Farmasevtika instituti farmakologiya va klinik farmatsiya kafedrasi

―Second Messenger‖ System in the Postsynaptic Neuron. 
Many functions of the 
nervous system—for instance, the process of memory—require prolonged changes in neurons for 
seconds to months after the initial transmitter substance is gone.
 
Somatic Sensations: I. General Organization, the Tactile and Position Senses 
The 
somatic senses 
are the nervous mechanisms that collect sensory information from all over the 
body. These senses are in contradistinction to the 
special senses, 
which meanspecifically ision, 
hearing, smell, taste, and equilibrium. 
Classification of Somatic Senses
The somatic senses can be classified into three 
physiologic types: (1) the 
mechanoreceptive somatic senses, 
which include both 
tactile 
and 
position 
sensations that are stimulated by mechanical displacement of some tissue of the body; (2) the 
thermoreceptive senses, 
which detect heat and cold; and (3) the 
pain sense, 
which is activated by 
factors that damage the tissues. 
Other Classifications of Somatic Sensations. 
Somatic sensations are also often grouped together in other classes, as follows. 
Exteroreceptive 
sensations 
are those from the surface of the body. 
Proprioceptive sensations 
are those relating to the 
physical state of the body, including position sensations, tendon and muscle sensations, pressure 
sensations from the bottom of the feet, and even the sensation of equilibrium (which is often 
considered a ―special‖ sensation rather than a somatic sensation).
Tactile Receptors. 
There are at least six entirely dif ferent types of tactile receptors, but many 
more similar to these also exist. Some were shown in Figure 46-1 of 
the previous chapter; their special characteristics are the following.