Lecture 5 12b/c Flashcards
where does a chemical synapse occur
at the neuromuscular junction
a ____ experiences an action potential
presynaptic neuron
an action potential comes down an axon, opens ___ gated channels and creates a ___ that causes the vesicles to undergo exocytosis
ligand, calcium influx
the more a neuron fires, the more __ is going to influx and more __is going to be released.
calcium, neurotransmitter
can synapses be modified anatomically
yes
an ___ is a connection between an axon of one neuron and the dendrites of another.
axodendritic synapse
Postsynaptic potentials are called
graded or local potentials
graded means
it could be strong or weak
decremental means
it dies out over a period of time
excitatory means __ is going to occur
depolarization
the __ is where the axon meet with the soma
axon hillock
the ___releases the neurotransmitters at the synapse
presynaptic neuron
the ___ has the ligand gated channels and experiences the excitatory postsynaptic potential.
postsynaptic neuron
what is the purpose of an action potential occurring at a postsynaptic neuron
to release neurotransmitters
anything that’s inhibitory causes
hyperpolarization
if the __ and ligand gated __ open in an IPSP this causes ___
K+ channels, Cl- channels, hyper polarization
Cl- have a higher concentration in the ___ than the ___
ECF, ICF
the ___ rush into the cell to make it less positive during an IPSP
chloride ions
___ is the increasing of frequency stimulus
temporal summation
___ is when we look at more than one presynaptic neuron
spatial summation
can spatial and temporal summation occur at the same time?
yes
through ___ you can see summation of EPSPs
facilitation
___ a neuron makes it easier to reach threshold
facilitating
____ can suppress pain like during childbirth
presynaptic inhibition
____ are responsible for depolarization in a neuron
voltage gated sodium channels
at the peak of depolarization __ causes repolarization
K+ voltage gated channels
is an action potential reversble
no
can temporal summation ever override the absolute refractory period?
no
what alters the frequency of the action potentials
stimulus strength
do all neurons have the same RMB
no
what is a motor unit
a somatic neuron and all the muscle fibers it innervates.
what is the difference between the discharge and facilitated zone
the discharge zone has more synapses than the facilitated zone.
what his the definition of a synapse
a junction that mediates information transfer from one neuron to the next, or from a neuron to an effector cell.
what is the definition of a presynaptic neuron
the synapse between two neurons that releases neurotransmitters which influence the membrane potential of the postsynaptic neuron.
what are the steps to a chemical synapse
- The presynaptic neuron will undergo an Action Potential
- As the action potential arrives at the synaptic knob voltage-gated calcium channels will open, causing calcium influx
- Calcium entry induces exocytosis of vesicles containing neurotransmitters
The greater the stimulus=greater calcium influx- greater neurotransmitter release - Neurotransmitters diffuse through the synaptic cleft and bind to specific receptors on the postsynaptic membrane. This may be excitatory or inhibitory.
is the effect of a chemical synapse long or short lived
short
what are the three ways neurotransmitter effects are terminated
- Reuptake by astrocytes or the presynaptic terminal
- Degradation by enzymes associated with postsynaptic membrane located in the synaptic cleft
- And diffusion away from the synapse
___ are the electrical responses of the dendrites and cell body to presynaptic neurons are collectively postsynaptic potentials.
postsynaptic potential
where do postsynaptic potentials take place
cell body and dendrites
what is the distance traveled of a postsynaptic potentials
a short distance, typically to the axon hillock
what is the amplitude of the postsynaptic potentials
graded, decremental, excitatory or inhibitory
are postsynaptic potentials reversible
yes
what type of channels are involved in postsynaptic potentials
ligand gated ion channels, mechanically gated ion channels, or leakage channels
what kind of stimulus are used with postsynaptic potentials
neurotransmitters, pressure, light, etc.
is positive feedback present in postsynaptic potentials
no
where is an action potential located
the axon hillock, axon, synaptic knobs
what is the distance traveled for a action potential
long distance, the entire axon
what Isi the amplitude of an action potential
“all or nothing” non-decremental, always excitatory
are action potentials reversible
no
what types of channels are involved in action potentials
voltage gated ion channels, leakage channels
Is positive feedback present in action potentials
yes
what is resting membrane potential measured as in neurons
-70mV
excitatory neurotransmitters will bind to and open what in an EPSP
ligand gated Na+ and K+ channels
in an EPSP the K+ and Na+ channels diffuse simultaneously but __ has a greater electromechanical gradient so the __ is greater than the __ influx
Na+, Na+, K+
if the wave of depolarization during an EPSP reaches the axon hillock and threshold a __ will occur
action potential
what is threshold for a neuron
-55mV
inhibitory neurotransmitters are released by
presynaptic neurons
an inhibitory NT will bind to and open __ in an IPSP
ligand gated K+ channels or ligand gated Cl- channels
what is summation
the cumulative effect of more than one functional mechanism.
facilitation occurs due to the
summation of subthreshold EPSPs
Summation of IPSPs will allow a presynaptic neuron to
reduce the sensitivity of a post-synaptic neuron to a threshold-level stimulus.
Long-term synaptic potentiation occurs due to
a repeated or continuous use of a synapse.
Neurotransmitters released by the presynaptic neuron ultimately ___ the number of receptors in the postsynaptic neuron.
increase
the release of additional neurotransmitters from the presynaptic neuron__
is highly responsible for long-term memory and is associated with phantom pain.
If the postsynaptic potential is excitatory and reaches threshold it will travel across the cell body and result in
the generation of an action potential at the axon hillock
the action potential that occurs within a neuron which is also called
nerve impulses in neurons.
what is the absolute refractory period
immediately following one AP a neuron cannot respond to another stimulus no matter how strong.
what is the relative refractory period
only strong stimuli can generate an AP. The K+ channels are still open, so it would take a massive amount of depolarization to make the internal environment positive enough to reach threshold.
what is neuron coding
stimuli such as pressure, sound, and light, are translated to the brain as quantitative information.
what are the two ways in which quantitative information is relayed
- Recruitment of neurons- neurons with lower threshold will respond to weaker stimuli while neurons with higher thresholds will require stronger stimuli.
- The stimulus strength alters the frequency of action potentials- high frequency of stimulus=strong stimulus while low frequency of stimulus=weak stimulus.
what are neural pools
functional groups of neurons that integrate incoming information received from receptors or different neuronal pools and forward the processed information to other destinations.
what is the discharge zone
are the neurons closest to input fiber. They are more likely to generate impulses because they receive the bulk of synaptic contacts.
what is the facilitated zone
are the neurons that are farther from the center. They remain facilitated by subthreshold stimuli from the input fiber but will reach threshold due to innervation by other fibers.
what are circuits
patterns of synaptic connections in neuronal pools.
what is serial processing
One neuron stimulates the next which stimulates the next and so on. This results in a specific anticipated response.
what is he best example of serial processing
reflex arcs
what is parallel processing
One stimulus results in activation of many input pathways which deliver information to many different neural circuits.
When Ach binds to certain receptors what kind of effect does it have
excitatory OR inhibitory
what is adenosine
an inhibitory NT that makes you tired
___ or __ classification can determine how long an effect is
direct or indirect
a __ is an example a cholinergic synapse
neuromuscular junction
___ transmitters us second messenger systems
indirect
___ are associated with norepinephrine and epinephrine. This is in the ___
adrenergic synapses, postsynaptic neuron
As a part of the second messenger system neurotransmitters are still
opening ligand gated ion channels
___ mechanisms have a longer lasting effect because it’s intracellular so you start to activate a lot of intracellular events.
indirect
__are molecules that are synthesized by a neuron released when a nerve signal reaches an axon terminal and have a specific effect on a receiving cell’s physiology.
neurotransmitters
the effect of a NT depends on
the receptor that it binds to
what are the 6 structural classifications of NTs
- ACh
- amino acids
- monoamines
- neuropeptides
- purine
- gases and lipids
what are the locations and actions of ACh
it excited skeletal muscle, inhibits cardiac muscle, and has excitatory and inhibitory effects on smooth muscle and glands depending on location
what are the locations and action of Glutamate
it accounts for about 75% of al excitatory synaptic transmission in the brain and is involved in learning and memory
what are the locations and action of GABA
it is the most common inhibitory neurotransmitter in the brain
what are the locations and action of norepinephrine
sympathetic nervous system, it is involved in dreaming, walking, and mood, excites cardiac muscle, and can excite or inhibit smooth muscle and glands depending not he location
what are the locations and action of epinephrine
adrenal medulla, effects similar to those of norepinephrine
what are the locations and action of dopamine
involved in the elevation of mood and control of skeletal muscles
what are the locations and action of serotonin
secreted by blood platelets and intestinal cells, it is involved in sleepiness, alertness, thermoregulation, and mood
what are the locations and action of substance P
mediates pain transmission
what are the locations and action of enkephalins
acts as analgesics by inhibiting substance P, inhibits intestinal mobility, secretion increases sharply in women in labor.
the types of amino acids include
glutamate and GABA
the types of monoamines include
norepinephrine, epinephrine, dopamine, serotonin
the types of neuropeptides include
substance P, enkephalins, and beta endorphines
what re the locations and actions of beta endorphines
suppresses pain, reduces perception off fatigue and may produce runners high in athletes
Neuromodulators are released by __ and have long-term effects on groups of neurons rather than quick effects on a single synapse
neurons
what are some examples of neuromodulators
- Neuropeptides
- Nitric oxide which is excitatory in regions of the CNS, it relaxes smooth muscle and dilates small arteries to increase blood-flow tissues.
- Endocannabinoids which are inhibitory through the CNS, associated with memory, appetite and nausea, and are similar to the THC compound in marijuana.
direct NTs bind to and open
ion channels, are short lived, and ACh and many acids.
Indirect NTs induce
intracellular second-messenger systems, are longer lasting and have more broad effects.
what are some examples of indirect NTs
biogenic amines, neuropeptides, and dissolved gases
what is an example of a direct excitatory mechanism
a cholinergic synapse
what are the steps of action in a cholinergic synapse
- A nerve impulse induces the exocytosis of ACh from the presynaptic neuron.
- Empty vesicles are refilled inside the synaptic knob of the presynaptic neuron.
- ACh diffuses across the synaptic cleft and binds to specific ligand-gated channels on the plasma membrane of the postsynaptic neuron.
- The ligand -gated channels are open, causing an influx of Na+ and efflux of K+.
- The postsynaptic membrane is depolarized, making an action potential more likely to occur at the axon hillock.
what is an example of an inhibitory mechanism
GABA-ergic synapse
what are the steps of action in a GABA-ergic synapse
- GABA is exocytosed from the synaptic knob of the presynaptic neuron
- GABA diffuses across the synaptic cleft to bind to specific ligand gated ion channels on the plasma membrane of the postsynaptic neurons
- The channels open, allowing an influx of Cl- ions in the postsynaptic neuron.
- The postsynaptic neuron undergoes hyperpolarization, making an action potential less likely to occur at the axon hillock.
what is an example of a indirect excitatory mechanism
adrenergic synapse
what are the steps of action in an adergenic synapse
- Norepinephrine (NE) is exocytosed from the presynaptic neuron
- NE diffuses across the synaptic cleft to bind to a G Protein-coupled receptor on the plasma membrane of the postsynaptic neuron
- The binding of NE to the receptor induces a conformational change, causing it to unbind from the G protein.
- The detached G protein moves across the membrane to bind to and activate the enzyme 5. Adenylate Cyclase
- Adenylate Cyclase catalyzes a reaction which uses ATP to form cAMP
cAMP has the ability to alter multiple cellular processes such as
Open ligand-gated channels to induce depolarization of the postsynaptic membrane
Activate existing cytoplasmic enzymes to alter cellular metabolism
Activate transcription factors which bind to DNA in the nucleus, resulting in the production of more enzymes within the cell
