LE 14-1
Posterior median sulcus
Dorsal root
Dorsal root
ganglion
Cervical
spinal cord
Rootlets
of C8
White matter
Gray
matter
Central
canal
Cervical spinal
nerves
Dorsal root
ganglion of C8
Spinal
nerve
Cervical
enlargement
Ventral
Anterior median fissure
root
C3
Dura mater
Dorsal root
ganglia of T4
and T5
Thoracic
spinal
nerves
Superior spinal cord,
posterior view
Lumbosacral
enlargement
Dura mater
Lumbar
spinal
nerves
Sacrum
(cut)
Inferior
tip of
spinal cord
Cauda equina
Dorsal root
ganglia of L2
and L3
1st sacral
nerve root
T3
Conus
medullaris
Conus medullaris
of spinal cord
Cauda equina
Posterior
median sulcus
L1
Sacral spinal
nerves
Coccygeal
nerve(Co1)
Filum terminale
(in coccygeal ligament)
Filum
terminale
S2
Transverse sections
of the spinal cord
Cauda equina, posterior view
Spinal cord, posterior view
LE 14-1a,d_1
Dorsal root
Dorsal root
ganglion
Central
canal
Posterior median sulcus
White matter
Gray
matter
Cervical spinal
nerves
Cervical
enlargement
Spinal
nerve
Ventral
root Anterior median fissure
C3
Thoracic
spinal
nerves
Posterior
median sulcus
Spinal cord, posterior view
T3
Transverse sections
of the spinal cord
LE 14-1a,d_2
Thoracic
spinal
nerves
Lumbar
spinal
nerves
Lumbosacral
enlargement
Conus
medullaris
Inferior
tip of
spinal cord
Cauda equina
L1
Sacral spinal
nerves
Filum terminale
(in coccygeal
ligament)
Coccygeal
nerve(Co1)
Spinal cord, posterior view
S2
Transverse sections
of the spinal cord
LE 14-1bc
Cervical
spinal cord
Conus medullaris
of spinal cord
Rootlets
of C8
Cauda equina
Dura mater
Dorsal root
ganglion of C8
Dorsal root
ganglia of L2
and L3
1st sacral
nerve root
Dura mater
Sacrum
(cut)
Dorsal root
ganglia of T4
and T5
Superior spinal cord,
posterior view
Filum
terminale
Cauda equina,
posterior view
LE 14-1d
Posterior median sulcus
Dorsal root
Dorsal root
ganglion
White matter
Gray
matter
Central
canal
Spinal
nerve
Ventral
root
Anterior median fissure
C3
T3
L1
S2
Transverse sections
of the spinal cord
LE 14-2
Spinal cord
White matter
Anterior median
fissure
Gray matter
Ventral root
Spinal nerve
Pia mater
Dorsal root
Dorsal root
ganglion
Pia mater
Denticulate
ligaments
Arachnoid mater
Dura mater
Arachnoid mater
(reflected)
Dura mater
(reflected)
Spinal blood
vessel
Posterior view
Dura mater
Dorsal root of
sixth cervical
nerve
Anterior view
Vertebral
body
Ventral root of
sixth cervical
nerve
ANTERIOR
Arachnoid mater
Subarachniod space
Autonomic (sympathetic)
ganglion
Pia mater
Ventral root of
spinal nerve
Rami
communicantes
Spinal cord
Ventral ramus
Filum terminale
Subarachnoid space
containing cerebrospinal
fluid and spinal nerve roots
L5 vertebra
Terminal portion
of filum terminale
S2 vertebra
MRI, sectional view
Spinal cord
Adipose tissue
in epidural space
Dorsal
ramus
Denticulate
ligament
POSTERIOR
Sectional view
Dorsal root
ganglion
LE 14-2a
Spinal cord
Anterior median
fissure
Pia mater
Denticulate
ligaments
Arachnoid mater
(reflected)
Dura mater
(reflected)
Spinal blood
vessel
Dorsal root of
sixth cervical nerve
Anterior view
Ventral root of
sixth cervical nerve
LE 14-2b
Spinal cord
Filum terminale
Subarachnoid space
containing cerebrospinal
fluid and spinal nerve roots
L5 vertebra
Terminal portion
of filum terminale
S2 vertebra
MRI, sectional view
LE 14-2c
White matter
Gray matter
Ventral root
Spinal nerve
Dorsal root
Dorsal root
ganglion
Pia mater
Arachnoid mater
Dura mater
Posterior view
LE 14-2d
Dura mater
ANTERIOR
Arachnoid mater
Subarachniod space
Vertebral body
Autonomic
(sympathetic)
ganglion
Pia mater
Ventral root of
spinal nerve
Rami
communicantes
Ventral ramus
Dorsal ramus
Spinal cord
Denticulate
ligament
Adipose tissue
in epidural space
POSTERIOR
Sectional view
Dorsal root
ganglion
LE 14-3
Occipital bone
Spinal cord emerging
from foramen magnum
Cervical plexus
(C1–C5)
Cervical spinal
nerves (C1–C8)
Brachial plexus
(C5–T1)
Thoracic spinal
nerves (T1–T12)
Lumbar spinal
nerves (L1–L5)
Sacral plexus
(L4–S4)
Coccygeal nerves (Co1)
Lumbar plexus
(T12–L4)
Sciatic
nerve
Sacral spinal nerves
(S1–S5) emerging from
sacral foramina
LE 14-3_1
Occipital bone
Spinal cord
emerging from
foramen magnum
Cervical plexus
(C1–C5)
Cervical
spinal nerves
(C1–C8)
Brachial plexus
(C5–T1)
Thoracic
spinal nerves
(T1–T12)
LE 14-3_2
Thoracic spinal
nerves (T1–T12)
Lumbar spinal
nerves (L1–L5)
Lumbar plexus
(T12–L4)
Sciatic nerve
Sacral plexus
(L4–S4)
Coccygeal nerves (Co1)
Sacral spinal nerves
(S1–S5) emerging from
sacral foramina
LE 14-4
Dura mater
Epidural space
Body of third
lumbar vertebra
Interspinous
ligament
Lumbar puncture
needle
Cauda equina in
subarachnoid space
Filum terminale
Cauda
equina
LE 14-4a
Dura mater
Epidural space
Body of third
lumbar vertebra
Interspinous
ligament
Lumbar puncture
needle
Cauda equina in
subarachnoid space
Filum terminale
LE 14-4b
Cauda
equina
Organization of Spinal Cord Gray
Matter
• Recall, it is divided into horns
– Dorsal, lateral (only in thoracic region), and ventral
• Dorsal half – sensory roots and ganglia
• Ventral half – motor roots
• Based on the type of neurons/cell bodies located in each
horn, it is specialized further into 4 regions
–
–
–
–
Somatic sensory (SS) - axons of somatic sensory neurons
Visceral sensory (VS) - neurons of visceral sensory neur.
Visceral motor (VM) - cell bodies of visceral motor neurons
Somatic motor (SM) - cell bodies of somatic motor neurons
Gray Matter: Organization
Figure 12.31
White Matter in the Spinal Cord
• Divided into three funiculi (columns) – posterior, lateral, and
anterior
– Columns contain 3 different types of fibers (Ascend., Descend., Trans.)
• Fibers run in three directions
– Ascending fibers - compose the sensory tracts
– Descending fibers - compose the motor tracts
– Commissural (transverse) fibers - connect opposite sides of cord
White Matter
Fiber Tract Generalizations
• Pathways decussate (most)
• Most consist of a chain of two or three neurons
• Most exhibit somatotopy (precise spatial
relationships)
• All pathways are paired
– one on each side of the spinal cord
White Matter: Pathway
Generalizations
Descending (Motor) Pathways
• Descending tracts deliver motor instructions
from the brain to the spinal cord
• Divided into two groups
– Pyramidal, or corticospinal, tracts
– Indirect pathways, essentially all others
• Motor pathways involve two neurons
– Upper motor neuron (UMN)
– Lower motor neuron (LMN)
• aka ‘anterior horn motor neuron” (also, final
common pathway)
Pyramidal (Corticospinal) Tracts
• Originate in the precentral gyrus of brain (aka, primary motor area)
– I.e., cell body of the UMN located in precentral gyrus
• Pyramidal neuron is the UMN
– Its axon forms the corticospinal tract
• UMN synapses in the anterior horn with LMN
– Some UMN decussate in pyramids = Lateral corticospinal tracts
– Others decussate at other levels of s.c. = Anterior corticospinal tracts
• LMN (anterior horn motor neurons)
– Exits spinal cord via anterior root
– Activates skeletal muscles
• Regulates fast and fine (skilled) movements
Corticospinal
tracts
1.
2.
3.
4.
Location of UMN cell
body in cerebral cortex
Decussation of UMN
axon in pyramids or at
level of exit of LMN
Synapse of UMN and
LMN occurs in anterior
horn of s.c.
LMN axon exits via
anterior root
Extrapyramidal Motor Tracts
• Includes all motor pathways not part of the pyramidal system
• Upper motor neuron (UMN) originates in nuclei deep in cerebrum (not in
cerebral cortex)
• UMN does not pass through the pyramids!
• LMN is an anterior horn motor neuron
• This system includes
–
–
–
–
Rubrospinal
Vestibulospinal
Reticulospinal
Tectospinal tracts
• Regulate:
– Axial muscles that maintain balance and posture
– Muscles controlling coarse movements of the proximal portions of limbs
– Head, neck, and eye movement
Extrapyramidal
Tract
Note:
1. UMN cell body location
2. UMN axon decussates in pons
3. Synapse between UMN and LMN
occurs in anterior horn of sc
3. LMN exits via ventral root
4. LMN axon stimulates skeletal
muscle
Extrapyramidal (Multineuronal)
Pathways
• Reticulospinal tracts – originates at reticular formation of brain;
maintain balance
• Rubrospinal tracts – originate in ‘red nucleus’ of midbrain;
control flexor muscles
• Tectospinal tracts - originate in superior colliculi and mediate
head and eye movements towards visual targets (flash of light)
Main Ascending Pathways
• The central processes of first-order neurons branch diffusely as
they enter the spinal cord and medulla
• Some branches take part in spinal cord reflexes
• Others synapse with second-order neurons in the cord and
medullary nuclei
Three Ascending Pathways
• The nonspecific and specific ascending pathways
send impulses to the sensory cortex
– These pathways are responsible for discriminative touch (2
pt. discrimination) and conscious proprioception (body
position sense).
• The spinocerebellar tracts send impulses to the
cerebellum and do not contribute to sensory
perception
Nonspecific Ascending Pathway
•
•
•
•
•
•
Include the lateral and anterior
spinothalamic tracts
Lateral: transmits impulses
concerned with pain and temp. to
opposite side of brain
Anterior: transmits impulses
concerned with crude touch and
pressure to opposite side of brain
1st order neuron: sensory neuron
2nd order neuron: interneurons of
dorsal horn; synapse with 3rd
order neuron in thalamus
3rd order neuron: carry impulse
from thalamus to postcentral
gyrus
Specific and Posterior Spinocerebellar Tracts
• Dorsal Column Tract
1. AKA Medial lemniscal pathway
2. Fibers run only in dorsal column
3. Transmit impulses from receptors in
skin and joints
4. Detect discriminative touch and
body position sense =proprioception
• 1st O.N.- a sensory neuron
• synapses with 2nd O.N. in nucleus
gracilis and nucleus cuneatus of
medulla
• 2nd O.N.- an interneuron
• decussate and ascend to thalamus
where it synapses with 3rd O.N.
• 3rd-order (thalamic neurons)
•transmits impulse to somatosensory cortex (postcentral gyrus)
Spinocerebellar Tract
• Transmit info. about trunk and lower
limb muscles and tendons to cerebellum
• No conscious sensation
LE 14-5a
POSTERIOR
Posterior
median sulcus
Posterior gray
commissure
Posterior
gray horn
Dura mater
Arachnoid mater
(broken)
Lateral
gray horn
Central canal
Dorsal root
Anterior gray
horn
Anterior gray
commissure
Anterior median
fissure
Pia mater
ANTERIOR
Dorsal root
ganglion
Ventral root
LE 14-5b
Posterior
gray horn
Posterior median sulcus
From dorsal root
Posterior gray
commissure
Lateral
gray horn
Somatic
Visceral
Anterior
gray horn
Anterior gray
commissure
Anterior median
fissure
To ventral
root
Visceral
Somatic
Sensory
nuclei
Motor
nuclei
LE 14-5c
Leg
Posterior white
column (funiculus)
Lateral
white
column
(funiculus)
Hip
Trunk
Arm
Flexors
Extensors
Hand
Forearm
Arm
Shoulder
Trunk
Anterior white
column (funiculus)
Anterior white
commissure
LE 14-6
Epineurium covering
peripheral nerve
Blood vessels
Perineurium
(around one
fascicle)
Endoneurium
Schwann cell
Myelinated
axon
Fascicle
Blood vessels
Perineurium
(around one
fascicle)
Endoneurium
LE 14-6a
Epineurium covering
peripheral nerve
Blood vessels
Perineurium
(around one
fascicle)
Endoneurium
Schwann cell
Myelinated
axon
Fascicle
LE 14-6b
Blood vessels
Perineurium
(around
one fascicle)
Endoneurium
LE 14-7a
To skeletal
muscles of back
Postganglionic fibers
to smooth muscles,
glands, etc., of back
Dorsal root
ganglion
Dorsal
root
Visceral
motor
Somatic
motor
Dorsal ramus
Ventral ramus
Spinal
nerve
To skeletal
muscles of
body wall, limbs
Ventral
root
Postganglionic fibers to
smooth muscles, glands,
etc., of body wall, limbs
Gray remus
(postganglionic)
Rami
communicantes
White remus
(preganglionic)
Sympathetic
ganglion
Sympathetic
nerve
Somatic motor
commands
Visceral motor
commands
Motor fibers
Postganglionic
fibers to smooth
muscles, glands,
visceral organs in
thoracic cavity
Preganglionic fibers
to sympathetic
ganglia innervating
abdominopelvic
viscera
LE 14-7b
From exteroceptors,
proprioceptors of back
From interoceptors
of back
Dorsal
root
Somatic
sensory
Visceral
sensory
Dorsal ramus
Ventral ramus
From exteroceptors,
proprioceptors of
body wall, limbs
Dorsal
root
ganglion
From interoceptors
of body wall, limbs
Rami
communicantes
Ventral
root
Somatic
sensations
Visceral
sensations
Sensory fibers
From interoceptors
of visceral organs
LE 14-8
ANTERIOR
POSTERIOR
LE 14-9
Lesser occipital nerve
Great auricular nerve
Cervical
plexus
Brachial
plexus
Transverse cervical nerve
Supraclavicular nerve
Phrenic nerve
Axillary nerve
Musculocutaneous
nerves
Thoracicl nerves
Radial nerve
Lumbar
plexus
Ulnar nerve
Median nerve
Sacral
plexus
Iliohypogastric
nerve
Ilioinguinal
nerve
Genitofemoral
nerve
Femoral nerve
Obturator nerve
Superior
Inferior
Gluteal
nerves
Pudendal nerve
Sciatic nerve
Lateral femoral cutaneous nerve
Saphenous nerve
Common fibular nerve
Tibial nerve
Medial sural cutaneous nerve
LE 14-9_1
Lesser occipital nerve
Great auricular nerve
Cervical
plexus
Brachial
plexus
Transverse cervical nerve
Supraclavicular nerve
Phrenic nerve
Axillary nerve
Musculocutaneous
nerves
Thoracicl nerves
LE 14-9_2
Radial nerve
Lumbar
plexus
Ulnar nerve
Median nerve
Iliohypogastric
nerve
Sacral
plexus
Ilioinguinal
nerve
Genitofemoral
nerve
Femoral nerve
Obturator nerve
Superior
Inferior
Gluteal
nerves
Pudendal nerve
Sciatic nerve
Lateral femoral cutaneous nerve
Saphenous nerve
Common fibular nerve
Tibial nerve
Medial sural cutaneous nerve
LE 14-10
Accessory
nerve (N XI)
Cranial
nerves Hypoglossal
nerve (N XII)
Great auricular
nerve
Lesser occipital
nerve
C1
C2
Nerve roots of
cervical plexus
C3
C4
C5
Geniohyoid
muscle
Transverse
cervical nerve
Thyrohyoid muscle
Ansa cervicalis
Omohyoid muscle
Supraclavicular
nerves
Clavicle
Phrenic nerve
Sternohyoid muscle
Sternothyroid muscle
LE 14-11a
Roots (ventral rami)
Trunks
Divisions
Cords
Peripheral nerves
Nerve to
subclavius muscle
Dorsal scapular
nerve
C5
SUPERIOR TRUNK
C6
Suprascapular nerve
Lateral cord
MIDDLE
TRUNK
C7
Posterior cord
Lateral pectoral nerve
C8
Medial pectoral nerve
Subscapular nerves
T1
Axillary nerve
INFERIOR
TRUNK
Medial cord
Musculocutaneous
nerve
Medial antebrachial
cutaneous nerve
Median nerve
Posterior brachial
cutaneous nerve
Long thoracic
nerve
Thoracodorsal
nerve
Ulnar nerve
Radial nerve
Anterior view
BRACHIAL
PLEXUS
LE 14-11b
Dorsal scapular nerve
C4
C5
C6
C7
C8
T1
Suprascapular nerve
Superior trunk
BRACHIAL
PLEXUS
Middle trunk
Inferior trunk
Musculocutaneous
nerve
Median nerve
Ulnar nerve
Radial nerve
Lateral antebrachial
cutaneous nerve
Deep radial nerve
Superficial branch
of radial nerve
Ulnar nerve
Median nerve
Anterior interosseous nerve
Deep branch of ulnar nerve
Superficial branch of ulnar nerve
Palmar digital
nerves
Anterior view
LE 14-11b_1
Dorsal scapular nerve
C4
Suprascapular nerve
BRACHIAL
PLEXUS
C5
C6
Superior trunk
Middle trunk
Inferior trunk
C7
C8
T1
Musculocutaneous
nerve
Median nerve
Ulnar nerve
Radial nerve
Anterior view
LE 14-11b_2
Lateral antebrachial
cutaneous nerve
Deep radial nerve
Ulnar nerve
Superficial branch
of radial nerve
Median nerve
Anterior interosseous
nerve
Radial
nerve
Deep branch
of ulnar nerve
Ulnar
nerve
Superficial branch
of ulnar nerve
Median
nerve
Palmar digital
nerves
Anterior
Anterior view
Posterior
Distribution of cutaneous nerves
LE 14-11c
Musculocutaneous nerve
Axillary nerve
Branches of axillary nerve
Radial nerve
Ulnar nerve
Median nerve
Posterior antebrachial
cutaneous nerve
Deep branch of radial nerve
Superficial branch of radial nerve
Dorsal digital nerves
Posterior view
LE 14-11c_1
Musculocutaneous
nerve
Axillary nerve
Branches of
axillary nerve
Radial nerve
Ulnar nerve
Median nerve
Posterior antebrachial
cutaneous nerve
Posterior view
LE 14-11c_2
Deep branch of
radial nerve
Superficial branch
of radial nerve
Dorsal digital nerves
Radial
nerve
Ulnar
nerve
Median
nerve
Anterior
Posterior
Distribution of cutaneous nerves
Posterior view
LE 14-12
Clavicle, cut
and removed
Cervical
plexus
Right common
carotid artery
Deltoid muscle
Musculocutaneous
nerve
Right axillary artery
over axillary nerve
Median nerve
Radial nerve
Biceps brachii,
long and short heads
Brachial plexus
(C5-T1)
Sternocleidomastoid muscle,
sternal head
Sternocleidomastoid muscle,
clavicular head
Right subclavian
artery
Ulnar nerve
Coracobrachialis
muscle
Skin
Right brachial
artery
Median
nerve
Retractor holding
pectoralis major
muscle (cut and
reflected)
LE 14-12_1
Right common
carotid artery
Clavicle, cut
and removed
Musculocutaneous
nerve
Cervical plexus
Brachial plexus
(C5-T1)
Deltoid muscle
Right axillary
artery over
axillary nerve
Median nerve
Radial nerve
Biceps
brachii,
long and
short heads
Sternocleidomastoid muscle,
sternal head
Sternocleidomastoid muscle,
clavicular head
Right
subclavian
artery
LE 14-12_2
Clavicle, cut
and removed
Brachial plexus
(C5-T1)
Deltoid muscle
Musculocutaneous
nerve
Sternocleidomastoid muscle,
sternal head
Right axillary artery
over axillary nerve
Sternocleidomastoid muscle,
clavicular head
Median nerve
Radial nerve
Right subclavian
artery
Biceps brachii,
long and short heads
Coracobrachialis
muscle
Skin
Right
brachial
artery
Ulnar
nerve
Median
nerve
Retractor holding
pectoralis major
muscle (cut and
reflected)
LE 14-13ab
T12 subcostal nerve
Lumbosacral trunk
Iliohypogastric nerve
Superior
gluteal nerve
LUMBAR
PLEXUS
Ilioinguinal nerve
Inferior
gluteal nerve
Genitofemoral nerve
Lateral femoral
cutaneous nerve
SACRAL
PLEXUS
Sciatic nerve
Branches of Femoral branch
genitofemoral
nerve Genital branch
Femoral nerve
Posterior femoral
cutaneous nerve
Lumbosacral
trunk
Obturator nerve
Lumbar plexus, anterior view
Co1
Pudendal
nerve
Sacral plexus, anterior view
LE 14-13a
T12 subcostal nerve
Iliohypogastric nerve
Ilioinguinal nerve
LUMBAR
PLEXUS
Genitofemoral nerve
Lateral femoral
cutaneous nerve
Branches of
genitofemoral
nerve
Femoral branch
Genital branch
Femoral nerve
Obturator nerve
Lumbosacral
trunk
Lumbar plexus, anterior view
LE 14-13b
Lumbosacral trunk
Superior gluteal nerve
Inferior gluteal nerve
SACRAL
PLEXUS
Sciatic nerve
Posterior femoral
cutaneous nerve
Co1
Pudendal nerve
Sacral plexus, anterior view
LE 14-13c-d
Subcostal nerve
Superior gluteal
nerve
Iliohypogastric nerve
Ilioinguinal nerve
Inferior gluteal
nerve
Genitofemoral nerve
Pudendal
nerve
Lateral femoral
cutaneous nerve
Posterior femoral
cutaneous nerve
Femoral nerve
Sciatic nerve
Superior gluteal nerve
Inferior gluteal nerve
Obturator nerve
Pudendal nerve
Sciatic nerve
Posterior femoral
cutaneous nerve (cut)
Saphenous
nerve
Sural
nerve
Saphenous nerve
Fibular
nerve
Tibial nerve
Medial sural
cutaneous nerve
Common fibular
nerve
Superficial fibular
nerve
Deep fibular
nerve
Common fibular
nerve
Sural
nerve
Lateral sural
cutaneous nerve
Tibial
nerve
Saphenous
nerve
Sural nerve
Saphenous
nerve
The lumbar and sacral
plexuses, anterior view
Tibial
nerve
Sural
nerve
Fibular
nerve
Medial plantar
nerve
Lateral plantar
nerve
The sacral plexus,
posterior view
LE 14-13c
Subcostal nerve
Iliohypogastric nerve
Ilioinguinal nerve
Genitofemoral nerve
Lateral femoral cutaneous nerve
Femoral nerve
Superior gluteal nerve
Inferior gluteal nerve
Obturator nerve
Pudendal nerve
Saphenous nerve
Sciatic nerve
Posterior femoral
cutaneous nerve (cut)
Sural nerve
Fibular nerve
Saphenous nerve
Common fibular nerve
Tibial nerve
Superficial fibular nerve
Sural nerve
Saphenous nerve
Deep fibular nerve
Saphenous nerve
The lumbar and sacral
plexuses, anterior view
Tibial nerve
Sural nerve
Fibular nerve
LE 14-13d
Superior gluteal nerve
Inferior gluteal nerve
Pudendal
nerve
Posterior femoral
cutaneous nerve
Sciatic nerve
Saphenous
nerve
Sural
nerve
Fibular
nerve
Tibial
nerve
Sural
nerve
Saphenous
nerve
Tibial
nerve
Common fibular nerve
Tibial nerve
Medial sural
cutaneous nerve
Saphenous
nerve
Lateral sural
cutaneous nerve
Sural
nerve
Fibular
nerve
Medial plantar
nerve
Sural nerve
Lateral plantar
nerve
The sacral plexus,
posterior view
LE 14-14a
Gluteus maximus
Superior gluteal nerve
Inferior gluteal nerve
Gluteus medius
Gluteus minimus
Internal
pudendal
artery
Tibial branch
Common fibular
branch
Pudendal
nerve
Components of
sciatic nerve
Greater trochanter
of femur
Posterior femoral
cutaneous nerve
Nerve to
gemellus
and
obturator
internus
Gluteus
maximus
Posterior gluteal region
LE 14-14b
Biceps femoris
Sartorius
Tibial nerve
Lateral sural
cutaneous nerve
Gracilis
Semimembranosus
Common fibular
nerve
Popliteal artery
Plantaris
Semitendinosus
Nerve to lateral
head of
gastrocnemius
Nerve to
medial head
of gastrocnemius
Gastrocnemius,
lateral head
Gastrocnemius,
medial head
Medial sural
cutaneous nerve
Popliteal region
LE 14-14c_1
Gluteus maximus
(cut)
Gluteus medius
(cut)
Gluteus minimus
Inferior gluteal
nerve
Pudendal nerve
Superior gluteal
nerve
Piriformis
Perineal branch
Hemorrhoidal
branch
Posterior femoral
cutaneous nerve
Perineal branches
Sciatic nerve
Descending
cutaneous
branch
Semitendinosus
Biceps femoris
(cut)
Posterior view
LE 14-14c_2
Tibial nerve
Common
fibular nerve
Popliteal artery
and vein
Medial sural
cutaneous nerve
Lateral sural
cutaneous
nerve
Gastrocnemius
Small saphenous
vein
Sural nerve
Calcaneal tendon
Tibial nerve
(medial calcaneal branch)
Posterior view
LE 14-15
Dorsal
root
Activation of a
sensory neuron
Arrival of
stimulus and
activation of
receptor
Receptor
Sensation
relayed to
the brain by
collateral
REFLEX
ARC
Stimulus
Effector
Ventral
root
Information
processing
in CNS
Response
by effector
Activation of a
motor neuron
Sensory neuron
(stimulated)
Excitatory
interneuron
Motor neuron
(stimulated)
LE 14-16
• Genetically
determined
by
development
can be
classified
• Learned
• Control skeletal
muscle contractions
• Include superficial
and stretch reflexes
by
response
by
processing
site
by
complexity
of circuit
• One synapse
• Control actions of
smooth and cardiac
muscles, glands
• Processing in
the spinal cord
• Processing in
the brain
• Multiple synapses
(two to several
hundred)
LE 14-17
Sensory
receptor
Ganglion
Sensory
neuron
Ganglion
Sensory
neuron
Motor
neuron
Interneurons
Circuit 1
Circuit 2
Sensory
receptor
(muscle
spindle)
Motor
neurons
Skeletal muscle
Monosynaptic reflex
Skeletal muscle 1
Skeletal muscle 2
Polysynaptic reflex
LE 14-18a
Stimulus.
Stretching of
muscle
stimulates
muscle spindles
Response.
Contraction
of muscle
Activation of a
sensory neuron
Activation of a
motor neuron
Stretch reflex
Information
processing at
motor neuron
LE 14-18b
Stretch
Receptor
(muscle
spindle)
Spinal cord
REFLEX
ARC
Stimulus
Effector
Contraction
Sensory neuron
(stimulated)
Motor neuron
(stimulated)
Response
Patellar reflex