1. Organization of the Nervous System
The CNS, composed of the spinal cord and brain, communicates with the PNS, which contains nerves. In the somatic system, nerves conduct impulses from sensory receptors to the CNS and motor impulses from the CNS to the skeletal muscles. In the autonomic system, consisting of the sympathetic and parasympathetic divisions, motor impulses travel to smooth muscle, cardiac muscle, and the glands.

2. The Peripheral Nervous System
The peripheral nervous system (PNS) contains nerves (bundles of axons) and ganglia (cell bodies).
Sensory nerves carry information to the CNS, Motor nerves carry information away, and Mixed nerves have both types of fibers.
Humans have 12 pairs of Cranial nerves and 31 pairs of Spinal nerves.

3. The dorsal root of a spinal nerve contains sensory fibers that conduct sensory impulses from sensory receptors toward the spinal cord.
Dorsal root ganglia near the spinal cord contain the cell bodies of sensory neurons.
The ventral root of a spinal nerve contains motor fibers that conduct impulses away from the spinal cord to effectors.

4. Somatic System
The Somatic System serves the skin, skeletal muscles, and tendons.
The brain is always involved in voluntary muscle actions but somatic system reflexes are automatic and may not require involvement of the brain.
Somatic Motor Nerves only require one Motor Neuron length to reach the effector.

5. Autonomic System – Think Automatic
The autonomic system of the PNS regulates the activity of cardiac and smooth muscle and glands.
Table 17.1 (page 337) contrasts the two divisions of the autonomic system with the features of somatic motor pathways.
Reflex actions of the autonomic system, such as those that regulate the blood pressure and breathing rate, are especially important to the maintenance of homeostasis.
Their motor nerves require TWO Neurons to bridge the gap to reach effector.

6. COMPARISON

7. The system is divided into Sympathetic and Parasympathetic divisions that:
Function automatically and involuntarily;
Innervate all internal organs; and
Use two neurons and one ganglion.

8. Sympathetic Division
The Sympathetic division is associated with responses that occur during times of stress, including “fight or flight” reactions.
The postganglionic axon releases mainly NOREPINEPHRINE which acts similar to adrenaline, the hormone from the adrenal medulla.
Everything is stimulated to prepare the body to flee danger or fight for survival. However, the digestive system processes are inhibited.
The preganglionic fibers of both the sympathetic and parasympathetic divisions release the neurotransmitter acetylcholine.
Note that the motor nerves branch off of spine in the Thoracic and Lumbar regions of spine

9. SYMPATHETIC DESIGN IN MOTOR PATHWAY – SHORT presynaptic neuron, with LONG post-ganglionic neuron. Therefore Ganglion is found FAR from the effector.
In the sympathetic division, preganglionic fibers arise from the middle, or thoracic-lumbar, portion of the cord and synapse in ganglia close to the cord. The preganglionic fiber is short, while the postganglionic fiber is long.

10. Parasympathetic Division
The Parasympathetic system is associated with responses that occur during times of relaxation and promotes “housekeeper” activities.
The postganglionic neurotransmitter used by the parasympathetic division is acetylcholine.
Everything is now stimulated to work at a slower more relaxed pace. However, digestive processes are now fully stimulated
Note that the motor nerves
Branch off of spine from the Sacral (Bottom of spine) and Cranial (Brain) regions of Central Nervous System.

11. PARASYMPATHETIC DESIGN IN MOTOR PATHWAY – LONG presynaptic neuron, with SHORT post-ganglionic neuron. Therefore Ganglion is found NEAR the effector
Preganglionic fibers of the parasympathetic division arise from the base of the brain or from the sacral spinal cord. The preganglionic fiber is long, the postganglionic fiber is short, and ganglia lie close to the effector organ.

12. Autonomic Nervous System
Sympathetic preganglionic fibers (left) arise from the cervical, thoracic, and lumbar portions of the spinal cord; parasympathetic preganglionic fibers (right) arise from the cranial and sacral portions of the spinal cord. Each system innervates the same organs but has contrary effects.

13. “Para-s.c.a.n.n.” S – Nerves off of SACRAL region of spinal cord
C- Nerves off of CRANIAL region of CNS (brain)
A – Use ACETYLCHOLINE for normal stimulation
N – Runs vital organs at NORMAL relaxed level
N – Ganglion is found NEAR the effector

14. “SYMPA-F.E.E.L.T.” F – Ganglion is found FAR from effector
E- Runs vital organs during EMERGENCY/EXCITATORY situations
E – Use norEPINEPHRINE for extra stimulation
L – Nerves off of LUMBAR region of spinal cord
T – Nerves off of THORACIC region of spinal cord