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Spinal Cord and Spinal Nerves. Spinal Cord. Enclosed in the vertebral canal, extends from the foramen magnum of the skull to the first or second lumbar vertebra where it terminates in the cone shaped conus medullaris. Spinal Cord. Spinal meninges; Dura Mater – outer Arachnoid Mater – middle

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spinal cord
Spinal Cord
  • Enclosed in the vertebral canal, extends from the foramen magnum of the skull to the first or second lumbar vertebra where it terminates in the cone shaped conus medullaris
spinal cord1
Spinal Cord
  • Spinal meninges;
  • Dura Mater – outer
  • Arachnoid Mater – middle
  • Pia Mater – inner
spinal cord2
Spinal Cord
  • Dura Mater – composed of dense, irregular connective tissue
spinal cord3
Spinal Cord
  • Arachnoid Mater – It is an avascular covering with a spider’s web arrangement of delicate collagen fibers and some elastic fibers
spinal cord4
Spinal Cord
  • Pia Mater – A vascular and thin transparent connective tissue layer composed of interlacing bundles of collagen fibers and some fine elastic fibers
spinal cord5
Spinal Cord
  • Subarachnoid space – between the arachnoid mater and pia mater which contains cerebrospinal fluid
spinal cord6
Spinal Cord
  • The dura mater and arachnoid meningeal coverings extend beyond the conus medullaris, approximately to the level of S2
spinal cord7
Spinal Cord
  • Filium terminale – a fibrous extension of the pia mater, extends farther and attaches to the posterior coccyx
spinal cord8
Spinal Cord
  • 31 pairs of spinal nerves, which exit via the intervertebral foramina
spinal cord9
Spinal Cord
  • Since the spinal cord doesn’t extend to the end of the vertebral column, the spinal nerves emerging from the inferior end must travel through the vertebral canal until reaching the appropriate intervertebral foramina
spinal cord10
Spinal Cord
  • This collection of spinal nerves are called the cauda equina
spinal cord gray matter1
Spinal Cord / Gray Matter
  • Posterior or dorsal horns – posterior projections
spinal cord gray matter2
Spinal Cord / Gray Matter
  • Anterior or ventral horns – anterior projections that contain cell bodies of motor neurons
spinal cord gray matter3
Spinal Cord / Gray Matter
  • Lateral Horns – In the thoracic and lumbar regions there is a lateral outpocketing of gray matter
spinal cord gray matter4
Spinal Cord / Gray Matter
  • Gray commissure – central area of gray matter
spinal cord gray matter5
Spinal Cord / Gray Matter
  • Dorsal root – Sensory fibers enter the cord here
spinal cord gray matter6
Spinal Cord / Gray Matter
  • Dorsal Root Ganglia – Cell bodies of sensory neurons located here
spinal cord gray matter7
Spinal Cord / Gray Matter
  • Ventral Roots – Motor neurons leave the cord here
spinal cord gray matter8
Spinal Cord / Gray Matter
  • Spinal nerves – are formed from the fusion of the dorsal and ventral roots
spinal cord gray matter9
Spinal Cord / Gray Matter

Spinal Nerves;

8 pairs of cervical nerves

12 pairs of thoracic nerves

5 pairs of lumbar nerves

5 pairs of sacral nerves

1 pair of coccygeal nerves

spinal cord white matter
Spinal Cord / White Matter
  • The anterior median fissure and the posterior median sulcus divide the spinal cord into R. and L. sides
spinal cord white matter1
Spinal Cord / White Matter
  • White matter is divided into columns;

Posterior Funiculus, Anterior Funiculus, and Lateral Funiculus

spinal cord white matter2
Spinal Cord / White Matter
  • Each column contains distinct bundles of nerve axons called tracts
spinal cord white matter3
Spinal Cord / White Matter

Two Types of Tracts

1. Sensory (ascending) tracts – conduct nerve impulses toward the brain

spinal cord white matter4
Spinal Cord / White Matter

2. Motor (descending) tracts – conduct impulses down the cord

connective tissue coverings of spinal nerves
Connective Tissue Coverings of Spinal Nerves
  • A fiber is a single axon within an endoneurium
connective tissue coverings of spinal nerves1
Connective Tissue Coverings of Spinal Nerves
  • A fascicle is a bundle of fibers within a perineurium
connective tissue coverings of spinal nerves2
Connective Tissue Coverings of Spinal Nerves
  • A nerve is a bundle of fascicles within an epineurium
spinal nerves and nerve plexus
Spinal Nerves and Nerve Plexus
  • Each nerve divides into dorsal and ventral rami
spinal nerves and nerve plexus1
Spinal Nerves and Nerve Plexus
  • Rami contains both motor and sensory rami
spinal nerves and nerve plexus2
Spinal Nerves and Nerve Plexus
  • Dorsal rami – serve the skin and musculture of the posterior body trunk at their approximate level of emergence
spinal nerves and nerve plexus3
Spinal Nerves and Nerve Plexus
  • Ventral rami of spinal nerves T2 –T12 – pass anteriorly to supply the muscles of intercostal spaces, and the skin and muscles of the anterior and lateral trunk
spinal nerves and nerve plexus4
Spinal Nerves and Nerve Plexus
  • Ventral rami of all other nerves – form complex networks of nerves called plexuses
spinal nerves and nerve plexus5
Spinal Nerves and Nerve Plexus
  • The plexuses diverge again to form peripheral nerves
spinal nerves and nerve plexus6
Spinal Nerves and Nerve Plexus

Four Plexuses

  • Cervical
  • Brachial
  • Lumbar
  • Sacral
spinal nerves and nerve plexus7
Spinal Nerves and Nerve Plexus
  • Cervical Plexus

Supplies the skin and muscles of the head, neck, and upper part of the shoulders and diaphragm

spinal nerves and nerve plexus8
Spinal Nerves and Nerve Plexus
  • Damage to the spinal cord above the origin of the phrenic nerves causes respiratory arrest.
spinal nerves and nerve plexus9
Spinal Nerves and Nerve Plexus
  • Breathing stops because the phrenic nerves stops sending impulses to the diaphragm
spinal nerves and nerve plexus10
Spinal Nerves and Nerve Plexus
  • Brachial Plexus

Supplies the upper extremities and a number of neck and shoulder muscles

spinal nerves and nerve plexus11
Spinal Nerves and Nerve Plexus
  • In carpal tunnel syndrome there is damage to the median nerve
spinal nerves and nerve plexus12
Spinal Nerves and Nerve Plexus
  • Lumbar Plexus

Supplies the anterolateral abdominal wall, external genitals, and part of the lower extremities

spinal nerves and nerve plexus13
Spinal Nerves and Nerve Plexus
  • Femoral Nerve - Largest nerve arising from the lumbar plexus
spinal nerves and nerve plexus14
Spinal Nerves and Nerve Plexus

4. Sacral Plexus

Supplies the buttocks and part of the lower extremities

spinal nerves and nerve plexus15
Spinal Nerves and Nerve Plexus
  • Sciatic Nerve – Largest nerve arising form the sacral plexus
spinal nerves and nerve plexus16
Spinal Nerves and Nerve Plexus
  • Sciatica – Pain that extends from the buttock down the back of the leg due to injury to the sciatic nerve
spinal cord physiology
Spinal Cord Physiology
  • The white matter tracts are highways for nerve impulse conduction to and from the brain
spinal cord physiology1
Spinal Cord Physiology
  • The gray matter receives and integrates incoming and outgoing information
spinal cord physiology sensory tracts
Spinal Cord Physiology / Sensory Tracts

Sensory information from receptors travels up the spinal cord via the;

  • Spinothalamic tracts
  • Posterior column tract
spinal cord physiology sensory tracts1
Spinal Cord Physiology / Sensory Tracts
  • Spinothalamic tracts carry pain, touch, and temperature impulses
spinal cord physiology sensory tracts2
Spinal Cord Physiology / Sensory Tracts
  • Posterior columns carry proprioception and vibration
spinal cord physiology motor tracts
Spinal Cord Physiology / Motor Tracts

Motor info. travels from the brain down the spinal cord to muscles and glands via the;

  • Pyramidal tracts
  • Extrapyramidal tracts
spinal cord physiology motor tracts1
Spinal Cord Physiology / Motor Tracts
  • Pyramidal tracts control voluntary, purposeful motor movement of eyes, mouth, face, arms, and legs
spinal cord physiology motor tracts2
Spinal Cord Physiology / Motor Tracts
  • Extrapyramidal tracts control more complex things like the accessory adjustments we make to muscle tone to adjust our posture
spinal cord physiology reflexes
Spinal Cord Physiology / Reflexes
  • The gray matter of the spinal cord serves as an integrating center for spinal reflexes
spinal cord physiology reflexes1
Spinal Cord Physiology / Reflexes
  • A reflex is a fast, predictable, automatic response to changes in the environment that helps to maintain homeostasis
spinal cord physiology reflex arc
Spinal Cord Physiology / Reflex Arc

Five functional components;

  • Receptor
  • Sensory Neuron
  • Motor Neuron
  • Integrating Center Neuron
  • Effector
stretch reflex
Stretch Reflex

1. Slight stretching of a muscle stimulates sensory receptors in the muscle called muscle spindles

stretch reflex1
Stretch Reflex

2. In response to being stretched the muscle spindle generates a nerve impulse along a somatic sensory neuron and enters the spinal cord via the posterior root

stretch reflex2
Stretch Reflex

3. In the integrating center of the spinal cord the sensory neuron makes an excitatory synapse with a motor neuron in the anterior gray horn

stretch reflex3
Stretch Reflex

4. If the excitation is strong enough a nerve impulse is propagated along the motor neuron which extends from the spinal cord to the muscle

stretch reflex4
Stretch Reflex

5. ACh is released at the NMJ which triggers a muscle action potential in the stretched muscle (effector) and the muscle contracts