Neurophys Review Part 1 Flashcards
What are the main differences between electrical and chemical synapses?
- Electrical synapses propagate a signal using gap junctions (connexon) as opposed to NTs.
- Electrical are comparatively rare
- electrical are dendro-dendritic (mostly)
What passes through gap junctions?
All ions
What is the function of the pre-synaptic process (axon)?
Provides neurotransmitter
What is the function of the post-synpatic process
To translate the neurotransmiatter into a useful signal (depolarization)
What is the role of astrocytes?
Astrocytes are a type of glia that provide metabolic support to neurons and may modulate synaptic function
What are the proteins that form the SNARE complex?
- synaptobrevin
- syntaxin
- synaptotagmin
- SNAP-25
Give the sequence of events of the vesicle docking
and synaptic transmission.
- vesicle docks
- entering Ca++ binds to synaptotagmin
- SNARE complexes form to pull PS membrane to vesicle membrane
- Ca++ bound to synaptotagamin catalyzes membrane fusion by binding to SNARES/plasma membrane
What chemical is used clinically and interferes with SNARE formation?
Botulinim toxin (Botox)
Each neuron releases how many neurotransmitters?
ONE
*but some also release a peptide in addition to the primary NT
What are the amino acid NTs?
glutamate
aspartate
GABA
glycine
What are the catecholamine neurotransmitters?
dopamine
norepinephrine
epinephrine
*part of larger biogenic amine class
What channel is defective in inherited Long QT Syndrome?
K+ Channel
What channel type is defective in cystic fibrosis?
Cl-
What effect does GABA have on the post-synaptic cell?
hyperpolarizes it
How do GABAb receptors modulate Ca++?
They are located on the pre-synaptic terminals and when activated by NT, cause reduced Ca++ influx, thereby reducing the amount of NT released.
What receptor type will additionally allow Ca++ into the cell under the right conditions?
NMDA
Memantine is a drug used for _______ patients and acts by antagonizing ________receptors.
Alzheimer’s; NMDA
*reduces glu/Ca2+ in cell
**works in about 1/3 of patients
What are the 3 major factors responsible for the uneven distribution of ions across the neuronal membrane?
- selective permeability
- large organic anions within the cytoplasm
- ion pumps (Na+/K+ ATPase)
What is the ratio of the Na+/K+ ATPase?
3:2
*net outward current causes small hyperpolarization
What is the reversal potential for K+?
about -85 mV
What is the reversal potential for Na+
about +57 mV
What channels are mutated in Epilepsy ?
K+ and nicotinic
What channels are mutated in Hyperekplexia?
Glycine
What is the mechanism of action of lidocaine?
Blocks Na+ channels and has some specificity for inhibitory neurons (blocks pain neurons)
What channels open first in the action potential?
voltage-gated Na+
What is the “information code” transmitted from neuron to neuron?
the pattern of action potentials
What are the spaces between myelin cells on a neuron called?
Nodes of ranvier
Conduction along a myelinated axon differs from an unmyelinated axon in what respect?
It is saltatory - it “jumps” from node to node
If an injected current does not reach threshold for a neuron, what happens?
Nothing
(In other words, an EPSP must reach threshold to get an action potential)
What is hyperkalemia?
elevated serum K+ usually caused by kidney dysfunction
*leads to depolarization of membrane
What happens during hyperkalemia that causes irregular cardiac rhythms and skeletal muscle weakness?
The membrane of neurons depolarize slowly (seconds) or have sustained depolarization, leading to so many Na+ channels being deactivated, no AP can occur
What gate opens first on Na+ voltage-gated channels?
M gate
depolarizing phase
What gate closes to de-activate Na+ voltage channels and when?
H gate
at the top of the depolarizing phase
When does the K+ voltage-gated channel open?
at the top of the depolarizing phase (n gate)
