Ballyk's week 1 lectures Flashcards
In neurons information transfer is….
UNIdirectional
What is involved in the electrical transfer of information in the neuron
- Dendrites
- Cell body
- Axon
NOT synaptic terminal
Where are bipolar neurons found?
- Inner ear cochlea
Where are pseudouipolar neurons found?
ALL somatic and visceral sensory neurons
still unidirectional flow
How does communication occur in the neurone?
Electrically, through a change in TM potential
Where is Vm graded in amplitude?
In dendrites and cell body
Graded: Amplitude of signal is proportional to intensity
Where is the Vm fixed in amplitude?
Action potential, in AXONS
Signal intensity is coded by AP frequency
Synaptic input can vary - name 2 types
- Sensory Ns generating a receptor potential
2. Synaptic input generating a synaptic potential
Where is the spike initiation zone located
- near cell body at axon hillock (multipolar Ns)
2. In periphery at dendrites (Pseudounipolar Ns)
What cellular organelles are present and missing in the axon?
- no ribosomes, but have mitochondria and CK proteins
Anteretrograde transport is fast to move…400mm/day
Membrane-bound substances, precursors of NTs - towards synaptic terminals + mitochondria
Anteretrograde transport is slow to move… 5mm/day
Cytosolic and cytoskeletal proteins synthesize in soma (axoplasmic flow)
(REMEMBER USES KINESIN)
Retrograde transport - fast 50-200mm/day
transports vesicles, endosomes, mitochondria, NGF, viruses, along DYNEIN
What are the conditions necessary for ions to move through a channel?
- An external force must induce ionic movement (specific electrochemical gradient for that ion)
a) Electrical gradient
b) Concentration gradient - channel must be permeable to the ion
a) nongated (RMP)
b) gated - voltage, ligand, mechanically gated
Ion flux =
Electrochemical gradient (FORCE) X Conductance (where channel is open or closed)
DEPOLARIZATION IS
A decrease in transmembrane potential
HYPERPOLARIZATION IS
An increase in Tm potential
sensory Ns in muscle spindles respond to what type of receptors?
Mechanoreceptors
Receptor potentials have 2 properties with respect to intensity of stimulus
- Graded - code the strength
2. Are decremental (decrease in amplitude over space)
describe key features of the AP
- ALL or none - NOT decremental
- Triggered at the spike initiation zone
- UNIdirectional
- Propagate regeneratively
- Information is coded in FREQUENCY AND PATTERN
How can you increase the frequency of the AP?
Allow greater depolarization
What happens to VG Na channels and VG K+ channels with sustained depolarization? (OVERSHOOT phase)
VGNa channels close - inactivate
VGK+ channels remain open!
What is the absolute refractory period?
Na+ channel inactivation prevents AP generation
During the relative refractory period what happens to Na+ channels?
They are resting and their population increases with repolarization
