Lecture 1: Learning Objectives and Provided Definitions. Flashcards
What is a neuron?
The basic functional unit of the nervous system.
What does the neuronal soma do?
Comparable to other cell types in its basic genetic and protein manufacturing/machinery components, however neuronal soma can also receive inputs and contain receptors and ion channels associated with signal processing.
What is an axon?
Neuronal process specialized for transmitting a self-propagating action potential. Axons are usually surrounded by several layers or myelin.
What is myelin?
A membranous wrapping around the axon, forming an insulating sheath that increases the speed of conduction. Myelin is not continuous along the axon. There are breaks called “Notes of Ranvier” and internodal segments. Action potentials passively flow from node to node, where voltage gated channels serve to renew action potentials (self propagating).
What are three types of filaments?
- Actin (microfilaments)
- Neurofilaments
- Microtubules
What is the function of actin (microfilaments)?
Function in neurons similar to that in other cell types, such as structural support, compartmentalization and protein trafficking (5 nm diameter).
What are Neurofilaments?
These are from a family of “intermediate filaments”, with the specific type in neurons called neurofilaments. They are wider than actin, 10 nm in diameter. They are found in all parts of the neuron but are most concentrated in the axon and the axon terminal. Thus, neurofilament stains have been used to localize axons and their terminals.
What are microtubules?
Wider, long tubular elements involved in protein transport and trafficking, found in almost all cell types. They are 20-26 nm in diameter. Special function in axonal transport.
What is axoplasmic transport?
Transport found only in axons. Uses microtubules and either dynein or kinesin.
What is retrograde axoplasmic transport?
Transport from terminal toward cell body. 50-250 mm/day. uses dynein and microbutules. Uptake into axon terminals (e.g. growth factors) and transport to soma in one function.
What is anterograde axoplasmic transport?
Transport from soma to terminal, 100-400 mm/day. uses kinesin and microtubules. Proteins such as neurotransmitters are sent to terminal.
What is the axon terminal?
Axons end in a terminal. This is not myelinated. It contains mitochondria, packages of chemical neurotransmitters (vesicles), vesicle related proteins and presynaptic specialization that forms a presynaptic density. Upon depolarization there is entrance of calcium and subsequent release of the contents of vesicles into the space between the axon terminal and its target called the synaptic cleft.
What are chemical synapses?
Has a chemical intermediary between neurons that allows for processing. Different chemicals can be released with different postsynaptic actions. The action is the function of the receptor not the transmitter/modulator itself. The same transmitter can have very different postsynaptic actions depending on the receptor. Chemical synapses are most often uni-directional.
What is a Grays Type I synapse?
An excitatory glutamatergic synapse.
What is a Grays Type II synapse?
an inhibitory GABA or glycine synapse.
