Flashcards in Neurotransmission Deck (51)
What do dendrites convey?
Graded electrical signals passively to the soma
What do dendrites receive inputs from?
What is the soma?
Synthetic and metabolic centre- containing nucleus, ribosomes, mitochondria, and ER.
What does the soma do?
Integrates incoming signals that are conducted passively to the axon hillock
What is the axon hillock and initial segment?
Site of initiation of the all or none ap
What does the axon do?
Conducts output signals as aps to other neurones (or cells).
Between what does the axon mediate transport of materials?
Soma and presynaptic terminal (anterograde direction) and vice versa (retrograde)
What is a synapse?
Point of chemical communication between neurones (or other cells)
What direction of transport do several virus' exploit to infect neurones?
What are the 4 types of neurone?
Unipolar, pseudounipolar, bipolar, multipolar
Describe a unipolar neurone and give an example
One neurite. Peripheral autonomic neurone
Describe a bipolar neurone and give an example
Two neurites. Retinal bipolar neurone
Describe a pseudounipolar neurone and give an example
One neurite that bifurcates. Dorsal Root Ganglion (DRG) neurone
Describe a multipolar neurone and give an example
Three or more neurites. Lower motor neurone (LMN) (motoneurone)
What are the four functional regions of neurones?
Input, integrative, conductile, output
What are Golgi Type I and Type II axons?
Type I is long, type II is short
What is overshoot?
Brief period when polarity is reversed to inside postive
What occurs in the upstroke of the ap?
Opening of voltage activated Na+ channels and inward Na+ movement
What occurs in the downstroke of ap?
Opening of voltage activated K+ channels and outward movement of K+
Why do passive signals not spread far from their site of origin?
The nerve cell membrane is leaky (not a perfect insulator). This is due to current loss across the membrane
In the axon does the ap have a constant or variable amplitude?
What kind of process is the membrane potential change?
Passive neuronal process that decays exponentially with distance
What does the distance over which current spreads depend upon?
Membrane resistance (rm) and axial resistance of the axoplasm (ri)- increased rm/ri increased length constant
What does greater local current spread increase?
AP conduction velocity
What does the ap do to the charges on each side of the membrane?
Swaps them (-ve on outside, +ve on inside)
How would you decrease ri?
Increasing axonal diameter (not feasible though)
How would you increase rm?
Adding an insulating material - myelin- provided by Schwann cells in PNS and oligodendrocytes in CNS (both types of macroglia)
What is the length constant equation?
What do many Schwann cells surround?
A single axon