Neurotransmitters and Neural Integration (2) Flashcards
Exam 2
Neurotransmitters Definition
molecules that are released when a signal reaches a synaptic nob (or varicosity)
How do synapses vary?
Excitatory or Inhibitory- differ based on type of receptor on postsynaptic cell
(some receptors are ligand-gated ion channels; others act though second messengers)
What are three examples of synapses with different modes of action?
- excitatory cholinergic synapse
- inhibitory GABA-ergic synapse
- excitatory adrenergic synapse
What are the six steps of excitatory cholinergic synapse?
- Nerve signals at axon terminal and opens voltage-gated calcium channels
- calcium enters knob and triggers exocytosis of ACh
- ACh diffuses across cleft- binds to postsynaptic receptors (ligands)
- Receptors are ion channels-open and allow sodium and potassium to diffuse
- Entery of sodium causes local depolarizing voltage shift- postsynaptic potential
- If depolarization is strong (persistent) enough, it will cause an action potential at the trigger zone
A nerve signal triggers the release of ____ into synaptic cleft
GABA
GABA receptors open?
chloride channels
Chloride enters the cell and makes the inside more negative than RMP. What is this called?
hyperpolarization
Norepinephrine and other neurotransmitters act through ___ ____ ___ ___
second messenger systems (cAMP)
A receptor is not an ion gate. What is it?
it is a transmembrane protein associated with a G-protein
it is slower to respond, bit has an advantage of signal amplification
What are the steps to excitatory adrenergic synapse?
- NE bind to receptor G-protein and dissociates
- binds to adenylate cyclase
- converts ATP to cAMP
What are the various responses to this process: NE bind to receptor G-protein and dissociates, binds to adenylate cyclase, converts ATP to cAMP
- binds to ligand gated channel- depolarize cell
- activate preexisting enzymes within the cell
- introduce genetic transcription leading to creation of new enzymes or proteins
What are the two way cessation of signals occur?
- Presynaptic cell stops
2. Eliminate neurotransmitters already there
What happens in Degradation?
acetylcholine is broken down by acetylcholinesterase (AChE) in the synaptic cleft
What happens in reuptake?
axon terminal reabsorbs (transport proteins) neurotransmitter/parts by endocytosis
What happens in when they diffuse?
neurotransmitter diffuses into neary ECF (acetate)
Synaptic delay does what?
slows that signal
Chemical Synapses =
processing; decision making
More synapses =
greater amount of information processing
What is trade- off?
chemical transmission involved a synaptic delay that makes information travel slower than it would be if there was no synapse
What is Neural Integration?
ability to process, store, and recall information and use it to make decisions
For a cell to fire an AP it must reach ____
threshold
Some chemical messengers ___ the postsynaptic cells
Inhibit
Different neurotransmitters cause different types of postsynaptic potential in the cells they blind to. One neurotransmitter might ___ some cells and ___ others
excite
inhibit
What is summation
process of adding up postsynaptic potentials and responding to their net effect (occurs in trigger zone/axon hillock)
(one neuron can receive input from thousands of other neurons)
In summation, response depends on whether the ___ ____ is excitatory or inhibitory
net input
Balance between EPSPs and IPSPs enables the nervous system to make ___
decisions
Temporal Summation definiton
single synapse generates EPSPs so quickly that each is generated before the previous one fades
(only need signal form one)
Spatial Summation definition
EPSPs from several different synapses add up to threshold at axon hillock (stimulation from all different places)
Presynaptic Facilitation definition
one presynaptic neuron enhances another one
increases necessary synaptic transmission
Presynaptic Inhibition definition
one presynaptic neuron surpasses another
reduces or halts unwanted synaptic transmission
Neural (sensory) Coding definition
how the nervous system converts information into a meaningful pattern of action potentials
What does qualitative information depend on?
which neurons fire
What is a labeled line code?
each sensory nerve fiber to the brain leads from a receptor that recognizes a specific stimulus type
(each nerve fiber is “tagged” or “labeled” for a specific stimulus)
Quantitative Information defintion
information about the intensity of a stimulus is encoded (two ways)
What are the two ways a stimulus is encoded with quantitative information?
- Different neurons -> different thresholds of excitation
- Weak stimuli cause neurons to fire at slower rates; strong stimuli cause a higher firing frequency (more action potentials per second)
True or False:
Neurons don’t work together
False
Neurons work together (thousands)
Neural Pool is a….
localized cluster of neurons that collaborate to perform specific functions
How are neural pools connected?
Connected via neural circuits
Information arrives at a ___ ___ through one or more ___ ____
neural pool
input neurons
Input neurons branch ___ and synapse with many target cells
repeatedly
Some form ___ synapses with a single postsynaptic cell
multiple
Discharge Zone definition
neuron can act alone to make postsynaptic cells fire
Facilitate Zones defintion
inout neurons makes fewer, less powerful synapses
can only stimulate targets with the assistance of other input neurons
Systems give neural pools ___ in integrating input from several sources; ____ on appropriate output
flexibility
deciding
Neural Circuit definitions
Function of neural pool depends on how the neurons are connected
Diverging Circuit definition
- one or few neurons produce output
- ultimately branches to multiple destinations
Converging Circuits definition
Multiple input neurons
converge on fewer and fewer neurons
(reach one or a few output neurons)
Reverberating Circuits definition
Neurons stimulate each other in linear sequence
one or more of the later cells restimulates the first cell [axon collateral] to start the process all over
Parallel After Discharge Circuits definition
input neurons diverges to stimulate several chains of neurons
(each chain has a different number of synapses—eventually they all reconvert on on for a few output neurons but with varying delays)
What is an example of a Diverging Circuit?
a small group of neurons in brain sends signals to thousands of muscle fibers
What is an example of a Converging Circuit?
Balance
Respiratory Center
What is an example of a Reverberating Circuit?
Diaphragm and intercostal muscles
What is an example of a Parallel After Discharge Circuit?
Pain (withdrawal reflex)
