Download Introduction to Anatomy

Spinal Nerves, Dermatomes, and
Cranial Nerves
Handout for Cranial Nerves
Spinal Nerves
1. 31 pairs
2. spinal canal emergence
3. distribution
a. 8 cervical
b. 12 thoracic
c. 5 lumbar
d. 5 sacral
e. 1 coccygeal
Cervical Plexus
Brachial plexus
Lumbar Plexus
Sacral and Coccygeal
Plexus
Typical Spinal Nerve
1. mixed nerve
2. connective tissues
a. endoneurium
b. perineurium
-- fascicles
c. epineurium
Dermatomes
Cranial Nerves
1. 12 pairs
2. motor components -- arise from brain
stem gray matter
3. sensory components -- arise in ganglia
outside brain
Cranial Nerves
Cranial Nerves Names
name
I.
II.
III.
IV.
V.
VI.
VII.
VIII.
IX.
X.
XI.
XII.
olfactory
optic
oculomotor
trochlear
trigeminal
abducens
facial
auditory
glossopharyngeal
vagus
accessory
hypoglossal
mnemonic
On
Old
Olympus'
Towering
Top
A
Finn
And
German
Viewed
A
Hop
Cranial Nerve Functions
name
I.
II.
III.
IV.
V.
VI.
VII.
VIII.
IX.
X.
XI.
XII.
olfactory
optic
oculomotor
trochlear
trigeminal
abducens
facial
auditory
glossopharyngeal
vagus
accessory
hypoglossal
function
sensory
sensory
motor
motor
both
motor
both
sensory
both
both
motor
motor
mnemonic
Some
Say
Marry
Money
But
My
Brother
Says
Bad
Business
Marrying
Money
Nervous Integration
Handout Spinal Tracts
A. Sensation
1. Levels of sensation
2. Modality
3. Components of a sensation
4. Generator potentials and
receptor potentials
5. Adaptation of sensory receptors
B. General senses
1. Cutaneous sensations
2. Proprioceptive sensations
C. Physiology of sensory pathways
1. Posterior column-medial lemniscus
pathway
2. Anterolateral (spinothalamic)
pathways
3. Somatosensory cortex
D. Physiology of motor pathways
1. Direct (pyramidal) pathways
2. Indirect (extrapyramidal) pathways
The three essential functions of
the nervous system are:
1. sense changes
2. integrate and interpret
3. respond
How do the various components of the
nervous system cooperate in
performing these functions?
Sensation versus Perception
A sensation may or not be perceived
(conscious awareness of the stimulus)
Modality-the type of stimulus or
sensation it produces –vision, hearing,
taste.
Levels of Sensation
1.
2.
3.
4.
spinal
brain stem
thalamus
cerebral cortex
Components of a Sensation
1.
2.
3.
4.
stimulation
transduction
conduction
translation
Generator Potentials
1. always produce depolarization
2. will initiate an action potential in a sensory
neuron if the stimulus is strong enough to
form threshold depolarization
3. all receptors except those for vision, hearing,
equilibrium, smell, and taste create generator
potentials
Receptor Potentials
1. may produce depolarization or
hyperpolarization
2. never directly initiate an action potential
in a sensory neuron
3. directly regulates release of
neurotransmitter onto a sensory neuron that
may initiate threshold depolarization
Types of Receptors
1. interceptors (visceroceptors)
2. exteroceptors
3. proprioceptors
__________________________
mechanoreceptors
thermoreceptors
chemoreceptors
nociceptors
photoreceptors
Adaptation of sensory receptors
1. fast-adapting (phasic) receptors
Adapt very quickly
Specialized for signaling changes in a particular stimulus
Pressure, touch, hot, smell
2. slow-adapting (tonic) receptors
Adapt slowly, continuing to initiate impulses as long as
stimulus persists
Pain, body position, cold, chemical composition of blood
Cutaneous Sensations
1. tactile, thermal, pain
2. receptor locations
3. receptor distribution
Proprioceptive Sensations
1.
2.
3.
4.
proprioceptors
locations
body position sense
adapt slowly
Physiology of Sensory Pathways
1. most sensory input decussates
2. somatosensory cortex
3. perception
4. Three neurons are required
a. first-order neuron
b. second-order neuron
c. third-order neuron
Tracts of the Spinal Cord
Posterior Column Pathway
1. fasciculus gracilis &
fasciculus cuneatus
2. nucleus gracilis &
nucleus cuneatus
3. decussation in medulla
4. medial lemniscus
5. Thalamus
6. Somatosensory Cortex
discriminative touch
stereognosis
kinesthesia
vibration
weight, discrimination
conscious proprioception
Anteriolateral Pathways
lateral spinothalamic
-Pain, thermal
anterior spinothalamic tracts
-Itch,tickle,pressure,crude touch
decussate at gray commissure
Somatosensory Cortex
1. homunculus
2. areas of representation
3. receptor to cortical
neuron ratio = 1:1
Motor Cortex
1.
2.
3.
4.
reflex vs voluntary action
homunculus
areas of representation
motor neuron to motor
unit ratio = 1:1
5. upper motor neuron
6. lower motor neuron
Direct Pyramidal Motor Pathways
1. lateral corticospinal tracts
-- decussate at medulla
2. anterior corticospinal tracts
-- decussate at gray commissure
3. corticobulbar tracts
-- decussate in brain stem
Indirect (extrapyramidal) pathways for coordination and
control of movement
cerebral cortex
upper motor neurons
of the pyramidal
tracts
cerebral nuclei
thalamus
cerebellum
brainstem
gray matter
spinal cord
association neurons
lower motor neurons
skeletal muscles
upper motor neurons of the
extrapyramidal tracts:
rubrospinal
tectospinal
vestibulospinal
reticulospinal
INDIRECT (EXTRAPYRAMIDAL) MOTOR PATHWAYS
cerebral cortex
upper motor neurons
of the pyramidal
tracts
cerebral nuclei
thalamus
cerebellum
brainstem
gray matter
upper motor neurons of the
extrapyramidal tracts:
rubrospinal
tectospinal
vestibulospinal
reticulospinal
spinal cord
association neurons
lower motor neurons
skeletal muscles
end