nervous system; PNS Flashcards
the PNS consists of
nerves extending from the brain and spinal cord. cranial and spinal nerves
-link all of the regions from the body to the CNS
-ganglia
ganglia
cluster of cell bodies of neurons
nerve fiber:
an axon, its neurolemma, and its surrounding endoneurial connective tissue
neurolemma
consists of cell membranes of schwann cells that surround the axon, separating it from other axons
-two types
-myelinated and unmyelinated
Schwann cells
myelin sheath producing cells
what does a nerve consist of
-bundle of fibers or fascicles
-the CT coverings that surround and bind the fibers or fascicles
-the blood vessels that nourish the nerve fibers and their coverings
what are the three CT coverings around nerves
- endoneurium
- perineurium
- epineurium
- endoneurorium
a delicate CT immediately surrounding the neurolemma cells and axons
- perinuerium
dense connective tissues that encloses the fascicle; providing an effective barrier against protection of a foreign body
- epineurium
thick CT sheath that surround and encloses a bundle of fascicles. it forms the outermost covering of the nerve.
describe the sensory and motor division of the PNS
-sensory (afferent): signals are picked by sensory receptors
-motor (efferent) signals are carried away from the CNS
describe the structures that make up a spinal nerve
- rootlets spinal nerves arise rootlets. There are two: ventral (motor) and dorsal (sensory)
- ventral and dorsal nerve root
3.mix at spinal nerve - dorsal and ventral rami.
how many spinal nerves are there
31 pairs
what are the regional divisions of the PNS
-somatic
-visceral
what are the subdivisons of the PNS
-sensory: somatic and visceral
-motor: somatic and visceral (ANS)
describe sensory somatic division
general: touch, pain , vibration, pressure, ant temp
-proprioreception: a sense that detects the amount of change in muscles,
-special somatic senses: hearing, equilibrium, and vision
describe sensory visceral division
general: stretch, pain , temp, nausea, and hunger
special: taste and smell. chemical senses with sensory receptors in oral and nasal cavities
motor somatic division
signals the contraction of skeletal muscles
-under voluntary control
motor visceral division
regulates the contraction of smooth and cardiac muscle, controls the secretion of glands
-ANS
-involuntary
what is a nerve plexus and the regions
network of nerves, form a new set of PNS nerves. allow room for excpetions.
-cervical, brachial, sacral, and lumbar region
dermatome
area of skin innervated by sensory fibers of one spinal nerve
myotome:
muscle mass recieving innervation from fibers of one spinal nerve
