The thoracic spinal cord has the smallest dorsal horn area because: a. the trunk is the most innervated area of the body and therefore there are more projections into the dorsal horn there. b. the trunk is the least innervated area of the body and therefore there are fewer projections into the dorsal horn there. c. most of the descending upper motor neurons have already entered the ventral horn. d. There are many motor neurons to control the small muscles around the spine.
Anatomy and Physiology of Special Sensory Organs
Sensory organs can be labeled as special sensory structures that permit sight, hearing, odor, and flavor. Sensory structures permitting proprioception, touch, thermal, and pain perception can be classified as more advanced sensory organs. The sensory neurons are trained to find out modifications in the external and internal conditions so that a person's body can react to that change. A stimulus is the first signal that is recognized by any sensory receptor of the body. Stimulus is an impulse generated when there is a change in the surroundings of a person. For example, a heated environment will alert the brain through the thermal sensory organs and generate a reflex accordingly.
Sensory Receptors
The human sensory system is one of the most complex and highly evolved structures, which processes a myriad of incoming messages. This well-coordinated system helps an organism or individual to respond to external stimuli, appropriately. The sensory receptors are an important part of the sensory system. These receptors are specialized epidermal cells that respond to external environmental stimuli. These receptors consist of structural and support cells that form the peripheral unit of the receptor and the neural dendrites which receive and detect the external stimuli.
The thoracic spinal cord has the smallest dorsal horn area because:
| a. |
the trunk is the most innervated area of the body and therefore there are more projections into the dorsal horn there.
|
|
| b. |
the trunk is the least innervated area of the body and therefore there are fewer projections into the dorsal horn there.
|
|
| c. |
most of the descending upper motor neurons have already entered the ventral horn.
|
|
| d. |
There are many motor neurons to control the small muscles around the spine. |
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