The receptors of special senses | CHAPTER 10 | Anatomy and Physiology

The receptors of special senses-The course is designed for the basic understanding of anatomical structures and physiological functions of human body, musculoskeletal system, digestive system, respiratory system; cardiovascular system; urinary system, endocrine system, reproductive system, nervous system, hematologic system, sensory organs, integumentary system, and immune system.The aim of the course is to acquire knowledge and skills regarding anatomy and physiology.

The receptors of special senses

The Receptors of Special senses :-

Sensation and describe the conditions needed for a sensation to occur

Definition of Sensation:

Sensation is the conscious or subconscious awareness of changes in the external or internal environment.

For a sensation to occur, four conditions must be satisfied:

• A stimulus, or change in the environment, capable of activating certain sensory neurons, must occur. A stimulus that activates a sensory receptor may be in the form of light, heat, pressure, mechanical energy, or chemical energy.
• A sensory receptor must convert the stimulus to an electrical signal, which ultimately produces one or more nerve impulses if it is large enough.
• The nerve impulses must be conducted along a neural pathway from the sensory receptor to the brain.
• A region of the brain must receive and integrate the nerve impulses into a sensation.

(Ref:- J. Tortora, 8th edition, P-298)

Referred pain & locations of skin areas to which visceral pain is referred

In many instances of visceral pain, the pain is felt in or just deep to the skin that overlies the stimulated organ, or in a surface area far from the stimulated organ. This phenomenon is called referred pain.

In general, the visceral organ involved and the area in which the pain is referred are served by the same segment of the spinal cord. For example, sensory neurons from the heart, the skin over the heart, and the skin along the medial aspect of the left arm enter spinal cord segments TI to TS. Thus, the pain of a heart attack typically is felt in the skin over the heart and along the left arm.

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