Anatomy: Nervous System Flashcards
CNS
Inside skull and vertebral column
Brain, spinal cord
spinal nerves and differential
31 pair
8 cervical
12 thoracic
5 lumbar
5 sacral
a collection of nerve cell bodies (or in some cases, a single nerve cell body) associated with peripheral nerves and located outside the CNS
Ganglia
Sensory ganglia are ______ polar
DRG — pseudounipolar
Cranial ganglia - some bipolar
Autonomic, motor or visceral ganglia are _____polar
mutlipolar
Gray matter
contains the Nerve Cell Bodies and Synapses (unmyelinated)
White Matter
consists of Axons which form Tracts (myelinated)
Variations in Spinal Cord
- Cord gets smaller caudally
- Progressive decrease in white matter at lower levels: number of nerve fibers decreases caudally as descending tracts gradually terminate and ascending tracts aren’t yet complete.
- Shape of cord: cervical segments are large and oval, while lumbar and sacral segments are smaller and rounder.
- Gray matter larger at cervical (C4-T1) and lumbosacral (L2-S3) levels: due to larger number of nerve cells associated with innervation of the limbs.
- Lateral horn present in T1-L2/L3 segmental levels (aka intermediolateral cell column): contains the cell bodies of preganglionic sympathetic neurons.
- Dorsal or posterior column (funiculus) divided into two fasciculi (f. gracilis and f. cuneatus) above T6.
Lateral horn contains
contains the cell bodies of preganglionic sympathetic neurons.
Only T1-L2
Dorsal or posterior horn
a. Sensory horn – involved in the relay of sensory information
b. Contains multipolar neurons that send their axons to:
i. higher levels in the CNS (upper spinal cord, brain stem or diencephalon
ii. ventral or anterior horn cells (these are interneurons)
Ventral Horn contains
Motor horn
i. alpha motor neurons (multipolar neurons) that send their axons to innervate extrafusal skeletal muscle fibers/cells. These alpha motor neurons are known also as lower motor neurons
ii. gamma motor neurons (multipolar neurons) that innervate the intrafusal muscle fibers/cells of the neuromuscular spindle
Dorsal column contains
mainly ascending nerve cell processes whose cell bodies are located in dorsal root ganglia.
Carries the sensory modalities of discriminative touch and proprioception (position sense).
Lateral column
a. Contains ascending sensory nerve fibers (tracts) and descending motor nerve fibers (tracts)
b. Sensory nerve fibers (tracts) have their cells of origin in the gray matter of the dorsal horn, while motor nerve tracts have their cells of origin in upper levels of the neuraxis (brain stem or cerebrum).
Ventral/anterior column
a. Contains ascending sensory nerve fibers (tracts) and descending motor nerve fibers (tracts)
b. Sensory nerve fibers (tracts) have their cells of origin in the gray matter of the dorsal horn, while motor nerve tracts have their cells of origin in upper levels of the neuraxis (brain stem or cerebrum).
i_mplies a relation to the body wall and the limbs_
somatic
Somatic nerves found in both ___ and ____ nerves
cranial and spinal nerves
Somatic sensory fibers
a. Sensory nerves to and from skin, skeletal muscle and joints
b. Nerve cell bodies located in cranial and spinal sensory ganglia
Somatic Motor Fibers
a. Responsible largely for voluntary control of skeletal muscle
b. Motor nerve cell bodies located in central nervous system (brain stem and spinal cord) - one efferent (motor) neuron (axon) for each cell body
implies a relation to the organs of the body cavities, and is extended in this case to include blood vessels and glands that lie outside the body cavities
Visceral
Visceral nerve fibers found in both ____ and ______ nerves
cranial and spinal nerves
Visceral sensory fibers
a. Sensory nerves from the viscera (heart, lungs, GI tract, urinary system, blood vessels, etc
b. Nerve cell bodies of these afferents are located in the cranial** and **spinal sensory ganglia
Visceral motor fibers responsible for involuntary regulation of____
smooth muscle, cardiac muscle and glands
ANS is a ____ neuron system
2
(1) The first located in the CNS
(2) The second located in an autonomic (visceral) ganglion
Major divisions of ANS
(1) Sympathetic nervous system
(2) Parasympathetic nervous system
(3) Enteric nervous system – neurons (nerve cell bodies and processes) located in the gastrointestinal tract
Dorsal root =
sensory root
Sensory or afferent nerve fibers
DRG or spinal ganglion on each DR
(1) Contains all peripheral sensory nerve cell bodies (somatic and visceral)
(2) Pseudounipolar neurons – found only in sensory ganglia (DRG and cranial nerve sensory ganglia)
(3) Central and adjacent peripheral processes of these nerve cells make up the dorsal root. The central process extends into the spinal cord, while the peripheral process forms the spinal nerve.
Ventral Root
a. Motor or efferent nerve fibers relative to the spinal cord
b. The cell bodies that send their axons through the ventral roots are located in the ventral and lateral horns (gray matter) of the spinal cord. The ventral root joins the dorsal root to form the spinal nerve.
Spinal nerves formed by
union of a dorsal root and a ventral root peripheral to the intervertebral foramina for each segment.
The spinal nerve contains all the motor and sensory axons leaving and entering a given spinal cord segment.
Typically, very short, i.e., about 1/4-inch.
Supplies muscular and cutaneous branches to the deep muscles and skin of the back and posterior head.
Dorsal (posterior) primary ramus
Supplies muscular and cutaneous branches to the skin and skeletal muscles of the lateral and anterior aspects of the trunk, and the skin and muscles of the limbs.
Ventral (anterior) primary rami
Cranial nerves (vs spinal nerves)
- Each cranial nerve may be purely sensory, purely motor, or mixed (motor/sensory).
- Cranial nerves do NOT have dorsal and ventral roots or dorsal and ventral rami.
There are ____ sympathetic ganglia associated w/ cranial nerves
none
only sensory and parasympathetic ganglia
Nucleus
collection of cell bodies in CNS
gray matter
