexes.

5. Spinal shock.

Lesson 12 Somato-sensor system investigation (skin and proprioceptive sensitivity, nociceptive sensitivity)

1.Topic studied actuality.

Reception role sensations especially is rather essential: alive organism establishes organism connection with environment and orientation in it. Sensitivity disorders are also important in clinical neurological practice (together with motor function disturbances). We will illustrate a bit some clinical aspects and types of sensitivity disorders:

Anesthesia – loosing one or another sensitivity type. There are several subtypes:

• tactile;

• pain or nociceptive (analgesia);

• temperature (thermanesthesia);

• localization sense loosing (topanesthesia);

• stereognostic sense loosing (astereognosis);

• joint-muscular sense loosing (batianesthesia);

• general total anesthesia – all sensitivity types loosing.

Hypoesthesia – sensitivity decreasing, sensations intensiveness reducing. It can touch both all sensitivity and its separate kinds.

Hyperesthesia – increased sensitivity – occurs as a result of summation of irritation applied at investigation and irritation existing due to pathological process on the way of sensitive impulse.

Dissociation - isolated disorder of one sensitivity types while normal other types at the same territory.

Hyperpathy – sensation threshold increasing.

Dysesthesia – touching is percepted like pain, warmth – like coldness and so on.

Polyesthesia – human being tells about many sensations after just 1 stimulus action.

Synesthesia – irritation feeling not only in the place of its making but in other region (from opposite side et al.).

Thalamic syndrom- is a collection of symptoms resulting from damage of posterior-ventral portion of thalamus due to thrombosis. It has 3 main features: loss of almost all sensation from the opposite body side; ataxia; after a few weeks some sensory perception in the opposite side of body returns, but poorly.

Herpes Zoster (Shingles). It is the infection of dorsal root ganglion. This causes severe pain in the dermatormal segment normally subserved by the ganglion, thus eliciting a segmental type of pain that circles halfway around the body. The disease is called herpes zoster, or “shingles” because of the eruption. The cause of the pain is presumably excitement of the neuronal cells of the dorsal root ganglion by the virus infection.

Tic doulourex - lancinating pains occurs in some people over one side of the face in part of the sensory distribution area of the fifth or nineth nerve; this phenomenon is called tic douloureux (or trigeminal neuralgia or glosso-pharyngeal neuralgia).

Allodyny – state at which pain is caused by non-harmful stimulation of normal skin (usual mechanic or thermal irritation causes pain).

Hyperalgesy – hypersensitivity to harmful stimuli.

Hyperpathy – painful syndrome the distinguishing feature to which is enforced reaction with lacked beginning and afteraction which is remained after stimulation ending.

2. Study aims:

To know: sensory information (noceoceptive, tactile, temperature and proprioceptive sensitivity) conduction ways; superficial and deep sensitivity physiological mechanisms.

To be able to: to investigate pain, temperature, tactile, deep sensitivity; to draw superficial and deep sensitivity conductive ways.

3. Pre-auditory self-work materials.

3.1.Basic knowledge, skills, experiences, necessary for study the topic:

Subject	To know	To be able to
Histology	Spine histological structure	Recognize spinal cord preparation
Anatomy	Spine anatomical structure and conductive motor and sensory ways	Draw spine ascending and descending conductive ways of superficial and deep sensitivity
Biochemistry	Nervous tissue metabolism peculiarities
Neurology	Spine external and internal structure, superficial and deep sensitivity conductive ways (norm and pathology)	Draw spine conductive sensory ways, assess sensitivity state in the patient.

3.2. Topic content.

Somato-sensor analizator – system providing organism connection with environment through skin and visible mucosae.

It contains 3 types of receptors:

• tactile (mechanoreceptors);

• thermal (of warmth and coldness);

• noceoceptive (of pain).

Tactile reception. Tactile reception is an important part of somato-sensor analizator. It is represented by touching and pressure receptors. These receptors are in strong functional interconnection with mechanoreceptors and proprioreceptors. They are located in skin different regions (maximal sensitivity is on fingers endings, foot). Touching sensation or pressure can be caused by indefinite points (tactile points). They are free nervous endings (Ruffini bodies, Pachini bodies et al.). Free nervous endings afferent fibers carry the information according to sensitivity type through spinal nerves, then through posterior columns fibers (Goll’s and Burdach’s fasciculi) to brain stem, thalamus and cortex (postcentral sulcus).

Tactile sensitivity gives the imagination about subjects shape and their surface. Multiple, frequent irritation of them causes vibration sensation. Simultaneous several Pachini bodies involvement into reaction is the essential condition of vibration occurrence in skin. Skin superficial layers local anaesthesia doesn’t liquidate vibrational sensitivity and high-frequented receptors answer reactions.

Temperature reception. Temperature analizator belongs to somato-sensor analizator too. Some sensor regions possess high sensitivity to temperature fluctuations. Temperature receptors are divided into receptors of warmth and of coldness. Coldness points amount is significantly predominant comparatively to warmth points. Their maximal accumulation is on face skin. Coldness receptors in human being are located in epidermis and directly under it and warmth receptors – primarily in derma (proper skin) superior and middle layer. Coldness receptors are connected with thin myelinized and warmth receptors – with non-myelinized fibers.

Nociceptive sensation can occur either at injured stimulus action to special “noceoceptive” receptor – nociceptor, or at superstrong irritations of other receptors. Nociceptors are 25-40 per cent of all receptors. Nociceptors both of skin and of mucosa are represented by free non-incapsulated nervous endings of different shape (hairiness, spirals, plates et al.).

Nervous fibers carrying impulses from these receptors reach spine posterior corns grey substance, where second neuron is originated from. Second neuron reaches brain columns white substance and further – thalamus from where it is projected widely into different cortical regions.

Pain is defined as an unpleasant sensation and emotional experience associated with or without actual tissue damage.