NEUROCYTOLOGY Flashcards
Significance of Dendritic Spines
Important for neuroplasticity (learning and memory) where the brain structure and synapses constantly change;
Spines extend if active and retract if not
Types of Receptors in CNS Synapses
Ion channels - FAST change of electrical activity in the membrane to relay signals
G-protein linked receptor - SLOW, transmit chemical information
Kinase receptors - really SLOW involving signal cascades
Nissl Bodies
Found in the soma and dendrites of neurons; absent in axons
make proteins, NTs and cytoplasm for neuron
Compare Kinesin, Dynein and Clathrin
Kinesin (+) transports away from cell body; anterograde
Dynein (-) transports towards cell body; retrograde
Clathrin - takes LARGER elements slowly away from cell body; usually anterograde
Describe the types of synapses.
Electrical synapse involves gap junctions to transport small ions and ATP. Chemical synapse involves the regulated release of transmitter signals (NTs)
Describe what occurs at the neuromuscular junction
An alpha neuron synapses on the end-plate region of muscle.
Path: AP from alpha neuron > Calcium channels open > Ca2+ activates Ca/Calmodulin Dependent Kinase > Synapsin I is phosphorylated > vesicles released into active zone…
Name the four ways to stop neuronal communication once relayed.
Enzymes degrade NTs, signals are recycled by the presynaptic terminal, picked up by the glia, or diffuse away
Describe the outcomes of an axonal lesion
Axon shrivels and soma dies due to reduced growth factors; the next neuron dies b/c of less trophic substances OR the axon of PNS tries to recover its distal attachment. The closer the cut to the soma, the worse the outcome.
Describe the 4 types of glial (support) cells in the CNS.
Ependymal cells - ciliated columnar epithelium lining the ventricles and central canal; adhering junctions
Microglia - derived from immune system; phagocytosis material and engulf inactive synapses
Astrocytes - lie between neurons, capillaries (blood-brain barrier) to control transport of substances
Oligodendrocytes - territorially wrap myelin around 40-50 CNS axons
Describe the significance of the Blood Brain Barrier (BBB).
Composed of capillary endothelium, tight junctions and astrocyte processes; selectively influence the factors that pass into the brain from blood; regulate the blood flow of capillaries
Compare the major dense line and intraperiod line.
Major dense line - inner leaflets of oligodendrocyte arms fuse
Intraperiod line - outer leaflets compact
Define the support cells of the PNS
Schwann cells - may engulf many axons to shield them BUT makes myelin for ONE AXON. Contains (Po) adhering proteins.
Satellite cells - associate with cell bodies to make GFs and phagocytosis debris; support PNS neurons
Explain why PNS lesions are more likely to heal than CNS.
Both myelinated and unmyelinated axons in PNS are covered by Schwann cells and organizations of connective tissue outside the axons. These provide the factors and a pathway for regeneration.
Describe the significance of Astrocytes in the CNS
They are involved at Nodes of Ranvier, tri-part synapses and BBB. Linked by gap junctions and function to transport ions/ NTs. Regulate blood flow of capillaries and passage of materials.
