Lecture 17: Spinal Cord 2 Flashcards
Three Types of Connective Tissue Layers in Spinal Nerves
Epineurium,
Perineurium,
Endoneurium
Epineurium
Outer layer,
Dense network of collagen fibers
Perineurium
Middle layer,
Divides nerve into fascicles (axon bundles)
Endoneurium
Inner layer,
Surrounds individual axons
Branches
Pathways to body areas
Rami Communicantes and Sympathetic Nerves
Pathways for visceral sensory neurons,
Part of ANS
Dorsal Ramus
Back of body pathway,
Motor and sensory neurons going to and from back of body
Ventral Ramus
Access from front to spinal cord pathway,
Motor and sensory neurons going to and from body wall and limbs
Nerve
Bundle of axons
Dermatome
Specific bilateral region of skin from which sensory information is carried by a pair of spinal nerves,
Each spinal nerve has its own,
Some overlap
Nerve Plexuses
Joining of rami that give off branches,
Complex, interwoven networks of nerve fibers,
Formed from blended fibers of ventral rami of adjacent spinal nerves
4 Major Plexuses of Ventral Rami
Cervical Plexus,
Brachial Plexus,
Lumbar Plexus,
Sacral Plexus
Cervical Plexus
Includes ventral rami of spinal nerves C1-C5,
Innervates neck, thoracic cavity, diaphragmatic muscles
Major Nerve of Cervical Plexus
Phrenic Nerve
Phrenic Nerve
Controls diaphragm
Brachial Plexus
Includes ventral rami of spinal nerves C5-T1,
Nerves that emerge from plexus innervate pectoral girdle and upper limbs,
Axillary area
Lumbosacral Plexus
Nerves that emerge innervate pelvis and lower extremities,
Sciatic nerve is biggest in body
How Many Sensory Neurons Are There?
10 million
What Do Sensory Neurons Do?
Deliver information to CNS
How Many Motor Neurons Are There?
500,000
What Do Motor Neurons Do?
Deliver commands to peripheral effectors
How Many Interneurons Are There?
20 billion mostly in CNS