The Peripheral Nervous System (PNS) is one of the two major components of the nervous system, the other being the Central Nervous System (CNS).
The PNS consists of all the nerves that lie outside the brain and spinal cord.
It connects the CNS to the limbs, organs, and skin, allowing for communication between the CNS and the rest of the body.
illustration of the Peripheral Nervous System (PNS), showing the network of nerves that connect the Central Nervous System (CNS) to the limbs, organs, and skin
Classification of the Peripheral Nervous System:
The PNS is classified into two main parts based on their function:
1) Somatic Nervous System (SNS)
Function: Controls voluntary movements and transmits sensory information to the CNS.
Components:
A. Sensory (Afferent) Neurons:
Carry sensory information from sensory receptors (skin, muscles, joints, etc.) to the CNS.
B. Motor (Efferent) Neurons:
Transmit motor signals from the CNS to skeletal muscles, controlling voluntary movement.
2) Autonomic Nervous System (ANS)
Function: Regulates involuntary functions such as heart rate, digestion, respiratory rate, and glandular activities.
Components: The ANS is further subdivided into three branches:
A. Sympathetic Nervous System:
Prepares the body for "fight or flight" responses.
It increases heart rate, dilates pupils, and redirects blood to muscles during stressful or emergency situations.
B. Parasympathetic Nervous System:
Promotes the "rest and digest" state.
It slows heart rate, increases digestion, and conserves energy by maintaining bodily functions during restful states.
C. Enteric Nervous System:
Often called the "second brain," it regulates the functions of the gastrointestinal system.
It operates semi-independently but communicates with the CNS through the sympathetic and parasympathetic branches.