Term
| What is the basic organization of the nervous system? |
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Definition
Major Subdivisions
Central Nervous System (CNS)
-Brain & Spinal Cord
Peripheral Nervous System (PNS)
•Cranial Nerves (12 pairs)
•Spinal Nerves (31 Pairs) |
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Term
| What is the composition of a gross nerve? |
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Definition
A gross nerve is composed of many individual neuron processes (mainly axons), plus supporting tissue (=neuroglia)
•Each neuron serves only one function. That function is designated as the “functional component” of the neuron.
•Each nerve may contain one or more functional types of neurons; therefore, each nerve may be described as having one, or, multiple functional components - note peripheral nerves usu. have multiple fn's |
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Term
| What are the basic functional types of neurons in spinal nerves? |
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Definition
Primary sensory neurons (afferent neurons)
-Relay input from periphery to the spinal cord (Afferent neurons Affect the spinal cord)
-Cell bodies located in clusters (=ganglia) outside the spinal cord
-These will be psuedounipolar
Spinal motor neurons (efferent neurons)
-Relay output from spinal cord to periphery
-Cell bodies located in clusters (=nuclei) within spinal cord motor columns
-These will be multipolar |
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Term
| Explain the somatic functional components |
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Definition
•General Somatic Afferent (GSA): Neurons relaying general sensation & muscle proprioception (position sense) from the body wall & limbs
•General Somatic Efferent (GSE): Neurons relaying motor innervation to skeletal muscle derived from myotomes
-Cell bodies of GSE are located in ventral horn of gray matter |
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Term
| Explain the visceral functional components |
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Definition
General Visceral Afferent (GVA): Neurons relaying general sensation from viscera (i.e., internal organs, glands, smooth & cardiac muscle)
- Input is Dorsal
General Visceral Efferent (GVE): Neurons relaying motor innervation to viscera (ie, glands, smooth muscle, cardiac muscle).
- The visceral motor system is referred to as the autonomic nervous system
- Have Output flow |
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Term
| Explain 1-Neuron system and 2-Neuron system |
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Definition
In GSE, GSA, & GVA systems, a single neuron extends from the CNS to a peripheral target
In GVE systems, the pathway from CNS to peripheral target includes 2 neurons
- Neuron #1: Preganglionic (=presynaptic) neuron
- Preganglionic autonomic neurons have cell bodies in lateral horn of gray matter (CNS)
- Neuron #2: Postganglionic (=postsynaptic) neuron have cell bodies in PNS |
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Term
| What is the location of sensory vs.motor cell bodies? |
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Definition
•Sensory (GSA & GVA) fibers have cell bodies in dorsal root ganglion
•Motor (GSE) fibers have cell bodies in anterior horn of spinal cord
-Motor neurons distribute to skeletal muscle
GVE is special because it is a 2-Neuron system |
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Term
| What is the separation of the nervous system's functional components |
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Definition
Somatic and visceral functional components have dorsal (posterior) and ventral (anterior) separation
there is NO left/right separation |
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Term
| What are the different components of the spinal cord? |
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Definition
ventral (anterior) median fissure
dorsal (posterior) median sulcus
anterolateral sulcus
posterolateral sulcus
gray matter
white matter
central canal
conus medullaris |
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Term
| What is the ventral median fissure |
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Definition
| Ventral (Anterior) Median fissure: A deep, longitudinal cleft along the ventral midline |
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Term
| What is the dorsal median sulcus? |
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Definition
| Dorsal (posterior) median sulcus: A shallow, longitudinal groove along the dorsal midline |
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Term
| What is the anterolateral sulcus |
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Definition
| Anterolateral sulcus: A shallow groove along the anterior lateral side of the cord, marking the line of attachment of the ventral rootlets |
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Term
| What is the posterolateral sulcus |
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Definition
| Posterolateral sulcus: a shallow groove along the posterior lateral side of the cord, marking the line of attachment of the dorsal rootlets |
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Term
| Explain gray matter in the spinal cord |
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Definition
The H-shaped inner core of tissue, composed largely of nerve cell bodies
•Dorsal (posterior) horn: Houses mainly cell bodies of interneurons that receive input from afferent neurons and/or other interneurons
•Ventral (anterior) horn: Houses mainly cell bodies of spinal motor neurons - GSE
•Lateral (intermediolateral) horn:
-Houses cell bodies of preganglionic autonomic neurons (GVE)
-Restricted to cord levels T1-L2/3 & S2-4 |
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Term
| Explain white matter in the spinal cord |
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Definition
Peripheral columns of tissue surrounding the gray matter
•Composed mainly of neuron processes, neuroglia, & blood vessels.
•The large proportion of myelinated fibers gives a white, glistening color in fresh tissue |
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Term
| What is the central canal? |
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Definition
| The lumen of the neural tube, containing cerebrospinal fluid. This is continuous with the ventricles within the brain |
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Term
| What is the conus medullaris? |
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Definition
| The tapered, terminal end of spinal cord that terminates at L2 vertebrae (or the intervertebral disk between L1 & L2) |
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Term
| Explain spinal nerve formation |
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Definition
•Spinal nerves are attached to spinal cord by dorsal/ventral roots
•Ventral roots are motor, & dorsal roots are sensory
-Dorsal/Ventral Rootlets (=filaments) will coalesce together to from dorsal/ventral root
•Also, each dorsal root possesses a dorsal root ganglion
•As the spinal nerve roots pass through the intervertebral foramina, they unite to form the spinal nerves
•Spinal nerve then divides into a large ventral ramus & small dorsal ramus (each ramus contains both motor & sensory fibers) |
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Term
| What is the cauda equina? |
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Definition
| Cauda equina: Horse’s tail-like bundle of nerve roots extending below the conus medullaris |
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Term
| Explain dorsal/ventral primary rami |
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Definition
| Each spinal nerve will immediately divide into its branches. A branch is a ramus & since it is the first branch, will be called a primary ramus |
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Term
| What is a spinal segment? |
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Definition
| The portion of the spinal cord that gives rise to each paired set of spinal rootlets/roots/nerves |
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Term
| What effects does the cutting of different nerves in the CNS have? |
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Definition
•If you cut the ventral roots = lose motor pathway
•If you cut the dorsal roots = lose sensory pathway
•If you cut the dorsal primary rami = lose both sensory & motor
•If you cut the ventral primary rami = lose both sensory & motor
•If you cut the spinal nerve = lose both sensory & motor |
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Term
| How is the myotome split in spinal nerves? |
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Definition
Each myotome splits into large & small piece (myotome is split into hypomore & epimere)
•Large is the ventral piece & will be at the hypomere
•Small is the dorsal piece & will be at the epimere |
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Term
| How are dorsal primary rami distributed? |
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Definition
Dorsal primary rami = Distribute to epaxial tissues
•Epaxial = above the axis
•Any muscle that forms out of the epimere is innervated from the dorsal primary rami
•Intrinsic muscles of the back = deep muscles
- These come from the epimere |
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Term
| How are ventral primary rami distributed? |
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Definition
Ventral Primary Rami: Distrubute to hypaxial (below the axis) tissues, in one of two patterns:
1) Simple segmentation: Independent distribution of nerve rami to the trunk of the body
2) Nerve plexuses: Intermixing of rami in complex networks; therefore, less of gross identity of spinal segments of origin.
-Cervical plexus
-Brachial plexus
-Lumbosacral plexus
-Dorsal/ventral divisions of plexuses (within the limbs)
-Terminal peripheral nerves |
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