BASIC NEUROPHYSIOLOGY Flashcards
how do neurons transmit signal
via chemical or electrical transmission
how are neurons classified
based on morphology
Where do synapses (and communication) occur
dendritic spines
What is the most dynamic part of the dendrite
the spines - grow and prune
A chain of neurons is reffered to as a ____
pathway
A bundle of axons is referred to as a ___
tract
What do polydendrocytes do
generate new oligodendrocytes or other new cells in nervous system
What do astrocytes do
- Support cells
- Ioin hemeostasis
- transmitter uptake
- Modulation of synaptic activity
- Blood brain barrier
What are the differences between oligodendrocytes and schwann cells
Oligodendrocytes - CNS - Can myelinate multiple axons Schwann Cell - PNS - Can ensheath only one axon
Where is K+ low? high?
Outside of cell
Inside of cell
Where is Na+ low? High?
In cell
Outside of cell
How does the NA+/K+ pump work
ATPase moves 3 Na+ out of cell and 2 K+ into cell
When is equilibrium potential or electrochemical equilibrium achieve
When there is a balance between the concentration gradient and the electrical gradient
What does the Nernst equation describe
The equilibrium potential of 1 ion
What does the Goldmann equation describe
the equilibrium potential of multiple ions and their respective gradients
What occurs during depolarization of cell
Na+ influx inward current following chemical gradient
What occurs at peak of action potential
Na+ can not flow in because it is repelled by electrical gradient
Na+ channels close
K+ channels open and K+ leaves cell
When does the Na+/K+ pump kick in
In hyperpolarization
What is active current
The movement of ions through ion channels
i.e. action potential
What is passive current
The shuttling of charge along a neuronal process
What decreases capitance
decreasing axon diameter or by preventing the accumulation of charge
What decreases resistance
Increasing diameter of axon
The velocity of an AP is determined by…
both active and passive current
What is resistance? what is it measured in
Difficulty of moving ions, measured in Ohm
What is capicitance
How much charge the membrane can hold
Where are Na+ channels located
At the nodes of ranvier
Do you have a membrane acting as a capacitor at the nodes of ranvier
yes but the area is so small it is not a problem
What occurs at the nodes of ranvier
You are regenerating the action potential. Costs you ATP
What occurs if you lose your myelin
- The next set of NA channels is way too far away and you cant transport the AP
- you can insert additional Na+ channels but then you are using more ATP and the signal is travelling slower
What does the distance between nodes depend on
The axon diameter (which influences resistance) and the thickness of the myelin sheath (which prevents leak current)
How do you decrease capacitance
myelination
how do you decrease resistance
increase axon diameter
Electrical synapses are coupled by____
gap junctions
What are the steps to an electrochemical synapse
- action potential
- voltage gated Ca2+ channels open
- Ca2+ influx causes neurotransmitter-filled vesicles to fuse with the cell membrane
- Neurotransmitter is released into the synaptic cleft and binds to receptors, this causes the opening of ion channels
- Post-synaptic cells depolarizes and an action potential is generated
What occurs once a glutamate receptor is activated
allow positive ions to enter cell causing an excitatory post synaptic potential
Neurotransmitter receptors can be couples to ____ or _____
ion channels or intracellular signalling cascades
What are Neurotransmitter receptors that are coupled to ion channels called
ionotropic receptors
What are Neurotransmitter receptors that are coupled to intracellular signalling cascades called
metabotropic receptors
What are the differences between C-fibres and delta fibres
C-fibre - small diameter, unmyelinated, dull pain
Delta fibres - medium diameter and myelinated. Sharp pain
What are the characteristics of motor nerves
fast and super responsive therefore large diameter and myelinated
How do stretch receptors in the body work
they generate a depolarization that is proportional to the amount of stretch - Generator potential
What occurs when the generator potential is large enough
an action potential is produced
Sensory receptors change one form of energy into…
electrical signalling - The receptor potential
