Flashcards in Neural Signaling Deck (33):
Charge in biological systems is carried by what?.
What are ions
Ions are charged particles which are charged due to an excess or deficit of electrons in their outer shell.
Ion channels are the equivalent of ----- in an electrical system?
Resistors (or conductors depending on whether ion flow is being sped up or slowed down.
Lipid bilayers have properties of a capacitor (two plates which conduct electricity very well with a thin insulation strip between the plates).
Membranes are said to be semi-permeable which means what
They are permeable to some ions and impermeable to others.
At rest, neuronal cell membranes are primarily permable to what?
High K concentration inside the cell and high Na outside the cell primarily maintained by>
What makes the Na/K pump electrogenic?
Pumps 3 Na out for every 2 potassium moved in. Electrogenic means it contributes to the membrane potential of the cell
Cell membrane potential at rest
Events which enhance membrane potential (make the membrane more negative) are referred to as
Larger depolarizing stimuli that result in rapid and sizeable depolarization followed by repolarization and undershoot is called?
What is the "threshold" of an action potential?
Threshold is the point at which depolarization (inward) current is just balanced out by repolarization (outward current). ANy further depolarization leads to AP.
During an action potential is ion selectivity maintained?
Yes, but it changes. The fact that membrane potential doesnt stop at 0 means that the membrane is still selective for a certain ion...Na in this case vs K at rest.
Upon repolarization, membrane potential undershoots original resing potential. what is this called
Action potential upstroke due to
Increase in membrane permeability to Na
Action potential downstroke is due to
Inactivation of Na channels as well as activation of voltage gated ion channels
Afterhyperpolarization due to
increased potassium conductance relative to original resting potential
Relative refractory period of an AP
Due to increased K permeability during repolarization, a larger action potential is required to elicit another AP
Absolute refractory period
No stimulus, no matter how large, will wlicit an AP
A larger electical stimulus = larger AP?
NO....potentially more APs but not larger
KNOW Signaling via Action Potentials is advantageous because it allows rapid signaling with no decrease in signal over distance. How?
Because it is regenerated at each node of ranvier. This is all in contrast to a graded potential where the signla loses amplitude as it travels away from its point of origin. This makes action potentials better at carrying signals over long distances.
Conduction velocity for an axon (the rate of advance for an AP) can be increased how?
By increasing the diameter of the axon
Conduction velocity also increased by myelination
Decreases the ability of the membrane to act as a capacitor (store charge) so that more more charge passes to the next node of ranvier
The conduction velocity of an unmyelinated axon is proportional to what
In myelinated axons, conduction velocity is increased by restricting the APs to the nodes of Ranvier and by facilitating electronic movement of cahrge between nodes.
The latter is done by increasing the resistance of the membrane to leakage of ions (myelination) and decreasing the ability of the membrane to act as a capacitor.
What is saltatory conduction
Describes the conductance of myelinated axons...saltatory means "leap". APs jump between nodes
loss of myelin
Point mutations ot the alpha subunit of the sodium channel can lead to what disease
GEFS....Generalized Epilepsy with Febrile Seizures...cause slowed inactivation of Na channels
Myotonia and Periodic Paralysis are caused by
Na channel mutations in skeletal muscle
Familial hemiplegic migraine associated with what?
P/Q type Ca channels mutations
Episodic ataxia type 2
calcium channel mutation
Congenital Stationary Night Blindness
truncated L-type calcium channels in the retina