Neuroanatomy Week 3 - PNS Flashcards
What do sensory receptors respond to?
pain, temperature, touch, and pressure.
Where are sensory receptors found?
throughout the whole body
What are sensory receptors?
- transducers,
- Stimulate chemical stimuli to create action potentials
What are the 2 categories of afferent neurons?
- Somatic
- Visceral
Afferent neurons
What are somatic afferent neurons associated with?
the skin, bones,
muscles,
and connective tissue
that makes up most of the
mass of the body (soma)
What are visceral afferent neurons associated with?
for the internal organs of the circulatory, respiratory, alimentary, excretory,
and reproductive systems.
Where are somatic efferent neurons (motor neurons) found?
ventral grayhorns of the spinal
cord
and motor nuclei of cranial nerves.
How are the fibers of peripheral nerves (except the very small ones)
arranged?
in bundles or fascicles
What is the entire PNS nerve is surrounded by?
epineurium
What do epineurial collagen fibres help with?
-stretching the nerve
- flexion of joints and movements
What is the perinerium?
The perineurium is a sheath that surrounds small bundle of fibers (fascile) in a nerve
What is another name for endoneurium?
Henle’s sheath or intrafascicular connective tissue
What is the endoneurium?
connective tissue sheath that directly surrounds individual Schwann cell–axon units
What is a neurolemma?
- outermost layer of Schwann cells
- surrounds the axon of the neuron.
- thin sheath around a nerve fiber
The cytoplasm (axoplasm) of an axon contains what 4 organelles?
- neurofilaments,
- microtubules,
- smooth endoplasmic reticulum,
- mitochondria.
What is an axolemma?
Plasma membrane around the nerve cell is called axolemma
The axolemma is responsible for maintaining the membrane potential of the axon, and contains ion channels through which ions can flow rapidly.
What is an axoplasm?
Cytoplasms of an axon
What is neurilemma?
Neurilemma is the plasma membrane of Schwann cells that surrounds the myelinated nerve fibers of PNS
Define saltatory conduction
propagation of action potentials along myelinated axons from one node of Ranvier to the next
The most rapidly conducting myelinated fibers in a nerve are ?
largest diameters and the longest internodes.
Are there nodes of ranvier on unmyelinated neurons?
no
What is an unmyelinated fibre surrounded by?
a single layer of the glial cell’s plasma membrane
Do schwann cells cover unmyelinated neurons in the PNS?
Yes, only a single layer
They are not insulated
They may cover multiple axons at a time
Where are unmyelinated neurons found?
Olfactory system
Enteric system
alimentary canals
