Nerve Tissue Flashcards
Organization of nerve tissue
CNS - brain and spinal cord
PNS - cranial and spinal nerves
ANS - controls gland secretion…cell bodies found in CNS while process and postganglionic bodies in the PNS
Composition of PNS and CNS
Both have neurons and supporting cells
CNS - uses neurolgia…divided into Gray and White matter
PNS - Schwann and satellite cells…divided into ganglia and nerves
Gray and white matter
Gray - neuron cell bodies and neuoglia…unmyelinated…astrocytes
White - neuronal processes and neuroglia…myelinated…astrocytes and oligodendrocytes
Gnaglia and nerves
Ganglia - neuron cell bodies, schwann and satellite cells
Nerves - axons, dendrites and schwann cells
Strutcture of a neuron
Nucelus - owl’s eye with dark nucleolus
Nissl substance - RER
Axon hillock - lacks nissl substances and cytoskeletal elements funnel into axon from cell body
Dendrite
Multiple places for synapse…rarely myelinated
Dendritic spines
Receive synapses (input) toward the cell body
Types of neurons and where found
Bipolar - special sense (except taste)…one of each
Multipolar - motor (both vaso and somato)…one axon and multiple dendrites
Psuedounipolar - sensory…have fused axon and dendrite
Schwann cells (myelination of the PNS)
Schwann cell membrane provides the myelin sheath of the axon…mesaxon where invagination occurs
In the PNS
One schwann cell myelinates ONE internode of ONE neuronal process
Node of ranvier (and what is in the CNS)
SC cytoplasm is what covers here…no SC membrane
In the CNS, astrocytic end-foot
CNS myelination
One oligodendrocyte myelinates ONE internode on as many adjacent neuronal process as the oligodendrocyte has processes
unmyelination of the PNS
Axons arranged in circular pattern around the nucleus…SC cytoplasm surrounds entire thing with each axon having one layer of SC membrane around it
Terminal buttons are made of
Schwann cell cytoplasm
Types of synapses and most common
Axosomatic (terminates on soma of the neuron)
Axoaxonic
Axodendritic**
Axospinous
Morphology of the synapse
Can see presynaptic vesicle and post synaptic thickening
Vesicles travel down MT tract
Major trnasmittors of the CNS and which are excitatory and inhibitory
AA
Ex - glutamate; cortex, basal gang, thalamus, cerebellum
In - GABA; cerebellum, basal ganglia and glycine; lower brainstem (medulla) and spinal cord
Amine NTs
dopamine
NE
Serotoninn
Ach
Used by cranial nerve motor nuclei (nucleus ambiguus, hypoglossal, DMV)
Spinal cord neurons of the ventral horn (efferent axons to muscles)
Basal nucleus of meynert
Dopamine
Sustantia negra
Regulates motor function and limbic function…lactation
NE
Locus cerulus…innervates thalamus, hypop, and limbic ofrebrain
Serotonin
Raphe system
Rostral - diencephalon and telencephaolon
Caudal - spinal cord
Neuropeptides
Enkephalins and substance P
Dorsal horn and afarent nuclei
Pain
Structure of peripheral nerve
Endoneurium surrounds each axon
Perineurium wraps nerve fibers into fascicles
Epineurium surrounds entire nerve that contains blood vessels
Neuroglial cells of CNS
Astrocytes - BBB
Microglia - phagocytosis
Epnndymal cells
Oligodendrocytes
Astrocytes
Have feet that help form BBB…also the glia limitans
Protoplasmic astrocytes
Gray matter
Make tight junctions with endothelial cells and create BBB
Fibrous astrocytes
White matter
Contact axon at node of ranvier
Remove excess K+ in extra cellular space during impulse condcutiin
Microglial cells
Immune cells
From embryonic yolk sac
If injured, can have activation and lead to dysfunctional state if chronic
Ependyma
Ventricels of brain and central canal of spinal cord
Ependymal cells - cilia and microvilli and contact astrocytes…attached by belt desmosomes
Tanycytes - 3rd ventricle only…through the astorfcyte process and attached by tight junctions
Nucleus
Assumulation of nerve cell bodies in gray matter
Nerve vs. ganglion
Nerve- accumulation of ONLY cell processes (axons) with any type of CT and blood vessels
Ganglion - presence of a single cell body
Schwann vs satellite cell
Schwann - only the processes
Satellite - only the cell body
Appearance of CNS vs PNS
CNS - support cells randomly arranged
PNS - form a capsule
Sensory ganglia of the pNS
Psuedounipolar neurones that have discrete organization because of thick bundles
Sympathetic ganglia of the PNS
Multipolar neurons that are randomly distrubuted and a thinner CT capsule
Lie outside of the muscle wall
Parasympathetic ganglia of the PNS
Have small numbers of multipolar nuerons…CT capsule very veyr thiner and in wall of organ
Auerbach’s plexus in between muscle of GI
If lesion of axon
Chromatolysis where Nissls substance degenerate
Neurite club forms as neurons leave and try to come back
Eventually, if one makes contact with schwann cell, then will grow and others will die
Schwann and fibroblasts can scar
Both retrograde and anterograde degeneration
