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Figure 16.26. In the autonomic worried system, a preganglionic neuron the the CNS synapses with a postganglionic neuron of the PNS. The postganglionic neuron, in turn, acts on a target organ. Autonomic responses space mediated by the sympathetic and the parasympathetic systems, which room antagonistic come one another. The sympathetic device activates the “fight or flight” response, if the parasympathetic device activates the “rest and also digest” response.

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The sympathetic nervous device is responsible for the “fight or flight” solution that occurs once an pet encounters a dangerous situation. One method to psychic this is come think the the surprise a human feels when encountering a line (“snake” and “sympathetic” both start with “s”). Examples of functions managed by the sympathetic worried system encompass an sped up heart rate and inhibited digestion. These functions help prepare an organism’s body for the physics strain required to escape a perhaps dangerous case or come fend turn off a predator.

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Figure 16.27. The sympathetic and parasympathetic nervous systems often have opposing impacts on target organs.

The sensory-somatic nervous system is consisted of of cranial and spinal nerves and contains both sensory and motor neurons. Sensory neurons transmit sensory information from the skin, skeletal muscle, and sensory organs to the CNS. Engine neurons transmit messages about desired activity from the CNS come the muscles to do them contract. Without its sensory-somatic nervous system, an animal would be can not to procedure any information around its environment (what the sees, feels, hears, and so on) and could not regulate motor movements. Unlike the autonomic nervous system, which has two synapses between the CNS and also the target organ, sensory and motor neurons have only one synapse—one finishing of the neuron is in ~ the organ and the other straight contacts a CNS neuron. Acetylcholine is the key neurotransmitter released at these synapses.

Humans have actually 12 cranial nerves, nerves that arise from or go into the skull (cranium), together opposed to the spinal nerves, which arise from the vertebral column. Every cranial nerve is accorded a name, i m sorry are thorough in figure 16.28. Part cranial nerves transmit only sensory information. For example, the olfactory nerve transmits information about smells native the nose to the brainstem. Various other cranial nerves transmit almost solely engine information. For example, the oculomotor nerve controls the opening and also closing of the eyelid and some eye movements. Other cranial nerves contain a mix the sensory and motor fibers. Because that example, the glossopharyngeal nerve has a duty in both taste (sensory) and swallowing (motor).

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Figure 16.28. The human brain contains 12 cranial nerves that receive sensory input and also control motor calculation for the head and neck.

Spinal nerves transmit sensory and motor information in between the spinal cord and the rest of the body. Each of the 31 spinal nerves (in humans) consists of both sensory and also motor axons. The sensory neuron cell bodies space grouped in structures dubbed dorsal source ganglia and are shown in figure 16.29. Each sensory neuron has one projection—with a sensory receptor ending in skin, muscle, or sensory organs—and an additional that synapses with a neuron in the dorsal spinal cord. Engine neurons have cell body in the ventral gray issue of the spinal cord that job to muscle v the ventral root. These neurons room usually engendered by interneurons in ~ the spinal cord however are sometimes directly stimulated through sensory neurons.

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Figure 16.29. Spinal nerves save both sensory and motor axons. The somas that sensory neurons are located in dorsal source ganglia. The somas of motor neurons are uncovered in the ventral section of the gray issue of the spinal cord.