Neurons and Nerves
Neurotransmitter
The Brain
Spinal Cord
Peripheral Nervous System
Autonomic Nervous System
Senses: Sight,
Senses,
Smell,
Taste, Senses,
Senses
Memory
Higher Functions
Altered States
The exact function of the terminal nerve in human is
still under investigation, which is hampered by its small size and
proximity to the olfactory nerve. For mouse and other animals at
least, it is connected to the
vomeronasal organ (vestige in human), which leads to a pathway for controlling sexual arousal.
The spinal nerves Á functions
This table explains the spinal nerve their function and symptoms of dysfunction.
| Spinal Nerve(s) |
Innervated Body Part(s) |
Symptom(s) of injury |
| C1 |
C1 nerve supplies
Head and Neck |
Quadriplegia at C1 dislocation |
| C2-C4 |
C2-C4 nerve root supply
Diaphragm |
Breathing problem resulting from lesion |
| C5 roots |
Deltoids, biceps |
No control at wrist or hand with lesion |
| C6 root |
Wrist extenders |
No hand function |
| C7-T1 roots |
Triceps |
hand dexterity problems with hand and fingers |
| T2-T8 |
Chest muscles |
Paraplegia, poor trunk control |
| T9-T12 |
Abdominal muscles |
Paraplegia |
| Lumbar and Sacral |
Leg muscles, bowel, bladder, sexual organs |
Decreasing control of hip flexors and legs, dysfunction of bowel, bladder, and sex |
Table 01 Symptom(s) of Spinal Cord Injury
Note: Other effects of SCI may include low blood pressure, inability to regulate blood pressure effectively, reduced control of body
temperature, inability to sweat below the level of injury, and chronic pain.
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One division of the autonomic nervous system, called the tem, dominates in times of stress. It controls the "fight or flight" reaction, increasing blood pressure,
heart rate, breathing rate, and blood flow to the muscles. Another division, called the parasympathetic nervous system, has the opposite effect. It conserves energy by slowing the heartbeat and breathing rate, and by promoting digestion and
elimination (of waste). Most glands, smooth muscles, and cardiac muscles constantly get inputs from both the sympathetic and parasympathetic systems. The CNS controls the activity by varying the ratio of the signals. Depending
on which motor neurons are selected by the CNS, the net effect of the arriving signals
will either stimulate or inhibit the organ.
Figure 07 shows the various organs and actions, which are related to the two different divisions. Motor fibers that govern involuntary responses, do not lMotor fibers that govern involuntary responses, do not lead directly
to the organs they innervate. Instead, they make their trips in two stages. The first set of fibers leads from the CNS to ganglia (which are collections of nerve cell bodies) that lie outside
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the CNS (the preganglionic fibers). At the ganglia the fibers form synaptic junctions with the dendrites of as many as twenty different cell bodies. The axons of these cell bodies form a second set of fibers, the
postganglionic fibers. It is these postganglionic fibers that lead to the organs.autonomic nervous system form two lines running down either side of the spinal column. They are outside the bony vertebrae. These two lines
of ganglia outside the column resemble a pair of long beaded cords. At the lower end, the two cords join and finish in a single central stretch. These lines of ganglia are sometimes
called the sympathetic trunks (used by the sympathetic nervous system). Not all ganglia are located in the sympathetic trunks. Some are not; and it is possible for a preganglionic fiber to go right through, making no synaptic
junction there at all, joining instead with ganglia located in front of the vertebrae. For the parasympathetic nervous system, some of the ganglia separating the preganglionic fibers from the postganglionic fibers are actually located
within the organ the nerve is servicing. In that case, the preganglionic fiber runs almost the full length of the total track, whereas the postganglionic fiber is at most just a few millimeters long.
The splanchnic nerves, which originate from some of the thoracic nerves, have their preganglionic fibers ending in a mass of ganglia lying just behind the stomach. It represents the largest mass of nerve cells that is not within the CNS
and is sometimes called the "abdominal brain". It is a vital spot to be protected during boxing.
Figure 08 is the front view of a more detailed ANS anatomy.
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