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peripheral nervous system
nervous system located outside the brain and spinal cord
provides vital links to the body and outside world
provides communication between the central nervous system (CNS) and the rest of the body
contains cranial and spinal nerves
somatic sensory system
General: includes touch, pain, pressure, vibration, temperature, and proprioception in skin, body wall, and limbs
Special includes hearing, equilibrium, and vision.
visceral sensory system
General: includes stretch, pain, temperature, chemical changes, and irritation in viscera; nausea and hunger
Special includes taste and smell.
somatic nervous system
a voluntary somatic (muscle) motor system that conducts impulses from the CNS to skeletal muscles.
autonomic nervous system
an involuntary visceral (organ) motor system that conducts impulses from the CNS to cardiac muscles, smooth muscles and glands. It is further divided into the sympathetic and parasympathetic divisions.
sympathetic
mobilizes body systems during activity
responsible for the fight or fight response, an activity that is evident during vigorous exercise, excitement or emergency dangerous situations
Examples:
pounding heart
fast and deep breathing
dilated pupils
cold/sweaty skin
parasympathetic
conserves energy by promoting housekeeping functions during rest such as digestion and elimination of feces and urine
Example:
a person relaxing after dinner and reading the newspaper because the heart rate are at low-normal levels, and the gastrointestinal tract is digesting food
pupils are constricted as the eyes focus for close vision.
sensory receptors
pick up stimuli (environmental changes) from inside and outside the body and then initiate impulses in sensory axons, which carry the impulse to the CNS
nerves
bundles of peripheral axons, can be sensory only, motor only or sensory and motor (called a mixed nerve, most common)
ganglia
clusters of peripheral cell bodies
motor endings
axon terminals of motor neurons that innervate the effector organs, muscles and glands
CN I: Olfactory
contain special sensory nerves of smell
CN II: Optic
contain special sensory nerves of vision, since it develops as an outgrowth of brain is is not a true nerve, but a brain tract.
CN III: Oculomotor
innervates four of the extrinsic eye muscles (muscles that move the eyeball in the orbit, oculomotor means "eye mover").
CN IV: Trochlear
innervates an extrinsic eye muscle that hooks through a pulley-shaped ligament in the orbit (trochlear means "pulley").
CV V: Trigeminal
provides general sensory innervation to the face and motor innervation to the chewing muscles (trigeminal means "threefold" which refers to the nerves three major branches), called the great sensory nerve of the face.
CN VI: Abducens
innervates the muscle that abducts (turns laterally) the eye
CN VII: Facial
nerve that innervates the muscles of facial expression, taste, as well as other structures
CN VIII: Vestibulocochlear
contain special sensory nerves of hearing and equilibrium
CN IX: Glossopharyngeal
helps innervate the tongue and pharynx, taste (glossopharyngeal means "tongue" and "pharynx").
CN X: Vagus
a nerves that wanders beyond the head into the thorax and abdomen (vagus means "wanderer").
CN XI : Accessory
it originates from the cervical region of the spinal cord, enters the skull through an opening and exits the skull to carry motor innervation to the trapezius and sternocleidomastoid muscles.
XII: Hypoglossal
runs below the tongue and innervates the tongue muscles (hypoglossal means "below the tongue".
spinal nerves
31 pairs, exit from the spinal cord through spaces between the vertebrae called intervertebral foramina
- Nerves are named according to their point of issue from the vertebral column
Cervical (8)
C1-C8
Thoracic (12)
T1-T12
Lumbar (5)
L1-L5
Sacral (5)
S1-S5
Coccygeal (1)
Co1
dorsal roots
contain axonal processes of sensory neurons arising from cell bodies in the dorsal root ganglion
meets the ventral root to form a spinal nerve
ventral roots
contain axonal processes of motor neurons whose cell bodies are located in ventral gray column of the spinal cord
spinal nerve
connects to the spinal cord by a dorsal (posterior) root and a ventral (anterior) root
exits the intervertebral foramina and divides into two branches
dorsal (posterior) ramus
(smaller branch) going to the posterior part of the body, area behind the transverse processes of the vertebral column
ventral (anterior) ramus
(much larger branch) going to the anterolateral part of the body
ventral (anterior) rami
_ of all the spinal nerves (except T2-T12 branch) join one another lateral to the vertebral column, forming nerve plexuses
cervical nerve plexus
formed by the ventral rami of C1 through C4
an important nerve of the cervical plexus is the phrenic nerve that originates from spinal cord segments C3, C4 and C5
the phrenic nerve travels through the thorax passing along sides of the pericardial sac to innervate the diaphragm
brachial nerve plexus
formed by the ventral rami of C5 through T1 and are responsible for innervation to the arm, forearm and hand
Important nerve is the median nerve, innervates most muscles of the anterior forearm and lateral palm.
lumbar nerve plexus
formed by the ventral rami of L1 through L4 and lies within the muscles of the posterior abdominal wall
main branches innervate the anterior region of the thigh, important nerve of the plexus is the femoral nerve.
sacral nerve plexus
formed by the ventral rami of L4 through S4, because some fibers from the lumbar plexus contribute to the sacral plexus we can refer to these two plexuses as the lumbosacral plexus
innervates the lower limb and buttocks
An important nerve of the plexus is the sciatic nerve which is the thickest and longest nerve in the body
The sciatic nerve supplies all of the lower limb except the anterior and lateral region of the thigh.
thoracic region
each ventral ramus (branches) travels along the lower border of the rib and form the intercostal nerves (not a plexus)
they travel with an intercostal artery and vein forming the neurovascularbundle to supply the corresponding rib space.
dermatomes
area of skin that is mainly supplied by one spinal nerve
area of skin is innervated by cutaneous (skin) sensory branches from a single spinal nerve.
all spinal nerves except C1 participate in dermatomes
Examples
C3 supplies the skin around the neck
S1/S2 supply the skin on back of lower limb
autonomic nervous sytem
system of motor neurons that innervate smooth muscle, cardiac muscle and glands of the body (effectors).
by controlling these effectors, the ANS regulates such visceral (organ) functions as heart rate, blood pressure, digestion, and urination, which are essential for maintaining the stability of the body's internal environment.
general visceral (organ) motor division of the peripheral nervous system
somatic motor system
focuses on the motor innervation of skeletal muscle (targets the skeletal muscle) and is a one-neuron pathway
autonomic motor system
targets smooth muscle, cardiac, smooth, and glands and isa two-neuron pathway with a synapse in an autonomic ganglion
preganglionic neuron
axon of the_ synapses with the cell body of the second postganglionic neuron in a peripheral autonomic ganglion (motor ganglia)