TYPES OF NERVES
SENSORY OR AFFERENT NERVES .
1.
When action potentials are generated by sensory
receptors on the dendrites of these neurons, they ate transmitted to to the
spinal cord by the sensory nerve fibres.
2.
The impulses may then pass to the brain or to
connector neurons of reflex arcs in the spinal cord.
SENSORY RECEPTORS
1.
Specialized endings of sensory neurons respond
to different stimuli (changes) inside and outside the body .
v Somatic,cutaneous
or common senses:
1.
These are originate in the skin.
2.
They are pain,touch, heat and cold .
3.
Sensory nerve endings in the skin are fine
branching filaments without myelin sheaths.
4.
When stimulated, an impulse is generated and
transmitted by the sensory nerves to the brain where the sensation is
perceived.
v Proprioceptor
senses.
These originate in muscles and joints and contribute to the maintenance
of balance and posture.
v Special
senses.
These are sight,hearing,smell,touch and taste.
v Autonomic
afferent nerves.
These
originate in internal organs,glands and tissues,e.g baroreceptors,
chemoreceptors, and are associated with reflex regulation of involuntary
activity and visceral pain.
MOTOR OR EFFERENT NERVES
1.
Motor nerves orginate in the
brain,spinal cord and autonomic ganglia.
2.
They transmit impulses to the
effector organs:muscles and glands.
These are two types.
v Somatic
nerves: these are involved in voluntary and reflex skeletal muscle
contraction.
v Autonomic
nerves:these are sympathetic and para sympathetic nerves involved in
cardiac and smooth muscle contraction and glandular secretion.
MIXED NERVES
1.
In the spinal cord , sensory and
motor nerves are arranged in seprate groups, or traits.
2.
Outside the spinal cord , when
sensory and motor nerves are enclosed within the same sheath of connective
tissue they are called MIXED NERVES
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