Spinal cord and its structure in detail
The spinal
cord is in fact a tubular bundle of nerves.it starts from brain stem and
extends to lower back. Like brain, the spinal cord is also covered in meninges.the
vertebral column surrounds and protects spinal cord.it is supported by the back
bone .consist of liquid- fluid inside called bone marrow.
The outer
region of spinal cord is made of white matter (containg myelinated axons).the
centeral region is butterfiy shaped that surrounds the centeral canal. It is
made of grey matter (containing neuron cell bodies).
31 pairs of
spinal nerves arise along spinal cord.these are “mixed” nerves becouse each
contains axons of both sensory and motor nerves (neurons). At the point where a
spinal nerves arises from spinal cord, there are two roots of spinal
nerves.both roots unite and forms one mixed spinal nerves.
·
The dorsal
root contains sensory axons and a ganglion where cell bodies are located.
·
The ventral
roots contain axons of motor nerves.
Spinal cord
performs two main functions
·
It serves
as a link between body parts and the brain. Spinal cord transmits nerves
impulses from body parts to the brain and from the brain to the body parts.
·
Spinal cord
also act as a coordinator , responsible for some simple reflexes.
Peripheral
nervous system also involves in spinal cord
The
peripheral nervous system is composed of nervous and ganglia. Ganglia are the
clusters of neuron cell bodies outside CNS.nerves arises or lead to the brain
and spinal cord. So they are named as cranial and spinal nerves. Humans have 12
pairs of cranial nerves and 31 pairs of spinal nerves. Some cranial nerves are
sensory, some are motor and some are mixed. On the other hand,all spinal nerves
ARTE mixed nerves.
The cranial
and spinal nerves make two pathways i.e sensory
pathway (conducting impulses from receptors to CNS) and motor pathway
(conducting impulses from CNS to effectors).motor pathway makes two systems.
SOMATIC NERVOUS SYSTEM
It is
responsible for the conscious and voluntary actions. It is includes all of the
motor neurons that conduct impulses from CNS to skeletal muscles.
AUTONOMIC NERVOUS SYSTEM
It is
responsible for the activities, which are not under conscious control. It
consists of motor neurons that send impulses to cardiac muscles, smooth muscles
and parasympathetic system. Sympathetic nervous system prepares body to deal
with emergency stuations.this is often called fight or fights response.the
major function of this system is to control the stress in the body in time of
stress.they nerves contract to control the stress and relex when the saree disappears. Spinal cord is
the continuation os medulla the part of the brain.
Spinal cord
is roughly 40 centi metre long and about as wide as your thumb for most of its
length.
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