Lecture 4 Flashcards
difference in electrical charge between the inside and the outside of a cell
membrane potential
membrane potential is measured with the use of _______
microelectrodes
resting membrane potential is measured as about _____
-70 mV charge
neuron state of resting membrane potential
polarized
membrane potential of a polarized neuron
not 0
in resting neurons, there are more _____ ions outside the cell while there are more ____ ions inside the cell
- Na+ ions
- K+ ions
specialized pores in the neural membrane
ion channels
2 types of pressure
- electrostatic pressure
- pressure from random motion
transporter discovered by Alan Hodgkin and Andrew Huxley in the 1950s
sodium-potassium pumps
disturbance of the resting membrane potential
postsynaptic potentials (PSPs)
2 effects when neurotransmitters are released
- depolarize of receptive membrane
- hyperpolarize of receptive membrane
decreasing the resting membrane potential
depolarize of receptive membrane
increasing the resting membrane potential
hyperpolarize of receptive membrane
this depolarization is an upward deflection on the oscilloscope
postsynaptic depolarization
other term for postsynaptic depolarization
excitatory postsynaptic potentials (ESPs)
postsynaptic depolarization ___ the likelihood that the neuron will fire
increase
this hyperpolarization is a downward deflection on the oscilloscope
postsynaptic hyperpolarization
postsynaptic hyperpolarization is also called
inhibitory postsynaptic potentials
postsynaptic hyperpolarization ____ the likelihood that the neuron will fire
derease
ESPs and ISPs are all ____
PSPs
ESPs and ISPs are ______, meaning the amplitudes of PSPs are proportional to the intensity of the signals that elicit them
(e.g., weak signals elicit small PSPs, and strong signals elicit large ones)
graded potential
important characteristics of transmission of PSPs
- it is rapid
- is is decremental
determines whether a neuron fires
- net effect of synapsis activity
- balance between excitatory and inhibitory signals
a massive but momentary—lasting for 1 millisecond—reversal of the membrane potential from about −70 to about +50 mV.
action potential
action potential are _____ responses
all-or-none
what does “all-or-none” responses mean
they either occur to their full extent or do not occur at all
summation of postsynaptic potentials
- spatial summation
- temporal summation
summation occurs when EPSPs and IPSPs from different locations on neurons make their way to the axon initial segment and summate there
spatial summation
occurs when EPSPs and IPSPs from a single location on a neuron make their way to the axon initial segment and summate there
temporal summation
3 possible combinations under spatial summation
- 2 EPSPs summated to produce a greater EPSP
- 2 IPSPs summated to produce a greater IPSP
- 1 EPSP and 1 IPSP cancel each other out
conduction of action potentials
- ionic basis
- refractory periods
- axonal conduction
- the hodgkin-huxley model in perspective
an action potential is brought on by momentary variations in the permeability of the membrane for diffusible ions from the perspective of ions
ionic basis
(refractory period) period during which it is possible to fire the neuron again but only by applying higher-than normal levels of stimulation
relative refractory period
[refractory period wherein] there is a brief period of about 1 to 2 milliseconds after the initiation of an AP during which it is impossible to elicit a second AP; followed by the relative refractory period
absolute refractory period
responsible for two important characteristics of neural activity
refractory periods
2 important characteristics of neural activity:
- responsible for the normal travel of Als along axons in one direction
- responsible for the relationship between neural firing rate and the intensity of the stimulation
2 important ways of how AP conduction along an axon differs from PSP conduction
- Al conduction is non-decremental
- APs are conducted more slowly than PSPs
an action potential will be generated and will
travel along the axon back to the cell body, given that the electrical stimulation of sufficient intensity is applied to the terminal end of an axon
antidromic conduction
axonal conduction in the natural direction from cell body to terminal buttons
orthodromic conduction
transmission of action potentials in myelinated actions
saltatory conduction
provided a simple, effective introduction to what we now understand about the general ways in which neurons conduct signals
Hodgkin-Huxley model
synaptic transmission: from electrical signals to ______ signals
chemical
synapses of axon terminal buttons on dendrites
axodendritic synapses
small nodules on dendrite surfaces where many axodendritic synapses terminate
dendritic spines
synaptic arrangement examples:
- axodendritic synapses
- axosomatic synapses
- dendrodendritic synapses
- axoaxonic synapses