Lectures 8-9: Nervous Tissue I And II Flashcards
main functions of nervous tissue (3)
-coordinate body function with internal/external environment
-coordinate and integrate cellular signals
-long distance communication
2 types of neurons
-sensory input
-motor output
sensory input neurons aka
afferent
afferent means
carrying towards a center
efferent means
carried away from
sensory input neurons carry what kind of info
brought from periphery to cns
motor output neurons carry what kind of info
leave cns for periphery
skeletal muscle is an example of what kind of neuron
motor output/efferent
examples of sensory input/afferent neurons
proprioceptive, pain, temperature, touch
how is nervous system organized
-central
-peripheral
2 parts of cns (general)
-brain
-spinal cord
2 parts of pns (general)
-cranial nerves
-spinal nerves
2 parts of cns (structural)
-gray matter and nuclei
-white matter and tracts
2 parts of pns (structural)
-ganglia
-nerves
functional unit of nervous system
neuron
3 types of neurons(morphology)
-multipolar
-bipolar
-pseudounipolar
majority of axons are what morphological type
multipolar
glial cells definition
cells that support neurons
what are the 2 fundamental cells in nervous tissue
neurons and glial cells
neuropil definition
synaptically dense regions composed of unmyelinated axons, dendrites and processes of glial cells
is there any connective tissue within cns
no
primary function of neuron
generate and propagate action potentials
what kind of signals do neurons receive
chemical and electrical
anatomy of basic neuron (8)
-dendrites
-cell body
-axon hillock
-initial segment
-internodal segment
-node of ranvier
-terminal arborizations
-terminal boutons
what is the first part of the axon where the action potential begins
initial segment
dendrites function
receive info from other neurons and carry info to the cell body
cell body aka
perikaryon
function of dendritic spines
-increase surface area
what can dendrites change about their membranes
membrane potential of membrane
what structures do neuron cell bodies contain that dendrites and axons don’t
-cell body contains nissl bodies, golgi complexes and nucleus
what passes from cell body to axon
cytoskeleton and secretory vesicles
where are action potentials generated
initial segment
7 components of neuron cell body: organelles and structures
-nucleus
-nucleolus
-nissl bodies
-golgi complex
-mitochondria
-neurofilaments
-microtubules
function of golgi complexes in neuron
produce regulated synaptic vesicles to package and deliver neurotransmitter to end of axon
what are contained within nissl bodies
rough ER and ribosomes
neurofilaments in axon: definition and function
-intermediate filaments
-stability/structure
function/definition of microtubules in axon
-grow and shrink to move material around (from and to)
function of myelin
insulate cells during propagation of signal
Length of axons vs dendrites
Axons much longer (up to meters long)
Axonal transport is ____________ (directional term)
Bidirectional
Axonal transport: 2 directions
-anterograde
-retrograde
Anterograde axon transport
-Away from cell body
-transport synaptic vesicle protein down axon for potential exocytosis release
Is anterograde axon transport fast or slow
Can be either
Retrograde axon transport
-toward cell body
-cell membranes returned to cell body for reuse or degradation
Is retrograde axon transport fast or slow
Fast
Axonal transport: 2 speeds
-fast
-slow
Axonal transport: fast transport (what is used/transported)
-microtubules and motor proteins (lines in)
-transport organelles, synaptic vesicles
Slow anterograde transport
-transports cytoskeleton precursors and elements that contribute to stability of axon
4 steps of Axonal transport
-synthesis, assembly and export
-anterograde transport
-release of neurotransmitter
-retrograde transport
Where do axons end
Terminal boutons
Synapse definition
Connection between neurons for communication
Synaptic cleft definition
Cells separated by narrow gap
What initiates neurotransmitter release
Action potential
Where does neurotransmitter cross
Synaptic cleft
Effect of neurotransmitter crossing synaptic cleft
Depolarizes postsynaptic membrane or hyperpolarization
4 types of synapses
-axodendritic
-axosomatic
-axoaxonic
-neuromuscular
Axodendritic synapse
Between axon of one cell and dendrite of another cell
Axosomatic synapse
Between axon of one cell and cell body of another cell
Axoaxonic synapse
Between 2 axons
Neuromuscular synapse
Between motor neuron of one cell and muscular tissue
All synapses possess what kind of elements (2)
Pre synaptic and post synaptic
Anatomy of synapse
-presynaptic and postsynaptic membrane with synaptic cleft in the middle
-synaptic vesicles surrounding
-mitochondrion
-dendrites
Presynaptic element: definition
Axon of 1st neuron
What structure contains neurotransmitter
Synaptic vesicles
Are synaptic vesicles part of the presynaptic element or postsynaptic element
Presynaptic
Postsynaptic element definition
2nd neuron
-postsynaptic density
General properties of neurotransmitter reuptake and recycling (3)
-transporter mediated
-recycled enzymatic products
-vesicle is recycled
Neuromuscular synapse definition
Release of Ach from motor neuron propagates action potential within muscle fiber
Sarcoplasma definition
Plasma membrane of muscle cell
Transverse tubules general function
Action potential travels through to reach internal muscle fibers
How does action potential travel in neuromuscular synapse
Through sarcolemma and t tubules
Sarcolemma
Plasma membrane of muscle cell
Sarcoplasmic reticulum
-smooth ER
-stores calcium
Neuromuscular synapse: how it works
-depolarization propagates through t tubules to sarcoplasma reticula
-activates calcium channels to release calcium and cause contraction
Where do t tubules contact/touch
Terminal cistern are of sarcoplasmic reticulum
Ganglia definition
Clusters of cell bodies outside CNS
Where are psuedounipolar neurons found
Sensory ganglia
How do you know you’re looking at a histological section from the peripheral nervous system
Connective tissue stained blue
Satellite cells
Glia that form a complete ring around pseudounipolar neuron cell bodies
99% of all neurons are what morphological type
Multipolar
2 types of non neuronal cells in nervous system
-glial cells (CNS)
-PNS non neuronal cells
4 types of glia
-Astrocytes
-microglia
-Schwann cells
-oligodendrocytes
Microglia functions
-remove damaged neurons and infectious agents
-can become phagocytes
-primary immune defense
Microglia: PNS or CNS
CNS
Astrocytes function/support (3)
-blood brain barrier
-form glia limitans
-proliferation at sites of injury
Glia limitans definition
Barrier between pia mater and CNS
Schwann cells function
Myelinate PNS axons
Oligodendrotytes function
Myelinate CNS axons
Schwann cells vs oligodendrotyes
-Schwann cells myelinate 1 single internodal segment forever
-oligodendrocytes Myelinate more than 1 axon
What is myelin
Insulating series of glial cell plasma membranes (wrapped around and compressed in a loop around axon)
At which parts of axon is myelin absent
-initial segment
-axon terminals
-nodes of ranvier
Regions where myelin is present are called
Internodal segments
What are unmyelinated axons
-not truly without Schwann cells
-axons are enveloped by glial cell but not wrapped by glial cell
Where are unmyelinated axons found (general importance)
In places where conduction speed is not important
CNS myelin vs PNS myelin
-CNS myelin made of oligodendrocytes
-PNS myelin made of Schwann cells
How do peripheral nerves appear under light microscopy and why
Wavy because body wall moves and nerves have to accommodate for that movement
Collections of axons in periphery are called
Peripheral nerves
3 layers of connective tissue around peripheral nerve
-epineurium
-perineurium
-endoneurium
Epineurium
-around whole nerve and many axons
-very dense, fills space between nerve fibers
-outermost layer
Perineurium
Surrounds each bundle of nerve fibers
Endoneurium
-Envelops myelin sheath of individual axons
-composed of reticular fibers produced by Schwann cells
