Spinal Cord
the anterior rami of C8 and T1 joint to form the
inferior trunk
Nerve Plexuses The ______________ perform simple functions (to elevate or depress the ribs), which is why the intercostal nerves remain segmented.
intercostal muscles
lumbar region has 5 pairs of spinal nerves and provides most of the innervation of what?
lower extremities
sacral region has 5 pairs of spinal nerves and contribute to innervation of what?
lower extremities
the lumbosacral plexus gives rise to the nerves of which extremity?
lower extremities
Spinal nerves from lumbar and sacral spinal cord segments join together to form what?
lumbosacral plexus
the ______________ delivers motor to, and sensory from, the lower extremity.
lumbosacral plexus
the anterior branch of the inferior trunk forms the
medial cord
the anterior ramus of C7 forms the
middle trunk
This type of reflex is the simplest type of reflex. It involves a sensory neuron synapsing with a motor neuron.
monosynaptic reflex
since plexuses are formed from spinal nerves (mixed), the nerves they give rise to are comprised of ______________.
motor and sensory fibers
this type of neuron is referred to as the efferents
motor neurons (lower)
interneurons are what type of neurons?
multipolar neurons
motor neurons are what type of neuron?
multipolar neurons
these neurons have a single axon and multiple dendritic processes
multipolar neurons
motor neurons deliver impulses (motor commands) to where?
muscles and glands
Radial Nerve Motor
muscles of the posterior arm and forearm
multipolar neurons relay impulses to what?
muscles, glands, other neurons
the lateral cord gives rise to which nerves?
musculocutaneous nerve and part of the median nerve
The white matter of the spinal cord is mainly composed of
myelinated axons
the joining of spinal nerves to form nerves comprised of more than one level of the spinal cord
nerve plexuses
Gray matter of the spinal cord is mostly composed of
neuronal cell bodies
in unipolar neurons, the single process divides into...
peripheral and central processes
which process of the unipolar neuron carries sensation from skin to cell body?
peripheral process
Spinal nerves contain
peripheral processes of unipolar (afferent) neurons the axons of motor neurons (efferents).
in the spinal cord, this is attached to the surface of the spinal cord.
pia mater (1 in image)
The spinal cord is protected by the same 3 layers of the meninges as found around the brain which are what?
pia mater arachnoid mater dura mater (as well as cerebrospinal fluid in subarachnoid space):
the posterior branches of all 3 trunks form the
posterior cord
The afferent neuron in a polysynaptic reflex synapses with several interneurons in which horn?
posterior horn
the anterior rami of C5 and C6 join to form the
superior trunk
Median Nerve Motor
teres, flexor carpi radialis, palmaris longus, flexor digitorum superficialis, flexor digitorum profundus (1/2), pronator quadratus, thenar muscles, and 2 lumbricals
the brachial plexus extends from where to where?
the lower neck, between the clavicle and first rib and then into the axilla
What is the response when the sensory (afferent) neuron synapses with a motor neuron?
the motor (efferent) neuron causes the muscle (that was stretched) to contract
the central processes of sensory neurons enter what?
the spinal cord
what are two possibilities of interneurons?
they may decide to send the information up to the cerebral cortex for awareness. they may decide to send the information to motor neurons in anterior horn for motor response
what is the function of interneurons?
they receive information from sensory neurons and "decide" what to do with it
Why is a lumbar puncture or "spinal tap" performed below the L1 vertebral level?
this is well below the termination of the spinal cord in most patients
this region has 12 pairs of spinal nerves
thoracic region
Deep Fibular (Peroneal) Nerve Motor:
tibialis anterior, extensor digitorum longus and extensor hallucis longus (anterior compartment).
the medial cord gives rise to which neves?
ulnar nerve and part of the median nerve
____________ neurons have cell bodies that has a single process attached.
unipolar
sensory neurons are what type of neurons?
unipolar neurons
the cervical region has 8 pairs of spinal nerves and provides most of the innervation of what?
upper extremities
the brachial plexus innervates the skeletal muscles and carries sensation from the skin of which extremity?
upper extremity
in the spinal cord, which horns are comprised of cell bodies of motor neurons which deliver impulses to muscles and glands of the body?
ventral horns
the anterior wings of gray matter are known as
ventral horns
the spinal cord has _______ cervical segments, _________ thoracic segments, _________ lumbar segments, and _________ sacral segments
8, 12, 5, 5
In a polysynaptic reflex, the ___________ recruit several muscles in order to remove the body part from the painful stimulus. The interneurons will activate as many motor neurons as it takes (to as many muscles as it takes) to remove the body from the painful stimulus.
interneurons
these neurons are also referred to as association neurons.
interneurons
the anterior branches of the superior and middle trunks form the
lateral cord
However, the ______________ continues to lengthen after the spinal cord has reached its full length. This causes a lengthening of the spinal nerves at the end of the spinal cord.
vertebral column
Deep Fibular Peroneal Nerve Most Noticeable Weakness With Damage:
1) Dorsiflexion and inversion of the foot 2) extension of the toes
Tibial Nerve Most Noticeable Weakness With Damage
1) Extension of the thigh (at the hip) 2) flexion of the leg (at knee) 3) plantarflexion of the foot 4) flexion of the toes.
neurons can be functionally classified as....
1) sensory neurons 2) motor neurons 3) interneurons
how is the spinal cord protected?
1. vertebral canal 2. meninges (pia, arachnoid, dura) 3. cerebrospinal fluid
the brachial plexus is formed bu the anterior rami of spinal nerves...
C5-T1
Femoral Nerve Most Noticeable Weakness With Damage
Flexion of the thigh (at the hip) and extension of the leg
Why is there a collection of nerve roots at end of spinal cord called cauda equina?
In a newborn, the spinal cord fills the vertebral canal and spinal nerves pass laterally through their respective intervertebral foramina:
Median Nerve Sensation
Skin of the lateral palm, thumb, index finger, middle finger, and 1/2 of ring finger
Obturator Nerve Most Noticeable Weakness With Damage
adduction of the thigh (at the hip)
Obturator Nerve Motor
adductor longus, adductor brevis, adductor magnus and gracilis.
in the spinal cord, the ___________ is loose around spinal cord with subarachnoid space containing CSF
arachnoid mater (2 in image)
ventral roots are comprised of what?
axons of motor neurons in ventral horns
Musculocutaneous Nerve Motor:
biceps brachii, coracobrachialis, brachialis
Tibial Nerve Motor
biceps femoris, semitendinosus, semimembranosus, gastrocnemius, soleus, flexor hallucis longus, tibialis posterior, flexor digitorum longus and muscles of the foot.
the ____________ delivers motor to, and sensory from, the upper extremity
brachial plexus
the spinal cord is a link between what?
brain and the rest of the body
the part of the spinal cord that has a collection of nerve roots at the end called?
cauda equina (horse's tail"
dorsal root ganglia are clusters of what?
cell bodies of unipolar neurons
The spinal coord is a part of which nervous system?
central nervous system
which process carries information away from cell body to the spinal cord?
central process
dorsal roots are comprised of what?
central processes of unipolar neurons
the _________ and ____________ regions are enlarged for the extremities.
cervical, lumbar
the spinal cord ends at the L1 level of the vertebral column as _________.
conus medullaris
the spinal cord ends at the L1 level of the vertebral column as what?
conus medullaris
Axillary Nerve Motor:
deltoid and teres minor
hanging off the end of the spinal cord is a collection of __________________, called cauda equina.
dorsal and ventral roots
The posterior wings of the gray matter are known as
dorsal horns
in the spinal cord, which horns are comprised of cell bodies of interneurons and receive input from afferents?
dorsal horns
the thick outer layer of the spinal cord
dura mater (3 in image)
Musculocutaneous Nerve Most Noticeable Weakness With Damage
elbow flexion and supination
Where are interneurons located?
entirely within the CNS
Superificial Fibular (Peroneal) Nerve Most Noticeable Weakness with Damage:
eversion of the foot
Radial Nerve Most Noticeable Weakness With Damage
extension of the elbow, wrist and fingers; supination.
Superficial Fibular (Peroneal) Nerve Motor
fibularis longus and brevis (lateral compartment).
the extension of pia mater off conus medullaris is called what?
filum terminale
Median Nerve Most Noticeable Weakness With Damage
flexion of the wrist and fingers; pronation
Femoral Nerve Motor:
flexor iliopsoas and quadriceps femoris muscles
Axillary Nerve Sensation:
from skin of lateral shoulder
since sensory neurons are unipolar neurons with a cell body, this means that their cell bodies form what?
ganglia
the cell bodies of unipolar neurons are located outside the spinal cord and form what?
ganglia
the gluteal nerves exit the pelvis and innervate the
gluteal muscles
Common Fibular (Peroneal) Nerve Motor
hort head of biceps femoris - helps to flex the leg
What do axons of motor neurons do?
project out to their targets
monosynaptic reflex is also called a "stretch reflex" because it is initiated by what?
quick stretch of a skeletal muscle
the posterior cord gives rise to which nerves?
radial and axillary nerves
_______________ are a type of motor response that occurs as the result of some type of sensory stimulus that takes place without conscious control
reflex
compression of the sciatic nerve can result in pain down the back of the lower extremity called
sciatia
tibial nerve and common fibular nerve joined by connective tissue make up which nerve?
sciatic nerve
In the monosynaptic reflex, an impulse is carried by which neuron into the spinal cord and synapses with a motor neuron? Which horn does this event take place in?
sensory (afferent) neuron anterior horn
coccygeal region has one pair of spinal nerves for what?
sensory around the anus
this neurons is also referred to as afferents
sensory neurons
Axillary Nerve Most Noticeable Weakness with Damage
shoulder abduction and external rotation
Deep Fibular (Peroneal) Nerve Sensation:
skin between first two toes
Femoral Nerve Sensation
skin of anterior thigh, medial leg (in blue)
Superficial Fibular (Peroneal) Nerve Sensation
skin of dorsal foot except between first two toes
Musculocutaneous Nerve Sensation:
skin of lateral forearm
Radial Nerve Sensation:
skin of posterior arm, forearm and hand
Obturator Nerve Sensation
skin of superior medial thigh
Tibial Nerve Sensation:
skin of the sole of the foot
sensory neurons carry sensation from where to where?
skin to CNS
In a polysynaptic reflex, a sensory (afferent) neuron carries some kind of painful stimulus from the skin to what?
spinal cord
Where are the cell bodies of motor neurons located?
spinal cord
the region of the spinal cord with a pair of spinal nerves attached to it. Notice that the multiple dorsal and ventral roots define the thickness of the spinal cord segment.
spinal cord segment
____________ are where dorsal roots and ventral roots join
spinal nerves
Common Fibular (peroneal) Nerve divide into
superficial fibular nerve, deep fibular nerve
