Page 2 - LN-NEURAL CONTROL & COORDINATION

The CNS includes the brain and the spinal cord and is the site of information

processing and control.
The PNS comprises of all the nerves of the body associated with the CNS (brain
and spinal cord).
The nerve fibres of the PNS are of two types
(a) Afferent Fibres They transmit impulses from tissues/organs to the CNS.
(b) Efferent Fibres They transmit regulatory impulses from the CNS to the
concerned peripheral tissues/organs.
The PNS is divided into two divisions i.e., somatic neural system and autonomic

neural system.
The somatic neural system relays impulses from the CNS to skeletal muscles
while, the autonomic neural system transmits impulses from the CNS to the
involuntary organs and smooth muscles of the body.
The autonomic neural system is further classified into sympathetic neural
system and parasympathetic neural system.
Neuron (Structural and Functional Unit of Neural System)

Neurons are the longest cells in the body. Human neural system has about 100
billion neurons. Majority of the neurons occur in the brain. Fully formed
neurons never divide and remain in interphase throughout life.
A neuron is a microscopic structure composed of three major parts
1. Cell Body (Cyton or Soma)
Like a typical cell it consists of cytoplasm, nucleus and cell membrane. The
cytoplasm has typical cell organelles like mitochondria, Golgi apparatus, rough
endoplasmic reticulum, ribosomes, lysosomes, certain granular bodies,

neurofibrils, neurotubules and Nissl’s granules.
Presence of neurofibrils and Nissl’s granules is the characteristic to all neurons.
Neurofibrils play a role in the transmission of impulses.