Download Spinal Cord and the Peripheral Nervous System

Peripheral Nerves and
Arteries
Information IN
Sensory or “afferent” neurons carry
information into the CNS from receptors
located throughout the body.
Information OUT
Motor or “efferent neurons” carry
electrical impulses away from the CNS
to innervate “effector organs,” like
muscles and glands.
Sensory Receptors in Skin
•They detect
sensory input and
convert them into
electrical impulses
that will travel up
neurons along the
spinal cord.
•Sensory input
about touch, pain,
heat, cold, pressure.
Proprioceptors
•Sensory receptors
that report on
internal events in
your muscles and
joints.
•They report on
muscle stretch and
joint position.
•They generate
electrical impulses
that will travel up
neurons to the
CNS.
The Reflex Arc
Dorsal root ganglia
contain cell bodies
of sensory neurons
Upper and Lower Motor Neurons
 Of course, the signal to initiate motor
movement does not begin at the neuron cell
body in the spinal cord; it begins in the brain.
 The motor neuron whose cell body is in the
brain is called an upper motor neuron.
 It relays the signal to the motor neuron whose
cell body is in the spinal cord, called the lower
motor neuron.
 The lower motor neuron synapses on a
muscle, causing contraction.
Lower Motor Neurons “Innervate” Muscle
Cells at the Neuromuscular Junction
Motor Neurons “Innervate” Muscle Cells
Neuron “innervates” muscle
and triggers it to contract by
the release of a chemical
neurotransmitter.
Order of Nerves Firing
 To pick up an object, you wrap your hand
around the object. This gives you a sensory
input as you feel the object.
 The sensory neuron sends the impulse to the
spinal cord where it synapses on an
interneuron.
 The interneuron synapses on a motor neuron
 The motor neuron tells your muscles to
contract so you can pick up the object.
Upper and Lower Motor Neuron
Diseases
 Some diseases only effect the UMN, and
some only effect the LMN.
 Lower motor neuron disorders:


Multiple Sclerosis
Polio
 Upper motor neuron disorder:

Cerebral palsy
Autonomic Neuropathy
 Autonomic neuropathy is damage to
autonomic nerves.
 The autonomic nerves are those that supply
involuntary body functions, including heart
rate, blood pressure, perspiration and
digestion.
 A common symptom in autonomic
neuropathy is dizziness. Muscle twitches and
lack of sensation are NOT symptoms, since
they are not supplied by autonomic nerves.
XS of the Spinal Cord
Dorsal median sulcus
Roots
Rami
Ventral median fissure
Spinal Nerve
Spinal Nerve Plexi
 A network of ventral
rami
 Interlacing network
 Each branch carries
fibers from several
spinal nerves
 Gives redundancy in
case of nerve damage
C1-C4- Cervical
plexus
C5-T1- Brachial
plexus
L1-L4- Lumbar
Plexus
L4-S4- Sacral
Plexus
Cervical Plexus
Nerves innervate skin of
neck, back of head and
upper shoulder.
Phrenic nerve
(important for
breathing!) from C3, C4,
C5. Carries afferent
and efferent fibers to the
respiratory diaphragm.
Brachial
Plexus
ROOTS
TRUNKS
DIVISIONS
CORDS
NERVES
Brachial
Plexus
Brachial Plexus
 Damage to Brachial Plexus


Klumpke’s paralysis (brachial plexus damaged
during birth)
Acquired Brachial Plexus injuries
 Crutch paralysis (total upper extremity paralysis)
 Claw Hand / Ape hand
 Hand of benediction
 Wrist Drop (Waiter’s Hand)
Peripheral damage to the
Brachial Plexus
“Funny Bone”
damage
Carpal Tunnel
Axillary
Musculocutaneus
Major Nerves
of the Upper
Extremity
Axillary Nerve
 Deltoid
 Teres minor
Musculocutaneus Nerve
 Supplies anterior muscles of the arm
Median Nerve
 Supplies no muscles of the arm
 Supplies anterior forearm (except flexor carpi
ulnaris)
 Carpal Tunnel Syndrome
 Hand of benediction
Ulnar Nerve
 Supplies flexor carpi ulnaris
 “Funny Bone”
 Damage can cause claw/ape hand
Radial Nerve
 Supplies muscles on the posterior arm and
forearm



Triceps brachii
Extensor carpi radialis
Extensor digitorum communis
 Damage can cause wrist drop
Lumbo-Sacral Plexus
• Lumbar:
– Femoral nerve
• Sacral:
– Sciatic nerve
Obturator
Femoral
Nerves of the
Lower
Extremity
Obturator Nerve
 Supplies adductor muscles
Sciatic Nerve
 Supplies back of thigh



Biceps femoris
Semimembranosis
Semitendonosis
 Supplies leg and foot
Femoral Nerve
 Anterior Thigh

Quadriceps femoris
Tibial Nerve
 Posterior leg and foot



Gastrocnemius
Soleus
Tibialis Posterior
Common Peroneal Nerve
 Superficial branch


Lateral side of leg
Supplies peroneal muscles
 Deep branch


Supplies anterior leg muscles
Injury causes “Foot Drop”
Dermatomes
 The area of skin innervated by a cutaneous
branch of a spinal nerve at a particular level.
Arteries of the
Upper Extremity
Arteries of the Upper Extremity
 Subclavian (becomes axillary artery in armpit)
 Axillary (becomes brachial artery in arm)

Supplies triceps brachii
 Brachial (divides into radial and ulnar arteries
when it reaches the elbow)

Supplies arm muscles except triceps brachii
 Radial
 Ulnar
External
Iliac artery
Arteries of
the Lower
Extremity
Arteries of the Lower Extremity
 External iliac (becomes femoral artery)
 Femoral (becomes popliteal artery at knee)

Femoral artery supplies muscles of thigh
(including adductor muscles)
 Popliteal (becomes tibial artery in leg)
 Tibal

Leg muscles
Peripheral Vascular Disease (PVD)
 Refers to the obstruction of large arteries, frequently in
the lower extremity. Usually caused from
atherosclerosis (fatty plaques).
 Symptoms
 Claudication: pain, weakness, numbness, or
cramping in muscles due to decreased blood flow
 Sores, wounds, or ulcers that heal slowly or not at all
 Change in color (blueness or paleness) or
temperature (coolness) when compared to the other
limb
 Diminished hair and nail growth on affected limb and
digits (shiny, hairless skin)