Transcript Spinal Cord Anatomy

Week 11
The Spinal Cord
Activity 1:
The Spinal Cord
The Spinal Cord
Cervical
enlargement
Cervical
spinal
nerves
Thoracic
spinal
nerves
Lumbar
enlargement
Conus
medullaris
Cauda
equina
Lumbar
spinal nerves
Sacral
spinal nerves
L2
L3
Conus Medullaris
L4
L5
Cauda Equina
(horse’s tail)
Lumbar Tap
T12
Cauda equina
Subarachnoid
space
L5
L4
L5
Cross Section of SC Between C2 and C3
Spinous
process
Subarachnoid
space
Body of
vertebra
Vertebral vein & artery
Which is the dorsal side?
Pia mater
Arachnoid
mater
Dura mater
Physiology
Dorsal
In 
Ventral
 Out
Spinal Cord Anatomy
Gray matter
White matter
Dorsal horn
Posterior
funiculus
Lateral horn
Ventral horn
Lateral
funiculus
Gray
commisure
Anterior
funiculus
Pia mater
Arachnoid mater
Dura mater
Gray matter = Inside, cell bodies & unmyelinated fiber tracts
White matter = Outside, myelinated fiber tracts
Spinal Cord Anatomy
Central canal
Posterior median sulcus
Anterior median fissure
Spinal Cord / Spinal Nerve Anatomy
Dorsal Root
Dorsal Root Ganglion
Spinal Nerve
Ventral Root
Spinal Cord / Spinal Nerve Anatomy
Dorsal root
Spinal
nerve
Dorsal root
ganglion
Dorsal
ramus
Ventral
ramus
to
Plexus
Ventral root
Cross sectional anatomy of the
spinal cord
A visual analogy?
Dorsal horns
•sensory neurons
Dorsal
horn?
Ventral
horn?
Gray commissure
Ventral horns
•motor neurons
PMS
AMF
Regional Differences
Cervical
Thoracic
Cervical
enlargement
Lateral
horn
Lumbar
enlargement
Lumbar
Sacral
White Matter
•fiber tracts for transmission of information
•ascending (sensory) tracts
•descending (motor) tracts
Posterior funiculus
Lateral funiculus
Anterior funiculus
Some fiber tracts in the different funiculi
Posterior funiculus:
•Faciculus cuneatus and gracilis
•Ascending sensory
Lateral funiculus
•Spinothalamic tract
•Ascending sensory
•Corticospinal tract
•Descending motor
Anterior funiculus
•Spinothalamic tract
•Ascending sensory
•Corticospinal tract
•Descending motor
Anatomy of a Spinal Nerve
Dorsal root: afferent, sensory
Ventral root: efferent, motor
Dorsal ramus: mixed, motor and sensory to
trunk
Ventral ramus: mixed motor and sensory form
nerve plexi
Dorsal root ganglion
Pseudounipolar neuron cell bodies
What is the
structural
classification
of these
neurons?
Activity 2: Nerve Plexi & Peripheral Nerves
There are 31
pairs of spinal
nerves
Cervical
Plexus
The phrenic
nerve innervates
the respiratory
diaphragm
“ C3,4,5 keeps the
diaphragm alive!
Brachial Plexus
Lumbar Plexus
Sacral Plexus
Activity 2:
Human Reflex Physiology
Structural Organization of the Nervous System
Central
Nervous
System
Peripheral
Nervous
System
Reflex Arc
1) Receptor - reacts to stimulus
2) Sensory Neurons - afferent impulses to CNS
3) Integration centers - synapses in CNS
4) Motor Neurons - efferent impulses from Integration
centers to effector
5) Effector - muscle or glands
Sensory Receptors
Soma
Receptors
Receptive
Endings
Axon
Classifications of Sensory Receptors
by Location
Exteroceptors
Interoceptors
Proprioceptors*
Respond to stimuli arising
outside the body:
Touch
Pain
Detect stretch
Temperature
Pressure
Respond to stimuli
inside the body
(viscera, vessels)
Therefore, for a Reflex Arc:
1) Receptor = Proprioceptors of ?? muscle
2) Sensory Neuron - ?? Nerve holding the sensory neurons
3) Integration centers – which CNS organ?
4) Motor Neurons - ?? Nerve holding the motor neurons
5) Effector - ?? Muscle
Patellar Reflex
Receptor is the
proprioceptors of
the muscle group
associated with
the tendon being
tapped
Note that the
Afferent & Efferent
neurons can travel
through the same
peripheral nerve
Effector is the
muscle group that
contracts to
extend the leg
Patellar Reflex
3 Tests
1. Simultaneous muscle activity
2. Mental distraction
3. Fatigue
Will the
velocity
increase
or
decrease
from
baseline?
Pupillary Reflex
Contralateral?
– or -
Ipsilateral?