nervous tissue Flashcards
what is the perikaryon
the cell body of the neuron
what extends from the cell body of the neuron
an axon and dendrites
what are dendrites
highly branched tapering processes which end in either specialised receptors or form synapses with neighboring neurons they receive stimuli from
what are primary sensory neurons
those with dendrites that end in specialisaed sensory receptors
what is the function of dendrites
major sites of information input into the neuron
what do axons carry information from
perikaryon
what do axons carry information to
synapse
in which neurons are schwann cells found
in those of the peripheral nervous system
what is the function of schwann cells
envelop PNS axons to provide structural and metabolic support
what are small diameter axons
those of the autonomic nervous system and pain fibres
what envelops small diameter axons
the cytoplasm of schwann cells - meaning they are unmyelinated
what are large diameter fibres wrapped by
variable number of cocentric layers of the schwann cell plasma membrane to form a myelin sheath
what provides the myelin sheath to axons of the peripheral nervous system
many schwann cells
what provides the myelin sheath in the central nervous system axons
oligodendrocytes
how much of the axon can be covered by a single schwann cell
only a segment
what are nodes of ranvier
short intervals where the axon is not covered by myelin, found in between the schwann cells
what does the myelin sheath function to do
prevent the nerve action potential from being propagated continuously along the axon
how does action potential travel
by jumping from one node of ranvier to the next and so on
what is saltatory conduction
the conduction pathway of action potential down myelinated axons
what are the nodes of ranvier important for
action potential propagation and allowing the diffusion of nutrients and waste from and into the neuron
what is the myelin sheath rich with
lipids
what does the myelin sheath act as a barrier to
the diffusion of sodium ions
where are sodium channels enrinched within the myelin sheaths of axons
at the nodes of ranvier
what is endoneurium
loose vascular supporting tissue that surrounds each individual nerve fibre with its investing schwann cell
what is the perineurium
a condensed layer of robust collagenous tissue that is invested by a layer of flat epithelial cells that surrounds each neuron fascicle
what is the epineurium
loose collagenous tissue that binds the fascicles together, and is condensed peripherally to form a strong cylindrical sheath. found in peripheral nerves consisting of more than one fascicle
what is calibre
the diameter of the axon
what does greater lipid solubility of a substance enhance
its ability to diffuse through nerve sheaths and the neural membranes of individual axons comprising a nerve trunk
how is lidocaine prepared
at 2% concentration
what is the potency of an anaesthetic associated with
its lipid solubility
how is bupivacaine prepared
0.5% concentration
how do myelin sheaths appear when they are stained
circular
what happens to myelin sheaths as the calibre of axons increases
the myelin sheaths are thicker and longer as the calibre increases
which nervous system are motor neurons part of
the somatic motor system
what do the neurons from the lumbar region of the spinal cord innervate
the lower limbs
what do the neurons of the cervical region innervate
upper limbs
what does ventral horn grey matter contain
the cell bodies of motor neurons
how does information travel in the spinal cord for skeletal muscle innervation
from the central nervous system to the muscles, downwards
which information of the spinal cord is relayed downward
motor innervation
which information of the spinal cord is relayed upward
sensory
what does dorsal horn matter contain
cell bodies of small second order sensory neurons
what do second order sensory neurons of the dorsal horn grey matter relay
sensory information on pain and temperature to participate in spinal reflexes
where are small lateral horns found
the thoracic and upper lumbar regions
what do the small lateral horns of the spinal cord contain
cell bodies of sympathetic nervous system efferent neurons
what are preganglionic neurons
sympathetic nervous system efferent neurons
describe the structure of purkinje fibres
large round cell bodies with numerous branching dendrites
