Transcript The Peripheral Nervous System

Biology 211
Anatomy & Physiology I
Dr. Thompson
The Peripheral Nervous System
Recall: All organs are composed of
Epithelial tissue
Muscle tissue
Connective tissue
Nervous tissue
Nervous tissue: Excitable cells (neurons)
Nonexcitable (supporting) cells
Connective tissue: Meninges in central nervous system
Endoneurium
Perineurium
in peripheral nervous system
Epineurium
Epithelium
found only in blood vessels of PNS
Muscle (smooth)
Cells of Nervous Tissue:
1) Excitable cells = Neurons
Carry electrical signals
from one place to another
Pass these signals to other cells
2) Nonexcitable cells = Glia in CNS
Satellite cells
Schwann cells
in PNS
In Peripheral Nervous System:
Neuron cell bodies
grouped into ganglia
(single = ganglion)
Axons grouped into
nerves
Nerve:
Each axon surrounded by
Schwann cells, which may
or may not form a myelin
sheath.
Outside the Schwann
cells, each axon is
surrounded by layer of
connective tissue
called endoneureum
Axons (surrounded by
Schwann cells and
endoneureum) form
bundles called fascicles,
each of which is
surrounded by a thicker
layer of connective tissue
called perineureum
Fascicles group together
to form a nerve, which is
surrounded by an even
thicker layer of
connective tissue called
epineureum
Cranial Nerves connect to the
brain. Three carry only sensory
information, five carry mostly
motor information (with a small
amount of sensory), and four
carry both motor and sensory
information
Spinal Nerves connect to the
spinal cord. All of these carry
both motor and sensory
information
Cranial Nerves:
-
Originate from the brain
- Pass through foramina in the
skull to reach the periphery
12 pairs, numbered from superior to inferior.
They carry the special senses (smell, vision, hearing, taste,
and equilibrium)
They carry sensory information from the head, face, and
much of the neck.
They carry motor innervation to muscles of the eye, face,
larynx, and tongue; some muscles of the neck and back.
One (CN X) carries autonomic information to organs of the
thorax and abdomen.
You will not be asked to identify
cranial nerves on either
diagrams or specimens
The names, functions, origins, terminations, foramina,
and effects of damage are listed and described in your
Saladin text for all of the cranial nerves.
Using this information, you will be expected to know
a) The names and numbers of all 12 pairs of cranial nerves,
including the subdivisions of cranial nerve V
b) The foramen through which each cranial nerve passes
c) The primary functions of each cranial nerve
d) The effects of damage to each cranial nerve
Using this information, you will be expected to know
a) The names and numbers of all 12 pairs of cranial nerves,
including the subdivisions of cranial nerve V
b) The foramen through which each cranial nerve passes
c) The primary functions of each cranial nerve
d) The effects of damage to each cranial nerve
Example: The abducens nerve (VI) originates from the pons
and exits the skull through the superior orbital fissure. It
innervates the lateral rectus muscle which causes the eye to
rotate laterally. Injury to this nerve on either side causes an
inability to rotate that eye laterally, and unopposed function
of the other muscles often cause the eye rotate medially.
Spinal Nerves:
-
Originate from the
spinal cord by dorsal
and ventral roots
-
Pass between vertebrae
through intervertebral
foramina to reach the
periphery
Spinal Nerves:
-
Originate from the
spinal cord by dorsal
and ventral roots
-
Pass between vertebrae
through intervertebral
foramina to reach the
periphery
-
31 pairs, numbered from
superior to inferior in
each region of the back
Naming Spinal Nerves:
Cervical nerves #1 through #7
leave the vertebral canal through
the intervertebral foramina ABOVE
the vertebrae with the same
numbers.
Example: Cervical nerve #3 passes
above cervical vertebra #3 (between
cervical vertebra #2 and #3)
Cervical nerve #8 leaves the vertebral
canal through the intervertebral foramen between
cervical vertebra #7 and thoracic vertebra #1 .
Naming Spinal Nerves:
Cervical nerve #8 leaves the
vertebral canal through the
intervertebral foramen between
cervical vertebra #7 and thoracic
vertebra #1 .
All thoracic, lumbar, and sacral
nerves plus the single coccygeal
nerve leave the vertebral canal
through the intervertebral foramina
BELOW the vertebrae with the same numbers.
Example: Thoracic nerve #3 passes below thoracic
vertebra #3 (between thoracic vertebra #3 and #4)
Spinal nerves passing
through intervertebral
foramina
Spinal nerve passing
through intervertebral
foramina
Immediately distal to
the intervertebral
foramen, each spinal
nerve divides into a
dorsal ramus and a
ventral ramus.
Both rami are mixed,
carrying both afferent
& efferent information
Dorsal rami of all spinal
nerves innervate the
muscles and the skin of
the back at their level.
For example: the dorsal
ramus of nerve
thoracic-2 innervates
the muscles and skin of
the back at the level of
vertebra thoracic-2
Ventral rami of spinal
nerves Thoracic 2 -12
innervate muscles and
skin of body wall (thorax
and abdomen)
Ventral rami of spinal
nerves Thoracic 2 -12
innervate muscles and
skin of body wall (thorax
and abdomen)
But:
Ventral rami of all other
spinal nerves
Cervical 1-8,
Thoracic 1,
Lumbar 1-5,
Sacral 1-5
enter into plexes
(singular = plexus)
A plexus is an interchange which allows nerves from
different spinal cord levels to combine to serve common
structures.
1. Each nerve distal to a
plexus carries axons to
& from more than
one level of the spinal
cord.
Example: Radial nerve
carries information to
& from five levels of
the spinal cord:
C5, C6, C7, C8, T1
1. Each nerve distal to a plexus carries axons to / from
more than one level of the spinal cord.
Example: Radial nerve carries information to and from
five levels of the spinal cord: C5, C6, C7, C8, T1
2. Axons carrying
information to / from a
single spinal cord level
are distributed through
more than one nerve
distal to the plexus
Example: Spinal cord
level C7 sends and
receives information
through more than 20
different nerves
Four plexes:
Cervical plexus
Brachial plexus
Lumbar plexus
Sacral plexus
Cervical Plexus
Originates from ventral rami of
nerves C1, C2, C3, C4 (+C5)
Carries efferent neurons to
many muscles of the neck.
Carries afferent neurons from
skin of the neck, shoulder, and
scalp near ear
Brachial Plexus
Originates from ventral rami of
nerves C5, C6, C7, C8, T1,
(+C4)
Carries efferent neurons to
muscles of the shoulder, arm,
forearm, and hand
Carries afferent neurons from
skin of the shoulder, arm,
forearm, and hand
Lumbar Plexus
Originates from ventral rami of
nerves L1, L2, L3, L4, (L5)
Carries efferent neurons to
muscles of the anterior pelvis,
anterior and medial thigh
Carries afferent neurons from
skin of the anterior pelvis,
anterior and medial thigh, and
medial leg.
Sacral Plexus
Originates from ventral rami of
nerves (L4), L5, S1, S2, S3,
S4, (S5, Cx1)
Carries efferent neurons to
muscles of the posterior
pelvis, posterior thigh, anterior
and posterior leg, and foot
Carries afferent neurons from
skin of the posterior pelvis,
posterior thigh, anterior and
posterior leg, and foot.
We will go into greater detail about the bracheal plexus,
but you will not be held responsible for details of the
cervical, lumbar, or sacral plexes EXCEPT:
You need to know which spinal nerves contribute their
ventral rami to each plexus.
You need to know which plexus gives rise to each of the
following nerves, and which area of the body each of them
innervates:
Ansa cervicalis
Femoral
Fibular (common peroneal)
Genitofemoral
Inferior and superior gluteal
Obturator
Phrenic
Pudendal
Tibial
(Sciatic)
Summary of the Brachial Plexus
Roots
Trunks Upper
Middle
Lower
Divisons
Anterior
Posterior
Cords:
Lateral
Posterior
Medial
More than 20 nerves leave the brachial plexus to supply
both afferent (sensory) and efferent (motor) innervation to
the shoulder, arm, forearm, hand, and parts of the neck and
thoracic wall.
We will follow five of these:
1. Musculocutaneous nerve:
Arises from the lateral cord of
the brachial plexus.
Innervates muscles of the
anterior compartment of the
arm; skin of lateral forearm
1. Musculocutaneous nerve: Arises from the
lateral cord of the brachial plexus.
Innervates muscles of the anterior compartment
of the arm; skin of lateral forearm
2. Ulnar Nerve: Arises from
the medial cord of the brachial
plexus.
Innervates muscles in the
anterior compartment of the
forearm & some intrinsic
muscles of the hand; skin on
medial third of hand (both
anterior and posterior
surfaces)
2. Ulnar nerve: Arises from the medial cord of brachial
plexus. Innervates muscles of the anterior compartment
of forearm & some muscles of hand; skin on medial third
of hand (posterior & anterior)
3. Median Nerve: Arises
from medial AND lateral cords
of the brachial plexus.
Innervates muscles in the
anterior compartment of the
forearm & some intrinsic
muscles of the hand; skin on
anterior surface of lateral twothirds of hand
3. Median Nerve: Arises from medial AND lateral cords
of the brachial plexus. Innervates muscles in the anterior
compartment of the forearm & some muscles of hand;
skin on anterior surface of lateral two-thirds of hand
4. Radial Nerve: Arises from
posterior cord of brachial
plexus.
Innervates muscles in posterior
compartment of arm & posterior
compartment of forearm; skin on
posterior surface of lateral twothirds of hand & skin on
posterior surfaces of forearm
and arm
4. Radial Nerve: Arises: posterior cord of brachial plexus.
Innervates muscles in posterior compartments of arm &
forearm; skin on posterior surface of lateral two-thirds of
hand & skin on posterior surfaces of forearm and arm
5. Axillary Nerve: Arises from
posterior cord of brachial
plexus.
Innervates shoulder joint,
deltoid and teres minor
muscles; skin of shoulder
Cutaneous Innervation
Axillary
(Medial
antebrachial
cutaneous)
Radial
Musculocutaneous
Ulnar
Median
Anterior
Posterior