The baroreceptors from the carotid arteries have axons in the glossopharyngeal nerve, and those from the aorta have axons in the vagus nerve. The baroreceptor apparatus is part of the ending of a unipolar neuron that has a cell body in a sensory ganglion.
The sensory neuron is essentially the same as any other general sensory neuron. You do not have a conscious perception of having high blood pressure, but that is an important afferent branch of the cardiovascular and, particularly, vasomotor reflexes.
For example, there is a specific type of mechanoreceptor, called a baroreceptor, in the walls of the aorta and carotid sinuses that senses the stretch of those organs when blood volume or pressure increases. Many of the inputs to visceral reflexes are from special or somatic senses, but particular senses are associated with the viscera that are not part of the conscious perception of the environment through the somatic nervous system. The afferent branch of a reflex arc does differ between somatic and visceral reflexes in some instances. The Latin root “effere” means “to carry.” Adding the prefix “ef-” suggests the meaning “to carry away,” whereas adding the prefix “af-” suggests “to carry toward or inward.” Sensory neurons receiving input from the periphery-with cell bodies in the sensory ganglia, either of a cranial nerve or a dorsal root ganglion adjacent to the spinal cord-project into the CNS to initiate the reflex ( ). The other part of a reflex, the afferent branch, is often the same between the two systems. The output of a visceral reflex is a two-step pathway starting with the preganglionic fiber emerging from a lateral horn neuron in the spinal cord, or a cranial nucleus neuron in the brain stem, to a ganglion-followed by the postganglionic fiber projecting to a target effector. The output of a somatic reflex is the lower motor neuron in the ventral horn of the spinal cord that projects directly to a skeletal muscle to cause its contraction. One difference between a somatic reflex, such as the withdrawal reflex, and a visceral reflex, which is an autonomic reflex, is in the efferent branch. Whereas the basic circuit is a reflex arc, there are differences in the structure of those reflexes for the somatic and autonomic systems. The autonomic system, however, targets cardiac and smooth muscle, as well as glandular tissue. Somatic responses are solely based on skeletal muscle contraction. The main difference between the somatic and autonomic systems is in what target tissues are effectors. The autonomic nervous system regulates organ systems through circuits that resemble the reflexes described in the somatic nervous system.
0 kommentar(er)
