Nervous System Flashcards
Somatic nervous system correlates to?
Voluntary movements
Autonomic nervous system correlates to?
Parasympathetic and sympathetic systems
What is the structural and functional unit of the nervous system?
Neuron
What are the four supporting glial cells of CNS?
Oligodendrocytes
Astrocytes
Ependymal cells
Microglial cells
What are the two supporting glial cells of the PNS?
Schwann cell
Satellite cells
What is another name for cell body Soma?
Perikaryon
What is Nissl substance?
Aggregates of rER and polyribosomes
What is a telodendron?
End of axon in terminal arborization
What does each branch of a telodendron end in?
Boutons terminal
Where are neurotransmitters held?
Terminal Bouton
What do sensory afferent neurons do?
Convey information/impulses TO CNS, FROM receptors
What do motor efferent neurons do?
Convey inorfmation/impulses to the target cells FROM CNS
Where are interneurons/intercalated neurons located?
CNS and autonomic ganglia
What do interneurons/intercalated neurons do?
Integrate sensory and motor neurons
What is a multipolar neuron?
One axon and 2 or more dendrites
Where are multipolar neurons located?
Brain, spinal cord, autonomic ganglia
What is function of multipolar neuron?
Motor and interneurons
What is a bipolar neuron?
One axon and one dendrite
Where are bipolar neurons located?
Olfactory, retina, spiral ganglia of ear
What is a pseudounipolar neuron?
One long peripheral process, one short central process
Where are pseudounipolar neurons located?
Dorsal root ganglia
What is the function of pseudounipolar neurons?
Sensory
What is another term for sensory neuron?
Afferent neuron
What is another term for motor neuron?
Efferent neuron
What is the cytoskeleton of neuronal cell body made of?
Actin filaments, intermediate filaments, microtubules with centrosome
What protein do microtubules hold?
Tau proteins
Why does soma/perikaryon have lipofuscin granules?
Lysosomal digestion
What are tau proteins?
They stabilize microtubules
What is the clinical representation of misfolded and abnormally phosphorylated tau proteins?
Alzhiemers disease
What other factor plays a role in Alzheimers disease
Amyloid plaques/neuritic plaques; aggregates of beta amyloid protein outside of neuronal regions
Are dendrites myelinated?
No
What is function of dendritic spines?
Increase surface area available for synaptic contact
What organelles are present in axon hillock?
Mitochondria, microtubules, neurofilaments, and vesicles; help with transport of substances down the axon
What is the region between axon hillock and myelin sheath?
Initial segment
What is importance of initial segment?
Initiation of action potential
What is the cytoplasm of an axon called?
Axoplasm
What does axoplasm contain?
Neurotubules/microtubules, neurofilaments, mitochondria, vesicles
What does neurotubules/microtubules of axoplasm provide?
Tracks along which material is transported to and from cell body
What does neurofilaments provide axoplasm?
Structural support
What is anterograde transport in axoplasm?
Movement of mitochondria/substances DOWN the axon, *Kinesin protein
What is retrograde transport in axoplasm?
Movement of mitochondria/substances UP the axon, *Dyenin protein
What is axoplasm surrounded by?
Axolemma
What is presynaptic destiny of axon?
Aggregation of dense material in cytoplasm, Site where vesicles attach
What is postsynaptic density of dendrite?
Aggregation of dense material in cytoplasm, site where receptor proteins and channels are prevalent
What is between presynaptic and postsynaptic densities?
Synaptic cleft
What is important feature of synapse structure?
ER that regulates calcium levels
What is an electrical synapse?
Terminal boutons containing gap junctions, permit movement of electrical current between cells
Where are oligodedrocytes, ependymal cells, and astrocytes derived from?
Neuroectoderm
Where are microglial cells derived from?
Mesoderm
Where are schwann cells and satellite cells derived from?
Neural crest
What does every internode of PNS represent?
ONE schwann cells
What does every internode of PNS represent?
ONE schwann cell
What junctional complexes are found in nodes of ranvier?
Tight junctions
What do satellite cells surround?
Ganglion cells
What is role of satellite cell?
Structural and metabolic support for neural cell bodies, insulation and nutrition
Where are oligodendrocytes located?
Gray and white matter, predominantly in white matter
What are two types of oligodendrocytes?
Interfascicular- white matter
Perineuronal satellite cell- gray matter
What do perineuronal satellite cells do?
Regulate the neuronal microenvironment to protect neuron
What foot process covers the rode of ranvier?
Astrocytic foot process
What does oligodendrocytes NOT contain?
Glial fibers
What DO oligodendrocytes contain?
Microtubules
What does EM of oligodendrocytes show?
Inclusion bodies, clumps of chromatin, short cisternae of rER with mitochondria
What are two types of astrocytes?
Fibrous- white matter
Protoplasmic- gray matter
What junctional complexes do astrocytes hold?
Gap junctions
What do astrocytes contain that need a special stain to see?
GFAP, and intermediate filaments
What functions do astrocytes have?
Physical barrier between cells for protection, maintain ionic and pH equilibrium, modify chemical environment
Metabolize neurotransmitters, ex. Glutamate
What type of lining do astrocytes form around external surface of CNS?
Glial limitans
What type of lining do astrocytes form around blood vessels?
Perivascular feet
During injury, what do astrocytes proliferate into?
Phagocytic cells, forms glial scar
What do ependymal cells line?
3rd and 4th ventricle of brain, central canal of spinal cord
What is special feature about ependymal cells in the ventricles?
They do not rest on basal lamina, no basal lamina between cells and brain tissue
What do ependymal cells have on apical surface that moves CSF in the ventricles?
Microvilli and cilia
What are the intercellular junctions of ependymal cells?
Tight junctions
When the ependymal cells are modified to form layers of cuboidal epithelium in rich vasculature of choroid plexus, they do have a _____?
Basal lamina, formed by outgrowth of pia
What does choroid plexus secrete?
CSF, transport of water and electrolytes from capillary endothelium to form CSF
What are tanycytes?
Specialized ependymal cells present only in THIRD ventricle
What is special feature of tanycytes?
Basal processes extend through the astrocytic process layer to form end feet on blood vessels
What is function of tanycytes?
Control body weight and energy balance
What are microglial cells?
Phagocytic cells, remove debris of cells that die or during injury
What system are microglial cells part of?
MPS Mononuclear phagocytic system
Where are microglial cells prominent in?
Gray matter
When do the numbers of microglial cells increase?
During injury
What is PNS composed of?
Nerves, ganglia, nerve endings
What do epineurium and perineurium contain that endoneurium doesnt?
Blood vessels
What do peripheral nerve ganglia contain?
Cell bodies of ganglionic neuron, supporting satellite cells, nerve fibers
What are peripheral nerve ganglia associated with?
Cranial, dorsal root and autonomic ganglia
What is peripheral nerve sensory ganglia associated with?
Cranial ganglia, dorsal roots spiral ganglia
What type of neurons are in peripheral nerve sensory ganglia?
Pseudounipolar
What are sensory ganglia supported by?
CT capsule and internal framework
What are peripheral nerve autonomic ganglia?
Bulbous dilations associated with autonomic nerves, poorly defined capsule
Where are peripheral nerve autonomic ganglia located
Within organs, ex. GIT
Autonomic nerves use a two neuron circuit, what is involved?
First neuron of chain-preganglionic neurons located in CNS
Postganglionic fibers of second neruron-multipolar neurons located in peripheral autonomic ganglia
What is length of parasympathetic pre and post ganglions?
Long pre, short post
What is length of sympathetic pre and post ganglions?
Short pre, long post
Where are cell bodies of preganglionic sympathetic nerves located?
Lateral horn T1-L2
Where are cell bodies of preganglionic parasympathetic nerves located?
Medulla and midbrain, lateral horn S2-S4
Where are cell bodies of postganglionic sympathetic nerves located? (second order neurons)
Paravetebral neurons, sympathetic chain
Where are cell bodies of postganglionic parasympathetic nerves located? (second order neurons)
Ganglia always near effector organ
What is Endoneurium type of collagen?
Type 3
What is epineurium type of collagen?
Type 1
Where are the collagen fibers of endoneurium and perineurium synthesized from?
Schwann cells
What is present in endoneurium CT?
Macrophages and mast cells
What is special about perineural CT?
Specialized cells called perineurial cells, cells are contractile with actin filaments, each layer has a basal lamina on both surfaces
Forms blood nerve barrier
What does perineurial cells form?
Blood nerve barrier, forms tight junctions
Where is epineurium absent in?
Small nerves
What are the three parts of brain?
Cerebrum, cerebellum, brain stem
What does cortex or gray matter hold?
Nerve cell bodies, axons, dendrites, glial cells
Where is site of synapse?
Gray matter or cortex
What does medulla or white matter hold?
Myelinated axons of nerve cells, and glial cells
Cerebrum neocortex is organized into how many layers?
6 layers; molecular layer, external granular, external pyramidal, internal granular, internal pyramidal, multiform
Cerebellum is arranged in three layers, what are they?
Outer molecular layer, middle purkinjie layer, inner granular layer
Brain and spinal cord are covered by meninges, what are the three?
Dura mater, Arachnoid mater, Pia mater
What does dura mater consist of?
Thick sheet of CT, two layers; outer periosteal layer, inner meningeal layer, between two layers are dural venous sinuses
What is function of dural venous sinuses?
Drain venous blood from brain into internal jugular vein
What partitions does meningeal layer of dura form?
Falx cerebri, tentorium cerebelli
What does arachnoid mater consist of?
CT sheet, small tufts of arachnoid tissue projects into superior sagittal sinus to drain CSF into venous sinuses
What is subarachnoid space filled with?
CSF, blood vessels
What does pia mater consist of?
Delicate CT sheet, lies on surface of brain on glial limitans
What does pia mater follow penetrating branches of?
Large blood vessels of brain, narrow space between blood vessels and pia is called perivascular space
What does perivascular space hold?
CSF from subarachnoid space, facilitates movement of CSF deep into brain tissue
What is blood brain barrier?
Physiological barrier, extensive tight junctions, thick layer of basement membrane, astrocyte end feet, strong basal lamina
What are three layers of blood brain barrier basal lamina?
EC layer formed by laminin-4 and lamin-5
Astrocyte derived layer, formed by laminin and lamin-2
Collagen IV layer
A number of astrocyte released factors contribute to BBB integrity, including?
Glial derived neurotrophic factor GDNF
What cells are present with surrounding basal lamina of endothelial cell?
Pericytes
What do pericytes do for BBB?
Involved in restricted BBB permeability
What are two events in neuron response to injury?
Axonal degeneration, neural degeneration
Can axons of CNS regenerate?
No, due to myelin debris containing inhibitors of axonal degeneration, and due to BBB restriction of macrophage migration
Degeneration of axons in PNS of distal part is called?
Anterograde degeneration or Wallerian degeneration
Degeneration of axons in PNS of proximal part is called?
Retrograde degeneration or traumatic degeneration
Describe anterograde degeneration in PNS
Microtubules and cytoskeleton break down, axon fragments, this causes schwann cells to differentiate and results in breakdown of myelin sheath, remenants are phagocytized by schwann cells and phagocytes, then recruitment of monocyte derived macrophages occurs, complete disruption of blood nerve barrier along entire nerve, dedifferentiated schwann cells stop forming myelin, start to divide and arrange themselves longitudinally along external lamina
Describe axon regeneration in PNS
Schwann cells start to form bands of bungner, these bands guide growth of neurites to correct destination, schwann cells around regenerated axon redifferentiate and make myelin sheath
Describe retrograde degeneration in PNS
Axon proximal to injured site undergoes degeneration, this upregulate the gene C-jun, C-jun expression causes the cell body to undergo chromatolysis; neuron swells, nucleus and nissl substance is moved peripherally
Describe response to injury in CNS
If oligodendrocytes lose contact with axon, they undergo apoptosis, BBB is disrupted only at site of injury (not along entire length of axon), this limits infiltration of macrophages, myelin removal takes a very long time, astrocyte forms glial scar that replaces empty spaces left by degenerated axons
