Overview
The peripheral nervous system links the central nervous system with the body: it consists of spinal and cranial nerves, their ganglia and branches, and is divided functionally into somatic and autonomic parts. This topic also covers the general characteristics of the 12 pairs of cranial nerves.
Acts as a communication network between the CNS and the periphery.
Somatic nervous system
responsible for voluntary control of skeletal muscles and the reception of sensory information from the external environment.
Sensory (Afferent)
Carries info. from receptors in the body to the CNS.
Motor (Efferent)
Sends motor commands from the CNS to muscles.
Autonomic nervous system
Regulates involuntary physiological functions such as heart rate, digestion...
Sympathetic
“fight or flight”
preparing the body for increased energy expenditure.
* Sympathetic nerves arise from the thoracic & lumbar regions of the spinal cord.
Parasympathetic
“rest and digest”
conserving energy & promoting relaxation.
* Parasympathetic nerves arise from the cranial & sacral regions.
Components of the peripheral nervous system
- The PNS is composed mainly of spinal nerves, cranial nerves, their ganglia & their ramifications.
Spinal nerves:
- 31 pairs, arise from the spinal cord and are responsible for transmitting signals to and from different regions of the body.
- Each spinal nerve has both sensory & motor fibers.