2 - Neuronal Synapses Flashcards
___ = where a neuron transfers information to 1 or more other neurons or a muscle
synapse
3 parts of the synapse?
- presynaptic terminal
- synaptic cleft
- postsynaptic terminal
which neuron conducts impulses toward the synapse?
presynaptic
which neuron conducts impulses away from the synapse?
postsynaptic
If synapse is neuromuscular, ___ or ____, the ions flowing through ligand-gated channels cause local membrane potentials.
axosomatic, axodentric
if synapse is ____, presynaptic effects occur
axoaxonic
Steps of synaptic transmission:
1. action potential comes to the ____ terminal
presynaptic
Steps of synaptic transmission:
1. action potential comes to the presynaptic terminal
2. presynaptic terminal membrane depolarizes which opens the voltage-gated ____ channels
Ca+
Steps of synaptic transmission:
1. action potential comes to the presynaptic terminal
2. presynaptic terminal membrane depolarizes which opens the voltage-gated Ca2+ channels
3. Ca2+ flows in and frees Ca2+ stored inside the cell - vesicles containing ____ are triggered to move toward release site on presynaptic membrane
neurotransmitters
Steps of synaptic transmission
1. action potential comes to the presynaptic terminal
2. presynaptic terminal membrane depolarizes which opens the voltage-gated Ca2+ channels
3. Ca2+ flows in and frees Ca2+ stored inside the cell - vesicles containing neurotransmitters are triggered to move toward release site on presynaptic membrane
4. vesicles fuse with presynaptic membrane and release neurotransmitters into ___ ___
5. neurotransmitter spreads across cleft
6. neurotransmitter that touches matching ___ ___ then binds to it
7. postsynaptic receptor alters its ___ and opens associated ___ ___ or triggers associated ___ ___
synaptic cleft
postsynaptic receptor
ion channel
intracellular messengers
each neuron can have different ___ of inputs in each region
numbers
Strong excitatory stimuli in presynaptic neuron leads to ____ APs
more! - does NOT make APs stronger, just makes more
Does the total number of AP’s that reach the presynaptic terminal directly relate to amount of neurotransmitter released?
yes!
When stimulation duration is longer in presynaptic cell, the series of AP’s is ____
longer
__ __: local changes in ion concentrations across the postsynaptic membrane
postsynaptic potentials
____ postsynaptic potential:
- local depolarization occurs with flow of Na+ and Ca2+ into neuron
- summation facilitates AP generation
- common throughout CNS and PNS
excitatory
Excitatory postsynaptic potential:
- local depolarization occurs with flow of ___ or ___ into neuron
- summation of EPSP’s facilitates AP generation
- common throughout ___ and ____
Na+, Ca2+
CNS, PNS
____ postsynaptic potential:
- local hyperpolarization occurs with influx of Cl- into or K+ out of the neuron
- summation with EPSPs determines if AP is generated or not
Inhibitory
Inhibitory postsynaptic potential:
- local hyperpolarization occurs influx of ___ into or ___ out of neuron
- summation with EPSPs determines if AP is generated or not
Cl-, K+
___:
- 1st presynaptic neuron releases neurotransmitters that causes slight local depolarization of 2nd neuron’s presynaptic terminal
- when AP’s arrive, AP duration increases allowing more Ca2+ influx and vesicles of neurotransmitter to move and be released
facilitation
Facilitation:
- 1st presynaptic neuron releases neurotransmitters that causes slight local ____ of 2nd neurons presynaptic terminal
- when APs arrive, AP duration increases allowing more ___ influx and vesicles of neurotransmitter to move and be released
depolarization
Ca2+
___:
- 1st causes slight local hyperpolarization
- When APs arrive, AP duration decreases allowing less Ca2+ influx and less neurotransmitter release
inhibition
Inhibition:
- 1st causes slight local ____
- when APs arrive, AP duration decreases allowing less ____ influx and less neurotransmitter release
hyperpolarization
Ca2+
2 types of neuromessengers?
neurotransmitters, neuromodulators
are neuromessengers facilitative, inhibitory or could be both?
both
Neurotransmitters location of action?
synapse
neuromodulators location of action?
extracellular space
neurotransmitters method of action?
EPSP or IPSP
neuromodulators method of action?
alter gene expression, open ion channels, change metabolism, affects many neurons
neurotransmitters time?
ms to mins
neuromodulators time?
mins to days
The same chemical can function as a neurotransmitter or neuromodulator. the effect depends on what 2 things?
- depends if released at specific synapses or into extracellular space
- depends on what part of nervous system it is released
Is the effect of a neurotransmitter related to the receptor it binds to or the chemical it is?
receptor
ligand gated ion channels are also called ___ receptor
ionotropic
G protein triggering of ion chennels is also called ____ receptor
metabotropic
are ligand-gated ion channels fast or slow? G protein triggering of ion channels?
ligand = fast
G protein = slow
G Protein 2nd messenger system:
____ is 1st messenger and ___ produced inside neuron is 2nd messenger.
neuromodulator, chemical
G protein 2nd messenger system cascade of events:
1. cell produces neurotransmitters or other cellular products due to activation of ___.
2. opens ion channels
3. releases ___ to regulate metabolism and other processes
genes, Ca2+
___: drugs that bind to receptors and copy actions of neurotranmitter
agonists
___: drugs that block binding of neurotransmitters to receptors, drugs that inhibit release of neurotransmitters in presynaptic neurons
antagonists
Acetylcholine is produced in __ ___ and ____
basal forebrain, midbrain
3 places of acetylcholines effect?
- skeletal muscles
- autonomic nervous system
- brain
Acetylcholine effects on skeletal muscles:
- ALL skeletal muscles use Ach to elicit ___-acting effects on muscle membranes
-it is ___ neurotransmitter found in neuromuscular junctions to promote muscle contractions
- blocking Ach receptors causes weakness, fatigue, or paralysis - what disease destroys Ach receptors?
fast, excitatory, myasthenia gravis
Ach effect on autonomic nervous system:
- ___ HR
- __ pupils
- ____ smooth muscle contractions and digestive processes
slows, constricts, increases
so works with parasympathetic ns
Ach effect on brain:
- arousal, pleasure, cognitive function
- acts as __ neuromodulator in control of movement and attention
- impicated in ___ addiction and ___ disease
slow, nicotine, alzheimers
___: principal fast excitatory neurotransmitter of CNS
glutamate
___: neurotransmitter in virtually every brain region, neural changes with learning and development (neuroplasticity)
glutamate
what are some diseases associated with glutamate?
changes in transmission implicated in chronic pain, parkinsons, schizophrenia, and neuron death in acute stroke
what could happen with excessive levels of glutamate?
excitotoxicity and neuron death, epileptic seizures
___: inhibits postsynaptic membranes mostly in brainstem and spinal cord
glycine
___: primary inhibitory neurotransmitter in CNS, especially with interneurons in spinal cord
GABA
which two neurotransmitters?
- prevent excessive neural activity
- low levels implicated in seizure, unwanted or involuntary muscle contractions or anxiety
- alcohol, barbiturates, benzodiazepines, anticonvulsants and baclofan mimic GABA
- huntingtons disease causes loss of neurons in striatum that use it with jerky involuntary movements and cognitive decline
Glycine and GABA
where is dopamine produced in the brain?
substantia nigra
___: affects motor function, cognition and behavior
- associated with reward seeking behaviors
- can be good for eating
- can be bad leading to addiction
dopamine
all dopamine receptors are ___ messenger systems
2nd
dopamine abnormalities seen in:
- ___ ___: not enough dopamine produced with bradykinesia and other symptoms presnent - precursors to dopamine given medically
- ___ or ____: signaling pathways - drugs that prevent binding to receptors to alter thinking also impact motor function
- excessive dopamine levels seen in cocaine or amphetamine abuse by preventing reuptake by presynatic terminals
parkinsons disease, schizophrenia or psychoses
___: involved with mood, pain perception, arousal, motor activity
serotonin
serotonin levels are ___ when alert and ___ during REM sleep
highest, lowest
2 different types of receptors for seratonin?
2nd messenger systems, ligand-gated
drugs for ___ may selectively block serotonin receptors to keep serotonin available
depression
___ ___:
- endogenous examples include endorphins, enkephalins and dynorphins
- produced within nervous system and bind same receptors as opium
- receptors found mostly in spinal cord, hypothalamus and areas in brainstem to inhibit perception of pain
opioid peptides
___: produced in brainstem, hypothalamus, and thalamus
norepinephrine
___:
- released by neurons of ANS and secreted by adrenal glands
- responsible for vigilance and “fight or flight”
norepinephrine
___ __: with tissue injury, it stimulate nerve endings at injury site
substance P
