Nervous system I

Adequate stimulus

the specific stimulus for which the receptor has the smallest threshold, i.e. receptor has the highest sensitivity for that, and the receptor is activated by that.

Receptor is a neuron specialized in detecting an adequate stimulus.
Sensation depends onthe receptor and not on the stimulus

Sensation

form of the reflexion of the outside world, subjective experience; sensation usually refers to the immediate, relatively unprocessed result of stimulation of sensory receptors

Perception

integrative function, the elementary sensations become arranged into definite shape

Recognition

comparison of actual perceptions and which is stored as engramma

Sense modality

category constructed on the basis of subjective experience, vision, hearing, taste, smell, touch, pressure, kinesthetic sense

Absolute stimulus threshold

the minimum stimulus intensity which just evoke sense

Differential threshold

a just noticeable difference in the stimulus intensity

Localization

Ability of resolution in space and time

Receptive field

the spatial region where application of a stimulus causes a sensory neuron to respond.

Sensory unit

a primary afferent and the receptors that define its receptive field.

Pain

subjective filling, evoked by intensive tissue damaging stimuli

There is no specific stimulus for pain, but any harmful effects can stimulate the free nerve endings (no myelin) leading to the sense of pain.

Pain is conducted by the spinothalamic tract

Superficial pain

activation of the Aδ fibers, sharp, circumscribed and well localized, fast conduction

Deep pain

resulted in the activation of C type fibres, diffuse, hard to localize, and concomitant vegetative reactions can be seen

Ischemic pain

evoked by hypoxia in the tissues. Characteristic symptom is the angina pectoris which derives from the poor blood supply to the heart.

Referred pain

pain perceived at a location other than the site of the painful stimulus, e.g. the angina pectoris refers to the leg arm.

„Défense musculaire

a protective mechanism, spasm of the skeletal muscle originated from the same somite than the internal organ affected by injury (inflammation, irritation)

Smell

The fast-adapting receptors are located in the olfactory epithelium. Dissolved chemical substances act as adequate stimuli.

Taste

The sense of taste is evoked by the chemoreceptor stimulation in the mouth. The different regions of the tongue show different sensitivity to the taste modalities. The taste sense plays very important role in the gastrointestinal reflexes (stimulation of digestive juice secretion).