neurons and glia 2

Once an action potential reaches an axon terminal, it stimulates the axon terminal to release of ______ at synapses

neurotransmitters

what is a synapse

the connection between the axon terminal of a pre-synaptic neuron and the dendrite of another post-synaptic neuron

what are neurotransmitters

small molecules that bind to receptors and generate post synaptic potentials

where are neurotransmitters stored

in synaptic vesicles

true or false: neurons typically only release one type of neurotransmitter

true

when do synaptic vesicles release neurotransmitters into the synaptic cleft

when an action potential reaches the axon terminal

synaptic transmission overview

1. action potentials depolarize axon terminals

2. open voltage-gated Ca2+ channels

3. Ca2+ promotes fusion of synaptic vesicles with plasma membrane and releases NT to synaptic cleft

4. NT diffuse across synaptic cleft and binds to receptors on post-synaptic neuron to produce post-synaptic potentials

5. NTs are removed from synaptic cleft to stop signal

what is a neuromuscular junction

synapse between an acetylcholine-releasing motor neuron and a muscle fiber

what are the two main receptors neurotransmitters bind to

• ligand-gated ion channels

• g protein coupled receptors

what are post-synaptic potentials

changes in membrane potential in post-synaptic neurons

what does it mean for a post-synaptic potential to be graded

intensity of the depolarization or the hyperpolarization varies depending on ESPSs and ISPSs

what do ESPSs do and what do ISPSs do

ESPSs: depolarize; brings membrane potential closer to threshold

ISPSs: hyperpolarize; move membrane potential further from threshold

what does the net effect of ESPSs and ISPSs on the axon hillock of post-synaptic neurons reflect

the summation of ESPSs and ISPSs in that point in time

ESPSs have an ______ effect and ISPSs have a ______ effect

additive; subtractive

what happens if ESPSs outcompete ISPSs and raise the membrane potential of the post-synaptic axon hillock to the -55mV threshold

the post-synaptic axon hillock will fire an action potential

what does the summation of PSPs depend on

the quantity of frequency (spatial summation and temporal summation)

what is spatial summation

summation of EPSPs and IPSPs on the post-synaptic axon hillock at a singular point in time

what is temporal summation

summation of EPSPs and IPSPs that occur in quick succession over a short period of time

how can neurotransmitters be removed from the synaptic cleft

• reuptake of the neurotransmitter by the pre-synaptic neuron

• degradation of the neurotransmitter by the synapse

how do drugs, toxins, or diseases that effect our nervous system exert their effects

by targeting synaptic transmission by either

• blocking neurotransmitter removal

• enhancing or inhibiting neurotransmitter receptors

drugs and toxins that alter the removal of neurotransmitters from they synaptic cleft

• SSRI anti-depressants: block serotonin reuptake

• Adderall: blocks dopamine norepinephrine reuptake

• Cocaine: blocks dopamine reuptake

• Sarin gas: inhibits the enzyme acetylcholinesterase that breaks down acetylcholine (causes muscles to be in a state of permanent contraction)

what is the primary inhibitory neurotransmitter in the CNS

GABA

what happens when GABA bind and opens its receptor

Cl- diffuses into the post synaptic neuron and generates an IPSP

what binds to GABA receptors and enhances the effect of GABA in post-synaptic neurons

alcohol (why alcohol is a nervous system depressant)

what parts of the brain does alcohol effect

effects the parts of the brain involved in self-control, inhibition, coordination, balance, and speech

what is adenosine

a metabolic waste product from ATP that accumulates in synapses throughout the day

what does adenosine bind

adenosine receptors which initiate IPSPs and inhibit post-synaptic neurons

what happens at night when adenosine levels are highest

adenosine receptors inhibit neurons which slows down neuronal firing in the brain and causes drowsiness

what can inhibit adenosine from binding to adenosine receptors

caffeine