Exam 2 Flashcards
Electrical Signaling Via Membrane Potential Changes
- look at graph
- signal is a very brief change in voltage in membrane at one spot
- start at depolarization: Na+ dominant but only open for a little bit then they inactivate and close which causes repolarization: K+ open and brings potential back down then hyperpolarization: so much K+ in brings potential down even more negative than beginning point
Graded Potentials
- congressman example
- as a congressmen you get inputs from many constituents telling you how to vote. One vote is smaller than two votes
- hyperpolarizing is when you vote no and there’s a dip; if there’s a yes it goes up and is depolarizing
- look at graphs
- threshold is the decision point when the congressman he has enough votes to act and action potential is the actual casting of the congressman’s vote
- a transmitter binds to a receptor to trigger some leakiness of ions; each unit of activation makes a change in membrane potential
- graded potentials get the membrane to threshold which then starts the action potential
- excitatory signal is when Na+ open and inhibitory is when K+ open
Action Potential
- when you decide to vote-it’s the actual action
- look at graph
Explain how graded potentials can summate to reach the threshold for an action potential on either a spatial or temporal basis.
- spatial: different neurons influencing cell-vote yes-pushing toward threshold
- temporal: one neural input repeatedly
How do changing ion conductances occur?
- resting membrane potential: activation gate closed but capable of opening, inactivation gate open–>depolarization opens activation gate and inactivation gate open–>1 ms activation gate open and inactivation gate closed (incapable of opening until return to resting state
- can’t use it again till it goes through period of recovery (refractory period) which is why the gates slam closed
- the change in molecular shape means they have to reconfigure to go again
All-or-none Law
- 1 kind of action potential that either happens all at once or not at all
- has nothing to do with gradation/amplitude of the action potential, it’s either there or it isn’t
- all action potentials are identical
Refractory Period
-takes a while to recover to be ready to go again
Why is there an absolute refractory period-a time during which now stimulus can elicit an action potential
-after the peak of action potential all the sodium channels close and they cannot open until they go through this period
How can nervous system distinguish between different stimuli like light touch vs. heavy touch or sharp pain vs. sharp pain?
- number of action potentials per time
- pattern of action potentials
- change in sensitivity-long term effect
- how many receptors are activated
- number of classes of receptors
Coding for Stimulus Intensity
- look at graph
- number of potentials influenced by the strength of the stimuli
Conduction of the Impulse
- positive attracted to negative which changes threshold and signal continues to move down neuron
- look at image
Axon Potential Propagation in Myelinated Axons
- enough insulation that when it reaches threshold it is enough for current to jump to next node
- voltage spreads a distance and if it goes far enough the signal is able to jump from node to node thus skipping the myelinated sections
- the myelinated sections allow the voltage to spread far enough for the jump to happen
MS attacks and destroys myelin sheath of CNS neurons and oligodendrocytes that form the myelin. What are some symptoms of MS that might be expected and how these might arise from loss of myelin?
- action potentials cannot move quick enough down axons to deliver stimulus
- loss of control
- slower rate of AP means you lose energy and there’s a delay
- makes motor and sensory pathways slower
- weakened muscles, touch receptors are numb
- lose coordination
How Chemical Synapses Work
- AP travels down axon and tells Ca2+ channels to open and Ca2+ ions allow neurotransmitters to be released into synapse
- neurotransmitters attach to receptor which gives a signal to cell which results in response
3 Ways to End Synaptic Activity
- diffusion away
- reuptake
- enzymatic breakdown
If action potential frequency increases, what adaptations could occur to either increase or decrease the response of the postsynaptic neuron?
-change numberof Ca2+ channels, change number of receptors, change sensitivity of receptors, change number of neurotransmitters released
Excitatory and Inhibitory Post-Synaptic Potentials
- EPSP’s and IPSP’s
- these are the “votes” received from constituents
- excitatory increases voltage and inhibitory decreases voltage
- bumps in the membrane potential when an interaction happens with the congressman
Divergent Neuronal Integration
-one neuron has effects on many separate neurons
Convergent Neuronal Integration
-on neuron is affected by many separate neurons
Spatial and Temporal Summation
- multiple inputs happen at same time to increase the potential more than a single input would=spatial
- have two EPSP’s and one IPSP on an axon so one EPSP will cancel with the IPSP and will be left with one EPSP which generates the response
- temporal is when one neuron repeatedly sends the same message in a short period of time
Pre-synaptic Facilitation and Inhibition
- one neuron is a part of another neuron that’s attached to the cell body and together they cause a higher spike in the membrane potential thus bringing it to threshold more easily and producing an AP
- opposite could also be true where one inhibits voting of other and then hyperpolarizing could happen thus bringing it further away from threshold and AP
- look at image
Why did dogs learn to salivate every time Pavlov’s assistant came into room even without food? What neural adaptations underlie this phenomenon?
- assistant became presynaptically linked with being fed
- neurons that fire together wire together
- neuronal circuits are plastic
In certain areas of the brain neurons are difficult to activate a first time, but repeated activation makes subsequent activation much easier. List some reasons why this fits with our experience of how learning develops.
-repetition reinforces information gathered
Would you like to see potentiation (greater and greater neural activation) of all incoming stimuli if the same synapses are used? List examples of sensory inputs that adapt to repetitive stimuli with decreased neural activation
- seeing unchanging things (nose on face)
- sounds you hear constantly (fans, trains if near tracks, sirens in bloomington)
- getting used to sharp smell after some time
- pressure/touch