2.1 neuro - spinal nerves Flashcards
Describe the organization of the cervical spinal nerves and the rest of the spinal nerves
C1 emerges between the first vertebrae and the base of the skull, C8 emerges between C7 and T1, 1 more nerve than vertebrae
Other spinal nerves observe from below the intervertebral foramen below the vertebrae of the same number
What is the functional unit of the spinal cord called
Spinal segment
What does a spinal segment consist of
All the gray and white matter that send and receive information from one set (right and left) of spinal nerves
The dorsal roots of spinal nerves send or receive information
Receive sensory / afferent information
The ventral roots of spinal nerves send or receive information
Send motor / efferent information
What is a dermatome
The area of the body’s surface innervated (sensory) by one pair of spinal nerves; they overlap
What is a receptive field
Area of skin innervated by one dorsal root ganglia neuron; subset of a dermatome
What is a motor unit
Total number of skeletal muscle fibers innervated by one Alpha Motor Neuron
Describe how the number of fibers innervated by a motor unit affects fine vs. gross control
More motor neurons innervating one muscle = finer control. One motor neuron innervating many fibers = gross control
Describe the organization of general sensory / motor afferent / efferent information in gray matter
Proximal dorsal horn = general sensory afferent
Distal dorsal horn = general visceral afferent
Proximal ventral horn = general sensory efferent
Distal ventral horn = general visceral efferent
How many total pairs of spinal nerves do we have, and how many are in each spinal region
31 pairs
* 8 cervical
* 12 thoracic
* 5 lumbar
* 5 sacral
* 1 coccygeal
What level of the vertebral column is the cervical plexus on?
C1-5
What level of the vertebral column is the brachial plexus on?
C5-T1
What level of the vertebral column is the lumbar plexus on?
L1-5
What level of the vertebral column is the sacral plexus on?
L4-S5
What are the terminal branches of the cervical plexus, and what regions do they innervate?
Motor:
- phrenic n., diaphragm
Sensory:
- lesser occipical n., skin behind ear
- great auricular n., skin in front of ear
- transverse cervical n., skin of anterior neck
- supraclavicular n., skin above clavicles
What are the terminal branches of the brachial plexus, and what regions do they innervate?
- axillary n., deltoid
- musculocutaneous n., elbow flexors
- median n., wrist / finger flexors
- radial n., elbow / wrist / finger extensors
- ulnar n., wrist / finger flexors
What are the terminal branches of the lumbar plexus, and what regions do they innervate?
- illiohypogastric n., skin / muscle of anterior body wall
- illioinguinal n., skin / muscle of anterior body wall
- genitofemoral n., skin of scrotum / labia majora, cremaster muscle
- lateral cutaneous n., skin of lateral thigh
- femoral n., skin of anterior thigh / knee extensors
- obturator n., skin of medial thigh / adductors
What are the terminal branches of the sacral plexus, and what regions do they innervate?
- superior gluteal n., gluteus medius / minimus
- interior gluteal n., gluteus maximus
- pudendal n., perineum
- sciatic n., muscles of posterior thigh
- tibial n. (split from sciatic at knee), posterior leg / calf
- common fibular n. (split from sciatic at knee), anterior and lateral leg
What types of tissues / cells do you find in peripheral nerves
Blood vessels, connective tissue, fibroblasts, schwann cells, macrophages
What sheath surrounds every nerve
Epineurium
What sheath surrounds bundles of axons within a nerve
Perineurium
What sheath surrounds each nerve fiber
Endoneurium
What is a node of ranvier
Portion of axons not wrapped in schwann cells, where the electrophysiology happens; space between schwann cells
What is an axon internode
Portion on axon surrounded by schwann cells
