Sensation is an ability of an organism to

Sensation is an ability of an organism to accept stimuli from external and internal environment

Reception is a set of all afferent systems, which accept stimuli from external and internal environment and carry them out to the center § Reception is wider concept, than sensation. One doesn’t not feel everything he accepts. § Sensation is a part of reception, which one feels and can analyze by certain structures of his brain. It means that sensation is closely connected with activity of analyzers.

Analyzer is a sole functional system that consists of three parts: 1. Receiving apparatus (receptors) receptor part 2. Sensory explorers - conductive part 3. Part of cortex, which receives information, analyzes and synthesizes it

Receptors are sensitive structures that have ability to accept different changes of external and internal environment and transmit them as impulse. Receptors are divided into: § Exteroreceptors (in skin and external mucose membrane) § Proprioreceptors (in muscles, tendons, joints) § Interoreceptors (in inner organs, in vessels)

Exteroreceptors accept superficial sensitiveness (light touch (tactile), pain and temperature sense). mechanoreceptors (touch, pressure) thermoreceptors (cold, hot) nociceptors (accept pain)

Proprioreceptors are situated in deep tissues (muscles, joints, tendons). § § § nervous - muscular cords. They react to tension of muscles. They are covered by a connective tissue case and are situated intra- and extrafusally between the fibers of striated muscles. The Goldie’s and Matson’s bodies accept joint feeling. They are situated between muscles and tendons. Osmoreceptors Chemoreceptors baroreceptors

Types of fibers § Type A - thin myelin fibers, which carry out deep and light touch sense; the speed of impulse transmission by these fibers is 40 -60 m/s § Type B - myelin fibers, which carry out pain and temperature sense; the speed is 10 -15 m/s § Type C - without myelin fibers, which carry out diffuse pain sense with speed 1 -1, 5 m/s.

Classification of sensation І. Classification, which is based on the place of originating of stimuli: § Exteroceptive § Interoceptive § Proprioceptive ІІ. Classification, which is based on biological principle of originating of sensation: § Protopatical (vital, nociceptive, thalamic). This ancient sensation is typical for the primitive nervous system of our ancestors. § Epicritical sensation is connected with cortex and it is based on the differentiation of stimuli according to their modality, intensity, localization etc. In clinical practice usually we use classification, which is based on the kind of stimuli: § Superficial § Deep § Complicated

Superficial sensation This term includes the modalities of light touch, pain and temperature. § Light touch (tactile) sensation – is feeling of touch, which may be examined by touch of cotton, end of hammer, paintbrush § Superficial pain – is a feeling of pain, which may be tested with a corsage pin or pinwheel (acutely or bluntly, pricks or does not prick) § Temperature sensation – is feeling of cold or hot, which may be tested by application of glass tubes filled with iced (100 C) and hot (430 C) water to the skin § Trihoesthesia – is a sensation of touch of hair § Hydroesthesia – is a sensation of humidity § Sensation of electrical current § Feeling of tickling

Deep sensation This includes joint and vibratory sense and pain from the deep-lying somatic structures, namely, muscle, ligaments, fascia, bone, and so on. § Joint sense – is a sense of position and passive movements § Vibration sense § Feeling of mass § Feeling of pressure § Kinesthesia

Complicated sensation § Stereognosis (Three-point distinction) is the ability to identify familiar object placed in the palm of the patient by palpation when the eyes are closed. It is complicated kind of sensation, which is based on the reception of separate properties of object (weight, form, surface, and sizes), synthesis and analysis of all these properties § Graphism – is the ability to determine figures and numbers traced on the skin with the closed eyes. Graphesthesia – impaired graphism is very sensitive indicator of parietal lobe damage. § Localization sense - is the ability to point an exact place of the stimuli. § Discrimination sense (two-point discrimination) - tests the ability of the patient to differentiate one stimulus from two. It may be examined by Weber’s circus. § Baragnosis – is the impaired ability to distinguish different weights.

Sensory passway

Anatomy of Superficial and deep sensation pathways

Diagnostic value of spinothalamic tracts § The decussating in front of white soldering occurs not in a horizontal plane at a level of segment, but obliquely from below upwards during 1 -2 segments. Therefore if we have lesion of lateral funiculus, the sensitive disturbance occurs on the opposite side 1 -2 segments below than the level of a pathological focus. § The caudal contributions to the spinothalamic tract are pushed laterally by the incoming contributions from higher up results in a lamination of the tract, with the fibers from the lowers segments of the spinal cord placed more dorsolaterally on each side. This explains the “sacral” sings and symptoms that result from more or less superficial involvement of the lateral funiculus even at the highest level of the cord. It is the Auerbah. Flatau’s law of eccentrically allocation of longer explorers.

Symptoms of sensory disturbances § § § § Anesthesia - complete loss of any sorts of sensation. For example: Analgesia - loss of pain sense. Thermoanesthesia - loss of a temperature sense Bathyanesthesia - loss of deep joint sense Astereognosia - loss of stereognostic sense Topanesthesia - loss of localization sense Pallanesthesia – loss of vibratory sense Hypoesthesia - lowering of sensation. Hyperesthesia - sensitization as result of lowering a threshold of energization in cortex of brain. Dysesthesia - distortion of sensitivity, when instead of one stimulus the patient feels absolutely other. For example, warm touch one feels as cold. Hyperpathia - results from rise of a threshold of energization, when there are strong, unpleasant, badly localized sensations of stimuli. Thus the mild stimuli are not received absolutely. In basis of hyperpathia the disturbance of the analytical function of cortex lays. Synesthesia - sensation of stimuli not only in a place of its plotting, but also in the other place. Polyesthesia - means sensation of one stimulus as several ones. Alloheyria - sensation of stimuli in symmetrical sites on an opposite body part. Alloesthesia - sensation of stimuli in the other place. Dissociation of sense - phenomenon of fallout of some kind of sensitivity while saving others in the area of segment innervation.

Subjective sorts of sensory disturbances: § Paresthesia is a creeping sensation, cold, burning sensation, fever, numbness, itch, the pricking etc. Frequently paresthesia is the first sign of nervous system lesion. § Pain. The pain sensations can arise at stimuli by the pathological process of sensitive analyzers at any level (from receptors up to cortex).

Sorts of pain 1. Local pain - is pain, for example, at palpation of the nervous trunk. That is pain, which coincides with the place of lesion. 2. Projectional pain - is a pain in zone of innervation not only in place of stimuli, but also distally on a course of nerves or roots. To projection belongs the stump neuralgia - pain in absent segments of an extremity after its ablation. Or other pain example: during a trauma of a ulna nerve in the field of a ulna joint the pain gives back in V fingers of a paintbrush. 3. Irradiating pains - are pains, which are distributed from one nerve branch to another, not struck. For example, at neuralgia of the first branch of trigeminal nerve the pain is distributed to zone of innervation of the second or the third branches, in upper or lower jaw, in ears etc. 4. Displayed pains - are pains in zones Zacharyin-Hed’s at diseases of inner organs, when irradiation arises to certain zone on skin through cells of dorsal horns of spinal cord. For example, pain on ulnar territory of the left forearm and paintbrush at angina pectoris. 5. Causalgia (Greek causes - burning sensation, algos - pain). It is intensive thermalgia originating, for example, at traumas. It is pain without stimulation. 6. Reactive pains - are pains that originate at expansion of nerves. The pains can arise at palpation of pain points and at band spread of nervous trunks.

Types of sensory disturbances Peripheral § Mononeuritic (or neural) § Polyneuritic § Plexal § “Saddle-area” Segmental (sectional) § Segmental - radicular § Segmental - dissociated Conductive type § Spinal § Cerebral

Types of sensory disturbances

Sectional body building

Spinal pattern § Complete transversal (is observed at a lesion that involves a diameter of a spinal cord, at which all sorts of sensation below that level of a lesion drop out, pain and temperature sense drop out on 1 -2 segments below than level of a lesion, and deep - from the same level. Usually, the deficits are in the lower trunk and legs, are bilateral and almost symmetric. § Half transversal or Brown-Sequard pattern - arises at a lesion of a lateral half diameter of a spinal cord, thus the deep feeling drops out on the side of a lesion, and pain and temperature senseon the opposite side, since a level on 1 -2 segments is lower. § Descending § Ascending, depending on extra- or intramedular lesion § Monotype § Hemitype

Conductive type a) Brain stem b) The thalamic c) Capsular d) Cortical

Types of sensory disorders