Ch. 3 - Cells Of The Nervous System Flashcards
What is the functional unit of the nervous system?
Neuron aka nerve cell (cell body & it’s processes)
What are the 3 components of a neuron?
- Cell body - soma
- Single axon
- Variable number of dendrites
Where do axons terminate? With what kind of synapse?
Telodendria; terminal bouton
(DNA) is located in the soma; prominent nucleolus (RNA) used for protein synthesis
Nucleus
Phospholipid bilayer /c hydrophilic ends facing the outer surfaces and the hydrophobic ends toward the center of the membrane
Plasma cell membrane
The plasma cell membrane effectively blocks diffusion of what?
Water soluble molecules across the membrane
What is embedded in the bilipid layer to permit the selective permeability of certain molecules?
Integral proteins
Possible continuous pores through the plasma cell membrane allowing some ions to flow passively, but at very high rates only when the “gate” is open
Channels (ionophores)
What proteins allow only a few ions to pass thru the cell membrane at a time?
Carrier proteins
What can work against a gradient to get things across the cell membrane, and requires ATP as an energy source?
Pumps
Proteins can also transducer chemical or physical stimulation (I.e. ________) to initiate the response of the neuron, muscles, or gland cells to a specific stimulation
Receptor proteins
True or False:
Receptor proteins can migrate and shift laterally within the membrane and new proteins can be produced
True (ex. ACh receptors at the motor end plate)
What is on the outer surface of the cell membrane & functions in cellular recognition?
Glycoproteins
What is composed of flattened granular endoplasmic reticulum studded /c ribosomes, free ribosomes, and polysomes which are clusters of ribosomes?
Nissl bodies
What 3 things do nissl bodies synthesize?
- Neurosecretory proteins
- Integral proteins
- Lysosome proteins
What do free ribosomes and polysomes synthesize?
Cytosol & non-integral proteins
__________ is essential to neurological function
Protein synthesis
Complex stacks of flattened cisternal sacs
- receives newly synthesized proteins by vehicle transport, for sorting and ultimate dispersion
Golgi apparatus
- membrane enclosed organelle involved in producing cellular energy
- energy from oxidation is stored as phosphate bound energy (ATP) and released by hydrolysis
- neurons are dependent for their energy on circulating glucose and oxygen (no glycogen storage)
Mitochondria
- enclosed by a membrane and contain hydrologic, degradation enzymes, involved in “recycling”
- may explain the yellow, “lipofuscin” in granules found in neurons of the elderly
Lysosomes
What are the 3 cytoskeleton transport organelles?
- Neurofiliaments
- Neurotubules
- Microfilaments
What are the cytoskeletal transport organelles composed of?
Protein polymers
What cytoskeletal transport organelle is…
-Semirigid; provide support and maintenance neuron shape
Neurofilaments
What cytoskeletal transport organelle is…
- involved in atonal transport and growth of the axon and dendrites
- contains several tracts
- allows for unidirectional and bidirectional movement on separate tracts
Neurotubules
What cytoskeletal transport organelle is…
- prominent in the growling tips of axons
Microfilaments
Axonal transport is movement of substances along the axon either away from the cell body (__________) or towards the cell body (_________)
Anterograde; retrograde
Fast component transport system is due to __________
- _________ carries membranous organelles, and vesicles of protein and transmitter precursors
- _________ carries worn out material to the lysosomes for recycling
Neurotubules; anterograde; retrograde
Slow component transport system is __________ to maintain the axoplasm and provide substrate for axon and dendrite growth
Anterograde
_________ transport can cause harmful results following infection /c neurotrophic viruses such as rabies, herpes simplex, poliomyelitis
Retrograde
True extensions of the soma, containing some cytoplasmic organelles
- often multiple, transmit incoming signals toward the soma
Dendrites
Single long projection from the soma
Axon
The axon arises at the _______, which does not contain nissl bodies
Axon hillock
The axon transmits a _________ action potential
All or none
The axon length range may range greatly before branching into ________
Telodendria
Each telodendron of an axon terminates as a ________ as the synaptic site of contact /c another cell
Bouton
Axons and dendrites are generically called _______
Nerve fibers
Site of contact of one neuron /c another
Synapse
What are the 3 most common types of synapses?
- Axosomatic
- Axodendritic
- Axoaxonic
The synapse of each motor neuron on a voluntary muscle is called _________
Motor end plate
Cell membrane of the axon at the synapse
- the bouton contains mitochondria and vesicles of neurotransmitter precursors
Presynaptic membrane
Cell membrane of the dendrite, cell body, muscle, or gland cell
Postsynaptic membrane
Part of the postsynaptic membrane within the synapse
Subsynaptic membrane
Structure of peripheral nerve:
Each fiber consists of an _______, surrounded by a ____________, surrounded by a connective tissues sheath (_______)
Axon; neurolemma (Schwann cell); endoneurium
Myelinated fibers in the PNS are formed by what?
Schwann cells wrapping many times as concentric layers around the fiber
Unmyelinated fibers in the PNS are formed by what?
A single layer of Schwann cell sheath, but no myelin
Myelinated fibers are > ___um; unmyleinated are < ___um
Myelinated > 2 um
Unmyleinated < 2 um
Points at which the myelin sheath is interrupted, occur at regular intervals
Node of ranvier
Interval btw adjacent nodes; ensheathed by one Schwann cell
Internode
What are non-neural cells of the CNS?
Neuroglia
Are neuroglia or neurons more prevalent in the CNS?
Neuroglia
Oligodendrocytes and astrocytes are __________ that function to support and maintain the neural environment; they also react to injury of neurons and can form scars
Macroglia
The neurolemma cells of the CNS; each cell forms internodes of several fibers
Oligodendrocytes
/c sheet-like processes, store and transfer metabolites from capillaries to neurons
Astrocytes
Myelin producing cells of the PNS
Schwann cells
Mesodermal cells, similar to macrophages, important in defense and repair
Microglia
Glial cells which line the ventricles and choroid plexus; produce CSF
Ependymal cells
If an axon is injured and the cell body survives, ________ can be done
Regeneration
Axon reaction:
- The _______ swells and the nucleus moves to an ________ position
- Ribosome concentration _________ in the periphery of the soma, resulting in _________ (lack of central staining of soma), preparing new sources of protein for the regeneration
- The ________ stump of the severed axons are sealed by newly formed plasma membrane
- In the next week (or months in CNS), the distal axons and myelin sheaths will ________ followed by myelin phagocytosis
- A cord formed by the dividing neurolemma cells of the distal segment outline the original course of the severed nerve fibers all the way down to the original nerve terminals
- Soma swells; nucleus moves eccentrically
- Ribosome contraction increases; Chromatolysis
- Proximal stump
- Fragment
Axon regeneration
- Each axon in the ______ stump grows out fo the stump and branches into many sprouts which spread randomly attempting to cross the neurolemma gap (narrow gap is better)
- Chemical factors in the __________ of the neurolemma attract the axon sprouts
- The axon sprouts enter ______ or more of the neurolemma cords
- The cords then ______ axons to their ultimate destination /c a growth rate of _____ per day
- If Previously myelinated, the regenerated axon will ______
- ________ matched axons-to-terminal will be functional (I.e. motor to motor, sensory to sensory)
- Proximal
- Basal lamina
- One
- Guide
- Remyelinate
- Appropriately
New growths from axons of non-damaged CNS neurons in the vicinity of injured tissue can form new synapses /c neurons that have lost innervation d/t injury
Axonal sprouting
Greater diameter and myelination will result in ______ conduction signal
Faster
Ia fibers
- largest
- fastest
- primary sensory from muscle spindles
Ib fibers
- fastest
- from golgi tendon organs and touch and pressure receptors
II fibers
- half as fast
- from encapsulated skin receptors fro touch, pressure, temp, and joint movement
III & IV fibers
- smaller
- slower
- from nonencapsulated endings for pain, touch, pressure
A fibers = __________
C fibers = __________
A fibers = myelinated
C fibers = unmyleinated
The ability of the CNS to form new neural circuits or reestablish damaged neural connections
Neural plasticity
Neural plasticity is accomplished by ___________ and forming new synapses
Axonal sprouting
When is neural plasticity optimally functioning?
Developmental years
