Lp 2 Flashcards
(20 cards)
Signal transmission occurs via release of neurotransmitters from the axon terminal
Chemical synapses (predominant)
Direct communication between cells through gap junction
Electrical synapses
Plasma membranes are?
-polarized: they exhibit an electrical potential difference between the inside and outside of the cell
-semi-permeable: more permeable to some substances than others
-selective: results in unequal distribution of ions across membranes, or a separation of charge
Surface of plasma membranes carry different charges:
-inside is negative
-outside is positivity
-the membrane is said to be polarized
Na/K ATPase pump maintains?
RMP
Integral proteins embedded in the plasma membrane
Gated channels
Types of gated channels
-chemical: stimulus is a substance
-electrical: stimulus is change in the membrane potential
-mechanical: stimulus is physical deformation
Gated channels conformation changes:
-occur when environmental conditions change- temp, pH,ion concentrations
-open/close the gates, allowing substances to move into or out of the cell
Gated channels regulate the movement of ions:
-Na+: channels allow entry of Na+ into the cell-open quickly and close slowly
-K+: channels allow K+ to leave the cell-open and close slowly
basic types of signals graded potential & action potential?
Graded potential: local, signal over a short distance & generator or receptor
Action potentials: widespread, travel over long distance
Gated potentials Membrane potential changes?
Depolarization: reduction in membrane potential (less negative)
Hyperpolarization: increase in membrane potential (more negative)
Depolarization & hyperpolarization of the membrane
Depolarization: allow diffusion of NA+ into the cell (the membrane potential moves towards 0 mV, the inside becoming less negative (more positive)
HyperpolarizationL K+ out ( the membrane potential increases, the inside becoming more negative)
Sequence of electrical events that occurs when a nerve impulse is generated and propagated?
Action potentials (AP)
Minimal membrane potential required to initiate AP (all-or-none)?
Threshold
Generation of action potential stages?
Stage 1: RMP (-70mv)
Stag 2: Depolarization
Stage 3: Repolarization
Stage 4: Hyperpolarization- Undershoot
-stimulus-induced opening of Na+ channels- Na+ enters cell
-membrane polarity changes due to influx of positive ions (cations) from -70mv to about +35mv & depolarization occurs
-change in polarity causes channels to close & the membrane is relatively impermeable to Na+
Stage 2: depolarization
-K+ channels slowly open-allow efflux of K+ from the cell
-membrane potential slowly returns to -70mv & repolarization occurs
Stage 3: repolarization
Restoring RMP: Na+ must exit & K+ must enter via ATPase Na/K pump
Stage 4: hyperpolarization- Undershoot
Propagation of action potential?
Moving the signal along the axon
*occurs along unmyelinated axons & sacrolemma (continuous conduction):
-depolarization
-local current continues to depolarize adjacent areas of membrane
-AP is self-propagating
-repolarization follows depolarization
Propagation of action potential
