The special senses are smell (olfaction), taste (gustation), vision, hearing and balance
Somatic senses are tactile (touch, pressure, vibration), thermal (warm and cold), pain, proprioception (joint and muscle position, movement of limbs)
Sensation: the conscious or subconscious awareness of changes in the external or internal environment
4 conditions for a sensation to occur
1- stimulus
2- sensory receptor
3- neural pathway
4- brain region for integration
A stimulus is a change in environment capable of activating certain sensory neurons (eg: light, heat, pressure)
A sensory receptor is needed to convert stimulus into electrical (AP)
Neural pathway is a signal conducted from a sensory receptor to the brain
Brain region for integration turns the AP into perception (eg: sounds, images, etc.)
Perception is the conscious awareness and interpretation of sensations. It is primarily a function of the cerebral cortex
Sensory neurons carry information for one type of sensation only (eg: neurons for touch do not conduct impulses for pain)
Sensory neuron action potentials arrive in a specific region of the cerebral cortex
Adaptation is a decrease in strength of sensation during a prolonged stimulation. It is a characteristic of most sensory receptors caused primarily by decrease in responsiveness of sensory receptors.
As a result of adaptation, the perception of a sensation may fade or disappear even though the stimulus persists
Receptors vary in how quickly they adapt
fast adaptation: pressure, touch, smell
slow adaptation: pain, body position, chemical levels in blood
