Peripheral Nervous system include the sensory systems and motor systems. There are twelve cranial nerves connecting the brain to the head and neck region and thirty one spinal nerves connecting the spinal cord to the thorax, abdomen and limb.
Detail of the description of the nervous system are ana...
Content
a. Somatic and Autonomic Nervous system
b. Differences between Hormonal and Nervous coordination
c. Structure and function of a Neuron
d. Reflex and Voluntary Action
The peripheral nervous system (PNS) consists of all nerves outside the brain and
spinal cord. These are made up of sensory nerves which arise from all parts of the
body to the central nervous system and the motor nerves running from the central
to all parts of the body. The peripheral nervous system receives signals changes
from the environment registered by the receptors or sense organs and send them
to the central nervous system which integrates the information.
The PNS consists of twelve (12) pairs of cranial nerves and thirty-one (31) pairs of
spinal nerves. The cranial nerves arise from the brain while the spinal nerves arise
from the spinal cord. The peripheral nervous system is subdivided into two
systems. These are;
(i) Somatic nervous system
(ii) Automatic nervous system.
SOMATIC NERVOUS SYSTEM
They deal mainly with external stimuli and their responses. The sensory nerves
transmit impulses from the external stimuli to the central nervous system and
relay responses through the motor neurons or the body causing the body
movement. The somatic nervous system controls activities that are mainly
voluntary.
AUTONOMIC NERVOUS SYSTEM (ANS)
The autonomic nervous system controls the involuntary actions inside the body
such as the rate of heart, sweating, and peristaltic contractions of the intestine.
The neuronal of the autonomic nervous system are connected to involuntary
muscles of the internal organs.
The autonomic nervous system consists of two parts namely
a) Sympathetic nervous system
, b) Parasympathetic nervous system.
Sympathetic Nervous System
Consists of nerves which connect internal organs to the thoracic and lumber area
of the spinal cord. The sympathetic nervous system stimulates many parts of the
body for necessary action in time of danger.
Para- Sympathetic Nervous System
Consists of nerves which connect internal organs to the tenth cranial nerves and
the sacral region of the same organ as sympathetic nervous system but its action is
opposite or antagonistic to sympathetic nervous system.
Differences between Sympathetic and Parasympathetic Nervous system
Sympathetic. N. System parasympathetic. N. system
i. Accelerates heart beat slow down heart beat
ii. Constricts arteries dilates arteries
iii. Dilate iris (pupil) constricts iris
iv. Slows gut movement speed up gut movement
v. contracts bladder and relaxes bladder and sphincters
Sphincters contraction of the bladder muscles
i. Relaxation of bladder lowers the blood pressure
Muscle
vii. Raises the blood pressure it stimulates the secretion of salivary
glands
THE NEURONES
A neuron or nerve cell is defined as the basic unit of nervous system which is
responsible for the transmission of impulses within the body. The neuron is the
functional unit of the nervous system. The neurons are found in the brain, spinal
cord or nerve fibers of animals which are responsible for receiving and
transmitting impulses.
STRUCTURE OF A NEURONE
A neuron consists of three major parts. The cell body, dendron/dendrite and
axon. The cell body (soma) consists of the nucleus and cytoplasm. The dendron are
projections from the cell body forming many fine dendrites. The dendrites carry
impulses towards the cell body. The axon is made up of single, long fibre which
transmits impulses away from the cell body. Each axon is enclosed within a fatty
myelin sheath and outer layer of neuralemma- The myelin sheath which is formed
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