week 3 lecture 6 NT receptors and integration

ionotropic receptors

transmembrane proteins that directly convert neurotransmitters into electrical signals by opening an ion pore upon ligand binding

metabotropic receptors

cell surface receptors that trigger slow, long-lasting cellular changes by activating internal G-proteins

EPSP mechanism

excitatory NTs bind to receptor channels opening them and shifting the membrane potential closer to the threshold for firing an action potential

IPSP mechanism

inhibitory NTs bind to the postsynaptic neuron's receptors opening channels and making the membrane potential more negative and further from the firing threshold

how are ion channels activated

by change in voltage

how are neurotransmitter receptors activated

when neurotransmitter binds

neurotransmitter receptors

ionotropic, metabotropic

ionotropic receptors relation between NT & ion channel

1:1

metabotropic receptors relation between NT & ion channel

1:1000

ionotropic receptor step 1

NT binds to receptor on ion channel

ionotropic receptor step 2

channel pops open and ions move in or out depending on receptor type

metabotropic receptor step 1

transmitter molecule substance binds with receptor

metabotropic receptor step 2

receptor activates G protein

metabotropic receptor step 3

alpha subunit breaks away and activates enzyme producing second messenger

metabotropic receptor step 4

ion channels opens

metabotropic receptor step 5

ions enter cell producing postsynaptic potential

metabotropic receptor step 6

second messenger goes to nucleus or other parts of cell

EPSP stands for

Excitatory postsynaptic potential

IPSP stands for

Inhibitory postsynaptic potential

neural integration

neurons combine multiple incoming signals from synaptic inputs to determine their output

summation

integrates multiple electrical signals from other neurons adding EPSPs and IPSPs inputs at the axon hillock

temporal summation

high-frequency, successive action potentials from a single presynaptic neuron accumulate at the postsynaptic neuron's membrane

spatial summation

EPSPs from different presynaptic neurons add together at the postsynaptic neuron trigger zone to reach the threshold for an action potential

EPSP-IPSP cancellation

EPSPs and IPSPs are summed allowing the negative voltage of the IPSP to neutralize the positive voltage of the EPSP

types of summations

temporal, spatial

spatial summation steps

simultaneous stimulation by several presynaptic neurons, EPSPs spread from several snapped to axon hillock, postsynaptic neuron fires

temporal summation steps

high freq stimulation by one presynaptic neuron, EPSPs spread from one synapse to axon hillock, postsynaptic neuron fires

what does IPSP do

makes a neuron less likely to fire an action potential creating a temporary hyperpolarization through the influx of negative ions or efflux of positive ions, which counters excitatory signals and regulates overall neural activity

what is EPSP

temporary depolarization of the postsynaptic membrane caused by the flow of positively charged ions into the postsynaptic cell

what are the positively charged ions in EPSP

Na+, Ca2+

IPSP steps

Neurotransmitter Release, Receptor Binding, Ion Channel Opening, Hyperpolarization, Inhibition, Graded & Decremental

EPSP steps

Neurotransmitter Release, Ionotropic Receptor Binding, Cation Influx, Depolarization, Action Potential Initiation

EPSP action potential

Depolarization

EPSP response

excitatory/more positive

how does EPSP work

moves the membrane potential closer to threshold and makes the cell more likely to fire an action potential

IPSP action potential

hyperpolarization

IPSP response

inhibitory/more negative

how does IPSP work

decreases chances of an action potential by moving membrane potential farther from threshold

order of how EPSP are graded

higher freq of APs, more neurotransmitter released, more neurotransmitter binds to and opens more receptors, more ions (Na+) flow through the receptors

what do the graded potentials of EPSPs determine

more graded potentials, greater depolarization and EPSP

which graded potentials are presynaptic

higher freq of APs, more neurotransmitter released

what does neural integration result in

coordinated brain function, complex behaviors, coherent thought

purpose of summation

to decide whether to fire an action potential

what does temporal summation cause

greater depolarization

EPSP-IPSP cancellation prevents

postsynaptic membrane from reaching the threshold required to fire an action potential

what action potential is the negative voltage of IPSP

hyperpolarizing

what action potential is the positive voltage of EPSP

depolarizing

action potential spatial summation step 1

simultaneous stimulation

what causes simultaneous stimulation in spatial summation step 1

several presynaptic neurons

action potential spatial summation step 2

EPSPs spread from several synapses to axon

action potential spatial summation step 3

postsynaptic neuron fires

action potential temporal summation step 1

high frequency stimulation

what causes high frequency stimulation in temporal summation step 1

one presynaptic neuron

action potential temporal summation step 2

EPSPs spread from one synapse to axon hillock

action potential temporal summation step 3

postsynaptic neuron fires

what kind of stimulation happens in spatial summation step 1

simultaneous

what kind of stimulation happens in temporal summation step 1

high frequency

how many synapses does EPSPs spread to the axon hillock in spatial summation step 2

several

how many synapses does EPSPs spread to the axon hillock in temporal summation step 2

one

what does the presynaptic neuron do

release NT

what does the postsynaptic neuron do

gets locally depolarized

what happens if the sum of all postsynaptic currents depolarizes the cell’s resting membrane potential above threshold

the neuron fires an action potential

where is the sum of all postsynaptic currents that depolarizes the cell’s resting membrane potential above threshold generated at

axon hillock

when will the neuro fire an action potential

if the sum of all postsynaptic currents depolarizes the cell’s resting membrane potential above threshold

chemical synaptic transmission step 1

transmitter is synthesized then stored in vesicles

chemical synaptic transmission step 2

an action potential invades presynaptic terminal

chemical synaptic transmission step 3

depolarization of presynaptic terminal

what does depolarization of presynaptic terminal in chemical synaptic transmission step 3 cause

opening of voltage-gated Ca2+ channels

chemical synaptic transmission step 4

influx of Ca2+ through channels

chemical synaptic transmission step 5

vesicles fuse with presynaptic membrane

what causes vesicles fuse with presynaptic membrane in chemical synaptic transmission step 5

Ca2+

chemical synaptic transmission step 6

transmitter is released into synaptic cleft

how are transmitters released into synaptic cleft in chemical synaptic transmission step 6

exocytosis

chemical synaptic transmission step 7

transmitter binds to receptor molecules

where does transmitter binds to receptor molecules in chemical synaptic transmission step 7

postsynaptic membrane

chemical synaptic transmission step 8

opening/closing postsynaptic channels

chemical synaptic transmission step 9

postsynaptic current causes EPSP/IPSP

what does the postsynaptic current that causes EPSP/IPSP in chemical synaptic transmission step 9 do

changes excitability of postsynaptic cell

chemical synaptic transmission step 10

removal of neurotransmitter

how is the neurotransmitter removed in chemical synaptic transmission step 10

by glial reuptake or enzymatic degradation

chemical synaptic transmission step 11

retrieval of vesicular membrane

where is the vesicular membrane retrieved from in chemical synaptic transmission step 11

plasma membrane