Lec 1 and 2 PNS Flashcards
The peripheral nervous system is composed of ____ and ____ systems
Somatic and visceral nervous system
Part of PNS system that innervates the internal organs.
Visceral (autonomic) nervous system
Spinal nerves arises from the spinal cord by 2 roots namely: ____ and _____
Dorsal and ventral root
Dorsal root contains fibers that convey somatic and visceral _____ (motor or sensory) information to the CNS
sensory
Ventral root of spinal nerve contains three fiber components which are the:
1.
2.
3.
These fibres have motor functions.
- Large diameter axons to the extrafusal muscle
fibers - Gamma efferents that innervate the intrafusal
muscle fibers - Preganglionic visceral efferent fibers
The spinal nerve formed by the union of the dorsal and ventral horn is a ______.
mixed nerve
The spinal nerve formed by the union of the dorsal and ventral horn is a mixed nerve. This common nerve trunk divides into four branches namely:
1.
2.
3.
4.
- Dorsal rami to the skin and deep muscles of the back
- Ventral rami to the ventrolateral portion of the body wall and extremities
- Meningeal ramus to the meninges, blood vessels, and vertebra
- Ramus communicans which connects the common spinal trunk with the sympathetic ganglia. Consist of gray and white ramus.
Cross section of a peripheral nerve discloses round fascicles of nerve fibers separated by connective tissue sheaths. Blood vessels penetrate the connective tissue sheath to nourish the nerve fibers. β’ The fascicles contain: 1. 2. 3. 4. 5.
Schwann cells and fibrocytes Axons Myelin sheaths Collagen fibrils of the endoneurium Blood vessels
Connective tissue sheath:
- __________ - consists of fibrocytes and collagen fibrils which run longitudinal to the nerve fibers
- ___________ β divides the nerve into fascicles
- ___________ β outermost sheath of peripheral
- Endoneurium
- Perineurium
- Epineurium
The Myelin Sheath is a segmented, multilamellar, lipid-rich wrapping of axons formed by the ________.
plasma membranes of oligodendrocytes (CNS) or Schwann cells (PNS)
Function of Myelin sheath is to increase speed of conduction by ______.
saltatory conduction
Formation (by oligodendrocytes):
- Formed by a cell-to-cell interaction in which the axon destined for myelination is recognized by
proteins on the oligodendrocyte surface - The oligodendrocyte responds by producing a
flattened, sheet-like process that wraps
repeatedly around the axon. - As layers of membrane accumulate, all _______ is
excluded. - The mature sheath consists of layers of ______ (organelle) oligodendrocyte plasma membrane firmly pressed together.
cytoplasm
Oligodendrocytes plasma membrane
The spinal and autonomic ganglia are part of the _______ nervous system.
peripheral
The ______ contains the cell bodies of the afferent fibers that innervate both somatic and visceral structures. It is purely sensory.
spinal ganglion
The _______ ganglion contains efferent visceral fibers. It is purely motor.
autonomic
The autonomic ganglion contains______ fibers. It is purely motor.
efferent visceral
A purely motor ganglion
Autonomic ganglion
A purely sensory ganglion
Spinal ganglion
A ______ contains bundles of fibers, either axons or dendrites, surrounded by connective tissue.
nerve
Sensory nerves contain only _____ fibers, long dendrites of sensory neurons.
Motor nerves have only ______ fibers, long axons of motor neurons.
afferent
efferent
_____ nerves contain both types of fibers.
Mixed
There are ___ pairs of segmentally arranged spinal nerves.
31
Classification of Nerve Fibers Anatomically: 1. 2. 3.
β Diameter
β Length
β Presence or absence of myelin sheath
Classification of Nerve Fibers
Functionally: 1. 2. 3. 4. 5.
β Conduction Velocity
β Conduction direction; afferent or efferent
β Type of sensory modality served
β Type of structure innervated; visceral or
somatic
β Type of neurotransmitter
True or false
Each pair of spinal nerves innervates asymmetrically paired somites.
False
-symmetrically
Each somite differentiates into a ___, ____, and _____.
myotome, sclerotome, and a dermatome.
EFFERENT FIBERS OF THE VENTRAL ROOTS innervate________ and some ventral roots contain preganglionic autonomic fibers which pass to autonomic ganglia which in turn give rise to POSTGANGLIONIC FIBERS that innervate ____, ____, and ____.
Somatic musculature
blood vessels, smooth muscles, and glandular epithelium.
The cutaneous area supplied by the sensory fibers from a single dorsal root and its ganglion is called a _______.
dermatome
During devβt, metameres migrate distally into the limb buds and arrange themselves to the ____ axis of future limb.
long
β’ During devβt, metameres migrate distally into the limb buds and arrange themselves to the long axis of future limb.
- As a consequence of limb devβt, C4 dermatome comes to lie adjacent to the ___ dermatome
- The dermatomes of ___ through___ lie in the upper extremity.
- Dermatomes of ___ and ___ are adjacent posteriorly
T2
C5 through T1
L2 and S3
Innervation of:
C2 -
occipital protuberance
C3 -
supraclavicular fossa
C4
Acromioclavicular joint
C5
Lateral antecubital fossa
C6
Thumb
C7
Middle finger
C8
Little finger
T1
Median antecubital fossa
T2
Apex of axilla
T4
Nipple line
T10
Level of umbilicus
L1
Upper anterior thigh
L2
Middle anterior thigh
L3
Medial femoral condyle