Nervous System 101

The nervous system is divided into two parts:

(1)  Central Nervous System (CNS) - brain and spinal cord

(2)  Peripheral Nervous System (PNS) - cranial and spinal nerves.

-    Sensory (afferent) Neurons - transmits impulses TO the CNS

-   Motor (efferent) Neuron System - transmits impulses FROM the CNS to effectors.

a) Somatic Nervous System - directs contraction of skeletal muscles

b)  Autonomic Nervous System - controls activities of organs and various involuntary muscles, such as cardiac and smooth muscles. Has 2 systems that generally target the same organs but are antagonistic.

  i.   Parasympathetic Nervous System “Rest and Digest”or “Brake” - activates tranquil functions. E.g. secretion of saliva or digestive enzymes.

  ii.  Sympathetic Nervous System “Fight or Flight”or “Accelerator” -    prepare body for action. E.g. increasing heart rate, increasing sugar release from liver to blood.