Neuro 3 PG Flashcards
(27 cards)
membrane potential
difference in electrical charge inside and outside of the cell
to record a neurons membrane potential
positions the tip of one electrode inside the neuron and the tip of another electrode outside the neuron in the extracellular fluid
What are intracellular electrodes called
micro electrodes: their tips are less than one-thousandth of a millimeter in diameter (cannot be seen by the naked eye)
when both electrode tips are in the extracellular fluid what is the voltage difference?
zero
When the tip of the intracellular electrode is inserted into a neuron, a potential of -70 mV is recorded. What does this indicate?
the potential inside the resting neuron is about 70 mV LESS than that outside of the neuron.
Resting potential
the steady membrane potential of a neuron at rest, usually about -70 mV
when a neuron is at its resting state with about -70 mV charge, what is the neuron said to be?
polarized
what are the positively and negatively charged particles in neural tissues?
ions
what is the abbreviation for sodium ions?
Na+
what is the abbreviation for potassium ions?
K+
What do the plus signs indicate on ions?
that they carry a single positive charge
Where are ions located in resting neurons?
Na+: more outside than inside
K+: more inside than outside
what are the kinds of pressure for Na+ to enter into resting neurons?
electrostatic pressure from resting membrane potential: opposites attract; -70 mV share attracts positively charges Na+ into resting neurons
pressure from random motion: Na+ ions move down their pressure gradient (more likely to move from areas of high concentration to low concentration)
why then do Na+ ions under electrostatic pressure and pressure from random movement not come rushing into neurons, thus reducing the resting membrane potential?
The sodium ion channels in resting neurons are closed, thus greatly reducing the flow of Na+ ions into the neuron. In contrast, the potassium channels are open in resting neurons, but only a few K+ ions exit because they are largely held inside by the negative resting membrane potential.
How do some Na+ ions manage to enter resting neurons despite the closed sodium channels and how do some K+ ions ext?
At the same rate that Na+ ions leaked into resting neurons, other Na+ ions were actively transported out; and at the same rate that K+ ions leaked out of resting neurons, other K+ ions were actively transported in
what are sodium-potassium pumps?
ion transport that continually exchanges three Na+ ions inside the neuron for two K+ ions outside.
what are transporters?
(mechanisms in the membrane of a cell that actively transport ions or molecules across the membrane
when neurons fire where do they release from?
terminal buttons called neurotransmitters
what do neurotransmitters do?
diffuse across synaptic clefts and interact with specialized receptor molecules not he receptive membranes of the next neurons in the circuit
what two effects can happen from neurotransmitter molecules binding to postsynaptic receptors?
-they may depolarize the receptive membrane (decreasing the resting membrane potential, from -70 to -67 mV)
-they may hyper-polarize (increase the resting membrane mediating postsynaptic potentials are different in different kinds of neurons)
what are excitatory postsynaptic potentials (EPSPs)
postsynaptic depolarizations increase the likelihood that the neuron will fire
inhibitory postsynaptic potentials (IPSPs)
postsynaptic hyperpolarizations decrease the likelihood that the neuron will fire
what things are graded responses
EPSPs and IPSPs
-the amplitude of EPSPs and IPSPs are proportional to the intensity of the signals that elect them
what do weak signals elicit?
small postsynaptic potentials
