Transcript Motor neuron

Functions of the Spinal Cord
• Transmit
• Transmit
• Integrate
Sensory Info
Brain
Spinal Cord
Motor Commands
Periphery
Transmitting Information
Ascending tracts
Fasciculus gracilis
Dorsal
Fasciculus cuneatus
white
column
Dorsal
spinocerebellar
tract
Ventral
spinocerebellar
tract
Lateral
spinothalamic tract
Ventral spinothalamic
tract
Descending tracts
Ventral white
commissure
Lateral
reticulospinal tract
Lateral
corticospinal tract
Rubrospinal
tract
Medial
reticulospinal
tract
Ventral corticospinal
tract
Vestibulospinal tract
Tectospinal tract
Stimulus
Integration - Reflexes
Skin
1 Receptor
Interneuron
2 Sensory neuron
3 Integration center
4 Motor neuron
5 Effector
Spinal cord
(in cross section)
Bone
Spinal Cord
Protected by
Meninges
Cerebrospinal
fluid
Bony Protection
Meninges
3 Membranes surrounding
the spinal cord
Pia mater
Arachnoid mater
Dura mater
Meninges
Basic Arrangement
Spinal Cord
Pia mater
Arachnoid mater
Dura mater
Epidural space
Subarachnoid space
CSF
Functions:
1. Support
2. Protect
3. Buffer
Produced from blood by specialized
capillaries (choroid plexuses) in the brain
Spinal Cord Anatomy
Foramen magnum – L1
Cervical
nerves
C1 – C8
Thoracic
nerves
T1 – T12
31 spinal nerve pairs
31 spinal segments
Lumbar
nerves
L1 – L5
Sacral nerves
S1 – S5
Coccygeal nerve Co1
C2
C3
C2
C3
C4
C5
C6
C7
C8
C4
C5
T1
T2
T3
T4
T5
T6
T7
T2
C6
C6
C7
T2
T8
T9
T10
T11
C5
L1
C8
L2
T12
S2
S3
T1
T2
T3
T4
T5
T6
T7
T8
T9
T10
C5
C6
C8
S1
L2
L4
L1
C8
L2
S3
S4
S5
C6
C7
S2
S2
S2
C6
C7
C8
S1
L1
L3
L5
L4
T11
T12
L1
L3
L5
C7
C6
S1
L3
C5
L2
L5
L4
L3
L5
L5
L4
S1
S1
L4
L5
L4
L5
S1
Spinal Cord Anatomy
Conus Medullaris & Cauda Equina
Filum Terminale
Spinal Cord – Cross Sectional Anatomy
Gray Matter –
Somata
Dendrites
Unmyelinatedaxons
White Matter – Myelinated axons
Spinal Cord – Cross Sectional Anatomy
White
columns
Dorsal column
Ventral column
Lateral column
Gray
commissure
Dorsal horn
Ventral horn
Lateral horn
Gray
matter
Central canal
Spinal Cord – Cross Sectional Anatomy
White Matter – Organized into columns and tracts
Ascending tracts
Fasciculus gracilis
Dorsal Fasciculus cuneatus
white
column
Dorsal
spinocerebellar
tract
Ventral
spinocerebellar
tract
Lateral
spinothalamic tract
Ventral spinothalamic
tract
Descending tracts
Ventral white
commissure
Lateral
reticulospinal tract
Lateral
corticospinal tract
Rubrospinal
tract
Medial
reticulospinal
tract
Ventral corticospinal
tract
Vestibulospinal tract
Spinal Cord – Cross Sectional Anatomy
Gray Matter Organization
Dorsal root (sensory)
Dorsal horn (interneurons)
Dorsal root ganglion
Somatic
sensory
neuron
Visceral
sensory
neuron
Visceral
motor
neuron
Somatic
motor neuron
Spinal nerve
Ventral root
(motor)
Ventral horn
(motor neurons)
Interneuronsreceiving input from somatic sensory neurons
Interneuronsreceiving input from visceral sensory neurons
Visceral motor (autonomic)neurons
Somatic motor neurons
Basic Structure of a Nerve
Endoneurium
Axon
Myelin sheath
Perineurium
Epineurium
Fascicle
Spinal Nerve Anatomy
Spinal Nerve Anatomy
Ventral
ramus
Dorsal
ramus
Motor and sensory signals
to/from the posterior trunk
Dorsal
ramus
Ventral ramus
Motor and
sensory signals
to/from the
anterior trunk
and limbs
Ventral ramus
Rami
communicantes
– carrying
autonomic
nerve fibers
All ventral rami
(Except T2-T12)
Form
Interlaced bundles
of nerve fibers
Nerve Plexuses
4 major
plexuses
Primarily serve
the limbs
Cervical Plexus
Brachial Plexus
Lumbar Plexus
Sacral Plexus
Mostly cutaneous nerves
Cervical Plexus
Ventral rami
Segmental
branches
Lesser occipital
nerve
Greater auricular
nerve
Transverse
cervical nerve
Ansa cervicalis
Phrenic nerve
Supraclavicular
nerves
Ventral
rami:
C1
C2
C3
C4
C5
Brachial Plexus
Supplies the upper limb
C4
C5
C6
C7
Gives rise to several
important nerves
Axillary
Musculocutaneous
Radial
Ulnar
C8
T1
Axillary Nerve
Carries sensory info from the
shoulder region and motor
commands to the deltoid muscle.
Musculocutaneous Nerve
Carries sensory info from the
lateral arm and motor
commands to the biceps brachii
and brachialis muscles.
Radial Nerve
Carries sensory info from the posterior arm and motor
commands to the triceps brachii, wrist extensors and
brachioradialis muscles.
Ulnar Nerve
Carries sensory info from the palm and the medial
hand/fingers and sends motor commands to the wrist
flexors and intrinsic hand muscles.
Part of the
lumbosacral
plexus
Lumbar Plexus
Supplies much of
the lower limb
L1
L2
Femoral
Gives rise to several
important nerves
L3
Obturator
L4
Obturator
Femoral
L5
Femoral Nerve
Carries sensory info from much
of the thigh, leg, and foot and
sends motor commands to
quadriceps femoris muscles.
Obturator Nerve
Carries sensory info from the
thigh and sends motor
commands to adductor
muscles.
Sacral Plexus
Part of the lumbosacral plexus
Gives rise to several Supplies much of the
pelvis, thigh, and leg
Superior gluteal
L4
Inferior gluteal
Pudendal
Superior
gluteal
L5
S1
Inferior
gluteal
S2
S3
S4
Pudendal
Sciatic
S5
Co1
Sciatic
Sciatic Nerve
Carries sensory info from the
skin of much of the lower limb
and sends motor commands to
hamstring muscles as well as
other muscles of the lower leg Sciatic
and feet.
Gluteal Nerves
Primarily send motor commands Superior gluteal
to adductor muscles of the thigh
Inferior gluteal
and to the gluteus maximus.
Pudendal Nerve
Carries sensory info from the
external genitalia and
supplies motor commands to
the external urethral and
anal sphincters.
•
From
sensation
to
perception
Sensation is the awareness of changes in the
internal and external environment
• Perception is the conscious interpretation of
those stimuli
Neural integration
1. Receptor level
2. Circuit level
3. Perceptual level
Motor control
Reflex arc
Stretch reflex
Flexor reflex (withdrawal reflex)
pain
contraction
Chapter 11 -Peripheral Nervous System
Consists of all nervous tissue found outside the CNS
Nerves (white), ganglia (gray), sensory receptors
 Two subdivisions - Sensory (
afferent
) and Motor (
) efferent
 Motor further subdivided into _________
autonomic
and _________
somatic

Ganglion
Nerve
Ganglion
Nerve
Autonomic
involuntary
Visceral
receptors
Effector –
smooth muscle
Ganglion
Cutaneous
receptors
Somatic
voluntary
Effector -skeletal muscle
Autonomic Nervous System (ANS)
conscious effort
• functions without _________
visceral activities
• controls _______
smoothmuscle, _______
cardiacmuscle, and _____glands
• regulates ______
gangliaoutside CNS
• efferent fibers typically lead to _______
Two Divisions
Sympathetic
• ____________–
prepares body for fight or flight situations
Parasympathetic – prepares body for resting and digesting activities
• _______________
Sympathetic
Anatomy
Sympathetic fibers arise from
lateral horns of Thoracolumbar
T1 to L2
regions ________

 Organ
with only pre ganglionic
Adrenal gland
stimulation______________
 Note the sympathetic chain ganglia
Match
Parasympathetic fibers arise
from Craniosacral regions

Four cranial nerves with
parasympathetic fibers are …


S2 – S4
Sacral region is _______

Organs with no parasympathetic?
Which has more widespread
influence? parasympathetic or
sympathetic

Parasympathetic
Anatomy

Somatic
 ____
one motor neuron
 _____ganglia
no
skeletal muscle
 effector _____________
Somatic

Autonomic
Autonomic
 _____motor
neurons
two
ganglion
 synapse between neurons occurs within a _________
glands ________________________
smooth and cardiac muscle
 effectors ______,
 Neurotransmitters - ACh (cholinergic) and Norepinephrine (adrenergic)
• Parasympathetic preganglionic fibers release ____;ACh
postganglionic ____ ACh
ACh
norepinephrine
• Sympathetic preganglionic fibers release ____;
postganglionic ____________
ACh
• Somatic release at neuromuscular junction ____
Comparison of Somatic Pathways to Autonomic Pathways
Actions of Autonomic Neurotransmitters
depend on receptor
Cholinergic receptors - bind to acetlycholine
• nicotinic - always excitatory
• muscarinic – usually excitatory
• atropine blocks (dilates pupil;
salivary secretion)
• pilocarpine activates
parasympathetic effects
Adrenergic Receptors - bind to
norepinephrine
• alpha - responses vary by effectors
• beta – responses vary by effectors
• beta 1 -increases heart rate;
rennin secretion; fat metabolism
• beta 2 - dilates blood vessels &
bronchioles