1. Peripheral nervous system

  • Somatic
  • Autonomic
    • Sympathetic
    • Parasympathetic
    • Enteric


1.1 Autonomic Nervous System


The autonomic nervous system (ANS) is a division of the peripheral nervous system that influences the function ofinternal organs.[1] The autonomic nervous system is a control system that acts largely unconsciously and regulates bodily functions such as the heart ratedigestionrespiratory ratepupillary responseurination, and sexual arousal


It is controlled by the hypothalamus.


1.1.1 Sympathetic Nervous System



The sympathetic nervous system's primary process is to stimulate the body's fight-or-flight response. It is, however, constantly active at a basic level to maintain homeostasis.[3]


The sympathetic nervous system is responsible for up- and down-regulating in many homeostatic mechanisms in living organisms. Fibers from the SN innervate tissues in almost every organ system, providing at least some regulatory function to things as diverse as pupil diameter, gut motility, and urinary system output and function.


1501 Connections of the Sympathetic Nervous System.jpg


Organ Effect
Eye Dilates pupil
Heart Increases rate and force of contraction
Lungs Dilates bronchioles via circulating adrenaline[10]
Blood Vessels Dilate in skeletal muscle (in animals).[11]
  Constricts in gastrointestinal organs
Sweat Glands Activates sweat secretion
Digestive tract Inhibits peristalsis
Kidney Increases renin secretion
Penis Promotes detumescence
Ductus deferens Promotes emission prior to ejaculation




1.1.2 Parasympathetic Nervous System



The parasympathetic system is responsible for stimulation of "rest-and-digest" or "feed and breed"[2] activities that occur when the body is at rest, especially after eating, including sexual arousalsalivationlacrimation (tears), urinationdigestion and defecation


Sympathetic and parasympathetic divisions typically function in opposition to each other.


1503 Connections of the Parasympathetic Nervous System.jpg