Psychology Study Material: Parts of Peripheral Nervous System

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Peripheral Nervous System (PNS)

Consists of the spinal and cranial nerves; these connect the CNS to the rest of the body. PNS connects the body՚s sensory receptors to the CNS, and the CNS to the muscles and glands.

Peripheral Nervous System (PNS)

The part of the nervous system that includes all parts of the nervous system except the brain and the spinal cord.


  • Somatic Division/Somatic Nervous System/SNS
  • Autonomic division/Autonomic Nervous System/ANS

Parts of Peripheral Nervous System

PNS has two important parts:

Skeletal/Somatic Nervous System

  • Controls the voluntary movements of our skeletal muscles.
  • It reports the current state of skeletal muscles and carries instructions back.
  • Controls the voluntary movements of the skeletal muscles.
  • Controls the involuntary movements all over the body, movements of the heart, lungs, stomach, glands and other organs.

Autonomic Nervous System (ANS)

  • Considered as the “self-governing or self-regulatory mechanism” because of its involuntary operation.
  • Controls the glands and muscles of internal organs e. g. heart, stomach, and glandular activity.
  • A. N. S. has a dual function, i.e.. both arousing and calming.
  • Comprises two sub systems: Sympathetic and parasympathetic nervous systems.

Sympathetic Nervous System (SNS)

  • This part of ANS arouses us for defensive action … . fight or flight.
  • If something alarms, endangers, excites, or enrages a person, the sympathetic nervous system accelerates heartbeat, slows digestion, raises the sugar level in blood, dilates the arteries and cools the body through perspiration; makes one alert and ready for action.

Parasympathetic Nervous System (PNS)

  • When the stressful situation subsides, parasympathetic nervous system begins its activity.
  • It produces an effect opposite to that of sympathetic nervous system.
  • It conserves energy by decreasing heartbeat, lowering blood pressure, lowering blood sugar and so on. In daily life situations, both sympathetic and parasympathetic systems work together to keep us in steady internal state maintaining the homeostasis.

Studying the Structure and Function of the Brain

  • Electroencephalogram (EEG) : recording of the electrical signals being transmitted within the brain, through electrodes attached to the skull.
  • Computerized Axial Tomography (CAT) : a computer constructs an image of the brain by combining thousands of separate X-rays taken from slightly different angles.
  • Magnetic Resonance Imaging (MRI) : the scan produces a powerful magnetic field to provide a computer generated, detailed image of the structure of the brain.
  • Super Conducting Quantum Interference Device (SQUID) : a scan sensitive to minute changes in the magnetic field occurring when neurons are firing.
  • Positron Emission Tomography (PET) : a scan showing biochemical activity within the brain at any given moment.

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