Week 2- Principles Of Electrical Signaling Flashcards
(24 cards)
What does generating RMP depend on?
Differences in conc of Na+ and K+both inside and outside the cell
Which glial cell regulates external k+ concentration?
Astrocytes
How is the RMP(relative membrane potential?
Goldmans Equation
Define resting potential?
Steady difference in electrical charge across the membrane is called the resting membrane potential (RMP).
Hodgkin and Huxley 1949 ( Squid )
experiments on squid axons revealed the existence of voltage-gated ion channels and their critical role in the generation of action potential
What causes depolarisation
Increase in Na+ permeability in the membrane
What causes hyperpolarisation
Increase in K+ permeability
What causes an action potential
The AP is generated by the opening and closing of voltage-gated Na+ and K+ channels.
Na+ current: inward, depolarising current.
K+ current: outward, hyperpolarising current.
how many voltage gated Na+ and K+ are there?
Three. the m-gate, h-gate and n-gate
What myelinates axons in the CNS
oligodendrocytes
what myelinates axons in the PS
Schwaan cells
What are nodes of ranvier?
Breaks in myelin sheath where ions can enter.
Voltage-gated Na+ channels are concentrated here.
Saltatory conduction: APs ‘jump’ from node to node. This allows current to spread farther & faster (increases velocity).
the larger the axon diameter…
the faster the propogation of action potentials
Define synapse?
junction between a nerve ending (presynaptic terminal) and its target cell (post synaptic cell)
what is the synaptic cleft?
space between the presynaptic terminal and postsynaptic terminal
Define synaptic transmission?
process by which nerve cells (neurons) pass information onto target cells (e.g. other neurons).
what are the 2 types of transmission?
Chemical transmission: chemical/neurotransmitter diffuses across the synaptic cleft (acts on postsynaptic receptors).
Electrical transmission: pre- and postsynaptic elements are electrically connected via gap junctions.
what is the role of excitatory neurotransmitters?
. Increase nerve activity (i.e. neuronal excitability).
. Cause depolarisation (as a result of synaptic activity):
. Initiate excitatory post-synaptic potentials (EPSPs).
what is the role of the Inhibitory neurotransmitters?
.Decrease nerve activity.
.Cause hyperpolarisation:
.Initiate inhibitory post-synaptic potentials (IPSPs).
define axo-dendritic synapse?
axons of the presynaptic neuron which make contact with the dendrite
Define excitatory synapse?
when the presynaptic activity increases the excitability of the postsynaptic neuron.
what is EPSP
Postsynaptic depolarisation in a neuron
what is spatial summation
when several excitatory postsynaptic potentials (EPSP) arrive at the axon hillock simultaneously
what is temporal summation
post synaptic potentials created at the same synapse in rapid succession can be summed up to reach the threshold for action potential.
